JP2010509101A - Fiber reinforced composite core and panel - Google Patents

Abstract

A fiber reinforced core panel is formed from a strip of plastic foam with a roving layer spirally wound to form a web that can be undulated and intersected with a transverse web. A hollow tube can be used instead of the foam strip. Axial roving cooperates with the overlying spiral wound roving to form a beam or column. The pattern of rovings that can be wrapped can be varied along the strip to provide structural efficiency. Wrapped strips can alternate with spaced apart strips and spacers between the strips increase the buckling strength of the web. Continuous winding roving between spaced strips allows folding to form a panel with reinforced edges. A continuously wound strip is spirally wrapped to form an annular structure, and the composite panel can use both a thermosetting resin and a thermoplastic resin. Continuously wound strips or strip cuts can be continuously fed in either the longitudinal or transverse direction into a molding apparatus that can receive the skin material and form a reinforced composite panel.
[Selection] Figure 49

Description

<Rights of the US Government>
This invention is supported by the United States Government under US Air Force contract number F29601-02-C-0169, and contracts F33615-99-C-3217, F33615-00-C-3018, F42650-03-C- 0029, FA8201-06-C-0091, US Navy Contract N00167-99-C-0042, and NASA Contract NNC04CA18C. The US federal government has certain rights in this invention.

  The present invention relates to a sandwich panel composite structure comprising fiber reinforced low density porous material, resin, fibrous and non-fibrous skin reinforcement, and more specifically, improved structural morphology, improved resin injection method and It relates to the production method.

  Structural sandwich panels having a core made of low density closed cell material, such as closed cell plastic foam material, and an opposing skin made of a fiber reinforced mat or fabric in a matrix of cured resin are available in a wide variety of products, such as It has been used for decades to build boat hulls and refrigerated trailers. The foam core serves to separate and stabilize the structural skin, withstand shear and compression loads, and provide thermal insulation.

  For example, as disclosed in Patent Document 1 of the present applicant and the like, by providing a structure of a fibrous reinforcing member in a foamed core, the core is reinforced and the adhesion of the core to the panel skin is improved. In addition, the structural performance of the sandwich panel having the foam core can be remarkably enhanced. When a porous fibrous reinforcement is introduced into a closed cell core and a porous fibrous skin reinforcing fabric or mat is applied to each side of the core, an adhesive resin such as polyester, vinyl ester, or epoxy is applied to the differential pressure. By using, for example, a vacuum bag, the porous skin and the core reinforcing material can be flowed all over. While impregnating the resin into the fibrous reinforcement, the resin does not completely soak the plastic foam core because of its closed cell composition. The resin is then cured together throughout the reinforced structure to achieve a strong monolithic panel.

US Pat. No. 5,834,082 U.S. Pat. No. 4,411,939 US Pat. No. 5,462,623 US Pat. No. 5,589,243 US Pat. No. 5,834,082 US Pat. No. 5,701,234 US Pat. No. 5,904,972 US Pat. No. 5,958,325 US Pat. No. 5,958,325 European Patent No. 0 672,805B1 US Pat. No. 5,904,972 US Pat. No. 5,834,082

  It would be desirable to produce sandwich panels with high structural performance by improving the structural connections and support within the foam core and between the reinforcement members between the core and the panel skin. This is in order to withstand buckling loads in the reinforcement members, to prevent premature separation of the reinforcement members under load from each other and from the skin, and to distribute the force applied to the panel. Desirable to give a route. Existing fiber reinforced core products have several significant improvements in this regard compared to non-reinforced foams, but are integrated and internally structurally supported structures that fully integrate the separate reinforcing elements of the core It can't be a thing. For example, in a fibrous reinforcing sheet type web in a lattice configuration where a first set of continuous webs intersects a second set of intermittent or discontinuous webs, the webs support each other against buckling. Fit. However, under severe loading conditions, discontinuous webs tend to be useless along their narrow intersections at the adhesive resin and continuous web joints. This tendency can be considerably reduced by providing a flat edge groove filled with resin in the foam along these intersecting lines as disclosed in the aforementioned patent. Furthermore, since the reinforcing fibers of the interrupted webs end at each intersection with the continuous web, the structural contribution of those fibers is virtually less than the fibers of the continuous web.

  In the case of strut or rod type core reinforcements containing rovings of glass or carbon fibers or other fibers that extend between the faces of the core, the individual struts in a given strut row cross each other in a grid. can do. This provides each strut with support for buckling, but only in the plane of the strut row. To obtain bi-directional support, the first row of struts must penetrate the filaments of the intersecting rows of struts. This requires a difficult and costly level of precision and control in machining because all struts must be accurately positioned in three dimensions.

  One embodiment of the present invention overcomes the limitations of both web-type and strut-type reinforced foam cores by combining these two types of reinforcement elements into a hybrid reinforcement configuration. In the hybrid structure, the foam core is provided with rows of spaced, parallel, fiber-reinforced webs or sheets that extend between the faces of the foam board at an acute or right angle. A spaced parallel array of reinforcing elements including a second set of rod-like fiber rovings or struts also extends between the faces of the foam board at an acute angle or at a right angle so that the rovings or struts are connected to the web. Intersect and penetrate. The web and strut thus constitute an intertwined three-dimensional support structure in which all the reinforcing fibers in the core are not interrupted. These interconnected webs and struts provide multiple load paths to effectively distribute vertical loads between the core reinforcement elements and between the core structure and the panel skin. Impact damage tends to be limited to the direct range of impact since the composite reinforcement structure resists the growth of shear planes in the core.

  In an alternative hybrid structure, the web comprises a continuous sheet of cloth or mat that is formed into corrugations with segments extending between the faces of the core, and the gaps between the corrugations are plugged with foam strips of matching cross section. Can be removed. The corrugations, along with their intersecting panel skins, can form a rectangular, triangular, parallelogram, or other geometric shape that provides other structurally efficient or manufacturing advantages.

  In a particularly cost-effective version of the hybrid core, the core reinforcing web has a rectangular shape with a relatively low cost fiber roving rather than gluing a substantially more expensive woven or stitched fabric to the surface of the foam strip. Produced by spirally winding on a foam strip. Additional rovings can be applied axially along the length of the strip during the winding operation to improve the structural properties of the strip or to serve as a low cost component of the finished panel skin. It is also possible to form a structural core without bonding foam strips wrapped with fibers together and adding a row of structural struts. In this configuration, the contact or adjacent side of the rectangular cross-section wound strip forms a web element having an I-beam flange for attachment to the panel skin. In contrast to the disclosure of U.S. Pat. No. 6,057,059, the fiber extension of each core web is attached to the panel skin on both sides as well as on one side of the web, significantly improving the shear strength of the resulting panel. This allows the use of a lighter and less expensive web for a given strength requirement. Similarly, the present invention provides significantly improved core and skin adhesion and shear strength when compared to the structures disclosed in the applicant's patents (Patent Document 3, Patent Document 4, and Patent Document 5). To do. In the test, webs consisting of circumferentially wound rovings show 75% higher shear strength than those whose end portions end adjacent to the panel skin. Each wound strip may be provided with an internal structural transverse reinforcing web to provide bi-directional strength and stiffness. A roving-wrapped core can also be formed using a strip having a triangular cross section.

  Winding rovings by machine and combining fiber wound strips into a single core has both economic and handling advantages. For a single composite bridge deck panel or yacht hull constructed in accordance with US Pat. The labor component of production of these individual cores is extremely high. Cut the reinforcing fabric into sheets and wrap them around each separate core with adhesive, or apply a smaller piece of fabric to each side of each core with adhesive, or first A tubular fabric is formed and the core is inserted therein. These processes become increasingly difficult as the dimensions of the core component decrease. Arranging these cores in the mold is also labor intensive, expensive and time consuming, thus limiting the number of panels that can be produced from the mold within a certain period of time. The positioning of the individual core blocks becomes increasingly troublesome as the mold curvature increases or as the mold surface deviates from the horizontal plane. The core that is the subject of the present invention substantially eliminates these deficiencies by utilizing a large number of components to make it a single easily handled core.

  In addition to their superior structural performance, the hybrid design allows for extremely complex and structurally effective configurations with relatively simple processes at high machine production rates and without the need for extreme levels of manufacturing accuracy To. As mentioned above, when it is desired that intersecting rows of rovings penetrate each other, bi-directional strut type cores require that the roving reinforcements be inserted into the foam board with an accuracy that is difficult to achieve. And Further, in order to arrange the struts at an angle in the direction of 2 to 4 in the plate material, it is necessary to create a large number of passages through a plurality of strut insertion devices.

  In contrast, a two-way hybrid core can be produced in just one passage through the strut insertion device. This stiffener web cooperates with intersecting struts to withstand loads in the plane of those struts. Also, since the web extends transversely to the strut rows, the web also provides strength to the struts transversely. Furthermore, they require a much more limited degree of precision in production because they only have to intersect the plane of the web, not a thin bundle of filaments.

  The hybrid core improves molded panel production by increasing the rate and reliability of resin impregnation or injection into both the core reinforcing element and the sandwich panel skin overlying the core. In the vacuum resin transfer molding (VARTM) process, the panel containing the dried porous skin reinforcement is placed in a single-sided or sealed mold that is covered by an air impermeable sealed bag. The panel is then evacuated, leaving the resin to flow and penetrate into the reinforcement under atmospheric pressure. Because of the complex interconnection between the web and struts in the core of the present invention, both air and resin can flow quickly and universally throughout the structure. This porous web and struts form a natural resin flow path between the skins, which quickly carries the resin from its source to numerous points on the porous skin. This is a race-tracking problem, i.e., the area of the dried skin fabric is isolated from the vacuum source by the forefront of the resin running irregularly, so that the skin is completely covered by the resin before it thickens and hardens. Minimize problems that prevent them from getting infiltrated.

  In one embodiment of the invention, no resin distribution medium of any kind is required between the panel skin and the mold surface or the vacuum bag membrane. This not only eliminates the cost of such a distribution medium, but also allows the production of panels having smooth surfaces on all sides. Compared with the prior art as disclosed in Patent Document 9, this foam core is disposed in the periphery of the core adjacent to the panel skin as a means for distributing the resin to the skin. There is no need to provide microgrooves or slots or holes in the foam that extend between the skins. In the present invention, all resin flows through the core reinforcement structure to the skin, while US Pat. The disadvantage of the surrounding microgrooves is that the size and spacing of the microgrooves depends on the type and amount of the fiber fabric of the panel to ensure that the skin and core reinforcement are fully impregnated before the resin cures. It must be chosen to fit. In the present invention, all resin injected into the skin passes through the core porous reinforcement structure to the skin, and the panel skin generally intersects with two or more porous reinforcement elements per square inch of panel surface. As such, the resin tends to spread quickly and uniformly across the skin surface. The complete impregnation of the panel skin that can be seen is a reliable indication that the core reinforcement structure has no dry parts and thus weak parts. This is an important advantage over other injection systems that introduce the resin close to the skin.

  According to the invention, the resin is supplied to the core reinforcement structure through a network of grooves that are inside the foam core, adjacent to the core reinforcing web, extend parallel to the web, and not adjacent to the panel skin. . The ends of these grooves typically intersect a supply channel having a larger cross-sectional area. The resin supplied to the supply channel quickly flows through the groove adjacent to the web, and then substantially all of the resin flows through the fibrous core reinforcing element to the panel skin and penetrates. If the resin groove is placed in a plane close to the center of the panel thickness, the resin only needs to flow in each direction from the center plane through half the panel thickness to reach full resin saturation. It is. This is significantly faster than conventional resin injection techniques where the resin is introduced from a single panel surface and must flow through the entire panel thickness to the opposite surface. Panels with thick cores or thick skins can be provided with an additional set or sets of resin channels and feed channels for faster injection.

  The injection method of the present invention is particularly suitable for the production of molded panels that require a good surface finish on both sides of the panel. Since the resin is introduced into the core and quickly flows from the core toward the skin reinforcement structure due to the differential pressure, both sides of the panel may be in contact with the mold surface of the desired shape and finish, and the vacuum bag The time required for injection does not increase significantly compared to injection performed under a flexible surface such as. In contrast, conventional differential pressure molding processes such as VARTM, where the skin reinforcement is united by pressure prior to the introduction of the resin, both maintain a substantial pressure and rapidly introduce the resin across the surface of the skin. If desired, it is necessary to cover one side of the panel with a flexible membrane such as a vacuum bag that contains the resin distribution media. Without this arrangement, the pressure on the rigid mold surfaces against both panel faces is forced into a long and slow injection path, and the resin flows along their length and width rather than through their thickness. Penetrates skin.

  Using the inside-out core injection method of the present invention, a resin having different characteristics from the resin injected into the outer skin layer of the panel can be injected into the fibrous core reinforcing material and the inner skin layer. It can be used, for example, to produce a sandwich panel having an outer skin layer comprising a refractory phenolic resin, an inner skin layer comprising a structural vinyl ester resin, and a core reinforcement structure. This is accomplished by providing, for example, an epoxy resin adhesive barrier in the form of a film between the inner and outer layers of the porous fibrous skin reinforcement. The first resin is supplied by injection from the core as described above, and the second resin is injected directly into the external skin reinforcement. Here, the barrier film serves to create a structural adhesive bond between the resins and to keep them separate.

  In a useful variant of the hybrid core of the invention, this reinforcing web does not extend between the faces of the panel. Instead, a porous fiber web sheet is sandwiched between two or more foamed plate materials and stacked in a sandwich structure. A porous roving strut or rod extends through the intermediate web sheet or group of sheets between the faces of the core. This web or group of webs serves to stabilize the struts against buckling under load and also distribute the resin to the struts and skins. The resin can be introduced through grooves spaced in parallel in the foam adjacent to the web. Alternatively, the resin can flow into the core through a feed channel that is perpendicular to the panel surface and ends in a radial groove adjacent to the web. This arrangement is useful for injection molding circular panels, such as manhole covers. In a third variation, the web sheet can incorporate a low density fiber mat or a non-structural porous infusion medium through which the resin fed through the feed channel across the center plane of the panel is directed toward the struts. Flows through the struts and into the panel skin.

  A further feature of the present invention is to provide an improved connection between the strut or rod type core reinforcing element and the sandwich panel skin. This improvement can be applied to a hybrid panel having both types of web and strut core reinforcement members, and to a panel in which the core reinforcement is composed of only struts. The porous fibrous struts extending between the faces of the core may end between the core and the skin, extend through the skin and end at their outer surface, and one or more of the panel skins It may be overlaid on the other layer. Under load, the struts are subject to substantial forces of stretching or compression at the intersection with the skin, which can cause the adhesive joint between the reinforcing element and the skin to break.

  For example, the prior art disclosed in U.S. Pat. No. 6,053,836 discloses providing a looped end portion on a reinforcing element adjacent to a skin. Under pressure during molding, the loop formed in the end portion of the strut provides a wide area of adhesive contact with the skin. However, a significant disadvantage of this design is that the loop, which is a bundle of folded fibers, forms a lump that deforms the panel skin under molding pressure and out of plane. This causes excessive resin build-up in the skin, increased tendency to buckle under in-plane compressive loading of the skin, and undesirable surface finish.

  In the present invention, the end portion of the strut-type reinforcing element is cut so that the filaments constituting the strut are spread laterally under compressive load, the end portion is remarkably flat with respect to the skin, and directly adjacent to the end portion of the stat. In this area, an extensive area of adhesive bonding between the end portion of each stat and the skin is achieved. The flatness of the skin surface applies a sufficient pressure to the panel surface prior to molding, sometimes simultaneously with heat, to create a recess to embed any reinforcement mass or peak in the foam core during the molding process. Further improvement can be achieved by providing. Alternatively, grooves may be formed in the foam face along the strut insertion line, and the strut end portion or overlying seam portion may be pushed into it during molding.

  The present invention also provides an alternative means of tethering the strut ends, which is effective even when the strut end portions do not overlap the panel skin. In this configuration, parallel grooves or slits are arranged on the surface of the foam plate, and the end portions of the strut type reinforcing members pass through the grooves. A porous reinforcing roving having a depth sufficient to hold the strut ends together by gluing is inserted into the groove prior to the insertion of the strut member, and the resin that flows into the structure during molding is the strut and groove. Realize the structural attachment of the inner roving. These rovings, which have a significant contact area with the overlying panel skin, complete the transmission of structural loads between the skin and the core. An important additional advantage of this structure is that the groove roving and strut members can be made to dimensions that make up an integrated truss structure, and the groove roving serves as the truss string. is there. Since the cost of roving is much lower than that of textiles, this allows economical panel production if a relatively thin skin is suitable between the truss rows.

  In the present invention, instead of attaching a more costly woven or knitted reinforcing material skin to the surface of the core, a low cost roving is directly applied to the surface of the foam plate, and the reinforcing member is inserted into the foam. A panel skin can be formed in between. In this method, multiple rovings are applied along a parallel line transverse to the length of the core, and the foam surface is covered somewhat by advancement of the foam core by a strut inserter. It is continuously drawn in the longitudinal direction from the supply creel with a sufficient number. Prior to insertion of the struts, the group of rovings is pulled laterally or acutely across the surface of the core from the creel and advanced with the core while the strut rovings are sewn to the core. Once the resin is applied to the panel, the overlying seam portion holds all surface rovings in the correct position to form the structural panel skin. If desired, a light bale of reinforcing material can be applied to the entire surface roving prior to sewing to improve the handling characteristics of the core prior to molding. As an alternative to continuous roving, random or oriented chopped roving can be laid between the core surface and the surface veil to form the structural mat.

  Sandwich panels that include a spiral wound roving that overlays and restrains the axial roving that has been used in place of the skin fabric reinforcements, even when the skin is not sewn to the core It is effective in that it resists delamination of the skin. This is quite useful, for example, in areas of irregular core thickness that are subject to delamination due to buckling or tensile loads in the skin, such as step down and taper at the panel edges.

  The present invention includes several useful variations of reinforced core panels that have a bi-directional core strength and that obtain all of the core reinforcement members by a helical wrapping process. In the most economical embodiment, a unidirectional core panel consisting of parallel wound foam strips is cut in a direction perpendicular to the axis of the strip into a uniform second strip, which is then rotated 90 degrees and united. A second integrated core panel. The initial spiral wound roving is then stretched between the faces of the core panel as separate strut roving segments whose end portions terminate adjacent to the face of the core. This core structure provides bi-directional shear strength and high compressive strength, but the panel skin and core bond strength is low. Skin adhesion is accomplished by winding the second strips in a spiral prior to their coalescence and stretching between the foam strips across the face of the core panel that is unbroken and adjacent to the skin. It can be increased by providing a winding reinforcement layer. Depending on the desired structural properties, the orientation of the wound second strip can be adjusted prior to coalescence to provide a double layer of rovings between or adjacent to the skins. The bi-directional core panel can also be provided with parallel rows of continuous rovings that are inserted into slits in the face of the core panel to form a support member between core reinforcing webs for thin panel skins. By winding a pair of foamed strips with reinforcing webs between the strips in the unidirectional core prior to winding, a skin support between the wrapped reinforcing webs can be provided.

  An important advantage of all the bi-directional cores described herein is that the cross reinforcing webs are mutually stable against buckling under load on adjacent low density, low strength foam strips It is to make it. The buckling resistance of a unidirectional core web can be improved by increasing the effective width of the web by providing spacer strips, such as high density foamed plastic, between adjacent wound foam strips. In an economical form of unidirectional core panel, roving wrap foam strips alternate with simple foam strips, thus allowing twice the panel production for a given amount of winding machine production. In this embodiment, spacer strips are provided between opposing winding layers on opposite sides of each wound strip in order to stabilize the web against buckling. Modified to provide bi-directional strength to a unidirectional strip by providing a torsional or other configuration strip that provides structural properties in directions other than the overall direction of the strip, so that the edges of the strip are not parallel can do. By using reinforcing fibers and low-cost thermoplastic material in the strip as individual components for subsequent coalescence under heat and pressure, a core panel comprising a strip of any configuration and incorporating a thermoplastic resin, Can be produced economically.

  The structural performance of a spirally wound strip can be improved by providing an axially extending roving along the corner of the strip below the wound roving. This addition causes the reinforcing web on each side of each foam strip to take the general form of a burjoist having top and bottom chords separated by a rod-like shear member. This structure is more resistant to impact and axial roving can allow for less use of reinforcing fibers in the panel skin. Individual strips constructed in this way can be used as individual structural members, e.g. pillars or box beams, whose performance is achieved by providing the strips with lateral reinforcement members and between the corners of the strip. This can be further enhanced by providing additional axial roving.

  The structural efficiency of certain panels containing wound strips is increased by changing the feed rate of the strips through the roving winding device so as to change the angle and density of the reinforcement wound along the length of the foam strip. Can do. This can achieve an increase in the compressive strength of the panel at the proof stress point, or a core shear resistance that is adjusted to match the expected shear load along the length of the panel.

  Shear loads in core panels containing unidirectionally wound foam strips are arranged at regular intervals during the winding process, and the strips are stacked one after the other before they are combined to form the core panel By doing so, it can be transmitted to the end of the strip and from there to the intersecting panel reinforcement. This positions these wound rovings of spaced segments between opposing ends of the foam strip and provides a strong structural bond with the panel edge reinforcement or with the adjacent core panel. It is also desirable to produce a sandwich panel having a continuous core panel reinforcement that does not end at the core joint, generally having a cylindrical structure, or other closed configuration, thereby avoiding structural discontinuities. This embodiment can be used, for example, to form jet engine casings that are designed to withstand very high energy shocks while maintaining the overall integrity of the casing. The core panel is produced by spirally winding a reinforcing roving around a continuous foam strip and then spiraling the strip around a cylindrical mandrel. Inside the wound roving, a continuous axial roving can be provided to obtain further hoop strength and impact resistance.

  A useful embodiment of the present invention uses a thin-walled tube instead of a foam strip and winds a reinforcing roving on it. The tube can comprise a low structural property material, such as stiff paper, or a high structural property material, such as roll-formed or extruded aluminum, preferably these have strong adhesion to the resin used as the fiber reinforcement matrix. Processed to get. This embodiment is useful when it is desirable to obtain a hollow structure, or to reduce the weight of a low density solid core, or to incorporate the structural properties of a tubular material into the panel.

  Another means of increasing the impact resistance of sandwich panels containing a spiral wound core and a thermosetting resin is to incorporate a thermoplastic resin, which is generally much less brittle than those thermosetting resins, into the outer portion of the panel skin. It is. This can be achieved by several means. The core reinforcement may be impregnated using a thermosetting resin, leaving the inner portion porous for subsequent impregnation, and heating the thermoplastic film into a fibrous reinforcement mat or outer portion of the fabric. it can. If desired, a cloth layer made of a mixture of glass fibers and thermoplastic fibers may be used in place of the thermoplastic film. The mixed fabric is heated to form a reinforced thermoplastic outer surface and allows the thermoplastic resin to flow partially through the thickness of the inner reinforcing mat. In yet another embodiment, the mixed fabric skin is placed adjacent to the reinforced core so that the thermosetting resin used to inject into the core impregnates both the glass fibers and the thermoplastic fibers of the skin. It can also be injected without applying heat.

1 is a perspective view of a portion of a reinforced foam core composite panel constructed in accordance with the present invention. FIG. 6 is a cross-sectional view of a portion of a reinforced foam core composite panel constructed in accordance with another embodiment of the present invention. FIG. 6 is a cross-sectional view of a portion of another embodiment of a reinforced foam core composite panel constructed in accordance with the present invention. FIG. 6 is a cross-sectional view of a portion of another embodiment of a reinforced foam core composite panel constructed in accordance with the present invention. FIG. 6 is a cross-sectional view of a portion of another embodiment of a reinforced foam core composite panel constructed in accordance with the present invention. FIG. 6 is a cross-sectional view of a portion of another embodiment of a reinforced foam core composite panel constructed in accordance with the present invention with a central portion cut away. FIG. 7 is a partial cross-sectional view taken along line 7-7 in FIG. FIG. 6 is a cross-sectional view of a portion of another embodiment of a reinforced foam core composite panel constructed in accordance with the present invention. FIG. 4 is a perspective view of a portion of a reinforced foam core composite panel constructed in accordance with another embodiment of the present invention. FIG. 6 is a perspective view of a portion of a reinforced foam core composite panel constructed in accordance with another embodiment of the present invention. FIG. 6 is a perspective view of a portion of a reinforced foam core composite panel constructed in accordance with a modification of the present invention. 1 is a schematic view of an apparatus for producing a fiber-wrapped foam strip according to the present invention. 1 is a perspective view of a portion of a fiber-wrapped foam strip constructed in accordance with the present invention. 1 is a perspective view of a portion of a reinforced foam core composite panel constructed in accordance with the present invention. 1 is a schematic view of an apparatus for producing a fiber reinforced foam core panel according to the present invention. 1 is a perspective view of a portion of a reinforced foam component constructed in accordance with the present invention. FIG. FIG. 17 is a perspective view of a part of a reinforcing foam component using the component of FIG. 16. FIG. 18 is a perspective view of a portion of a reinforced foam core constructed using the components of FIG. 17 in accordance with the present invention. FIG. 6 is a perspective view of a portion of another embodiment of a reinforced foam component constructed in accordance with the present invention. FIG. 6 is a perspective view of a portion of a core panel constructed in accordance with a variation of the present invention. It is a figure which shows the one part part expanded in FIG. It is a one part perspective view of the fragment | piece cut from the panel shown in FIG. FIG. 23 is a partial perspective view in which a part of a core panel made of the strip shown in FIG. 22 is disassembled. FIG. 23 is a perspective view of the strip shown in FIG. 22 with spiral wound roving. FIG. 25 is an enlarged perspective view of a part of the wound strip shown in FIG. 24. It is a one part perspective view of the panel core constructed | assembled using the strip shown in FIG. FIG. 25 is a perspective view of a portion of a core panel constructed using the strip shown in FIG. 24 in accordance with a modification of the present invention. FIG. 6 is a perspective view of a portion of a core strip formed in accordance with another modification of the present invention. FIG. 29 is an enlarged perspective view of a part of the core strip shown in FIG. 28. It is a one part perspective view of the core panel constructed | assembled using the core strip shown in FIG. FIG. 6 is a perspective view of a portion of a core panel formed in accordance with another modification of the present invention. FIG. 6 is a perspective view of a portion of a core panel constructed in accordance with another modification of the present invention. FIG. 5 is a perspective view of a portion of a core strip formed in accordance with a modification of the present invention. FIG. 6 is a perspective view of a portion of another core panel formed in accordance with a modification of the present invention. FIG. 3 is a perspective view of a portion of an annular core assembly formed by spirally wrapping a core strip constructed in accordance with the present invention. FIG. 4 is a perspective view of a portion of a core panel, each comprising a tubular core strip spirally wound with rovings, formed according to a modification of the present invention. FIG. 6 is a plan view of a portion of a core strip constructed in accordance with another further modification of the present invention. FIG. 38 is a plan view of a portion of a core panel made of the core strip shown in FIG. 37 in accordance with the present invention. FIG. 6 is a perspective view of a portion of a core panel formed in accordance with another modification of the present invention. FIG. 6 is a perspective view of a portion of a panel formed in accordance with another modification of the present invention. FIG. 6 is a perspective view of a portion of a composite panel formed in accordance with another modification of the present invention. FIG. 3 is a perspective view of a portion of a modified core panel formed in accordance with the present invention. FIG. 6 is a perspective view of a portion of another composite panel formed in accordance with the present invention. 1 is a perspective view of a portion of a core panel formed in accordance with the present invention. 1 is a perspective view of a portion of a core panel formed in accordance with the present invention. 1 is a perspective view of a portion of a core panel formed in accordance with the present invention. 1 is a perspective view of a portion of a core panel formed in accordance with the present invention. 1 is a schematic perspective view of an apparatus showing a method for producing a composite panel according to the present invention. FIG. 6 is another schematic perspective view of another apparatus showing another method of making a composite panel in accordance with the present invention. FIG. 6 is a further schematic perspective view of an apparatus for producing another form of composite panel in accordance with the present invention. 2 is an enlarged end view of a portion of a composite panel formed in accordance with the present invention. FIG.

  FIG. 1 illustrates a structural composite sandwich panel 30 that can be used, for example, as a highway truck cab floor, a boat hull or stern beam, a factory building roof, or as a vehicle or pedestrian bridge deck. . The panel 30 includes a fiber reinforced closed cell plastic foam core 31 and two opposing fiber reinforced skins 32. The foam core 31 includes a plurality of foam strips 33. Here, the structural properties of the strip 33 are insufficient to withstand the load in the core that matches the load that the skin 32 is designed for.

  The core reinforcing fibers selected to give the core the required structural properties are glass fibers or carbon fibers, or other reinforcing fibers. In one direction, the reinforcing fibers comprise a plurality of parallel sheets or webs 34 of porous fiber cloth or mats that extend between the faces of the core 31 and in the web material. It adheres to one side of each foaming strip 33 while maintaining the substantial porosity. If desired, the web 34 can also incorporate a reinforcement comprising a plurality of individual rovings that are adhesively affixed to a foam board (not shown) from which the strip 33 is cut. In the intersecting direction, a plurality of rods or struts 35 of spaced cores, generally spaced at right angles to the web 34, extend between both sides of the core and are spaced from a bundle or roving of porous reinforcing filaments. Configure parallel rows.

  Each row of struts includes a plurality of struts 35 inclined at acute angles opposite to the panel skin, eg, +58 degrees and -58 degrees or +45 degrees and -45 degrees. The two sets of opposing struts in each row are in the same plane and intersect each other to form a triangular or lattice type structure. The diameter and spacing of the struts 35 in the strut row depends on structural considerations, but is generally in the range of 0.01 to 0.12 inches in diameter and 0.25 to 2.0 inches in spacing. . In some cases, the struts may exceed 0.50 inches in diameter and 7.0 inches apart. The rows of struts 35 are generally spaced 0.5 to 1.0 inches apart. The closed cell foam strip or piece 33 can be polyurethane, polyvinyl chloride, polystyrene, phenolic resin, polyethylene, polymethacrylamide, or other foam material having desirable properties for a particular application. Generally the foam density is low, ranging from 2 to 5 pounds per cubic foot, but much higher densities can be used if desired.

  As shown in FIG. 1, the strut 35 intersects with the web 34, and the fibers constituting the strut penetrate the fibers constituting the web. The fiber rovings that make up the struts are inserted through the web into the foamed core during the stitching operation, so that the filaments that make up the struts pass through the filaments of the web without breaking any filament pairs, so The continuity of all elements of the reinforcement structure remains intact. In the preferred embodiment, the panel skin 32 includes an inner skin 36 and an outer skin 37. Further, the end portion 38 of the reinforcing strut 35 penetrates the inner skin 36 and spreads laterally so as to overlap the inner skin 36. After the inner skin 36 is covered with the outer skin 37, the panel 30 is molded with resin. Thus, the struts are mechanically attached to the skin and provide high resistance to delamination from the core 31 of the skin 32 under load. If desired, the end portion of the strut roving can be terminated adjacent to the face of the reinforced core 31.

  Impregnate or infuse the core and skin porous and fibrous reinforcements with adhesive resin flowing preferably under differential pressure throughout all the reinforcing material and cure to form a rigid load bearing structure . Prior to molding and curing the panel 30, the inner skin 36 and foam strip 33, together with the web 30 to which they are attached, the skin fibers that oppose the friction caused by the pressure of the plastic foam and the roving fibers that form the struts 35. And by a roving segment or end portion overlying the panel skin. The core 30 can vary widely in dimensions for a particular application, but actual core sizes include, for example, 0.25 inches to 5.0 inches x 2 feet to 8 feet wide x 2 feet long To 40 feet. The core is generally produced in a continuous length and cut to the desired length. To form a sandwich panel having a larger area than a single reinforced core constructed in accordance with the present invention, two or more cores can be placed adjacent to each other in the mold prior to resin introduction. .

  For the shear load in the core 31, the struts 35 mainly resist in one direction, and the web 34 mainly resists in the lateral direction. In addition, a complex integration of the web and struts is achieved by the rigid resin adhesion at each intersection of the strut and web and by the continuity of the reinforcing fibers through all such intersections. The web and struts support each other against buckling, allowing the use of lighter reinforcing members in thick panels that tend to buckle and break due to the thinness of the core reinforcing member. The configuration shown in FIG. 1 is capable of withstanding a large compressive load perpendicular to the skin because the orientation of the web 34 is set at right angles to the skin 32 and the struts 35 suppress buckling. The structural integration of the web and struts also provides multiple load paths to enhance the sharing of localized compressive loads between core reinforcement elements, and to the initiation and diffusion of delamination surfaces due to shear failure in the core. It gives considerable resistance to it. The mechanical attachment by adhesion of the core reinforcement member to the skin provides high resistance to penetration of the fitting into the panel skin.

  The foam core and skin fiber reinforcements are generally impregnated with resin by flowing the resin through the porous reinforcing fibers under differential pressure in processes such as vacuum molding, resin transfer molding, or vacuum assisted resin transfer molding (VARTM). Or injected. In VARTM molding, the core and skin are generally sealed in an airtight mold having one flexible mold surface, and air is exhausted from the mold. This applies atmospheric pressure through the flexible surface to conform the panel 30 to the mold and also compact the fibers of the skin 32. The catalyst-added resin is generally drawn into a mold by vacuum through a resin distribution medium or a network of channels provided on the panel surface, and is cured. The present invention can also incorporate an improved VARTM injection method if desired.

  The reinforced core 31 can be provided with a resin groove 39 in the foamed strip 33 which is cut and disposed adjacent to the web inside the foamed core 31. The grooves 39 are generally larger in cross-sectional area than the individual grooves 39, but end at the resin supply flow path 40, which may be the same size (FIG. 1). The flow path 40 serves to distribute the resin to the grooves 39 under a differential pressure. The supply channel 40 can be disposed along one or both edges of the reinforced core 31 where the reinforcing web 34 ends. Alternatively, the flow path 40 can be located completely inside the core. For illustrative purposes, FIG. 1 shows a flow path 40 at the core edge and FIG. 7 shows a supply flow path inside the core. If the channel 40 is provided only on one edge of the core 31, the groove 39 can extend to the opposite edge of the core 31; alternatively, the reinforced foam core and resin in the panel skin reinforcement Depending on the flow kinetics, it can be terminated inside the foam strip.

  The catalyst-added resin flows into the flow path 40 through a tube (not shown) connected to a resin source, typically a resin drum. The tube opening can be arranged at any location along the flow path 40. A preferred method of injecting into the reinforcing core of the present invention using a vacuum bag is to seal and evacuate the mold and then attach an optional resin supply device to the mold. The rigid resin connection or insertion tube is provided with a sharp pointed end and then crosses the supply channel 40 and through the vacuum bag membrane and panel skins 36, 37 or through the vacuum bag at the edge of the panel 30. It is inserted into the reinforced core 31. The insertion tube was provided with an opening around it to allow the resin to flow into the flow path 40. A tape sealer is affixed to the insertion point to prevent vacuum loss, the insertion tube is connected to a resin supply source, and the resin is drawn into the flow path 40 through the insertion tube by vacuum.

  In addition to the speed, ease, and low material cost of introducing this resin into the panel, additional resin connection pipes are in-progressed to guide additional resin to specific areas of the panel. You can also insert it into the panel at other locations while you are. Further, by providing one or a plurality of holes into which the resin connection pipe can be inserted in the mold surface, the pipe is inserted into the panel 30 completely enclosed in the rigid mold by using this pipe insertion method. You can also. As the resin fills the grooves 39, the resin also enters and throughout the porous fibrous web 34, into and across the intersecting porous fibrous struts 35, and into the intersecting panel skin 32. After flowing throughout, the resin cures to form a rigid reinforced sandwich panel structure. The reinforced core 31 provided with the channel 40 can be placed in the mold with the channels 40 adjacent to each other to form a single larger channel. The resin flowing into the larger flow path is cured to form a structural spline that is driven into the edge portion of the web 34 and resists shear forces between adjacent cores 31.

  This resin distribution system incorporated into the reinforced core 31 has significant advantages over existing VARTM methods. The resin quickly fills the grooves 39 and flows throughout the web and strut reinforcement structures toward the panel skin 32 through the web and strut connections with countless relatively evenly distributed skins. Minimize the possibility of non-impregnated areas. No resin microgroove or distribution media material is required around the core 31. Resin is introduced into a plurality of grooves 39 positioned in the central plane of the panel and moves a relatively short distance toward both skins 32. A vacuum can be applied to any desired location or locations on the outer skin 37 or on the fabric at the panel edge. If desired, introduce a perforated vacuum tube, fibrous drain flow media, or vacuum to ensure that a small area of dry porous skin reinforcement is not isolated from the vacuum by the surrounding resin flow Multiple rows of other means can be provided on the outer skin 37 surface. Panels with significantly thicker cores or skins can be provided with an additional set of resin grooves 39 and associated supply channels 40 arranged in a plane parallel to the skin 32. The resin introduced into the center of the panel travels a relatively short distance towards both skins 32. The inner core injection system just described is also useful for cores that include a web that extends between skins without intersecting fibrous struts. Closer web spacing may be necessary for uniform resin distribution.

  The mold surface in contact with the reinforced core panel may be either rigid or flexible without impairing the rapid flow of resin throughout the core reinforcement structure or skin. For example, a reinforced core with an associated porous fibrous skin is placed between a rigid mold base and a rigid cauldron with the cauldron covered by a vacuum bag sealed to the mold base. be able to. When atmospheric pressure is applied to the panel by evacuating the bag from one edge of the panel, the resin introduced to the opposite edge of the panel will be as in the normal VARTM method where both sides of the mold are rigid. It flows quickly through the corners of the core and skin reinforcement structure without having to flow longitudinally throughout the length or width of the panel skin.

  The reinforced panel 30 can be constructed to allow two types of resins with different properties to be co-injected into the core. For example, the outer skin of the panel can be impregnated with a refractory phenolic resin, and the inner skin and core reinforcing structure can be impregnated with a vinyl ester resin that is structurally superior but less refractory. If such a structure is desired, an adhesive barrier film 41 positioned between the inner skin 36 and the outer skin 37 is provided on the panel 30 prior to resin injection. The barrier film 41 is made of an adhesive material that prevents passage of the liquid resin from one side of the film to the other, for example, epoxy. It is cured by applying heat and moderate pressure to form a structural bond between the inner skin 36 and the outer skin 37.

  To inject into the panel, the reinforced core 31 and attached inner skin 36, adhesive barrier film 41, and outer skin 37 are placed in a closed mold and then evacuated by a vacuum pump. . The first resin is introduced into the inner surface of the core 31 through the channels 40 and 39 as previously described, leaving it to flow throughout the core reinforcing structure and the inner skin. At the same time, a second resin of different composition is introduced directly into the outer skin through the mold surface or outer skin edge. The adhesive barrier film 41 serves to prevent the mixing of two different resins, and the heat generated by the curing of the two resins also helps the adhesive film to cure, thus preventing the inner skin and A structural bond between the outer skins is obtained. If the adhesive film 41 is applied only to one side of the panel 30, the resin injected into the core 31 will also be injected into both the inner and outer skins on the opposite side of the panel.

  The embodiments of the present invention illustrated in FIGS. 1, 2, 6, 7, 13, 14, and 18 include an internal resin distribution groove adjacent to the core reinforcing web and an associated resin supply channel. Shown as a thing. This feature can be omitted from the embodiments of FIGS. 1, 2, 6, 7, 13, 14, 18 if desired, and this feature can be added to the embodiments shown in FIGS. 3, 4, 5, 9, 19, or It should be understood that it can be added to any other embodiment having a porous fibrous web sheet within the foam core.

  The sandwich panel 50 (FIG. 2) differs from the embodiment shown in FIG. 1 because the reinforcing struts only need to be inserted into the foam core at a single angle instead of two opposite angles. A reinforced foam core 52 that can be produced at improved production rates. The parallel fiber reinforced webs 51 extend between the faces of the foam core 52 at an acute angle with respect to the face of the core, for example 58 degrees or 45 degrees. These rows of webs 51 intersect a set of parallel rows of fiber reinforced struts 53 whose fibers generally penetrate web 51 and skin 54 in the manner described in connection with FIG.

  In the embodiment shown in FIG. 2, all struts are inclined at an angle with respect to the panel skin, which coincides with the angle of the web 51 except in the opposite direction. Web 51 and struts 53 support each other against buckling and cooperate to resist unidirectional shear loads, and the web also resists lateral shear loads. Any number of web reinforcing fabrics or mats can be selected, but the bi-directional structural function of the web is due to the use of web reinforcing fibers in which some of the fibers are oriented at an angle opposite to that of the struts 53. Can be increased. The transverse shear strength is effective by orienting the remaining fibers of the web 51 at those angles with respect to the panel skin, since the shear forces in the core typically break down to +45 and -45 degrees. Can be achieved. The core reinforcing web 34 of FIG. 1 and the core reinforcing web 51 of FIG. 2 end adjacent to the panel skins 32 and 54, respectively. Thus, a direct structural bond between the web and the skin is achieved by an adhesive bond of the resin matrix surrounding all the reinforcing fibers in the panel. The strength of the web-skin bond is such that the webs 34 and 51 are provided with fibers that extend out of the edges of the webs 34 or 51, or adjacent to the edges of the web as described in US Pat. This can be improved by providing a resin groove bottom on the web edge formed by carving the groove.

  Webs 34 and 51 also have indirect structural connections with skins 32 and 54, respectively, via struts 35 and 53, which adhere to both the web and skin, thus between the web and skin. Supports part of the load. The panel skins are also joined together by the configuration of roving struts shown in FIG. 2 that include a series of separate inclined rows of staples each having an extended strut end portion. This slanted staple configuration of strut structures can also be provided in a panel having opposing struts and will be described more fully in connection with FIG.

  When it is desirable to further increase the strength and stiffness of a composite panel having crossed webs and struts, the core reinforcing web is not a single, continuous fiber reinforced mat or fabric, but a plurality of separate web strips. Can be included. This embodiment is illustrated in FIGS. Referring to FIG. 3, a composite sandwich panel 60 includes a fiber reinforced skin 61 and a fiber reinforced foam core 62. The foam core 62 extends between the foam pieces or strips 63, spaced rows of spaced fiber roving struts 64, and panel skins, and is transverse to the strut rows. It includes a fibrous web sheet 65 formed into a rectangular corrugation. As in the case of FIG. 1, the struts 64 are inclined at equal and opposite angles with respect to the skin and intersect and penetrate the opposing struts and skin 61. The struts also intersect and penetrate the corrugated web segment 66. The corrugated web segment 66 extends through the web segment 67 that extends between and lies adjacent to the skin. The structure shown in FIG. 3 provides several structural enhancements to that shown in FIG. The corrugated web segment 67 makes it possible to increase the bonding area with the skin 61, and the strut 64 allows mechanical attachment by sewing between the web segment 67 and the skin 61. Also, the web structure corrugation provides significant additional strength and stiffness in the direction transverse to the strut rows.

  The reinforced sandwich panel 70 shown in FIG. 4 also provides the benefits of web and skin adhesion, corrugated strength and stiffness described in connection with FIG. In FIG. 4, the foam strip 71 has a parallelogram cross section, and the web segment 72 of the continuous corrugated web sheet 73 extends between the surfaces of the core 76 at an acute angle with respect to the skin 74. A plurality of parallel rows of spaced fiber roving struts 75 also extend between the faces of the reinforced core 76, the struts 75 being equal to the angle of the web segment 72, but at an opposite angle. Incline at. The struts intersect and penetrate the corrugated web segment 72, penetrate the web sheet segment 76 adjacent to the skin 74, and preferably penetrate one or more layers of the skin. The orientation of the fibers in the web can be optimized for overall core structural properties as described more fully in connection with FIG. Also, as in FIG. 2, orienting the struts at a single angle allows for the rapid and efficient production of reinforced cores since only a single insertion step is required.

  Another reinforced sandwich panel 80 shown in FIG. 5 also uses a continuous corrugated web sheet 81 as part of the foam core 82 reinforcement. The foam piece or strip 83 is triangular in cross section and the web segments 84 and 85 extending between the skins 87 are inclined at an angle opposite to the skin. Multiple rows of spaced fiber roving struts 86 are inclined at equal but opposite angles to intersect and penetrate web segments 84 and 85. The struts also intersect and preferably penetrate one or more layers of skin 87.

  In contrast to the configuration shown in FIGS. 3 and 4, the triangular web structure of FIG. 5 provides significant strength and stiffness to the panel 80 in both the longitudinal and lateral directions even without the reinforcing struts 86 present. The struts improve these properties by stabilizing the web segments 84 and 85 and by tying the skins 87 together. The struts 86 also provide more strength and stiffness in the direction of the strut rows. The strut angle is selected based on overall structural considerations and need not match the angle of the web segments 84 and 85. For example, the strut 86 can be perpendicular to the skin if desired. This not only provides the panel 80 with high compressive strength, but also requires only a single angle for strut insertion, thus simplifying panel production.

  6 and 7 show a plurality of parallel rows of stiffening roving struts 92 spaced apart in a reinforced foam core 91 and a plurality of stiffening roving struts 93 spaced apart. Illustrated is a sandwich panel 90 having intersecting parallel rows and only one continuous reinforcing web sheet 94 parallel to the skin 95. The foam core 91 includes a stacked foam board 96 separated by a web 94. The struts 92 may differ from the struts 93 in spacing, diameter, fiber composition, and angle if structural design requires. The struts can also be provided as a single set of parallel rows of struts if the structural requirements of the panel are essentially unidirectional. The compression and shear properties of panel 90 are primarily provided by struts 92 and 93. As the thickness of the core 91 increases or the strut diameter decreases, the strut becomes increasingly susceptible to buckling failure under structural loading conditions. The struts 92 or 93 in each row intersect each other in a lattice configuration and form a buckling support for each other in the plane of the strut rows. However, the only weak and often insufficient lateral buckling support is provided by the low density foam 96. A continuous fiber reinforced web 94, through which all struts 92 and 93 pass, provides the additional buckling support required. If desired, one or more additional support webs 94 can be provided, all spaced apart from one another and parallel to the panel skin 95.

  FIG. 6 also illustrates the strut end portion 97, as well as between the reinforcing member of the core 91 and the reinforcing member of the adjacent foam core molded as a component of a single sandwich panel, or other adjacent composite. A web edge portion 98 is shown protruding from the foam board 96 to provide a means for ensuring high structural continuity in a structure (not shown). If structural adhesion between adjacent cores in a given sandwich panel is desired, the foam plate 96 edge and foaming of adjacent reinforced cores are introduced before the resin is introduced into the core and skin reinforcement. The edge portion (not shown) of the board is abraded or otherwise removed to expose the fibrous strut end portion 97 and the web edge portion 98. These reinforced cores are then pressed, for example in a mold. The exposed end and edge portions from adjacent cores are mixed together and subsequently embedded in the resin. The resin flows into the panel reinforcement under differential pressure and cures to form a strong bond with the strut end portion and the web edge portion. Preferably, fiber reinforced mats or fabric strips extending between skins 95 are arranged between adjacent cores in the mold to enhance the load bearing properties of the joints between the cores.

  The strong structural bond between adjacent reinforced cores 31 or between the core 31 and the skin at the edge of the sandwich panel also causes the fibers to extend to the core 31 beyond the intersection with the edge of the core 31. This can also be achieved by providing the web 34. The extension of the web 31 is folded in the form of a tab at right angles to the foam strip 33. These tabs at the end of the web make it possible to expand the contact area for adhering the web reinforcing member to the adjacent reinforcing material when the panel 31 is impregnated with resin. If it is desired to achieve a strong structural bond between the resin impregnated and cured panel 90 and the adjacent composite structure, the foam board 91 is abraded to provide a hard cured strut end portion 97 and Web edge portions 98 are exposed and the edges and areas adjacent to the edge portions are filled with adhesive resin, mastic, or potting compound and pressed against the panel. The panel 90 will adhere to them while the resin cures.

  The reinforced core 91 shown in FIGS. 6 and 7 is provided with an integral resin injection system, as generally described above in connection with FIG. The sandwich panel 90 includes a porous fibrous skin and core reinforcement and is placed in a closed mold where air is evacuated. The resin is then introduced into the flow path at the end of the supply flow path 99 or through a hole (not shown) drilled from the panel surface. The resin then fills the resin supply channel 99 positioned within the reinforced core 91 and is positioned within or within the core 91 and adjacent to the porous fibrous web 94. Fill the resin groove 100 placed with the. The resin then hardens after it has flowed from the groove 100 to the porous web 94, from the web 94 to the porous struts 92 and 93, and from the strut to the porous skin 95. Form a structural panel. When the core 91 is to be used to produce a circular panel, the resin grooves 100 can be arranged radially from the center of the panel and in a state of supplying resin from the panel surface toward the center.

  The core reinforcing strut structure shown in FIGS. 1, 3, 5, 6, and 7 takes the form of a planar array of opposing struts that intersect each other within the foam core. The number and density of such crossings in the resulting lattice structure depends on the thickness of the core, the spacing between struts, and the steepness of the strut angle relative to the panel skin. An alternative strut structure is shown in FIG. 8, which can be used in place of the structure of FIGS. 1, 3, 5, 6, 7, but is most suitable for relatively thin panels or relatively thick struts. The core reinforcement structure of FIG. 8 includes either a unidirectional row of struts as shown, or a number of intersecting rows of struts, depending on the structural requirements and possibly for core reinforcement. Can be used with the web.

  Referring to FIG. 8, sandwich panel 110 has opposing skins 111 and a plurality of rows of fiber roving struts 113 extending between panel skins 111 and inclined at equal but opposite angles to the skin. A reinforced foam core 112. Opposing struts 113 intersect each other and penetrate the skin adjacent to the panel skin 111 in a simple triangular configuration. In the production of the reinforced core 110, continuous fiber rovings 114 are stitched through the skin 111 and the foam core 112 from opposite sides of the foam core. If desired, both sets of roving struts can be sewn through the skin and foam core from the same side of the core. In the stitching process, continuous roving 114 exits skin 111 and projects in the form of loop 115 (shown in phantom). The roving is then folded along the insertion line to form a strut 113 consisting of double roving segments.

  A roving segment 116 overlies the skin 111 as the panel 110 advances through the stitching device. The protruding robin group 115 formed during the stitching process is cut at a desired distance from the surface of the skin, for example 0.2 inches, to form a protruding strut end portion 117 (shown in phantom). To do. When pressure is applied to the panel skin during the resin molding process, the protruding strut end portion 117 expands and forms a flat end portion 118 with respect to the skin 111. As a result, strong adhesion to the skin and flatness from the skin 111 are achieved. And mechanical resistance against withdrawal of the strut end 118.

  Mechanical attachment can be improved by adding the outer skin shown in connection with FIG. The cut and widened strut end 118 also tends to form a mass adjacent to the skin, or prevents the panel from fitting tightly to the mold surface and deposits excess resin on the skin surface. Realizes a significant improvement over the skin properties obtained with loops. Surface flatness can be achieved by applying sufficient pressure to the panel 110 to conform the foam core 112 to the roving segment that protrudes beyond the surface of the skin 111, or to force the protruding roving segment into it under moderate molding pressure. Further improvements can be made by providing the foam core with a groove or dent that can be made.

  The slanted staple configuration including the strut 113, the cut strut end portion 118, and the roving segment 116 overlying the skin, shown in FIG. 8, ensure structural attachment between the core reinforcing strut and the panel skin. It provides an effective and effective means of producing, as well as a preferred method of producing any reinforced core of the present subject matter. It should be understood that other methods of stitching and other treatments of roving segments outside the face of the foam core, such as conventional type continuous fiber lock stitches or chain stitches, can also be used.

  The sandwich panels and cores illustrated in FIGS. 1-8 are generally greater in width than depth. A core reinforcing member comprising a porous fibrous web and struts can also be incorporated into a sandwich panel having a depth greater than the width. FIG. 9 illustrates a beam-type panel or beam 120 that incorporates a strut-type core reinforcement structure and is designed for use as a roof support in a corrosion-resistant building. The beam 120 includes opposing glass fiber or carbon fiber reinforced plastic skin 121 and a reinforced foam core 122. The foam core 122 includes a foam plate or piece 123 and opposed porous glass fiber or carbon fiber reinforcing member struts 124 that penetrate the foam core 122 at an acute angle with respect to the skin 121, which is generally versioned. If the structural design requires, in addition to struts 124 intersecting the additional struts, a grid-like configuration as illustrated in FIGS. 6 and 7 can be formed, and one or more additional parallels of the reinforcing struts. A simple row can also be incorporated into the panel or beam 120. The skin 121 acts as a structural chord flange whose fibers are essentially longitudinally oriented. The skin 121 includes an inner skin 125 and an outer skin 126 with fiber reinforcements extending through the end portion 127 of the reinforcing member 124 as described in connection with FIG. If desired, the skins 125 and 126 penetrate the fibers of the end portion 127 and widen the end by stitching the skin to the end portion with flexible fibers or thin rigid rods adjacent to the skins 125 and 126. The portion 127 can be attached more firmly.

  If desired, one or more porous fibrous support webs 128 may be incorporated into the beam 120 to stabilize the struts 124 against buckling under load. On the surface of the foam plate 123 extending between the opposing skins 121, a second set of porous fiber reinforced fabrics such as glass fibers is used to stabilize the beam 120 against lateral deformation under load. A skin 129 is provided. As previously mentioned, the curable resin introduced under differential pressure impregnates all the porous fiber reinforcement materials forming the beam 120 and cures to form a rigid bearing beam. If structural considerations are required, the beam can have an irregular cross-section, i.e. the depth can vary from the end of the beam toward the center of the beam, and can also be curved or bow-shaped. . If desired, the skin 120 can be quite thin, and the truss chording function can be combined into a roving bundle in the groove of the foam board adjacent to the skin as described more fully below in connection with FIG. Can also be given by inserting

  The sandwich panel core reinforcement structure with a panel width greater than the depth consists of a plurality of parallel true trusses in which rod or strut reinforcement members extend at opposite angles in a triangular configuration between upper and lower chord members Can take the form of a mold structure. This arrangement achieves excellent attachment of the strut end portion. It also uses a relatively low cost roving form of fiber reinforcement material, such as carbon fiber or glass fiber, as a truss chord member to replace a significant portion of the more expensive fabric skin reinforcement. As shown in FIG. 10, the sandwich panel 140 includes a reinforced closed cell foam core 141 and an opposing fiber reinforced skin 142. The reinforced core 141 is provided with a plurality of rows of parallel trusses 143 extending between the skins 142. Each truss 143 includes parallel bundles of fiber reinforced rovings 144, such as glass fibers or carbon fibers, which are positioned in grooves formed in the foam core 141 and upper and lower chords for each truss 143. It plays a role as a member. A fiber reinforced rod or strut 145 penetrates the string member, is anchored in the string member 143, extends between the panel skins 142 at opposite acute angles, and preferably penetrates one or more layers of the skin 142. Overlapping. As described above, the cured resin impregnates all the reinforcing materials. A truss structure including struts 145 and string members 143 can also be incorporated into the core having a reinforcing web extending between or parallel to the panel skins, for example as shown in FIGS.

  Referring to FIG. 11, the use of relatively economical fiber rovings instead of woven or knitted fiber reinforced fabrics can be expanded to form a full panel skin structure. The sandwich panel 150 includes a reinforced closed cell foam core 151 and an opposing fibrous skin 152. The core 151 includes a foam plate member 153 and a fiber reinforcing member or strut 154 extending between the skins. Each of the skins 152 includes a first layer of parallel reinforcing rovings 155 adjacent to the foam core 153 and substantially covering the face of the foam. A second layer of parallel reinforcing rovings 156 overlies and intersects the first roving layer 155 and substantially covers the surface of the first layer 155. If desired, a layer of fiber mat or bale 157 can be overlaid on the second roving layer 156.

  In the production of the panel 150, the end portion of the roving including the first skin layer 155 is fixed by a line intersecting the front edge of the foamed plate material 153. The board is advanced through a stitching device such as the apparatus shown in FIG. 15, and the forward movement of the board pulls the roving to form the skin layer 155 from the supply creel to cover the opposing faces of the board. Prior to insertion of struts 154 by the stitching device, a plurality of parallel skin rovings 156 are applied across the first roving layer 155 by a reciprocating mechanism having a guide that maintains the desired spacing and tension of the rovings 156. The second skin layer 156 is then covered by a fiber veil 157 drawn from the supply roll. Core reinforcing struts 154 are stitched through the bale 157, the layers of skin rovings 156 and 155, and the foam board 153 to produce the sandwich panel 150.

  If structural considerations are required, additional layers of skin roving can be applied to the panel surface at various angles prior to stitching. Alternatively, oriented or non-oriented roving fibers can be chopped to a desired length and affixed to the core surface instead of continuous roving. A segment 158 overlying the stitched strut roving 154 holds all skin rovings 155 and 156 in place until the panel 150 is aligned in the mold. Within the mold, a curable or hardenable resin flows throughout all the fiber reinforcements to produce a structural panel. This method of forming panel skins directly from roving can be incorporated into any of the embodiments shown in FIGS.

  In a preferred embodiment of the present invention, rather than using a woven or stitched fabric as the web, which is significantly more expensive than roving, the production of the web-type core reinforcement directly from the fiber roving results in considerable cost savings. Achieved. In this method, rovings are wrapped around a continuous foam strip to create a structural tube reinforcement structure around the strip. A particularly cost-effective means of forming the winding structure is by spirals or spirals. This wound strip is cut to the desired length and fed into the roving stitcher in the manner described in connection with FIG.

  Referring to FIG. 12, a convenient length of plastic foam strip 170 is passed end-to-end through the spiral wrapping device 171 illustrated schematically. The spiral winding of the core reinforcement provides a great economic advantage compared to existing processes. Roving form fibers occupy about 50 to 60% of the cost of fibers incorporated in a double diagonal 45 degree fabric, and the production rate of the winding machine is 5 to 10 times that of the assembling machine. If desired, the foam strip may be provided with one or more grooves 39 as described in connection with FIG. 1 to facilitate resin flow in subsequent molding operations. Foam strip 170 has a thickness equal to the thickness of the sandwich panel core to be produced from this strip and a width equal to the desired spacing of the reinforcing webs within the core.

  As the strip 170 travels through the winding device 171, the strip 170 passes through the axis of a rotating bobbin wheel 172 rotating in one direction and a bobbin wheel 173 rotating in the opposite direction. Each wheel is loaded with a plurality of bobbins 174 wound with fiber reinforced rovings 175. A rotating bobbin wheel 172 wraps a layer of roving 176 over the foam strip at a single angle determined by the advance speed of the strip 170 through the device 171 and the rotational speed of the bobbin wheel 172. This single wound strip then proceeds through a counter rotating bobbin wheel 173 that covers the wound roving layer 176 and winds the second layer 177.

  The winding device 171 can be scaled to efficiently process a wide range of foam strip sizes, eg, from a thickness of 1-1 / 4 inches to over a foot. The roving can be of various thicknesses depending on the structural requirements of the finished wrap strip and the composite panel that will incorporate it, and at tight intervals to cover the surface of the foam strip, or It can be arranged at wider intervals. The roving applied to the surface of the foam strip can have a total weight of only 0.1 ounces per square foot or less and more than 5.0 ounces per square foot. The rovings shown in FIGS. 12-14 are thicker than usual so that the details of the structure can be understood. Roving can also be wound at +45 degrees and -45 degrees to obtain maximum resistance to shear stress in applications where the strip is subjected to bending loads, or roving can be used for specific end products where they will be incorporated. It can also be applied at other angles that are inevitably determined by structural requirements.

  A continuous foam strip 170 having overlying wound layers 176 and 177 is cut to length by a traveling cutting device such as a circular saw (not shown) to form a finished wound strip 178. Since the wound foam strip 178 is used as the foam and web element of a hybrid sandwich panel, such as that shown in FIG. 14, their length is equal to the desired width of the sandwich core panel. Prior to cutting, wrapping roving, for example by wrapping with a thread 179 impregnated with hot melt adhesive on either side of the cut, or by sticking adhesive tape around the cutting point, or adhere to the roving Protect from fraying by applying agent. If desired, a barrier film can be wrapped around the foam strip 170 prior to the roving layer to protect the foam from moisture, resin attack, and the like.

  The completed strip 178 goes to the infeed end of the core forming apparatus 200 illustrated in FIG. 15 and is inserted into the apparatus as described in connection with FIG. Proceed to an apparatus (not shown) for attaching the adhesive veil 241 to the strip as shown. Labor costs per square foot of core produced are very low. In a variation of the winding process described in connection with FIG. 12, the longitudinal fiber roving layer 180 is applied to the foam strip 170 in a direction parallel to the longitudinal axis of the strip and prior to winding the roving 174 around the strip. Affixed to the surface, layer 180 is held in place by winding roving 174. A roving of the longitudinal layer 180 is supplied from a stationary roving package 181 and pulled through the wrapping device 171 by advancing movement of the advancing foam strip 170. The longitudinal roving can be applied to two opposing faces of the strip as shown in FIG. 12 to serve as a sandwich panel skin element, which will be described in connection with FIG. Alternatively, longitudinal roving can be applied to the entire surface of the foam strip to give the structural columns the necessary compression and buckling properties.

  FIG. 13 provides a detailed view of the wound foam strip 178 and shows the laying and orientation of four sets of porous fibrous rovings that are applied during the winding process illustrated in FIG. In FIG. 13, all the rovings are shown as having a flat cross section and are closely spaced so as to cover the surface of the closed cell plastic foam strip 170. The longitudinal roving layer 180 covers the upper and lower surfaces of the foam strip 170. A first layer 176 of wound roving, shown at an angle of +45 degrees, covers the longitudinal roving layer 180 and the sides of the foam strip 170. A second layer 177 of winding roving at an angle of −45 degrees covers the first winding layer 176. Thereafter, when impregnated with a curable thermosetting resin or a solidified thermoplastic resin, all fiber rovings together with the cured or solidified resin produce structural elements having the general characteristics of a rectangular tubular cross-section beam.

  FIG. 14 illustrates the reinforced foam core sandwich panel of the crossed web and strut hybrid structure described above in connection with FIG. 1, where the roving-wrapped strip 178 shown in FIG. It is used in place of the foam strip 33 to which the web sheet 34 shown in FIG. Further, FIG. 14 incorporates roving instead of woven or knitted fabric in the production method shown in FIG. 15 to form a sandwich panel skin. This combination of foam core strip wrapped with rovings and panel skins with rovings provides important structural and cost advantages. Referring again to FIG. 14, the structural composite panel 190 includes a fiber reinforced closed cell plastic foam core 191 and an opposing fiber reinforced skin 192. The reinforced foam core 191 includes a plurality of parallel strips 178 shown in FIG. If desired, the foam strip 178 may have a sandwich panel core formation so that adjacent winding edges are not both in the same orientation and are therefore structurally unbalanced and in positive and negative angular orientations. It is also possible to provide a roving wound obliquely in only one direction by staggering the right-handed and left-handed strips in between.

  A plurality of parallel rows of spaced rods or struts 193 extending between the faces of the core and made from a porous fibrous reinforcing roving intersect the wound foam strip 178 at right angles. The struts 193 in each row are inclined at acute angles opposite to each other with respect to the panel skin 192 and with respect to the flat surface of the wound strip 178. A layer of parallel porous fibrous skin rovings 194 parallel to the plane of the struts 193 and extending in a direction perpendicular to the encapsulated strips 178 and their longitudinal roving layers 180 is provided on the wound strip 178. Overlapping. A skin roving layer 194 in which a lightweight fiber veil, mat or scrim can be affixed to the panel 190 in the form of a plurality of discontinuous rovings or as a unidirectional fabric in which the roving has been previously bonded to the light weight bale. Overlapping. The end portion of the strut 193 passes through all layers of the longitudinal roving 180, the winding rovings 176 and 177, the skin roving 194, and the bale 195, and the end portions overlap the bail 195.

  The panel illustrated in FIG. 14 is reversed from the position in which it is produced in the apparatus of FIG. 15 to show continuous roving including struts 193. As shown in FIG. 14, a plurality of continuous rovings are stitched together at opposite angles and through the sandwich panel 190 from the same side of the panel, with each continuous roving segment 196 tangled in the form of a chain stitch. Yes. It should be understood that alternative stitching methods may be used, such as a lock stitch or cut loop as shown in FIG.

  An important feature of the fiber reinforced structure shown in FIG. 14 is that the longitudinal roving layer 180 on the wound strip 178 includes a transverse reinforcement of the sandwich panel skin 192 and overlaps the longitudinal layer 180 at +45 degrees and -45 degree roving layers 176 and 177 also constitute an element of the sandwich panel skin. That is, the web element of the core reinforcement consists of the same continuous winding roving as the +45 degree and -45 degree skin elements. This results in greater delamination resistance between the core and skin structure, since the web-type core reinforcing web does not end up adjacent to the panel skin as in FIG. Roving layers 180, 176, 177 covering the foam strip 178 also tether the end portions of the struts 193.

  The reinforced core 190 shown in FIG. 14 can also be produced without the roving layers 180, 194 and bale 195 including skin elements that are continuous throughout the length and / or width of the panel. This may be desirable when using these reinforced cores to produce large sandwich panels, such as boat hulls, typically consisting of a plurality of cores that are generally adjacent to each other and between the panel skins. In such a panel, the pre-attached skin may include a reinforcing fabric, but may consist of roving incorporated into the core as described in connection with FIG. 14, but the core with such pre-attached skin. It is generally preferable to use a skin with a length and width sufficient to provide structural continuity across the plurality of cores. When the continuous skin elements 180, 194, 195 are omitted, these wound strips 178 are one-sided by the friction of the strut roving 193 intersecting the adjacent core and by the continuous roving segments sewn along the upper and lower surfaces of the strip 178. It remains firmly held as a single core. In this configuration, the end portion 196 of the strut 193 is confined between the wrapped outer roving layer 177 and the panel skin affixed to the surface of the core, rather than penetrating the skin of the sandwich panel.

  The roving wrapped foam strip 178 of FIGS. 12-14 is shown as rectangular in cross section. If desired, these strips can have other cross-sections, such as parallelograms or triangles as shown in FIGS.

  U.S. Patent No. 6,057,031 discloses a sandwich panel core element consisting of discontinuous plastic foam blocks or strips encased with a reinforcing fabric. A plurality of encapsulated blocks are stacked in the form of a honeycomb between sandwich panel skins in the mold, with the end portions of the foam blocks and the edge portions of the encapsulating fabric being adjacent to the panel skins. The helically wound foam strip 178 shown in FIG. 13 of this application can be used in place of these encapsulated blocks to achieve equivalent structural properties with significant savings across the cost of the fabric and assembly workers. it can.

  Extending the edge of the reinforcing fabric beyond the end of the foam block as described in US Pat. No. 6,099,097 and folding them to form a flange for improved structural attachment with the sandwich panel skin. It may be desirable. Similar extensions of the encapsulated longitudinal roving layers 180, 176, 177 of FIG. 13 align sacrificial foam blocks (not shown) alternately with the core foam strip 170 end to end, as described above. Can be obtained by wrapping the foam, cutting the encapsulated strip through the center of the sacrificial foam block and removing the sacrificial block. It is also possible to provide surface microgrooves on the foam strip 170 prior to insertion into the winding device 171. Instead of the plastic foam used for the wound strips or blocks, other suitable core materials can be used, for example balsa materials of similar geometry or hollow sealed plastic bottles.

  Since the structural properties of the sandwich panel core shown in FIGS. 1-19 are generally provided primarily by a fibrous core reinforcement structure, the closed cell plastic foam containing the core can be made water or fire resistant, heat insulating, or light transmissive. The selection can be based on other desired panel characteristics such as rate. For example, translucent resin can be impregnated with translucent polyethylene foam and glass fiber reinforced material to produce light transmissive load-bearing panels for use as highway trailer roofs or building roofs. It is also within the scope of the present invention to use other porous materials such as carbon foam or balsa material instead of plastic foam.

  1-8, 10, 11, and 14 are fiber reinforcements produced in part by inserting or sewing porous fiber reinforcement elements such as glass fiber rovings through the thickness direction of the foamed plastic core material. 2 illustrates a core and a sandwich panel. This can be achieved by the apparatus 200 illustrated in FIG. A plurality of foam strips 201 are inserted into the stitching device 200 adjacent to each other. The strip 201 can be rectangular or other cross-section and can be provided with a porous fiber web with a reinforcing fabric attached as described above or a wound porous fiber reinforced roving. It should be understood that a foamed plastic material that is substantially greater in length than the width of the strip 201 may constitute the foamed plastic material if desired.

  The strip 201 is advanced towards the stitching heads 203 and 204 in a substantially equal process, for example by a reciprocating pressure bar (not shown) or a movable endless belt 202. These stitching heads 203 and 204 are strictly fitted with a plurality of tubular needles 205, cannulas or composite hooks which are adapted to pierce and insert into fiber rovings. The stitching heads 203 and 204 are inclined at an acute angle opposite to the surface of the strip 201. As strip 201 stops advancing at the end of each forward step, reciprocating stitching heads 203 and 204 insert needles 205 into strip 201 therethrough. The needles are accurately positioned by the needle guide 207 at the entry point to their strip 201. Porous fiber rovings 208 supplied from a rolled roving package (not shown) are inserted through the strip 201 by needles 205 and their entry points in the form of a general loop 115 as shown in FIG. Appears on the opposite surface.

  Referring to FIG. 15, the loops 115 are gripped by a device (not shown) that holds the loops formed over the surface of the strip where they appear, and if desired, engage them with other loops in FIG. Form a chain stitch as shown or engage a separately supplied roving to form a lock stitch. Stitching heads 203 and 204 then retract and advance a predetermined length of roving 208 into needle 205 to form the next stitch. After pulling back, the row of strips 201 advances a predetermined step or distance, stops, and the stitching heads 203 and 204 reciprocate to insert the next set of opposing struts. The assembly assembled into one of the strips 201 held by the stitched roving 208 intersecting the strip is cut into a core 209 of the desired length by a saw or other suitable means.

  The stitching device 200 can be used to produce a panel having a pre-attached porous fiber skin as shown in FIG. Referring again to FIG. 15, reinforcing skin fabric 210 is fed from the roll and proceeds toward stitching heads 203 and 204 adjacent to opposite sides of panel 206. As the roving is stitched through the strip 201 forming the panel 206, the roving overlaps the skin fabric 210 and mechanically attaches the fabric 210 to the panel 206.

  Also, the apparatus 200 shown in FIG. 15 can be used to produce a sandwich panel in which all structural reinforcement components, both core and skin, include the low cost fiber roving shown in FIG. A layer of longitudinal skin roving 194 (FIG. 14) is applied as the surface of panel 206 during its production in stitching apparatus 200 shown in FIG. Multiple porous fiber rovings 211 sufficient to cover the face of the panel are pulled out of the roving supply package (not shown) by the advancing panel 206 and toward the stitch head adjacent to the exposed face of the strip 201. Proceed toward. A thin porous bale, mat or scrim 210 is pulled from the roll by the advancing panel 206 and overlies the skin roving 211 and holds them in place after the roving 208 is stitched through the panel 206. . The strip 201 is provided with a longitudinal roving layer 180 as shown in FIG. 14, and the layers 180 and 194 of FIG. 14 provide the skin reinforcement in the lateral and longitudinal directions of the panel 206 produced in FIG. Constitute. It is also within the scope of the present invention to provide a panel production apparatus 200 having a reciprocating mechanism (not shown) for applying lateral and double bias angle rovings to the surface of the panel 206. This enables the production of the panel 150 shown in FIG. In this case, the foam core does not include the wound strip 178 with the roving layer 180.

  In another preferred embodiment of the present invention, bi-directional panel strength is achieved by providing an internal transverse reinforcement to the wound foam strip, rather than by inserting a structural roving 193 through the strip 177. Referring to FIG. 16, a reinforced foam strip 220 includes a plurality of blocks or pieces 221 of foam plastic separated by a sheet 222 of web-like fiber reinforcement material such as glass fiber or carbon fiber cloth. The foam piece 221 and the reinforcing web 222 are adhered to each other as described in US Pat. No. 6,057,086 to facilitate processing and handling while maintaining the substantial porosity of the web material. The reinforced strip 220 can also be provided with grooves 223 for resin flow. It should be understood that other materials, such as balsa or plastic blow molded cubes, can be used in place of the foam piece 221 without compromising the core morphology or structural integrity.

  Referring to FIG. 17, fiber reinforced layers 176 and 177 are provided on a reinforced strip 230 as shown in FIGS. 12 and 13 to form a wound reinforced strip 233. If high bending or axial strength is required, the roving layer 180 shown in FIG. 13 can also be provided. Referring to FIG. 18, the reinforced core 240 has a plurality of winding reinforcements integrally held as a structure united by a bail 241 bonded to a facing surface of the core 240 with a heat activated binder. It consists of a strip 233. If greater bending flexibility is desired, the bale 241 can be applied only to one side of the core. Other means of integrating the core structure include adhering parallel bands of hot melt yarn or scrim to the entire wound strip, or applying a pressure sensitive adhesive to the surfaces of the strip that are in contact with each other. It is done. Instead of the veil 241, a structural skin cloth or mat can be glued to the core surface to form a sandwich panel preform that can be impregnated at any time. When one or more cores 240 are placed between the fabric skin reinforcement and the resin in the mold, and the resin is allowed to flow through the core and skin structure and cured to form a structural composite panel, The cloth web 222 and the roving web 242 comprising four winding roving layers 176 and 177 form a grid-like reinforcing structure, and the portions of the winding layers 176 and 177 adjacent to the panel skin resist the shearing force. For extremely good adhesion. This articulated structure of the core 240 also allows a high degree of conformability to the curved mold surface.

  FIG. 19 illustrates an embodiment of a fiber wound core 250 where bi-directional strength and stiffness is achieved without adding either an internal web or roving struts. The fiber reinforced core 250 includes a plurality of triangular foam strips 251 with layers of spiral fiber rovings 252 and 253 to form a wound strip 254. The wrapped triangular strip 254 is held together as a united core structure by a bail 255 glued to the wound roving layer 253 outside the wrapped strip 254 with a heat activated binder. The angle at which the triangular strip 251 is cut can be selected to obtain the desired balance of shear and compressive strength.

  It is within the scope of the present invention to use either of two general types of solidifying resins for pouring or impregnating the core and skin porous fiber reinforcements. Thermosetting resins such as polyesters, vinyl esters, epoxies, and phenolic resins are liquid resins that solidify by the process of chemical curing, i.e., crosslinking, occurring during the molding process. Pre-crosslinked thermoplastics such as polyethylene, polypropylene, PET, PEEK, etc., liquefy by applying heat before being injected into the reinforcement and resolidify as it cools in the panel.

  As an alternative to injecting a liquid resin into the porous reinforcing material of the assembled panel structure, the reinforcing material may include a cloth and roving pre-impregnated with a partially cured thermosetting resin. Similarly, reinforcing rovings and fabric materials can be pre-impregnated with a thermoplastic resin or blended with thermoplastic fibers followed by application of heat and pressure.

  It is further within the scope of the present invention to join a rigid skin sheet material such as steel, aluminum, plywood or glass fiber reinforced plastic to the face of the reinforced foam core. This involves impregnating the core reinforcement structure with an adhesive by impregnating the core reinforcement with a curable or solidifying resin and applying pressure to the rigid skin as the resin cures or before joining the rigid skin to the core And can be achieved by curing.

  20-23 illustrate the process of construction of a fiber reinforced foam core panel that includes a spirally wound strip and has improved bi-directional strength and useful manufacturing advantages. In FIG. 20, spiral wound strips 178 are joined to form a unidirectional reinforcing core panel 260. If desired, the strip 178 containing the winding layers of rovings 176 and 177 (FIG. 2) incorporates a web sheet 94 that is generally parallel to the face of the core panel 260 as shown in FIGS. The rovings 176 and 177 can also be stabilized. A preferred method of stitching together a plurality of strips comprising low density foam and helically wound reinforcing rovings is shown in FIG. In this method, a glass fiber scrim 271 coated with a hot melt adhesive is applied to the opposite surface of the core panel by applying heat and pressure. Individual fiber scrims 271 or rows coated with adhesive may be used to connect adjacent strips in all core panel embodiments shown herein, including multiple strips or blocks. it can.

  The layers of rovings 176 and 177 can include materials that resist adhesion, such as partially cured prepreg resins or thermoplastic fibers. When such materials are used, the rovings 176 and 177 can be provided with additional spaced rovings including bondable fibers such as unimpregnated glass fibers or carbon fibers. Referring to FIG. 21, the layer of roving 177 intersects with and overlaps the layer of roving 176. If desired, these rovings can also be wound on the foam strip in a knitting process in which rovings 176 and 177 are alternately stacked on top of each other. This knitting option applies to all embodiments of the invention that include two or more layers of reinforcing fibers wound on a single strip of foamed plastic or other low density porous material. If the differential pressure process is intended to inject liquid thermoplastic resin into the core panel, the strip 170 includes closed cell foam. Both closed cell and open cell foams may be suitable for core panels that include pre-pre-globbing 176 and 177, or that include a solidified thermoplastic resin component. After molding the skin and the hardenable resin, the foam can be removed from the reinforced strip by grit blasting, solvent, or otherwise to produce a hollow composite panel.

  20 and 22, the core panel 260 is cut in a C direction perpendicular to the length of the strip 178 by a saw blade or other means to provide a plurality of first elongated fiber reinforced core panels 261 of the desired thickness. become. During this cutting step, the cut end portions 262 of the rovings 176 and 177 loosen due to the removal of the foam layer by the cutting step, causing the foam strip 170 to protrude from the surface. Referring to FIG. 23, a plurality of first elongate fiber reinforced core panels 261 are joined together using an adhesive scrim 271 to form a bi-directional core panel 270 with a reinforcing web extending in both the longitudinal and lateral directions. The protruding end portions 262 of the reinforcing rovings 176 and 177 help the adhesive bond to the opposing panel skin (not shown) when injecting a hardenable resin into the panel. If desired, each strip 170 may be spirally wound with a single layer of roving 176, with adjacent layers of roving 176 further including intersecting layers having balanced structural characteristics. Similarly, all core panels, including adjacent strips, described herein can be wound with a single layer of roving that extends spirally.

  As shown in FIG. 13, a higher compression strength core can be produced by providing a wound strip 178 having an axial roving 180 on one or more sides of the foam strip 170 prior to winding. In the finished core panel 270, these axial rovings, which can be applied to the core panels 290 and 300 as well, extend vertically between the faces of the panels. An important advantage of the bi-directional reinforcing core panel 270 is that the panel 260 is simply sliced from the pre-existing assortment of unidirectional core panels 260 into a first elongated core panel 261 whose width matches the desired panel thickness, and the strips are It can be quickly produced in any desired thickness by stitching together as described above.

  The core panel 270 can provide a substantially higher structural bond to the panel skin as shown in FIGS. That is, the elongated core panel 261 (FIG. 24) including the foam strip 170 and the winding layers of the rovings 176 and 177 is provided with the additional spiral winding roving layers 281 and 282 overlying the layers 176 and 177. The elongated core panel 280 is formed. A plurality of panels 280 are joined together using an adhesive scrim 271 or other means to form a reinforced core panel 290 shown in FIG. Winding roving layers 281 and 282 form a continuous web extending between the faces of core panel 290, while layers of rovings 176 and 177 form a discontinuous web that intersects the continuous web. When the hardenable resin is introduced into the sandwich panel, all four layers of these rovings are bonded to the sandwich panel skin 291. FIG. 25 shows in detail a greatly enlarged area where the fiber core reinforcing roving is attached to the panel skin. Referring again to FIG. 24, if the layer of roving 282 is omitted, the layer of roving 281 on the adjacent wound strip 280 forms a reinforced web where the roving 281 intersects at an opposite angle in the web. become.

  FIG. 27 shows a variation of the bi-directional reinforcing core panel 290 that rotates the second elongate core panel 280 90 degrees from the orientation shown in FIG. 26 before joining together. In the configuration of FIG. 27, the most dense layer of roving on each wound core panel 280 is positioned within the core rather than adjacent to the skin. The orientation of the wrapped panel 280 is selected to produce either the core panel 290 or the core panel 300 depending on the desired balance of strength and stiffness between the reinforcing web and the panel skin.

  A bi-directional core panel produced by helically winding a reinforcing member, such as that illustrated in FIGS. 23 and 26, comprises a plurality of foam blocks joined together. If the convex surface of the panel is integrated by a relatively low tensile strength scrim fiber, or if bending is achieved by applying heat to soften the adhesive that bonds the scrim to the panel surface, This articulated configuration allows the panel to adapt to the curved surface. Referring to FIG. 23, after pressing the panel against a forming tool to form a simple or complex curve, a high tensile strength adhesive scrim 271 such as glass fiber can be applied to each opposing surface of the core panel 270. . The pressure can be released after the scrim adhesive has solidified and the core panel 270 continues to retain its curvature. This method is useful for producing preforms that can be efficiently loaded into curved molds. Adhesive scrims can also be used to produce curved preforms that thus include unreinforced foamed plastic.

  Core panels used with thin skins, such as the core panels of trailer roofs, provide sufficient shear strength and stiffness in the core, but cannot provide sufficient support to the skin under conditions of impact or compression loading. The reason for this insufficient skin support is that there is no core stiffener overlying the core panel surface as in FIG. 23, or a relatively wide strip of spirally wound foam comprising the core panel. As a result of using the web, it is possible that the widely spaced web will support the skin. Means for providing additional skin support are shown in FIG. In this means, a rigid support member 301 is provided on a bi-directional core panel 300 including a plurality of elongated core panels 280. In a preferred embodiment, the support member 301 includes a fibrous roving, such as glass fiber. This fibrous roving is formed in the elongated core panel 261 as shown in FIG. 22 prior to spirally winding the reinforcing rovings 281 and 282 around the panel 261 to form the elongated core panel 280 shown in FIG. Inserted into the slit. In general, a support member 301 that draws a beam-like rectangular cross section is supported alternately at each point that intersects the core reinforcing web 302 that forms the wound layer of the rovings 176 and 177 shown in FIG. Referring again to FIG. 27, the compression and impact load applied to the panel skin 291 is transmitted to the reinforcing web 302 by the skin support member 301, thus preventing the skin 291 from being damaged.

  Figures 28-30 illustrate another embodiment of the present invention. In this embodiment, the fiber reinforced strip 310 includes a reinforcing strip that extends axially along one or both sides of the corners of the foam strip 170 and directly beneath one or more helical wrap layers of rovings 176 and 177. A roving 311 is provided. This structure is shown enlarged in FIG. When a plurality of reinforced strips 310 are joined together to form the reinforced core panel 320 shown in FIG. 30, as described above, adjacent pairs of reinforcing webs of intersecting spiral wound rovings are corner axes. Cooperating with directional roving 311 effectively forms a plurality of structural bar joints having upper and lower strings separated by a rod-like shear member. This structure provides excellent impact strength and high bond strength between the web reinforcement and the panel skin and allows the use of skin reinforcement to be reduced. An axial corner roving 311 can also be added to the structure of the bi-directional core panel, such as that shown in FIGS.

  Additional axial roving can be provided directly below the wound roving to cover any or all of the surface of the foam strip 170 in any of the embodiments of the invention having a helically wound reinforcing member. After molding with a hardenable resin, a single reinforced strip 310 (FIG. 28) can be used as a separate structural member, such as a column or box beam. The performance of such structural members can be further improved by providing transverse reinforcement members as shown in FIGS. 17 and 24 and by providing additional axial rovings to cover all exposed foam surfaces. Can do. The posts are made of reinforcing material such as glass fiber or the like around the foam strip 170 at the end portion of the strip or other desired region of the strip before winding the roving layer on the strip for the purpose of providing high strength of the structural attachment region. Further reinforcement can be obtained by wrapping the carbon fiber layer in a spiral.

  Formed columnar structural members directly and continuously feed the fiber reinforced foam product of the spiral wrapping device into a molding device such as a resin injection pultrusion device (not shown) for application and curing of thermosetting resins It can be produced economically by a continuous process. A device that continuously applies heat to a spirally wound glass fiber roving mixed with a thermoplastic filament, such as “Teintex” roving, manufactured by Saint-Gobain Vetrotex. (Not shown) can be continuously passed through and mixed by cooling and solidified into a fiber reinforced foam structure. It is also possible to provide a continuous process of cutting the fiber reinforced product of the spiral wrapping device to form a length component and feeding the component into a mold for subsequent use and resin solidification. Is within the scope of the present invention.

  FIG. 31 illustrates a unidirectional fiber reinforced core panel 330 that includes a plurality of spirally wound strips 331 grouped together with panel skin supports provided between the spiral wound core reinforcing webs. The at least two foam strips 170 may include a rigid strip material or an exterior 332 that may include a porous fibrous material, such as a glass fiber mat, into which the resin flows and solidifies during molding of the core panel. Is provided on one or both side surfaces. In a particularly economical embodiment, the foam strip 170 is cut from a low cost plastic foam insulation that is produced in a continuous process that introduces foam between successive sheets of glass fiber mat 332. Adjacent mat 332 pairs provide substantial support to the panel skin between the core reinforcing webs that make up the spiral wound roving. These segments of the glass fiber mat adjacent to this winding roving cooperate to form a structurally reinforced reinforcing web 333 comprising two layers of glass fiber mat 332 and four layers of winding rovings 176 and 177. To do. This structure achieves both an increase in the amount of reinforcing fibers and an improvement in the buckling resistance of the web under load compared to a web that is simply spirally wound due to the large thickness of the web. The strip 332 can include a variety of other materials including, for example, aluminum foil instead of a glass fiber mat. The aluminum foil can be used to protect the foam strip 170 while providing radiant heat applied to the strip 331 to melt the thermoplastic components of the rovings 176 and 177.

  FIG. 32 illustrates a reinforced core panel configuration that can be produced in very large quantities from a given roving wrap. The reinforced core panel 340 includes alternating roving wrapped plastic foam 178 and simple plastic foam strips 170. By increasing the weight of the reinforcing rovings wound on the strips 178, substantially the same structural characteristics as the homogeneous strip core panel 260 shown in FIG. 20 can be achieved in the alternating strip core panel shown in FIG. .

  The method of spirally winding the foam strip allows the production of sandwich panels having a core whose structural properties vary along the length of the core. This configuration is achieved by changing the spacing and angle of the rovings in a controlled manner as the rovings are subsequently wound onto a foam strip that is brought together into the core panel. FIG. 33 shows a wound strip 350 that includes a foam strip 170 and spaced apart spiral wound rovings 176 and 177. Referring to FIG. 12, the angle and spacing of the roving on the foam strip 170 is controlled by changing the speed at which the strip travels through the winding heads 172 and 173 at a given head rotational speed. This relationship can be tightly controlled through the use of a programmed strip conveyor drive motor. For example, as the strip feed rate is decreased, the winding roving spacing decreases and the angle at which the roving intersects the strip axis decreases. The spacing between the winding heads 172 and 173 is preferably adjustable to match the desired length of the strip 350. The wound strip 350 shown in FIG. 33 has the highest roving density and angular steepness at the end of the strip with respect to the surface of the strip 350 to provide high compressive strength to withstand concentrated loads on the panel support. Illustrate a high foam strip. In order to improve the bi-directional strength, the reinforced strip 261 shown in FIG. 22 or the reinforced strip 310 shown in FIG. 28 is used instead of the non-reinforced foam strip 170 shown in FIG.

  FIG. 33 also illustrates means for achieving improved skin strength in composite panels with non-uniform core thickness. It is common in structural sandwich panels that the edge of the panel is gradually reduced or stepped down to thinner thicknesses, and thickness changes are sometimes required inside the panel. If the fibers that make up the panel skin deviate from a flat surface, tensile or compressive stresses in the skin can cause the skin reinforcement to break and delaminate the skin from the panel core. The spirally wound strip 350 shown in FIG. 33 includes an axial roving 180 on the opposing surface of the strip 350 that will constitute the surface of the reinforced core panel, as described in connection with FIGS. Layers are provided. As described in connection with FIG. 14, the axial layer of the roving 180 extends in the direction of the strip to function as a skin fiber, and the axial roving has a layer of rovings 176 and 177 spiraled over it. Wrapped around. The tendency of the axial roving 180 to break at or near the core thickness transition region 351 under bending stress conditions is reduced because the spirally wound roving layer inhibits the axial roving from moving outward. . The stability of the axial roving can be further improved by providing a transverse reinforcement to the strip 350 as described above to prevent the roving layer 180 from buckling inward.

  In spiral wound unidirectional core panels containing low density foam, the buckling resistance of a relatively thin reinforcing web in a relatively thick panel under compression or shear loading is reduced by reducing the web thinness. It can be improved considerably. FIG. 34 shows a core panel 360 that includes a fiber reinforced foam strip 178 and a web spacer strip 361 that functions in cooperation with the layers of rovings 176 and 177 to form a composite reinforcing web 362. is there. The spacer strip 361 is made of foamed plastic having a compressive strength greater than that of the foam strip 170, porous mat material, or other sufficiently strong material so that the composite reinforcing web 362 functions as a thick structural web. Can be included. The spacers and roving components of the composite web 362 are structurally bonded together by the resin used to inject the sandwich panel. The spacer strip 361 serves to divide the resin mass present between the foam strips 170 and thereby reduce the shrinkage normally caused in the local mass of resin during the curing process. This reduction in shrinkage along the reinforcing web increases the flatness of the molded panel skin, which improves the appearance and allows the use of lighter skin reinforcements.

  Sandwich panels containing spirally wound strips have been found to be effective in maintaining substantial structural integrity after high energy ballistic impact. They are used in applications such as jet engine casings or armor plate structural backups that are designed to prevent penetration by projectiles. FIG. 35 illustrates a cylindrical or annular embodiment of the present invention useful as a jet engine casing. In this embodiment, the structural continuity of the core properties is optimized by eliminating the joints between the ends of the spiral wound foam strip so that all spiral wound rovings in the entire panel break. Not. A cylindrical or annular core panel 370 is produced from a single spiral wound foam strip 371 by continuously winding the strip 371 around a cylindrical or non-cylindrical mandrel.

  The wound strip 371 including the plastic foam strip 170 and the layers of spiral wound rovings 176 and 177 has a cross-sectional shape other than a rectangle, for example, a triangle as shown in FIG. Where the reinforcing web in the core is oriented at an opposite angle to provide transverse shear strength to the core. Lateral shear strength can also be achieved by providing an internal transverse reinforcement in the wound strip 371, for example as shown in FIG. To obtain higher strength, the second continuous strip 371 can be spirally wound, preferably at an intersecting angle, over the core panel 370 if desired. The hoop strength and impact resistance of the core panel 370 can also be improved by providing an axial roving 180 just below the winding rovings 176 and 177 as shown in FIG. The ballistic impact resistance of sandwich panels with helically wound core reinforcement and structural skin reinforcement is at an intersecting angle as previously described in connection with FIGS. 14 and 15 or perpendicular to the panel skin. It can be enhanced by stitching fiber reinforcement through the panel skin and core. A continuous reinforced strip 371 in one or more layers can also be formed into a cylindrical or box-like shape by forming a strip 371 around the entire surface of the container and providing a skin attached by a filament winding process. It can also be used to form a perimeter-enclosed container intended to withstand explosions.

  The continuous strip 371 is relatively low weight or relatively low so as to allow ballistic objects such as jet engine fan blades to penetrate the cylindrical casing without significantly impairing the shape or structural integrity of the panel. Brittle reinforcement fibers, such as carbon tow, can be used to wrap, and the penetrating objects are blocked outside the casing by an aramid fiber enclosure that is not impregnated with a resin such as Kevlar. Alternatively, the panel can be designed to accommodate impact objects while still maintaining the integrity of the panel. In this configuration, it is desirable to use a fiber such as aramid or steel that will stretch under impact and resist penetration as a reinforcement that is sewn through the core, skin, and panel. By using the resin film barrier 41 described with reference to FIG. 1, certain layers of these impact resistant reinforcements are substantially free of resin throughout molding to optimize ballistic impact performance. be able to.

  FIG. 36 shows that a hollow tube can be used instead of a foam strip for air or water distribution, or in particular when it is provided with a high thermal conductivity reinforcing fiber such as carbon, as an efficient heat exchanger. 3 illustrates an embodiment of the present invention that produces a non-insulated structural sandwich panel that can be made. Reinforced core panel 380 includes a plurality of thin tubes 381 in which layers of reinforcing rovings 176 and 177 are spirally wound, which can be rectangular, triangular, or other cross-sectional shapes. The tube 381 can serve as a mandrel for wrapping structural rovings first, and thus can include structurally weak materials such as reinforcing paper. Alternatively, the tube 381 is surfaced for structural adhesion with a material having important structural properties such as roll molded or extruded plastic or aluminum, preferably with a wrapping reinforcement layer and with a panel skin that is subsequently applied. It can also include processed materials.

  The wall of the tube 381 comprising a thin flexible material can be provided with a convex curvature to withstand the pressure during the molding process. It is also possible to withstand the molding pressure by sealing the end of the tube 381 during the production process of the core panel 380 or during the molding process. A sealed spiral wound flexible tube with a circular cross section containing air or other gas and containing a film-like plastic or other resin impervious material can be integrated to form the core panel 380. Also, the flexible tube can be adapted to a generally rectangular cross section during the molding process by applying pressure to the core panel surface using a rigid platen. The core panel 380 that is sealed so as to prevent the intrusion of the resin can be combined with the skin reinforcing material and molded using a liquid resin. When the rovings 176 and 177 include a partially cured prepreg thermosetting resin or a thermosoftening thermoplastic resin, the core panel 380 can be formed by applying heat without sealing the end of the tube 381.

  37 and 38 show embodiments of a reinforced core panel in which a spiral wound core reinforcement that extends between and extends over the faces of the core panel also extends over the edges of the core panel. This structure allows excellent transmission of structural loads in the core panel to adjacent core panels and to the edges of the sandwich panel, and is illustrated in FIG. Spaced foam strips 170, preferably provided with axial corner rovings 311 as described in connection with FIGS. 28-30, are passed through the previously described helical wrapping device, A continuous reinforced strip 390 is formed. Strip 390 includes a plurality of axially spaced helically wound foam strips 178. The foam strip 178 may be provided with spaced lateral reinforcement members as previously described, and they are joined together by layers of rovings 176 and 177, which are connected in the axial direction. An extending roving 311 is supported between the strips 178 to form a hollow winding segment 391. These wound roving layers remain intact across the space between the foam strips.

  In the second step shown in FIG. 38, the wound strip 178 is folded back and forth to form a core panel 400 in which these continuous strips are reinforced adjacent to each other. Reinforcing rovings including hollow wound segments 391 are folded and collapsed across the end of the strip 178 to provide excellent adhesion between adjacent panel components and the end of the strip to reinforce the inner core panel Transmits structural loads between the material and the outer core panel edges. Reinforced core panel 400 is produced in a continuous length by moving or folding strip segments 178 into contact with adjacent strips and then joining the strip segments 178 together by applying a continuous adhesive scrim. can do. In this continuous form, the core panel 400 is well suited for continuous molding processes such as pultrusion connected to a roving spiral wrap.

  In another embodiment of the present invention, the fiber reinforced foam core panel can be provided with bi-directional strength by helically wrapping a reinforcing roving on a serpentine foam strip. FIG. 39 illustrates a reinforced core panel 410 that includes a spirally wound foam strip 411 each having a tortuous profile and shown with respect to a sandwich panel skin reinforcement 291. A tortuous web 412 comprising intersecting layers of spiral wrap reinforcing rovings 176 and 177 provides both longitudinal and transverse shear strength to the core panel 410, the ratio of strength in each direction being a straight line of the web 412. It depends on the angular displacement from. The foam strip 170 may have a serpentine contoured parallel edge instead of the symmetrical non-parallel edge shown in FIG. The foam strip 170 can be cut from the foam board using multiple gang saw water jets or hot or abrasive wire, or can be formed by applying heat to a thermoformable linear foam strip. The winding angle of the winding roving on the strip having non-parallel edges can be controlled by changing the feed of the strip through the winding device as described above.

  The impact resistance of sandwich panels containing fiber reinforced cores impregnated with thermosetting resin has excellent impact properties on the outer part of the sandwich panel skin instead of extending the more brittle thermosetting resin to the outside of the panel It can be substantially increased by incorporating a thermoplastic resin. FIG. 40 illustrates a greatly enlarged cross-section of a composite sandwich panel 420 that includes a spirally wound fiber reinforced core 260 and panel skins 420 and 422. Foam strip 170 may be provided with a resin distribution groove 223 previously described as groove 39 in connection with FIGS. The panel skin 421 includes a fiber reinforced mat or cloth impregnated with a thermoplastic resin, such as polypropylene, in the outer portion 423, which extends from the outer surface of the skin 421 and partially penetrates the thickness direction of the skin.

  This thermoplastic resin layer can be provided by applying a thermoplastic film to one side of the fibrous skin 421 under heat and pressure before injecting the thermosetting resin into the panel 420. If desired, a fabric layer made of a blend of glass and thermoplastic fibers, such as a “Twintex” fabric available from Sangoban Betrotex, can be used in place of the thermoplastic film. The mixed fabric is heated to form a reinforced thermoplastic outer surface and allows the thermoplastic resin to flow partially through the thickness of the underlying reinforcing fabric. High impact resistance is also achieved by applying a “Twintex” skin cloth 422 that was not coalesced by applying heat to the reinforced core panel 260 and injecting a thermosetting resin throughout the core and skin reinforcement. It can also be obtained. The thermoplastic filaments that make up the skin 422 give the injected skin high impact resistance, and the skin can be heated after injection to melt the thermoplastic fibers.

  In a preferred method of producing a spirally wound fiber reinforced composite panel having a low density porous material such as foamed plastic, a fiber reinforcement that is affixed separately to the core panel rather than a mixed filament roving such as "Twintex" cloth And a solidified thermoplastic material is provided. Referring to FIG. 20, a foamed strip 170 is provided with a surrounding layer of a thermoplastic resin, for example, polypropylene, by applying a resin that is heated and liquefied to the strip in a continuous extrusion process, and then the resin is cooled and solidified before the strip. Reinforcement rovings 176 and 177 are spirally wrapped throughout. The encapsulated strips 178 can be joined together and impregnated the reinforcing fibers with thermoplastic resin by applying heat and pressure. A skin containing fiber reinforcement and a thermoplastic resin can be similarly attached to the core panel. As an alternative to extrusion, a strip of thermoplastic material may be provided between the foam strips 170 adjacent to the layers of rovings 176 and 177.

  In yet another method, the foam strip 170 is spirally wound with layers of rovings 176 and 177, each comprising a reinforcing roving such as a plurality of glass fibers and a thermoplastic roving. All of these methods of impregnating the reinforcing fibers by applying the fiber reinforcing component and the thermoplastic component separately to the foamed strip and subsequently applying heat and pressure are more than those achieved by the use of mixed filament roving. Generally not very complete. An advantage of the method of the present invention is that very low cost materials including recycled thermoplastic resins can be used in the production process. All fiber reinforced panels described in the present invention use monofilament fibers of various flexible materials, including metals and high tensile strength plastics, as reinforcements instead of fiber rovings containing multiple filaments. Please understand that you can.

  As described above, the embodiment of the present invention is adapted to use the liquid thermosetting molding resin in the step of flowing and impregnating the resin throughout the inner core reinforcing element under a differential pressure. These embodiments are illustrated in FIGS. 1-40 and include porous reinforcing elements within the core panel. The majority of the sandwich panel industry does not utilize differential pressure, or uses processes that are insufficient to infiltrate the resin into the core reinforcement. As the thickness of the sandwich panel core increases, the absence of differential pressure greatly limits the degree to which the molding resin can penetrate and flow throughout the core reinforcement in the core, such as glass fiber rovings. To do. The penetration and solidification of the resin is essential for achieving the structural properties of the fiber reinforced core and sandwich panel.

  Some embodiments described herein adapt the present invention to be used in a sandwich panel manufacturing process that does not use differential pressure. Such a process includes, for example, open mold molding using a liquid resin, open bath pultrusion molding, and adhesion bonding of a rigid skin and a panel core. In embodiments adapted for these processes, these portions of the reinforcement members placed in the sandwich panel core are impregnated and solidified during the production of the core panel, and these portions of the reinforcement members adjacent to the core panel surface. Remains porous. The solidification of the internal reinforcement member ensures the desired core structural properties, and the porosity of these portions of the reinforcement member adjacent to the core panel surface is such that the core is sandwiched with a sandwich panel skin that is subsequently attached to the core using an adhesive resin. To obtain a particularly strong structural adhesion.

  The solidified web core panel can also be used in molding processes that use differential pressure, such as resin injection, injection pultrusion, and resin transfer molding. These heat-generating resin curing processes significantly reduce the resin temperature in the core by reducing or eliminating the amount of uncured resin in the web, thus reducing the possibility of foam damage or the generation of volatile gases. cut back. It may be useful to perforate the solidified web core panel to allow the flow of skin molding resin from one side of the core panel to the other. Alternatively, the core panel web can only be partially impregnated and solidified so that some residual porosity remains in the web reinforcement to allow resin flow during the molding process.

  FIG. 41 illustrates a structural composite sandwich panel 430 useful as a refrigerated truck or recreational vehicle wall that includes a reinforced core panel 431 and a panel skin 432. The core panel 431 includes a plurality of helically wound strips 178 of plastic foam or other low density porous material that are typically constructed as described in connection with FIGS. 180 is not shown in FIG. 41, but an axial roving layer may be provided if desired. If desired, the wound foam strip 178 can omit the second roving layer 177 and, if desired, can be a pre-installed reinforcing mat 332 as shown in FIG. 31, or as described in connection with FIG. Such a lateral reinforcing member 222 can also be provided.

  Referring again to FIG. 41, prior to combining the plurality of strips 178 to form the core panel 431, a porous wound roving layer in which a solidifying adhesive resin 433, such as polyester or polyurethane, includes the reinforcing web of the core panel 431. 176 and 177 are applied to these portions. Resin 433 can be applied to both sides of the opposing web of each foam strip, or, when the strips 178 are joined together, applied only on one side in an amount sufficient to infiltrate the porous fibers of adjacent web surfaces. You can also If desired, some porosity can be retained by limiting the amount of resin applied. When the heated reinforcing material is brought into contact with the resin, the resin can be applied after heat is applied to the roving layer so as to facilitate the infiltration of the reinforcing fibers by reducing the viscosity thereof. Increasing the temperature also accelerates the cure rate of the resin after application of the resin. The web strips 178 are joined together by pressing adjacent strips into a stack while the resin 433 solidifies to form the composite reinforced web 434. Alternatively, the web portions of individual strips 178 can be solidified, and a stack of strips 178 can be merged to form core panel 431 using an adhesive scrim or other bonding means as previously described. .

  In the embodiment shown in FIG. 41, the web-setting resin so as to allow wicking or flow of the skin-attaching resin to the outer portion of the web reinforcement to improve the structural attachment of the web 434 and skin 432. 433 is placed on those portions of the core panel web that are directly adjacent to the end face or both sides of the core panel, for example, over a distance of 1/8 inch from the face of the core panel. It should be understood that the solidifying resin 433 may extend completely to both surfaces or end faces of the core panel if desired, and further the resin may partially or fully spread on each side of the core panel.

  FIG. 51 illustrates a core panel 500 in which a web-solidifying resin 433 extends laterally over a portion of the exposed surface or end face of an adjacent fiber wrap strip 178 to form a series of structural I-beams 501. This embodiment is useful to increase the strength and stiffness of the sandwich panel and attaches the skin to the core panel using a relatively low structural property adhesive. The resin 433 impregnates the winding fibers between the adjacent strips 178 and also impregnates a part of the winding fibers 502 spreading on each surface of the core panel 500, and the resin 433 solidifies to form the structural I-beam 501. Form. The skin 432 is attached to the core panel 500 using an adhesive 435 that penetrates into the porous wound fiber portion 502 to form a strong skin-core bond, while the solidified I-beam 501 provides high panel strength and Gives stiffness.

  When the resin 433 is completely impregnated on both surfaces or end faces of the core panel 431 and solidified, the core panel 431 becomes a rigid sandwich panel. The structural characteristics of the resulting sandwich panel and the I-beam 501 shown in FIG. 51 can be improved by providing a longitudinal fiber roving 180 on the wound strip 178 as described in connection with FIGS. . The web solidifying resin 433 can be applied by a roll coater, extrusion, spraying, or a distribution device. The resin can be a thermosetting resin, such as polyester, epoxy, or urethane, and can be a thermoplastic resin, such as polypropylene, PET, or nylon. The solidification rate of the thermosetting resin can be accelerated by utilizing high catalyst amounts, heat, ultraviolet light, or other methods to increase the rate of adhesion between the wound strips 178 to form the core panel 431. .

  Thermoplastics are surface coated with a blend of structural and thermoplastic filaments, such as “Twintex” manufactured by Sangoban Betrotex, or a thermoplastic resin manufactured by Hexcel Corporation. By preparing a roving containing the structural roving that has been made, it can be incorporated into the roving layers 176 and 177 during the winding process. The strips 178 containing thermoplastic resin are joined together by applying sufficient heat to the web portions of the strip to melt its thermoplastic matrix and then pressing the strips together. Alternatively, conductive fibers, such as carbon fibers, can be provided adjacent to the winding layers 176 and 177, and the thermoplastic matrix may be melted by passing an electric current through the conductive fibers. Layers 176 and 177 can also include a solidified fiber reinforced thermoplastic tape such as “Zenicon” manufactured by Crane Composites, if desired, instead of twin tech slabs. The thermoplastic tape can be wound on the strip 170 by applying sufficient heat to soften the tape prior to contact with the foam strip 170. The strips of tape are spliced together as described for Twintex. It is also within the scope of the present invention for layers 176 and 177 to include high tensile strength polymer fibers, such as MFT by Milliken and Curve by Propex.

  The completed core panel 431 (FIG. 41) is transferred to a molding or laminating process, where a sandwich panel skin 432 is attached to the core panel using an adhesive resin 435 as described above. The resin 435 used to attach the skin may or may not be of the same type as the resin 433 used to solidify the web 434. The resin 433 may include, for example, a catalyst-added polyester resin, and the resin 435 may include a moisture-curing polyurethane resin, or one resin may be thermoplastic and the other resin may be thermosetting. Skin attachment resin 435 infiltrates the porous portions of winding roving layers 176 and 177. The roving layers 176 and 177 include the surfaces or end faces on both sides of the core panel 431, and can also include the edge of the web adjacent to the core panel face if it allows strong structural attachment of the skin and the core. .

  If the adhesive resin for adhering the skin is impregnated and solidified in all parts of the roving layers 176 and 177 as described above, it is similarly applied. The sandwich panel skin 432 may be a porous fiber, such as a glass fiber cloth, prior to the resin 435 attachment, or may be a rigid, eg, aluminum or glass fiber reinforced plastic sheet. The skin mounting resin can be applied by any conventional application process, and since they are already solidified as described above, no differential pressure is required to flow into the web 434. If the core panel 431 includes a roving layer incorporating a thermoplastic matrix, the skin can be attached by heating the core surface to liquefy the exposed roving layer thermoplastic matrix.

  The sandwich panel 430 can be used as a construction panel or building wall by incorporating a skin 432 containing sheet material common in the construction industry, such as decorative plywood or thin painted metal. In addition, an adhesive resin 435 can be used to bond a plurality of pieces of individual clad materials such as tiles, bricks, or stones. In a useful variation of the panel shown in FIG. 41, the resin layer 435 can comprise a mastic-like material such as a fiber reinforced polymer stucco or other solidifying wall surface material. In this embodiment, the material comprising the layer 435 penetrates the fiber roving layers 176 and 177 before solidification to form a permanent structural bond with the face of the core panel 431 and cooperates with the solidified web 434. Withstand structural loads. If desired, hollow tubes may be used in place of the foam strip 170, as previously described in connection with FIG. 36, and these tubes may be filled with a dense material, such as sand or concrete, to hold the retainer shown in FIG. A sandwich panel 430 useful as a wall or highway sound insulation wall can be provided.

  It is also possible to provide a solidified web having a porous portion adjacent to the panel skin in a core panel in which the core reinforcement member comprises a flat web sheet of fiber reinforcement material, for example a glass fiber fabric or mat. FIG. 42 shows a reinforced core panel 440 that includes a plurality of foam strips 33 to which the porous fibrous web sheet 34 previously described in connection with FIG. 1 is attached. The step of providing the fiber strut 35 shown in FIG. 1 is omitted. Referring again to FIG. 42, the solidifying resin 433 is applied to the porous web sheet 34, and the plurality of foam strips 33 with the web sheet 34 attached thereto are joined together as described in connection with FIG. The web setting resin 433 shown in FIG. 42 so that the adhesive resin used to attach the skin as described in connection with FIG. 41 to the core panel will penetrate into the web to achieve high structural adhesion. Can be placed without being applied to the edge portions of the web 34 adjacent to either side or end face of the core panel 440. The web 434 can also include twintex mixed glass fibers and thermoplastic fabric if desired, and the web edge portion for attachment to the skin using a liquid resin by applying heat and pressure. It can be solidified while maintaining its porosity.

  The embodiment shown in FIG. 43 illustrates a sandwich panel having stiffened core strips spaced apart. A plurality of roving-wrapped foam strips 178 having a solidified web portion 451 and a porous surface portion 452 are gathered in a spaced apart arrangement or relationship and are opposed using a lamination process. It is attached to 453 using an adhesive resin 435. This embodiment is useful for structural sandwich panels that substantially reduce the volume of plastic foam required and do not require thermal insulation. If thermal insulation or continuous support for the panel skin is required, alternating strips of wrapped foam with simple foam and solidified web 451 can be connected to each other as generally described in connection with FIG. Can be joined together. The embodiment of the present invention shown in FIGS. 41 and 43 can incorporate the hollow tube 381 shown in FIG. 36 instead of the foam strip 33 if desired. In alternative embodiments, higher density materials, such as standard materials, can be used in place of the foam strip 170 to achieve improved structural properties.

  44-47 show the structure of a reinforced core panel that includes a spiral wound strip and a solidified structural web and has improved bi-directional strength. 44. The core panel 431 having the solidified web 434 shown in FIG. 44 and described in connection with FIG. 41 is cut in a direction perpendicular to the length of the strip 178 to provide a plurality of first elongated strips of the desired thickness. A fiber reinforced core panel 462 is formed. Referring to FIG. 46, intersecting roving layers 281 and 282 are spirally wound around a first core panel 462 to form a second reinforced strip 464. Referring to FIG. 47, a hardenable resin 433 is applied to adjacent surfaces of the plurality of second reinforced strips 464. Resin 433 infiltrates roving layers 177, 178, 281, and 282 shown in detail in FIG. 46 to form a solidified web 465 shown in FIG. The strips 464 are pressed together and joined together as the resin 433 solidifies to form a reinforced core panel 460 having a solidified web 465 extending in the longitudinal direction and a solidified web 434 extending in the lateral direction indicated by phantom lines. A sandwich panel skin can be affixed to the core panel 460 as described in connection with FIG. Referring to FIG. 45, the bi-directional core panel also applies a solidifying resin 433 to the winding roving of the elongated core panel 462, presses the winding edges together as the resin hardens, and has the structure shown in FIG. Can also be produced by forming a similar core panel.

  FIGS. 48-50 schematically illustrate an advantageous means of producing a continuous sandwich panel comprising a foam strip having a layer of helically wound reinforcement. In the panel forming apparatus 470 shown in FIG. 48, a plurality of continuous length foam strips 471 having a porous reinforcing roving layer are drawn from the reel 472 by a pulling apparatus (not shown) commonly used in the pultrusion industry. And enters a pultrusion molding apparatus 473 provided with a resin tank or resin injection module 474 and a heating die 475. The continuous winding strip 471 is wound onto the reel 472 during the winding process of the strip 177 shown in FIG. Note that the step of cutting the strip 177 into a predetermined length is omitted. If desired, a single continuous strip 471 can be provided instead of the plurality of strips shown in FIG. 48, and if desired, the strips 471 can be simultaneously drawn from multiple reels 472 into the pultrusion apparatus 473.

  The strip 471 may be provided with a transverse reinforcement member, an axial reinforcement, or other improvements previously described herein. As strip 471 travels through device 470, skin material 476, eg, fiberglass fabric, is applied to the surface of strip 471, the skin and core reinforcements are infiltrated in resin module 474, and the resin is in heating die 475. To form a reinforced sandwich panel 477 having a reinforced core 478, which is cut to the desired length (not shown). The continuous strip 471 provides unbroken reinforcement layers 176, 177, and 180 within the sandwich panel core 478 regardless of where the sandwich panel 477 is cut, thus providing uniform strength throughout its length. Generate a panel.

  As previously described herein, the spiral wound form of the present invention is well suited for continuous integrated production of molded composite panels. FIG. 49 illustrates an economical method of producing a continuous sandwich panel useful as a trailer wall or building wall and having a core comprising fiber reinforced foam strips 178 transverse to the length of the panel. Efficient integration of the transverse reinforcement is particularly difficult with traditional methods of continuous panel production such as pultrusion. The panel production device 480 includes a winding device 171 (FIG. 12), a wound strip advancement device 482, and a forming module 483. The wrapping device 171 described in connection with FIG. 12 produces a fiber wrapped foam strip 178 that enters and continuously advances through the resin module 483 by the advancement device 482 as shown in FIG. To do. The strip 178 can be advanced at right angles to the length of the strip (FIG. 49) or at an acute angle with respect to the direction of advancement of the strip.

  Wrapped strips can incorporate features previously described herein, such as transverse reinforcement members within the strips. If desired, the rolled foam strip 178 can be fed from reel 472 as described in connection with FIG. 48 and cut to the desired length before proceeding to resin module 483. A porous skin material 484 is applied to the stack of strips 178 prior to entering the molding module. The resin infiltrates the porous skin 484 and porous roving in the foam strip 178 and cures in the molding module 483 to form a continuous sandwich panel 485. In a particularly economical embodiment of the present invention, the wound strip 178 is provided with an axial roving layer 180 and a plurality of reinforcing rovings fed from a reel are used in place of the skin 484 so that the reinforcing fabric is Remove the weaving cost.

  Molding module 483 can be a pultrusion device as described in connection with FIG. 48, an extrusion device to be described in connection with FIG. 50, or other forming devices known in the industry. . An important advantage of this method is that panels of any desired width can be produced either directly from the winder output or from a single reel of continuous fiber reinforced foam strips. The roving wrap foam strip 178 can also include a pre-stiffened web 332, if desired, adjacent to one or both opposing faces of the foam strip as shown in FIG. In this configuration, the web 332 provides significant compressive and shear strength to the core and, if desired, can eliminate penetration of the molding resin used to attach the skin 484 into the roving layers 176 and 177.

  FIG. 50 illustrates an economical method of producing a continuous sandwich panel useful as a high strength, low material consumption, lightweight building plank, board or column and incorporating a plastic resin extrusion process. The panel production apparatus 490 includes winding apparatuses 171 ′ and 173 ′ and an extrusion module 491. The winding devices 171 'and 173' described in connection with FIG. 12 produce a continuous fiber-wrapped foam strip that passes through the extrusion module 491 as shown in FIG. In the module 491, a heated liquid thermoplastic resin such as PVC or polyethylene is applied to infiltrate the fibrous reinforcing layers 180, 176 and 177, and the resin cools and solidifies to form a continuous sandwich panel plank 492. Form. The strip 178 includes a plastic foam composition that can withstand the temperature of the heated extrusion resin, such as polyisocyanurate or phenolic resin.

  If desired, the fiber-wrapped foam strip 178 can include a fibrous mat reinforcement 332 as described in connection with FIG. 31 to provide high compressive strength to the sandwich panel 492, and FIGS. Additional skin material may be applied to the sandwich panel 492 as described in connection with. The reinforced foam core can also be supplied from a reel as described in connection with FIG. 48 if desired. If desired, the extruding resin can also include a filler material, such as cellulose wood flour, to produce useful surface properties, for example on the deck, in which case the extrusion process completely infiltrates the fiber reinforcement of the sandwich panel 492. An initial unfilled resin step can be included to ensure The panel board 492 can also be provided with an additional surface layer of surface-embossed or extruded resin for UV resistance, as is commonly done in the extrusion industry. Depending on the specific materials and properties required for the sandwich panel 492, the pultrusion module 473 described in connection with FIG. 48 can be used in place of the extrusion module 491 shown in FIG. A fiber wrapped hollow tube as described in connection with FIG. 36 can be used in place of the wound foam strip 178 if the hollow tube is strong enough to withstand the pressure of the extrusion process.

  Any of the fiber-reinforced core panels disclosed herein can be used to produce structural molded composite panels with a thickness that exceeds the thickness of the individual core panels. Two or more core panels can be stacked in a mold with fiber reinforcements on adjacent core panel surfaces in contact with each other or with a layer of reinforcement material, eg, glass fiber cloth separating the core panels. If desired, the fiber reinforcements of adjacent core panels can be placed in an intersecting orientation, for example by stacking the two layers of the core panel shown in FIG. 18 in an intersecting orientation to achieve specific structural characteristics. 32 can be provided with the transverse reinforcing member as described above, and two or more core panels 340 having the transverse reinforcing member are stacked in an array state in which the strips 178 intersect with each other. A second core panel having directional strength can be formed. If desired, the stacked core panels 340 can be separated by a reinforcing mat or cloth.

  For clarity and comparison, the core panels herein have been shown as having a rectangular shape and having a series of fiber reinforcements substantially parallel to the edges of the core panel. If required for structural considerations, these series of reinforcements can be oriented at any desired angle relative to the direction or edge of the core panel. For example, referring to FIG. 18, a laterally reinforced foam strip 233 can intersect the edge of the rectangular core panel 240 at a 45 degree angle.

  The forms of reinforced foam cores and core panels and the steps of their construction methods described herein constitute preferred embodiments of the present invention, but the present invention is not limited to these exact forms and steps of these methods. It should be understood that these are not limiting and that changes can be made therein without departing from the scope and spirit of the invention.

Claims (27)

Forming a continuous elongate strip of low density porous material having at least one layer of fiber roving that continuously and spirally surrounds the continuous elongate strip along its length;
Cutting the continuous strip into strips of a predetermined length;
With each adjacent strip separated by the layer of fiber roving, the strip is continuously advanced through a forming device so that the layer of fiber roving extends between the surfaces on both sides of the core panel. Forming a continuous core panel,
Supplying a solidifying resin in the fiber roving layer between the strips;
Solidifying the resin in the molding apparatus and joining the strips together by bonding to form a continuous composite panel;
Cutting the continuous composite panel to a predetermined length;
A method for producing a composite panel.   The method of claim 1, comprising forming transverse reinforcing members spaced longitudinally within the elongate strip.   The method of claim 1, comprising maintaining porosity within the fiber roving after the resin is solidified.   The method of claim 1, comprising advancing a skin material through the molding device adjacent to the continuous core panel and adhering the skin material to the core panel with the resin.   The method of claim 1, comprising activating the solidifying resin with heat.   The method of claim 1, comprising applying the solidifying resin to the roving between the strips.   The method of claim 1, comprising applying the hardenable resin on surfaces on both sides of the strip.   The method of claim 1, comprising applying a layer of longitudinally extending roving adjacent to the layer of spirally surrounding rovings to the elongate strip.   The method of claim 1, wherein the fiber roving layer is formed by a set of braided rovings.   The method of claim 1, wherein the strips are made to have a width greater than their length.   The method of claim 1, wherein the strip enters the forming apparatus in a direction perpendicular to the length of the strip.   The method of claim 1, wherein the strip enters the forming apparatus at an acute angle with respect to the direction of advance of the strip.   The method of claim 1, wherein the strip is advanced through the forming apparatus by applying pressure to the strip.   The method of claim 1, wherein the strip is advanced through the forming apparatus by pulling the continuous composite panel.   The method of claim 1, comprising applying continuous fiber roving onto the strip traveling through the forming apparatus. Forming at least one continuous strip of low density porous material having at least one layer of fiber roving continuously and spirally surrounding the continuous strip along its length To do,
Advancing the continuous strip through a forming device in a direction parallel to the length of the continuous strip;
Supplying a solidifying resin into the fiber roving;
A method for producing a composite panel, comprising solidifying the resin to form a continuous composite panel.   The method of claim 16, comprising forming transverse reinforcing members spaced longitudinally within the elongate strip.   The method of claim 16, comprising sending the continuous elongate strip into the forming apparatus from a secondary forming apparatus that applies the layer of roving to the strip.   The method of claim 16, comprising feeding the continuous elongate strip from at least one supply reel into the forming apparatus.   17. The method of claim 16, comprising advancing a skin material through the molding apparatus adjacent to the continuous strip and adhering the skin material to the core panel with the resin.   The method of claim 16, comprising heat activating the solidifiable resin.   17. The method of claim 16, comprising adding a longitudinally extending layer of roving adjacent to the spirally surrounding layer of roving.   The method of claim 16, wherein the layer of fiber roving is formed by a set of braided rovings. Low density porous material core panel, with surfaces on both sides,
A fiber reinforcing member extending between the surfaces on both sides,
A fibrous skin adjacent to the surfaces on both sides of the core panel;
A solidified thermosetting resin that passes through the fiber reinforcing member and extends only in the inner part of at least one of the skins, and a thermoplastic resin that extends only in the outer part of one of the skins;
Including reinforced composite panels. A plurality of parallel strips of low density porous material,
At least one layer of fiber roving continuously and spirally surrounding each said strip along its length;
A plurality of adjacent strips separated by layers of the fiber roving and forming a continuous core panel with the layers of fiber roving extending between opposite sides of the continuous core panel; and A solidified resin that is in a layer of the fiber roving in between and that joins the strips together,
Including composite panels.   26. The composite panel of claim 25, comprising a skin material attached by adhesive resin to the surfaces on both sides of the core panel. A plurality of parallel strips of low density porous material, wherein the adjacent strips are separated by fiber roving and extend between surfaces on opposite sides of a continuous core panel Forming the core panel with a layer of solidified resin in the fiber roving between the strips and joining the strips;
And a part of the fiber roving is adjacent to the surfaces on both sides not including the solidified resin.

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