JP7447512B2 - bonded structure - Google Patents

Description

The present invention relates to a bonded structure of carbon fiber composite resin and metal.

Thermoplastic carbon fiber composite resin (CFRTP) has a rigidity that can replace metals such as aluminum alloy, and is lightweight because it contains carbon fiber, so it is used as a structural material for aircraft and automobiles, sports equipment, etc. ing. Since CFRTP is thermoplastic, it can be molded using an injection molding machine. Therefore, compared to conventional thermosetting carbon fiber composite resins, CFRTP can achieve improved productivity and increased degree of freedom in shape.

In CFRTP, metal is used in some areas where the material strength is insufficient. In that case, bonding between CFRTP and metal is required.

The bonding method generally includes a method using an adhesive. However, in order to withstand shear stresses resulting from differential thermal expansion of the materials, the adhesives that can be used are limited to elastic adhesives. On the other hand, elastic adhesives exhibit swelling and degradability, which can make it difficult to maintain a bond. Therefore, a means for joining without using an adhesive has been desired.

For example, Patent Document 1 discloses a process in which the surface of an aluminum alloy shape is covered with ultra-fine recesses of a specific diameter and amine molecules are chemically adsorbed, and the aluminum alloy shape is injection molded. A process of inserting into a mold and injecting a specific resin or resin composition to produce an injection bonded product, loading the injection bonded product into a heat press mold, and placing an FRTP prepreg or FRTP prepreg containing a specific matrix resin thereon. A method for producing a composite of metal and FRTP is disclosed, which includes a step of stacking and loading FRTP molded products and a hot pressing step of heat-sealing the resins together.

Further, Patent Document 2 discloses a step of forming a perforated portion having an opening by irradiating the surface of a first member with a laser beam having a period of 15 ns or less, in which one pulse is composed of a plurality of sub-pulses, and a step of forming a perforated portion in the perforation. Disclosed is a method for manufacturing a joined structure, which includes a step of filling and solidifying two members.

In addition, Non-Patent Document 1 describes that mechanical bonding between CFRTP and metal was achieved by ultrasonic bonding.

Japanese Patent Application Publication No. 2016-60051 Japanese Patent Application Publication No. 2016-43382

Balle et al., Ultrasonic spot welding of aluminum sheet/carbon fiber reinforced polymer joints, Materialwissenschaft und Werkstofftechnik, Vol. 38, Issue 11, p. 934-938, 2007

The method for manufacturing a composite described in Patent Document 1 is said to have strong adhesion between the metal part and the resin part, and to ensure product stability even when mass-produced.

However, in the invention described in Patent Document 1, when forming a rough surface on a metal surface, the shape of the unevenness of the rough surface cannot be controlled. Therefore, even after the subsequent bonding process using NMT (Nano Molding Tech.), the bonded surface will have an uncontrolled and irregular surface shape. This causes variations in the anchor effect during bonding. Therefore, when processed into a complex joint shape that matches the actual product, there will be many points where stress is concentrated on the joint surface, and due to heat shrinkage stress after molding and repeated stress amplitude due to thermal shock tests, Peeling may occur at points where the stress is concentrated.

The method for manufacturing a bonded structure described in Patent Document 2 is said to be able to achieve stronger bonding between metal and resin by utilizing the anchor effect that occurs between the resin and the perforations. However, when thermoplastic carbon fiber composite resin is used as the resin, the carbon fibers are usually not sufficiently defibrated, so the entanglement effect between the carbon fibers and the perforations does not occur, which improves the joint strength at the joint. There was room for.

Furthermore, since the processing method is limited to sub-pulse laser and the shape of the perforation is also limited, there is room for improvement from the viewpoint of processability.

Further, although the bonded body described in Non-Patent Document 1 is obtained by directly bonding CFRTP and metal by ultrasonic bonding, there is room for improvement in shear strength.

One aspect of the present invention has been made in view of these circumstances, and an object thereof is to provide a bonded structure having high bonding strength and thermal shock resistance.

In order to solve the above-mentioned problems, the present invention employs the following configuration.

That is, a bonded structure according to one aspect of the present invention includes a first member that is a metal workpiece having at least one of protrusions and perforations formed on the surface, a thermoplastic resin, and a defibrated structure in the thermoplastic resin. a second member including carbon fibers dispersed in a dispersed state and joined to the first member via at least one of the protrusion and the perforation.

According to the above configuration, the projections of the metal workpiece of the first member bite into the thermoplastic resin of the second member, or the thermoplastic resin of the second member is filled into the holes of the metal workpiece of the first member. As a result, the first member and the second member are joined. In addition, the defibrated carbon fibers contained in the second member become intertwined with the protrusions or perforations of the metalwork in the first member. This results in a filler effect by the carbon fibers and an anchoring effect for the protrusions or perforations at the joint. Therefore, even when stress is applied, a strong bond can be maintained between the first member and the second member. Further, by forming a large number of protrusions or perforations in the first member and defibrating the carbon fibers in the second member, shear stress at the joint can be dispersed and stress concentration can be suppressed. Therefore, the bonded structure has resistance to repeated thermal shocks. Therefore, in one aspect of the present invention, compared to the prior art, it is possible to obtain a bonded structure that is more firmly bonded and has high thermal shock resistance.

As used herein, the term "defibrated state" refers to a state in which carbon fibers are present singly, rather than in aggregated bundles. All carbon fibers do not necessarily have to exist alone. The proportion of carbon fibers present alone can be defined as the defibration rate, which will be described later. Also, in this specification, the carbon fibers are "entangled" with the protrusions or perforations, which means that at least a portion of the carbon fibers are inserted between the protrusions or into the perforations.

In the bonded structure according to the above one aspect, the defibration rate of the carbon fibers derived from the following formula may be 50% or more. This configuration increases the proportion of carbon fibers intertwined with protrusions or perforations. Therefore, a bonded structure that is more firmly bonded can be obtained.
Defibration rate (%) = (number of carbon fibers existing alone) / (total number of carbon fibers) x 100
In the bonded structure according to the one aspect, the distance between the protrusions may be 5 to 150 μm. According to this configuration, the anchor effect is likely to be exhibited. As used herein, the term "interval between protrusions" refers to the distance at which the protrusion first contacts the outline of another adjacent protrusion when the protrusion's outline is enlarged by an equal distance when viewed from the tip side of the protrusion. Furthermore, in this specification, the term "tip of a protrusion" refers to the part of the protrusion that first comes into contact with a plane when the plane is approached from the side from which the protrusion protrudes.

In the bonded structure according to the one aspect, the protrusion may have a width of 10 to 200 μm. According to this configuration, the anchor effect is likely to be exhibited. In this specification, the term "width of the protrusion" means the maximum Feret diameter of the protrusion contour line viewed from the tip side of the protrusion.

In the bonded structure according to the above one aspect, the height of the protrusion may be 15 μm or more. According to this configuration, the anchor effect is likely to be exhibited. As used herein, "height of a protrusion" means the distance from the tip to the base of the protrusion.

In the bonded structure according to the one aspect, the opening diameter of the perforation may be 5 μm or more and 150 μm or less. According to this configuration, the bonding strength of the bonded structure is improved. In this specification, the "opening diameter of a perforation" means the minimum Feret diameter at the opening of a perforation. In addition, in this specification, the "opening of a perforation" refers to a non-metallic part of the surface of a metal workpiece that first comes into contact with a plane when the plane is approached from the side where the perforation is open, that is, there is no metal. It means a part.

In the bonded structure according to the one aspect, the depth of the perforation may be 15 μm or more. According to this configuration, the bonding strength of the bonded structure is improved. As used herein, "perforation depth" means the distance from the opening to the bottom of the perforation.

The method for manufacturing a bonded structure according to the above aspect includes a step of forming at least one of protrusions and perforations on the surface of a metal material to obtain a first member, and a step of forming carbon fibers in a thermoplastic resin using an internal feedback screw. The method includes the steps of obtaining a second member by dispersing the fibers in a defibrated state, that is, obtaining the second member by high shear processing, and joining the first member and the second member. According to the manufacturing method, since the carbon fibers are included in the second member in a defibrated state, the bonding strength is improved.

According to one aspect of the present invention, a bonded structure having high bonding strength and thermal shock resistance can be provided.

FIG. 1 schematically illustrates an example of a cross section of a bonded structure according to an embodiment. FIG. 2 schematically represents a laser irradiation method for forming protrusions according to the embodiment. FIG. 3 schematically represents the laser processing portion of the first member according to the example. FIG. 4 schematically represents the tensile test method according to the example. FIG. 5 schematically represents an example of the protrusion of the first member according to the embodiment. FIG. 6 schematically represents an example of the protrusion of the first member according to the embodiment. FIG. 7 schematically represents an example of the protrusion of the first member according to the embodiment. FIG. 8 schematically represents an example of the protrusion of the first member according to the embodiment. FIG. 9 schematically represents an example of the protrusion of the first member according to the embodiment. FIG. 10 schematically represents an example of perforation of the first member according to the embodiment. FIG. 11 schematically represents an example of perforation near the first part according to the embodiment. FIG. 12 schematically represents an example of the arrangement of the protrusions of the first member according to the embodiment. FIG. 13 schematically represents an example of the arrangement of the protrusions of the first member according to the embodiment. FIG. 14 schematically represents an example of the arrangement of the protrusions of the first member according to the embodiment. FIG. 15 schematically represents an example of the protrusion of the first member according to the embodiment. FIG. 16 schematically represents an example of the protrusion of the first member according to the embodiment. FIG. 17 schematically represents an example of perforation of the first member according to the embodiment. FIG. 18 schematically represents an example of perforation of the first member according to the embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment (hereinafter also referred to as "this embodiment") according to one aspect of the present invention will be described below based on the drawings.

§1 Application Example First, an overview of a joined structure according to one embodiment of the present invention will be described using FIG. 1. FIG. 1 schematically illustrates an example of a cross section of a bonded structure according to one embodiment.

In FIG. 1, two types of joining structures 101 and 102 are illustrated. First, the bonded structure 101 will be explained. The bonded structure 101 includes a first member 1 which is a metal workpiece having protrusions 3 formed on its surface, and carbon fibers 5 and thermoplastic resin which are bonded to the first member 1 via the protrusions 3. and a second member 2 containing the second member 2.

In the bonded structure 101, the thermoplastic resin of the second member 2 solidifies so as to wrap around the projections 3 formed on the first member 1, and in addition, the carbon fibers 5 included in the second member 2 and the projections 3 are solidified. Because they are intertwined and bonded, a physically strong anchor effect can be obtained. Therefore, a bonded structure exhibiting high bonding strength can be provided.

Next, the bonded structure 102 will be explained. The bonded structure 102 includes a first member 1, which is a metal workpiece with perforations 4 formed on its surface, and carbon fibers 5 and thermoplastic resin, which are joined to the first member 1 via the perforations 4. and a second member 2 containing the second member 2.

In the bonded structure 102, the thermoplastic resin of the second member 2 is solidified so as to fill the perforations 4 formed in the first member 1, and in addition, at least one of the carbon fibers 5 contained in the second member 2 is solidified. Since the part is inserted into the perforation 4, a physically strong anchor effect can be obtained. As a result, a bonded structure exhibiting high bonding strength can be provided.

Furthermore, in these bonded structures, the carbon fibers are dispersed in the thermoplastic resin in a defibrated state. Carbon fibers are generally not fully defibrated. When the carbon fibers are not defibrated and are present in a bundle, the carbon fibers themselves have high rigidity, so the bundle of carbon fibers may inhibit the joining of the first member and the second member by the protrusion or the perforation. By defibrating the carbon fibers, the carbon fibers are sufficiently entangled with the protrusions or perforations, and the bonding strength of the bonded structure is improved.

§2 Configuration example <First member>
The first member is a metal workpiece and has protrusions and/or perforations formed therein. Examples of the material for the metal workpiece include iron-based metals, stainless steel-based metals, copper-based metals, aluminum-based metals, magnesium-based metals, and alloys thereof. Further, the metal workpiece may be a metal molded body, zinc die casting, aluminum die casting, powder metallurgy, or the like.

<Protrusion>
The protrusion is formed on the surface of the first member. By providing the first member with the protrusion, an anchor effect can be obtained between the first member and the second member via the protrusion. Moreover, since the second member contains carbon fiber, an intertwining effect can be obtained between the second member and the protrusion. Therefore, the bonding strength is improved.

Preferably, the protrusion is formed integrally with the first member. That is, it is preferable that the protrusion formed as a separate member from the first member is not attached to the surface of the first member. This improves the bonding strength compared to the case where the protrusion is attached to the first member.

Preferably, the protrusions are aligned. As used herein, "aligned protrusions" means regularly arranged protrusions. This stabilizes the strength of the entire bonded structure.

The distance between the protrusions is preferably 5 μm or more and 150 μm or less, more preferably 20 μm or more and 100 μm or less. If the distance between the protrusions is 5 μm or more, the carbon fibers are likely to become entangled with the protrusions, improving bondability. Moreover, if it is 150 μm or less, the number of protrusions per unit area increases, and the anchoring effect and intertwining effect are improved.

The width of the protrusion is preferably 10 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less. If the width of the protrusion is 10 μm or more, it is easy to form the protrusion. Further, if the width of the protrusions is 200 μm or less, the number of protrusions per unit area increases, and the anchoring effect and intertwining effect are improved.

The height of the protrusion is preferably 15 μm or more, more preferably 20 μm or more. If the height of the protrusions is 15 μm or more, the anchor effect and entanglement effect will be improved. Although the upper limit of the height of the protrusion is not particularly limited, it is preferable that it is 300 μm or less because the processing time can be shortened.

The shape of the protrusion is not particularly limited. For example, the protrusion may have a constant diameter in a cross section perpendicular to the height direction, and at least one region in which the diameter in a cross section perpendicular to the height direction increases or decreases from the tip to the base of the protrusion. It may have one or the other. In particular, when the protrusion has a region in which the diameter of a cross section perpendicular to the height direction decreases from the tip of the protrusion toward the base, the protrusion has excellent vertical peel strength. Further, the shape of the tip of the protrusion is not particularly limited, and may be branched.

5 to 9 and 15 to 16 schematically illustrate examples of protrusions. The projection 3 shown in FIG. 5 includes a region 21 in which the diameter of a cross section perpendicular to the height direction increases from the tip of the projection toward the base, and then a region 22 that decreases. The projection 3 shown in FIG. 6 includes a region 21 in which the diameter of a cross section perpendicular to the height direction decreases from the tip to the base of the projection, followed by a region 21 that increases. Further, the projection 3 shown in FIG. 7 includes only a region 22 in which the diameter of a cross section perpendicular to the height direction decreases from the tip to the base of the projection. The projection 3 shown in FIG. 8 includes only a region 21 in which the diameter of a cross section perpendicular to the height direction increases from the tip to the base of the projection. The projection 3 shown in FIG. 9 has a constant diameter in a cross section perpendicular to the height direction from the tip to the base of the projection. The protrusion 3 shown in FIG. 15 has a branched tip side. Note that the interval between the protrusions in this case means the part indicated by the arrow 31 shown in FIG. 15, and does not include the interval between the branches present on the tip side of the protrusions. In the protrusion 3 shown in FIG. 16, the branch at the tip of the protrusion reaches the base. Note that if the interval between the branches is less than 5 μm, the entire branch may be regarded as one protrusion. That is, the interval between the protrusions in this case means the part indicated by the arrow 31 shown in FIG. 16, and does not include the interval between the branches. Further, protrusions of a plurality of shapes may be used partially. That is, for example, the shape shown in FIG. 5 and the shape shown in FIG. 6 may coexist.

As mentioned above, one large protrusion may be provided with a plurality of small branches. Furthermore, since the branches reach the base, a plurality of protrusions may appear to be in close contact with each other. However, it is preferred that the protrusions are independent. As used herein, "independent protrusions" means that when viewed from the tips of the protrusions, the outlines of the protrusions do not overlap or touch, and the boundaries between the protrusions are clear. That is, it is preferable to have only one tip and only one base per protrusion. This makes it possible to maximize the number of protrusions 3 and carbon fibers 5 that contribute to bonding, thereby improving the anchoring effect with the thermoplastic resin contained in the second member and the entanglement effect with carbon fibers, thereby improving the bonding effect. Improves sex.

The arrangement of the protrusions is not particularly limited. FIGS. 12 to 14 schematically illustrate an example of an arrangement of protrusions. For convenience, in FIGS. 12 to 14, the shapes in which the tips of the protrusions are connected are shown by thick lines. The arrangement of the protrusions viewed from the tip side of the protrusions may be, for example, square as shown in FIG. 12, triangular as shown in FIG. 13, or hexagonal as shown in FIG. good.

In this specification, the expression that the projections are arranged in a "square shape" means that the projections are arranged in a lattice shape. In this specification, the expression that the protrusions are arranged in a "triangular shape" means that the protrusions are arranged in a close-packed arrangement. Furthermore, in this specification, the expression that the protrusions are arranged in a "hexagonal shape" means that the protrusions are arranged in a hexagonal shape. Furthermore, a plurality of types of arrays may be partially used. That is, for example, the arrangement shown in FIG. 12 and the arrangement shown in FIG. 13 may coexist.

<Perforation>
Perforations are formed in the surface of the first member. By forming the perforations in the first member, an anchor effect can be obtained between the first member and the second member through the perforations. Moreover, since the second member contains carbon fiber, an intertwining effect can be obtained between the second member and the perforation. Therefore, the bonding strength is improved.

FIG. 10 schematically illustrates an example of perforation of the first member according to the embodiment. As shown in FIG. 10, the first member 1 is preferably provided with mutually independent perforations. That is, when viewed from a direction perpendicular to the surface on which the perforations are formed, it is preferable that the openings of the perforations do not overlap and that the boundaries between the perforations are clear. The perforations differ from continuous grooves. If the perforations are independent, the number of perforations 4 and carbon fibers 5 that contribute to bonding can be maximized, and the anchor effect with the thermoplastic resin contained in the second member and the entanglement effect with the carbon fibers 5 can be maximized. and bonding properties are improved.

The opening diameter of the perforation is preferably 5 to 150 μm, more preferably 10 to 100 μm. If the opening diameter is 5 μm or more, the effect of entanglement with carbon fibers will be improved. Further, if the opening diameter is 150 μm or less, the number of perforations per unit area increases, and the anchor effect and entanglement effect are improved.

The depth of the perforation is preferably 15 μm or more, more preferably 20 μm or more. When the depth is 15 μm or more, the anchor effect and entanglement effect in the perforation are improved, and as a result, the overall bonding strength is improved. Although the upper limit of the depth of the perforation is not particularly limited, it is preferable that it is 300 μm or less because the machining time can be shortened.

It is also preferable that the perforations are aligned. As used herein, "aligned perforations" means perforations that are regularly arranged. This stabilizes the strength of the entire bonded structure. The arrangement of the perforations is not particularly limited, and the same arrangement as the projections can be used. Further, similar to the above-mentioned protrusions, it is also possible to have a plurality of types of arrangements coexisting. In addition, perforations with different opening diameters may coexist.

The shape of the perforation is not particularly limited. For example, the perforation may have a constant diameter in a cross section perpendicular to the depth direction, and at least one of an area where the diameter of the cross section perpendicular to the depth expands from the opening toward the bottom and an area where the diameter decreases. It may have one or the other.

Figures 10-11 and 17-18 schematically illustrate an example of perforation. For example, as shown in FIG. 10, the shape may include a region where the diameter of the cross section perpendicular to the depth direction of the borehole decreases, followed by a region where the diameter increases. The diameter inside the perforation shown in FIG. 11 may be substantially constant. The shape shown in FIG. 17 may include a plurality of small perforations inside the perforation, or the shape shown in FIG. 18 may include a plurality of overlapping perforations. However, it is more preferable for the perforations to be independent as described above rather than for the perforations to overlap. Further, a plurality of shapes of perforations may be used selectively. That is, for example, the shape shown in FIG. 10 and the shape shown in FIG. 11 may coexist.

<Second member>
The second member includes thermoplastic resin and carbon fiber. It can also be said that the second member includes carbon fiber composite resin.

Thermoplastic resin materials include PVC (polyvinyl chloride), PS (polystyrene), AS (acrylonitrile styrene), ABS (acrylonitrile butadiene styrene), PMMA (polymethyl methacrylate), PE (polyethylene), PP ( polypropylene), PC (polycarbonate), m-PPE (modified polyphenylene ether), PA6 (polyamide 6), PA66 (polyamide 66), POM (polyacetal), PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PSF (polysulfone) ), PAR (polyarylate), PEI (polyetherimide), PPS (polyphenylene sulfide), PES (polyether sulfone), PEEK (polyetheretherketone), PAI (polyamideimide), LCP (liquid crystal polymer), PVDC (polyvinylidene chloride), PTFE (polytetrafluoroethylene), PCTFE (polychlorotrifluoroethylene), and PVDF (polyvinylidene fluoride). Further, the thermoplastic resin may be TPE (thermoplastic elastomer), and examples of TPE include TPO (olefin type), TPS (styrene type), TPEE (ester type), TPU (urethane type), and TPA. (nylon type) and TPVC (vinyl chloride type). From the viewpoint of material strength, thermoplastic resins having crystallinity are preferred among the above.

The second member may contain additives other than the thermoplastic resin and the carbon fibers, as necessary, within a range that does not impair the above-mentioned effects. Examples of additives include a sizing agent, a dispersant, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a lubricant, a crystal nucleating agent, to improve the affinity between the carbon fiber and the thermoplastic resin, Examples include plasticizers, dyes, pigments, carbon nanotubes, and the like.

In order to improve the material strength of the second member, it is preferable to use a layered silicate as the crystal nucleus material. In layered silicates, a tetrahedron in which Si is surrounded by four oxygen atoms forms a two-dimensionally expanded structural unit (tetrahedral sheet) by sharing three vertices with the neighboring tetrahedron. A group of silicates with a layered structure. Further, a part of Si may be replaced with Al. Examples of the silicates include mica, mica, talc, kaolin, montmorillonite, and the like. Further, an octahedral sheet, which is a two-dimensional connection of octahedrons in which Mg, Al, etc. are surrounded by six oxygens or OH in addition to Si, also serves as a crystal nucleating agent. The octahedral sheet has complete cleavage parallel to the layer plane, and is generally in the form of a plate or a flake. Chemically, the octahedral sheet is a hydrous silicate containing Al, Mg, Fe, alkali, etc. in addition to Si. Commercially available products can be used for both.

<Carbon fiber>
The carbon fiber is a filler that provides strength to the second member. Carbon fibers can be obtained, for example, by carbonizing organic polymer fibers while maintaining the fiber shape through a stepwise heat treatment at 800° C. or higher and 3000° C. or lower, or by heat treating spun pitch. Examples of organic polymer fibers include cellulose fibers and polyacrylonitrile fibers. Furthermore, commercially available carbon fibers may be used. The carbon fiber may be a new material or a recycled material. As the recycled material, carbon fibers that are recycled from carbon fiber reinforced plastic (CFRP) by a pyrolysis method that separates the resin component and recovers carbon fibers, a chemical dissolution method, or a supercritical fluid method may be used. .

The carbon fiber can be appropriately selected depending on the thermoplastic resin. Examples of carbon fibers include, but are not limited to, SIGRAFIL C C6-4.0/240-T190 (manufactured by SGL Carbon), SIGRAFIL C C6-4.0/240-T130 (manufactured by SGL Carbon), and HT C413 (manufactured by SGL Carbon). (manufactured by Toho Tenax), IM C702 (manufactured by Toho Tenax), TR06NE (manufactured by Mitsubishi Rayon), and MR06NE (manufactured by Mitsubishi Rayon).

The weight ratio of the thermoplastic resin to the carbon fiber (carbon fiber:thermoplastic resin) in the second member is preferably 10:90 to 60:40, more preferably 20:80 to 40: It is 60. If the proportion of carbon fiber is 10% by weight or more, the mechanical strength of the second member will improve. If the ratio of carbon fibers is 60% by weight or less, uneven mixing of carbon fibers and thermoplastic resin during the melt-kneading process will be reduced, so that the mechanical strength of the second member will be improved.

The fiber length of the carbon fiber is not particularly limited, but from the viewpoint of dispersibility in the thermoplastic resin, it is preferably 50 mm or less, and from the viewpoint of the dispersibility of the carbon fiber in the resin, it is more preferable. is 5 mm or less. Further, from the viewpoint of mechanical strength (tensile strength or bending strength) of the composite resin, the thickness is preferably 0.1 mm or more. Note that the fiber length of the carbon fibers does not need to be constant and may vary. In that case, carbon fibers having a fiber length outside the preferred range described above may be included.

The fibrillation rate of the carbon fiber is determined from the following formula, and is preferably 50% or more, more preferably 80% or more. When the defibration rate is 50% or more, the number of carbon fibers intertwined with the projections or the perforations increases, and the bonding strength of the bonded structure improves.
Defibration rate (%) = (number of carbon fibers existing alone) / (number of carbon fibers) x 100
The upper limit of the defibration rate is not particularly limited, and may be 100%.

<Method for manufacturing bonded structure>
The bonded structure includes, for example, a step of forming at least one of protrusions and perforations on the surface of a metal material to obtain a first member, and a state in which carbon fibers are defibrated in a thermoplastic resin by an internal feedback screw. The second member is obtained by dispersing the second member, and the second member is joined to the first member.

The method for forming the protrusions or perforations in the first member is not particularly limited, and may be performed by laser processing, chemical etching, electric discharge machining, ultra-precision molding, fine cutting, or the like.

Examples of lasers used to form the protrusions or perforations include fiber lasers, YAG lasers, YVO4 lasers, semiconductor lasers, carbon dioxide lasers, and excimer lasers. A pulsed laser is suitable when forming a protrusion having a region where the diameter of the outer circumference decreases from the tip of the protrusion toward the base, and a continuous wave laser may be used in other cases. As the pulse laser, a sub-pulse laser is more preferable.

FIG. 2 schematically represents a laser irradiation method for forming protrusions according to the embodiment. By laser processing the metal material so that the laser irradiation part 11 shown in FIG. 2 partially overlaps with the metal material, the non-laser irradiation part 13 becomes an independent protrusion. In FIG. 2, a region where the laser irradiation parts overlap is shown as a laser irradiation superimposition part 12.

The second member is produced, for example, as follows. First, carbon fibers are added to a thermoplastic resin and kneaded. Here, by kneading under shear conditions, the carbon fibers can be dispersed in a defibrated state. Although an ordinary twin-screw extruder may be used, preferably a high shear processing machine having an internal feedback screw is used for kneading.

An internal return screw is provided within the cylinder. By repeating steps 1 and 2 below, a molten resin composition containing a thermoplastic resin and carbon fibers is kneaded.
1. Rotation of the screw forces the molten resin composition to the front of the cylinder.
2. The molten resin composition returns to the rear of the cylinder through a passage provided in the axial direction of the screw.

This generates a strong shear flow field and elongation field inside the molten resin composition, thereby promoting fibrillation of the carbon fibers. The rotation speed of the internal feedback screw is preferably 200 rpm or more and 3000 rpm or less. Moreover, it is preferable that the shear rate is 300/s or more and 4500/s or less. The time for circulating the molten resin composition is preferably 10 seconds or more and 8 minutes or less.

Thereafter, the second member can be obtained by molding the obtained molten resin composition. A general injection molding method can be used for molding.

Examples of the method for joining the first member and the second member include laser joining, injection molding joining, ultrasonic welding, hot press welding, IH heating, and 3D printer lamination.

Laser bonding is performed, for example, as follows. The processed portion of the first member is irradiated with a laser while pressing the second member, and the second member is melted by heat. The laser is irradiated from the first member side. After that, when the laser irradiation is stopped, the second member is cooled and solidified with the carbon fibers contained in the second member intertwined with the protrusions or perforations, and the first member and the second member are joined. A bonded structure is obtained.

When performing laser bonding, the laser irradiation surface of the first member may be rough-processed using the same type of laser marker in order to improve the laser absorption efficiency of the first member. Furthermore, the method for improving the laser absorption efficiency of metal is not limited to the laser marker described above, but may also include rough processing with sandpaper, black body spraying, etc.

Injection molding joining is performed using, for example, an electric injection molding machine. Specifically, the first member is inserted into a mold installed in the molding machine, and the mold is filled with molten resin to mold the second member and obtain a bonded structure.

Ultrasonic welding is performed by overlapping a first member and a second member via a joint, and installing them in an ultrasonic welding device. Ultrasonic welding is performed via an ultrasonic welding horn to obtain a bonded structure.

Hot press adhesion is performed by overlapping the first member and the second member via the joint, and installing them in a hot press device or a mold. Heat and pressure are applied from the second member side to join them to obtain a joined structure.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. are also included within the technical scope of the present invention.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the following Examples.

[Evaluation of carbon fiber defibration rate]
The carbon fiber composite resin used for the second member was diluted 10 to 30 times by melting and kneading it with a thermoplastic resin of the same type that does not contain carbon fibers. Specifically, using a Laboplast Mill (manufactured by Toyo Seiki Seisakusho Co., Ltd.), the mixture of the carbon fiber composite resin and thermoplastic resin was heated to a temperature higher than the melting temperature of the thermoplastic resin, while the rotation speed was set to several tens of rpm. It was diluted by kneading at a certain level. By controlling the rotational speed in this manner, shear stress on the resin was suppressed and the fibrillated state of the carbon fibers did not change. A sheet sample with a size of 50 mm x 50 mm and a thickness of about 0.2 mm was produced from the diluted resin using a hot press machine. Three arbitrary points on the sheet sample were observed with an optical microscope in a field of Φ5 mm, and the number of individual carbon fibers and the number of carbon fibers present in a bundle of two or more were counted. Then, the defibration rate was determined from the above formula. The defibration rate was expressed as the average value obtained from the three points. In addition, the said average value was rounded off to the nearest 1 and expressed in 10% increments.

[Joining evaluation method]
FIG. 4 schematically represents the tensile test method according to the example. The bonded structure used for the bonding evaluation was obtained by bonding the first member so that the longitudinal direction of the first member and the second member were parallel to each other. A thermal shock test was conducted on the bonded structure using a thermal shock tester (manufactured by ESPEC), in which the bonded structure was subjected to treatment at low and high temperatures. Regarding the temperature conditions, one cycle was set at -40°C for 30 minutes on the low temperature side and 30 minutes at 70°C on the high temperature side. The number of cycles was 5 cycles, 50 cycles, or 1000 cycles. After the thermal shock test, the bonded structure was pulled in the shear direction (in the direction of the arrow shown in FIG. 4) using an electromechanical universal testing machine 5900 (manufactured by Instron). The tensile speed was 1 mm/min. Bondability was evaluated by observing the fractured surface and fractured part after the test, and based on the state of fracture. The evaluation was determined as follows. If the bonding interface peeled off after 5 cycles of thermal shock, it was judged as a failure because it could not withstand the thermal shock. After 5 cycles, only the resin material was destroyed, but after 50 cycles, there was a mixture of peeling of the bonding interface and destruction of the resin material. It was determined that the level is applicable to electrical equipment, etc. After 50 cycles, only the resin material was destroyed, but after 1000 cycles, a mixture of peeling of the bonding interface and destruction of the resin material is rated ◎, and it is used in an outdoor environment and requires a relatively long life. It has been determined that the level is applicable to equipment that will be used, such as transportation equipment. A case where only the resin material is destroyed after 1000 cycles is rated ◎◎, and it is judged that the level can be applied to equipment that is exposed to both low and high temperatures and is required to have a long life even in harsh usage environments, such as industrial equipment. .

[Example 1]
A first member was produced by forming protrusions on SUS316 (100 mm x 20 mm, thickness 0.5 mm), which is a metal material, by irradiating it with an infrared laser using a fiber laser marker MX-Z2000H (manufactured by OMRON). .

FIG. 3 schematically represents the laser processing section 6 of the first member. A laser processing section 6 was formed at one end of the first member 1 in the longitudinal direction. The laser irradiation conditions for forming protrusions were: output: 6 W, frequency: 10 kHz, number of scans: 30 times, sub-pulses: 20, scanning speed: 1060 mm/s, and the scanning trajectory was set so that the interval between protrusions was 20 μm and the width was 50 μm. was adjusted accordingly.

The shape of the projections was as shown in FIG. 6, and the arrangement of the projections was as shown in FIG. 13. In addition, the opposite side to the surface on which the protrusions were formed was rough-processed using the same type of laser.

Next, carbon fiber was added to the PBT resin at a ratio of 70:30 (weight ratio). High shear processing was performed using a fully automatic high shear forming device (NHSS2-28, manufactured by Niigata Machine Techno). The apparatus includes a plasticizing section and a high shear processing section.

First, PBT resin (Novaduran 5010L, manufactured by Mitsubishi Engineering Plastics) and carbon fiber (SIGRAFIL C C6-4.0/240-T130, manufactured by SGL Carbon) were added to the plasticized part. In the plasticizing section, PBT resin and carbon fiber were melt-kneaded using a single screw to obtain a resin composition. The conditions for melting and kneading were cylinder temperature: 250° C. and screw rotation speed: 20 rpm.

The obtained resin composition was supplied to a high shear processing section via a valve gate. By circulating the resin composition using an internal feedback screw, a carbon fiber composite resin in which defibrated carbon fibers were dispersed in a thermoplastic resin was obtained. In the high shear processing section, the cylinder temperature was 260°C, the screw rotation speed was 500 rpm, and the residence time was about 45 seconds.

A second member was obtained by molding the obtained carbon fiber composite resin into a molded article measuring 100 mm x 25 mm x 2.0 mm in thickness according to a general injection molding method.

The second member was superimposed on the first member so that the longitudinal ends were joined as shown in FIG. 4, and the two members were placed in a joining jig. Next, the opposite side of the processed surface of the first member was heated by repeatedly irradiating it with an infrared laser using an LD laser (manufactured by Jenoptik). The laser irradiation conditions were as follows; output: 24 W, wavelength: 808 nm, laser spot diameter: 2 mm, number of scans: 10 times. The surface of the second member was melted by the heat transfer of the first member, and a bonded structure was obtained by pressurizing the first member and the second member. Pressurization was performed by arranging a cylinder CQ2Φ20 (manufactured by SMC) perpendicular to the bonded structure. The pressurization conditions were a cylinder air pressure of 0.3 MPa.

[Example 2]
Among the laser irradiation conditions for forming the protrusions on the first member, the output was 3 W, the processing shape of the first member was the drilling shape shown in FIG. 10, and the drilling arrangement was the shape shown in FIG. 13. A bonded structure was obtained in the same manner as in Example 1. The opening diameter of the perforation was 20 μm, and the depth of the perforation was 50 μm.

[Example 3]
A bonded structure was obtained in the same manner as in Example 1, except that the high shear processing conditions were a screw rotation speed of 300 rpm, a residence time of about 30 seconds, and a fibrillation rate of carbon fibers of 50%.

[Example 4]
A bonded structure was obtained in the same manner as in Example 2, except that the high shear processing conditions were a screw rotation speed of 300 rpm, a residence time of about 30 seconds, and a fibrillation rate of carbon fibers of 50%.

[Comparative example 1]
A bonded structure was obtained in the same manner as in Example 1, except that high shear processing was not performed and the fibrillation rate of the carbon fibers was set to 0%.

[Comparative example 2]
A bonded structure was obtained in the same manner as in Example 2, except that high shear processing was not performed and the fibrillation rate of the carbon fibers was set to 0%.

The test results of Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Table 1.

From Table 1, it was found that Examples 1 to 4 in which the carbon fibers were defibrated showed stronger thermal shock resistance and bonding compared to Comparative Examples 1 and 2 in which the carbon fibers were not defibrated at all.

[Example 5]
The laser irradiation conditions for forming the protrusions on the first member were changed as follows, and the laser scanning trajectory was appropriately adjusted so that the protrusion arrangement was as shown in FIG. 12 and the protrusion shape was as shown in FIG. A bonded structure was obtained in the same manner as in Example 1 except for this. Output: 3W, frequency: 10kHz, scanning speed: 380mm/s, number of scans: 20 times, sub-pulses: 20.

[Example 6]
Welding was performed in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions on the first member were changed as follows, and the scanning trajectory was appropriately adjusted so that the protrusion shape was as shown in FIG. I got a structure. Output: 6W, frequency: 10kHz, scanning speed: 900mm/s, number of scans: 30 times, sub-pulses: 20.

[Example 7]
The laser irradiation conditions for forming the protrusions on the first member were changed as follows, and the scanning trajectory was appropriately adjusted so that the protrusion arrangement was as shown in FIG. 12 and the protrusion shape was as shown in FIG. 8. A bonded structure was obtained in the same manner as in Example 1 except for this. Output: 6W, frequency: 10kHz, scanning speed: 700mm/s, number of scans: 20 times, sub-pulses: 20.

[Example 8]
The laser irradiation conditions for forming the protrusions on the first member were changed as follows, and the scanning trajectory was appropriately adjusted so that the protrusion arrangement was as shown in FIG. 12 and the protrusion shape was as shown in FIG. 9. A bonded structure was obtained in the same manner as in Example 1 except for this. Output: 1W, frequency: 10kHz, scanning speed: 380mm/s, number of scans: 20 times, sub-pulses: 20.

[Example 9]
The laser irradiation conditions for forming the protrusions on the first member were changed as follows, and the scanning trajectory was appropriately adjusted so that the perforation arrangement was as shown in FIG. 13 and the perforation shape was as shown in FIG. 11. A bonded structure was obtained in the same manner as in Example 1 except for this. Output: 3W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 20 times, sub-pulse: 5.

[Comparative example 3]
A joined structure was obtained in the same manner as in Example 1 except that the first member was not processed.

The results of Examples 5 to 9 and Comparative Example 3 are shown in Table 2.

From Table 2, it was found that Examples 5 to 9, which had protrusions or perforations, showed stronger thermal shock resistance and bonding compared to Comparative Example 3, which did not have either.

[Example 10]
A bonded structure was obtained in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions of the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 1200mm/s, number of scans: 40 times, sub-pulses: 20.

[Example 11]
A bonded structure was obtained in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions of the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 40 times, sub-pulses: 20.

[Example 12]
A bonded structure was obtained in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions of the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 600mm/s, number of scans: 30 times, sub-pulses: 20.

[Example 13]
The bonded structure was fabricated in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions on the first member were changed as follows, and the scanning trajectory was appropriately adjusted so that the interval between the protrusions was approximately 100 μm. I got it. Output: 6W, frequency: 10kHz, scanning speed: 1040mm/s, number of scans: 40 times, sub-pulses: 20.

[Example 14]
The bonded structure was fabricated in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions on the first member were changed as follows, and the scanning trajectory was appropriately adjusted so that the interval between the protrusions was approximately 150 μm. I got it. Output: 6W, frequency: 10kHz, scanning speed: 1040mm/s, number of scans: 30 times, sub-pulses: 20.

The test results of Examples 1 and 10 to 14 are shown in Table 3.

From Table 3, Examples 10 to 14 in which the distance between the protrusions is 5 to 150 μm all exhibit good thermal shock resistance and strong bonding. In particular, it was found that better resistance and bonding were exhibited when the spacing between the protrusions was 10 to 100 μm, and the strongest resistance and bonding were exhibited when the spacing between the protrusions was 20 to 50 μm.

[Example 15]
A bonded structure was obtained in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions of the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 380mm/s, number of scans: 40 times, sub-pulses: 20.

[Example 16]
A bonded structure was obtained in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions of the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 520mm/s, number of scans: 30 times, sub-pulses: 20.

[Example 17]
The bonded structure was fabricated in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions on the first member were changed as follows, and the scanning trajectory was appropriately adjusted so that the width of the protrusions was approximately 100 μm. I got it. Output: 6W, frequency: 10kHz, scanning speed: 1040mm/s, number of scans: 40 times, sub-pulses: 20.

[Example 18]
The bonded structure was fabricated in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions on the first member were changed as follows, and the scanning trajectory was adjusted appropriately so that the width of the protrusions was approximately 200 μm. I got it. Output: 6W, frequency: 10kHz, scanning speed: 1040mm/s, number of scans: 40 times, sub-pulses: 20.

The test results of Examples 1 and 15 to 18 are shown in Table 4.

From Table 4, Examples 15 to 18 in which the protrusion width is 10 to 200 μm all exhibit good thermal shock resistance and bonding. In particular, it was found that better resistance and bonding were exhibited when the width of the protrusions was 10 to 100 μm, and the strongest resistance and bonding were exhibited when the width of the protrusions was 20 to 50 μm.

[Example 19]
A bonded structure was obtained in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions of the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 5 times, sub-pulses: 20.

[Example 20]
A bonded structure was obtained in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions of the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 10 times, sub-pulses: 20.

[Example 21]
A bonded structure was obtained in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions of the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 65 times, sub-pulses: 20.

[Example 22]
A bonded structure was obtained in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions of the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 130 times, 10 subpulses.

[Example 23]
A bonded structure was obtained in the same manner as in Example 1, except that the laser irradiation conditions for forming the protrusions of the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 200 times, sub-pulses: 10.

The test results of Examples 1 and 19 to 23 are shown in Table 5.

From Table 5, Examples 19 to 23, in which the height of the protrusions is 15 μm or more, all exhibit good thermal shock resistance and bonding. In particular, it was found that better resistance and bonding were exhibited when the height of the protrusions was 20 μm or more, and the strongest resistance and bonding were exhibited when the height of the protrusions was 50 μm or more.

[Example 24]
A bonded structure was obtained in the same manner as in Example 2, except that the laser irradiation conditions for forming the perforations in the first member were changed as follows. Output: 1W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 30 times, sub-pulses: 20.

[Example 25]
A bonded structure was obtained in the same manner as in Example 2, except that the laser irradiation conditions for forming the perforations in the first member were changed as follows. Output: 1W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 20 times, sub-pulses: 20.

[Example 26]
A bonded structure was obtained in the same manner as in Example 2, except that the laser irradiation conditions for forming the perforations in the first member were changed as follows. Output: 3W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 20 times, sub-pulses: 10.

[Example 27]
A bonded structure was obtained in the same manner as in Example 2, except that the laser irradiation conditions for forming the perforations in the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 1470mm/s, number of scans: 30 times, sub-pulses: 20.

[Example 28]
A bonded structure was obtained in the same manner as in Example 2, except that the laser irradiation conditions for forming the perforations in the first member were changed as follows. Output: 6W, frequency: 10kHz, scanning speed: 1840mm/s, number of scans: 20 times, sub-pulses: 10.

The test results of Examples 2 and 24 to 28 are shown in Table 6.

From Table 6, Examples 24 to 28 in which the opening diameter of the holes was 5 to 150 μm all exhibited good thermal shock resistance and bonding. In particular, it was found that better resistance and bonding were exhibited when the diameter of the perforations was 10 to 100 μm, and the strongest resistance and bonding were exhibited when the diameter of the perforations was 50 μm.

[Example 29]
A bonded structure was obtained in the same manner as in Example 2, except that the laser irradiation conditions for forming the perforations in the first member were changed as follows. Output: 3W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 5 times, sub-pulses: 20.

[Example 30]
A bonded structure was obtained in the same manner as in Example 2, except that the laser irradiation conditions for forming the perforations in the first member were changed as follows. Output: 3W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 10 times, sub-pulses: 20.

[Example 31]
A bonded structure was obtained in the same manner as in Example 2, except that the laser irradiation conditions for forming the perforations in the first member were changed as follows. Output: 3W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 65 times, sub-pulses: 15.

[Example 32]
A bonded structure was obtained in the same manner as in Example 2, except that the laser irradiation conditions for forming the perforations in the first member were changed as follows. Output: 3W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 130 times, sub-pulses: 10.

[Example 33]
A bonded structure was obtained in the same manner as in Example 2, except that the laser irradiation conditions for forming the perforations in the first member were changed as follows. Output: 3W, frequency: 10kHz, scanning speed: 1060mm/s, number of scans: 200 times, sub-pulses: 5.

The test results of Examples 2 and 29 to 33 are shown in Table 7.

From Table 7, Examples 29 to 33, in which the perforation depth was 15 to 300 μm, all exhibited good thermal shock resistance and bonding. In particular, it was found that better resistance and bonding were exhibited when the depth of the perforation was 20 μm or more.

One embodiment of the present invention can be used, for example, in general equipment that requires bonding between metal and carbon fiber composite resin.

1 First member 2 Second member 3 Protrusion 4 Perforation 5 Carbon fiber 6 Laser processing section 11 Laser irradiation section 12 Laser irradiation superimposition section 13 Laser non-irradiation section 21 Area where the diameter increases 22 Area where the diameter decreases 31 Interval between protrusions 101 , 102 joint structure

Claims (6)

a first member that is a metal workpiece having at least one of protrusions and perforations formed on its surface;
A second member comprising a thermoplastic resin and carbon fibers dispersed in a defibrated state in the thermoplastic resin, and joined to the first member through at least one of the protrusion and the perforation. and,
The perforation has a depth of 15 μm or more,
The protrusions are independent, and the interval between the protrusions is 5 to 150 μm,
The interval between the protrusions is the distance from the contour line of the protrusion to the contour line of another adjacent protrusion when viewed from the tip side of the protrusion.
bonded structure. The bonded structure according to claim 1, wherein the carbon fiber has a defibration rate derived from the following formula of 50% or more.
Defibration rate (%) = (number of carbon fibers existing alone) / (total number of carbon fibers) x 100 The bonded structure according to claim 1 or 2, wherein the protrusion has a width of 10 to 200 μm. The bonded structure according to any one of claims 1 to 3, wherein the height of the protrusion is 15 μm or more. The joining structure according to any one of claims 1 to 4, wherein the perforation has an opening diameter of 5 to 150 μm. forming at least one of protrusions and perforations on the surface of the metal material to obtain a first member;
obtaining a second member by dispersing carbon fibers in a defibrated state in a thermoplastic resin using an internal feedback screw;
a step of joining the first member and the second member,
The perforation has a depth of 15 μm or more,
The protrusions are independent, and the interval between the protrusions is 5 to 150 μm,
The interval between the protrusions is the distance from the contour line of the protrusion to the contour line of another adjacent protrusion when viewed from the tip side of the protrusion.
A method for manufacturing a bonded structure.

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