Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/28—Shaping operations therefor
  • B29C70/40—Shaping or impregnating by compression not applied
  • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
  • B29C70/44—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding
  • B29C70/446—Moulding structures having an axis of symmetry or at least one channel, e.g. tubular structures, frames
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2023/00—Tubular articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2031/00—Other particular articles
  • B29L2031/30—Vehicles, e.g. ships or aircraft, or body parts thereof

Definitions

• the present invention can be implemented in connection with the moulding of plastic components which comprise reinforced plastic.
• the plastic components in question are hollow or comprise a porous core and are referred to, 5 in accordance with the invention, by the expression hollow bodies.
• the invention relates to an arrangement for the moulding of hollow bodies which comprise reinforced plastic, in 0 accordance with the pre-characterizing clause of Patent Claim 1 which follows.
• the arrangement in this case comprises a flexible pressure membrane and a preformed core which is self-supporting.
• the invention also relates to a method for the moulding of hollow bodies using an arrangement according to the invention, and to a hollow body which has been manufactured according to the method.
• the invention can be applied within many different areas where there is a need for hollow bodies or other similar components which comprise reinforced plastic. Such applications exist, for example, within the area of the manufacture of vehicle components made of reinforced 5 plastic. Particularly preferred applications which may be mentioned are the use of hollow bodies according to the invention for load-bearing elements, for example pillars or beams in motor vehicles.
• the pressure bag method involves placing reinforcement material in the form of cut-out bits of fabric, netting,
• SMC or preformed glass-fibre reinforcement in a two-part mould A pressure bag or the like made of a soft, flexible material is placed inside the mould, within the reinforcement material, after which the mould halves are closed. Matrix material in the form of hardening-in- itiated polyester resin is then injected into the mould in order to impregnate the reinforcement material, the pressure bag being subjected to a pressure of the order of 0.5 - 1 MPa. In this way the reinforcement material, which is now impregnated with hardening matrix material, is pressed against the inside of the mould. After the matrix material has hardened sufficiently, the mould halves are opened and the hollow body of glass-fibre- reinforced polyester plastic is removed.
• a modified variant of the pressure bag method is used in the manufacture of elongate hollow bodies such as masts and flagpoles.
• the reinforcement material is cut up and placed on a foil which will serve both as an external mould and as a release layer.
• a bladder of soft and flexible material is placed on top of the reinforcement material, which bladder, in the inflated state, will have approximately the internal dimensions of the finished product.
• the bladder is then subjected to a low pressure, at the same time as the reinforcement material is folded round the inflated bladder and is fixed in this position. It can be fixed with the aid of clamping rulers or the like.
• Polymerization-initiated polyester resin with hardener, or other similar hardenable matrix material is then poured into the "mould" which is formed between the folded-round foil on the outside and the inflated bladder on the inside, the reinforcement material being impregna- ted with the matrix material.
• the "mould” is kept in this state until the matrix material has hardened sufficiently to allow mould release.
• Another known manufacturing process for components made of reinforced plastic involves using a core of expanding thermoplastic.
• This process is mainly suitable for the manufacture of smaller components such as guitar necks and canoe paddles.
• reinforcement materi- al is placed in a two-part mould, after which a core of hot-expanding thermoplastic is placed inside the reinforcement material, the mould halves are pressed together and at the same time are heated, the thermoplastic expanding and filling out the cavity inside the mould at the same time as the melted thermoplastic impregnates the reinforcement material.
• a plastic component is obtained having a core of expanded thermoplastic with reinforcement material enclosed in the matrix material on the surfaces of the component.
• hollow bodies can be manufactured using solid cores which can either be removed or can remain as a permanent part of the finished plastic component.
• This process can also be used for manufacturing hollow bodies made of reinforced plastic, in which case the reinforcement material is applied to the core in the form of a finish-woven stocking which is passed over the core or in the form of cut- up bits of reinforcement material which are draped around the core, after which core and reinforcement material are placed inside an open moulding tool, which is then closed around the core and reinforcement material.
• a hardening- initiated polyester resin or the like is then injected under pressure as matrix material into the moulding tool, fixed in the closed position, in order to impregnate the reinforcement material.
• the matrix material can also be sucked in by vacuum or by a combination of pressure and vacuum.
• RTM Resin Transfer Moulding
• polyurethane cellular plastic are the most commonly used material for permanent cores in RTM.
• removable cores possible materials are wax, paraffin, sand with binder, and metal alloys with low melting point.
• a further previously disclosed manufacturing process for simpler hollow bodies of reinforced plastic is so-called winding.
• rigid hollow bodies can be used as a permanent core, and resin-impregnated reinforcement material in the form of so-called roving or fabric is wound around the core in a defined pattern and is thereafter hardened.
• Solid cores of a conventional type certainly provide an excellent support for application of reinforcement material, but they require that the pressure force is applied from the outside. This can complicate the moulding tool design and the manufacturing process. Processes which use conventional solid cores can also cause problems in terms of the fact that the reinforcement material is not pressed in satisfactory contact with the internal walls of the moulding tool.
• the first object of the present invention is to make available an arrangement intended to be used in the moulding of hollow bodies comprising reinforced plastic, which arrangement eliminates the afore-mentioned difficulties which may be experienced with the prior art.
• the arrangement comprises a preformed core which is self-supporting, a material charge, and a two-part moulding tool, and that the arrangement additionally comprises a flexible pressure membrane, a pressurizing attachment and a pressurizing means, and that the pressure membrane is in this case adapted to be able to surround the preformed core at the same time as the material charge is applied to the outside of the pressure membrane, and that the pressurizing means is arranged to subject the pressure membrane to an internal pressure via the pressurizing attachment when the moulding tool is in a closed state.
• the second object of the present invention is to make available a method for the moulding of hollow bodies which comprise reinforced plastic, the method utilizing the arrangement according to the invention.
• the method comprises using a preformed core which is self-support- ing, a material charge, and a two-part moulding tool, and that the method in this case comprises applying a flexible pressure membrane round the outside of the preformed core, thereafter applying the material charge on the outside of the pressure membrane in order to form a blank for moulding of a hollow body, introducing the blank into the moulding tool in an open position, in order thereafter to bring the moulding tool into a closed position around the blank, and applying an internal pressure to the pressure membrane of the blank located inside the moulding tool in its closed position, and then moulding and consolidating the material charge.
• a third object of the present invention is to make available a hollow body with a high degree of stiffness and load-bearing capacity, which has been produced by the method according to the invention and using the arrangement according to the invention.
• the hollow body comprises a first layer with a reinforcement material and a matrix material, and that most of the reinforcement fibres included in the reinforcement material follow the direction of stress of the loads which the hollow body is expected to be exposed to when taking up loads.
• Fig. 1 is a diagrammatic representation of a method which uses an arrangement according to the invention for moulding a hollow body
• Fig. 2 shows diagrammatically, in constituent figures
• the arrangement according to the invention comprises a preformed core 1, 1', 1'' which is self-supporting.
• the core 1, 1', 1'' consists of a porous material.
• the arrangement according to the invention further comprises a material charge 3, 3', and a two-part moulding tool 8.
• the arrangement in the first embodiment comprises a flexible pressure membrane 2, 2', a pressurizing attachment 12 and a pressurizing means 13, the pressure membrane 2' being adapted to be able to enclose the preformed core 1 ' at the same time as the material charge 3 ' is applied to the outside of the pressure membrane 2 ' .
• the pressurizing means 13 in the described embodiment is designed to be able to subject the pressure membrane to an internal pressure via the pressurizing attachment 12, and via the porous core 1 ' , when the moulding tool 8 is in a closed position.
• the preformed core 1, 1', 1'' which is self-supporting, consists of a porous foam core of polyurethane foam.
• the preformed core 1, 1', 1'' can, however, be made of other materials, for example using manufacturing methods familiar to those skilled in the art for the manufacture of components of foamed plastic or cellular plastic, as long as the core 1, 1', 1'' provides sufficient stiffness and other suitable properties for the application.
• the choice of material for the core 1, 1', 1'' is also relatively flexible.
• the core 1, 1', 1'' is preferably manufactured using a porous material in order to facilitate pressurization.
• the external dimensions of the preformed core 1, 1', 1'' are slightly smaller than the internal dimensions of the cavity (not shown) in the two-part moulding tool 8 in which the moulding is to take place, i.e. slightly smaller than the external dimensions of the finished hollow body 16.
• the external dimensions of the preformed core 1, 1', 1' ' are about 5 mm smaller than the internal cavity (not shown) of the moulding tool 8, i.e. with a 5 mm offset.
• This offset is adapted, however, on the basis of the thickness of the material charge 3, 3' and other process conditions, for example the nature of the pressure membrane 2, 2' and the shape of the hollow body 16 which is to be moulded.
• the preformed core 1, 1', 1'' which is used in the invention thus has a shape which essentially matches the shape of the internal cavity of the aforementioned moulding tool 8, and thus also the shape of the hollow body 16 which is to be moulded.
• the pressure membrane 2, 2' consists of a thin, flexible foil of polyamide plastic, nylon 6-66, in the form of a bag.
• the pressure membrane 2, 2' can be used for many other materials as long as the material provides sufficient flexibility and stretchability and is able to function as a non-permeable membrane for the pressure medium which is to be used for pressurizing the pressure membrane 2, 2'.
• the material thickness of the pressure membrane 2, 2' can vary depending on the application, for example depending on the shape of the hollow body 16 which is to be moulded.
• the pressure membrane 2 is intended to be applied to the outside of the preformed core 1 in such a way that it essentially surrounds the latter.
• the pressure membrane 2 is in the form of a bag with a closed "bottom" and an open end. This allows the pressure membrane 2 ' to be passed over the preformed core 1 ' and allows the pressure membrane 2 ' , with its surrounding material charge 3 ' , to be pressurized internally via a pressurizing attachment 12 which runs through one end wall of the moulding tool 8.
• the moulding tool 8 is fixed in a closed position around the preformed core 1' with surrounding pressure membrane 2 ' and material charge 3 ' , the internal pressure delivered via the pressurizing attachment 12 being conveyed onwards to all areas in the pressure membrane 2' via the preformed core 1', since the latter is of course porous in the described embodiment.
• one end of the tubular pressurizing attachment 12 is secured to the open end of the bag-like pressure membrane 2, 2' with the aid of a tape or the like, so that a sufficiently tight connection is obtained to permit pressurizing of the pressure membrane 2, 2'.
• the other end of the pressurizing attachment 12 is passed through a hole in one end wall 14 of the moulding tool 8 and, with the aid of a coupling arrangement according to the prior art, is connected to the pressurizing means 13 via a pressure line.
• the pressure membrane 2, 2' can be designed in many different ways.
• pressure membranes which are in the form of a bag with a valve prepared in the "bottom" of the bag, and an open end which is used to draw the bag onto a porous core.
• the open end of the pressure membrane is in this case sealed at one "end wall" of the porous core in a suitable manner, for example by means of a tape or by heat sealing or the like.
• a great many different types of connections and seals according to the prior art can be used, all of which permit pressurization of the pressure membrane 2, 2 ' in implementing the invention.
• the material charge 3, 3' comprises both reinforcement material and a thermoplastic matrix material.
• the material charge 3 comprises approximately 50% by volume of continuous glass fibre as reinforcement material and 50% by volume of thermoplastic polyester fibres as matrix material.
• the contents of reinforcement material and matrix material can, however, be varied within wide limits depending on the application. However, the content of reinforcement material is preferably in the range of 25 to 60 % by volume.
• the material in the material charge 3, 3' consists of an inner layer which faces the pressure membrane and an outer layer which, during moulding, faces the internal surfaces of the moulding tool.
• the inner layer (not shown in detail) of the material charge 3, 3' consists of a warp knit fabric in which the fibres in one direction consist of so-called hybrid yarns of continuous glass fibres and continuous polyester fibres, while the fibres in the other direction consist only of continuous polyester fibres.
• a sheet or piece of the warp knit fabric material is wound around the preformed core 1, 1' and is fixed with tape, yarn ends or other fixing means 6 so that the hybrid yarn and thus the continuous reinforcement fibres essentially follow the longitudinal direction of the finished hollow body 16 and thus form angles of almost 0° to the said longitudinal direction.
• an outer layer (not shown in detail) of braided material consisting of the same type of hybrid yarn as in the inner layer.
• the braiding is advantageously carried out directly on the preformed core 1 ' with the surrounding pressure membrane 2 ' , and the inner layer of reinforcement materi- al (not shown) surrounding the pressure membrane.
• the braiding can be carried out, for example, using a braiding machine according to the state of the art, of the type which is still used, for example, in the manufacture of braided shoelaces.
• the effect of the braiding is that the hybrid yarn and thus also the reinforcement fibres in the described embodiment will form angles of between approximately 20 and 70° in relation to the longitudinal direction of the finished hollow body 16.
• the material charge 3, 3' is partly in the form of a first layer of warp knit fabric which is draped around the pressure membrane 2 ' surrounding the preformed core, and partly in the form of a second layer which is braided on top of the first layer.
• the material charge 3, 3' to be provided in the form of a nonwoven sheet or the like, with suitable structure and composition, which is draped around the porous core 1 ' with its surrounding pressure membrane 2 ' .
• that layer of the material charge 3, 3' which, during moulding, is intended to be in contact with the internal surfaces of the moulding tool 8 can be designed as a release layer, i.e. a layer with low adhesion to the surfaces of the moulding tool. This can be done by modifying the chemical composition of the outermost layer, for example by using fibres or filaments of a chemically inert material in the outermost layer.
• Embodiments are also possible in which the material charge 3, 3' consists of more than two layers.
• the abovementioned structures of the material charge 3, 3' and the stated angles should only be seen as approximate indications intended to facilitate the skilled person's appreciation of the invention.
• many other embodi- ments are conceivable within the scope of the invention.
• a typical feature of preferred embodiments of hollow bodies according to the invention is that most of the reinforcement fibres included in the material charge run in the direction of stressing of the loads which are expected to occur on the finished hollow body during its use, and that the reinforcement fibres are continuous.
• the two-part moulding tool 8 which is included in the arrangement according to the invention can be of a construction familiar to the skilled person, comprising at least two mould halves 9 , 9 ' , and some form of movement means (not shown) functioning for example by pneumatics or hydraulics, which are provided in a known manner to be able to move the moulding tool 8 both in an open position (not shown) and in a closed, fixed position (shown in Fig. 1 ) .
• the two-part moulding tool 8 has two mould halves 9 and 9', with a pressurizing attachment 12 running through the end wall 14 of one half 9' .
• the internal surfaces of the moulding tool 8 can be treated to give a release effect on contact with a material charge.
• This so-called non-stick treatment can consist, for example, of a plasma coating with Teflon or the like.
• a pressurizing means 13 is arranged to be connected in a suitable way to the pressurizing attachment 12 which, in the described embodiment, conveys the pressure created by the pressurizing means 13 onwards to the inside of the pressure membrane.
• the pressurizing means 13 is a compressed-air compressor according to the prior art.
• the pressurizing means 13 can also consist, for example, of an oil pump or of a device which generates high-pressure steam.
• the internal pressurizing of the pressure membrane can take place both pneumatically and hydraulically.
• the choice of pressurizing method can influence the choice of material for the pressure membrane 2, 2', which must of course be essentially non-permeable to the pressurizing medium which is used.
• the choice of material for the porous core 1, 1', 1'' may also to some extent be influenced by the pressurizing method chosen.
• a flexible pressure membrane 2 is engaged over a preformed core 1 which is self-supporting.
• a material charge 3 is applied on the outside of the flexible pressure membrane 2 and the preformed core 1 so as to form 4 a blank 5 for moulding a hollow body 16.
• the material charge has a structure in accordance with what has already been described above.
• the core 1, 1' Since the core 1, 1' is self-supporting, it constitutes a stable support for application of the pressure membrane 2, 2' and the material charge 3, 3' thereon. Since the core 1, 1' is additionally preformed in a shape which essentially matches the shape of the hollow body 16 to be moulded, and matches the internal dimensions of the moulding tool 8, an even distribution of the material charge 3, 3' in different areas of the walls in the finished hollow body 16 is ensured. In addition, it is possible to control to some extent the material thickness in different wall areas of the moulded hollow body 16.
• the application of the pressure membrane 2 and of the material charge 3 onto the preformed core 1 is done essentially manually, but it is entirely possible to achieve a fairly high degree of automation of these stages using techniques familiar to the skilled person.
• the material charge 3' applied to the outside of the preformed core 1 ' with its surrounding pressure membrane 2 ' , forms a blank 5 for moulding a hollow body 16.
• the blank 5 is placed inside a two-part moulding tool 8 which is in an open position (not shown).
• the tool parts or mould halves 9, 9' of the moulding tool 8 are then closed 7 around the blank 5 and are locked in the closed position (as shown in Fig. 1).
• the pressurizing attachment 12 is connected to the pressurizing means 13, and the pressure membrane 2' is pressurized internally by means of the fact that the pressure membrane 2' communicates with the pressurizing means 13 via the pressurizing attachment 12.
• the pressure membrane 2' is pressurized internally to about 2 bar overpressure.
• the internal walls of the moulding tool 8 are heated with the aid of heating members 11 which, in the described first embodiment, function with hot oil which is circulated through channels inside the walls of the moulding tool 8.
• the reason for carrying out the first pressurization stage in the described embodiment is to counteract the shrinkage which often occurs in the thermoplastic matrix material near the glass transition temperature of the polyester.
• the pressurization is carried out with the full moulding pressure being applied from the start of the heating phase and being maintained at this level till moulding and consolidation of the material charge have taken place.
• the heating is carried out by means of heating members 11 in the walls of the moulding tool 8, but embodiments of the invention are also conceivable in which the heating of the material charge 3 ' is carried out before the blank 5 is placed in the moulding tool 8.
• the circulation of oil for heating the heating member 11 is provided by means of an oil pump (not shown) appropriate for this purpose.
• the oil is heated using an external device (not shown) comprising electrical resistors for heating.
• the external device (not shown) in this case also comprises cooling members for cooling the circulated oil.
• these cooling members (not shown) consist of tubular coils for cold water circulation which are immersed in the oil.
• moulding tool prefferably heated using superheated steam or another medium, or for the cooling to be able to take place in a suitable way other than that described here.
• the internal walls of the moulding tool 8 and the material charge 3 ' inside the moulding tool 8 are heated, with the aid of the heating member 11, to the softening temperature of the thermo- plastic matrix material, which softening point is approximately 250°C in the described embodiment.
• the in- ternal pressure inside the pressure membrane 2' is increased to approximately 6 bar and is maintained at this level for approximately 5 minutes.
• thermoplastic matrix material of the material charge 3' melts, and this material charge 3', by virtue of the internal pressure in the pressure membrane 2' lying to the inside of it, is pressed into tight contact against the internal walls of the moulding tool 8, locked in a closed position, and is then consoli- dated and moulded to the outer shape matching the shape of the internal walls of the moulding tool 8.
• the pressurization of the pressure membrane ensures that air bubbles which may have become enclosed in the material charge 3' are removed.
• the moulding tool 8 After this moulding process, the moulding tool 8, and thus also the material charge 3 ' , are cooled to a tempe- rature near to ambient temperature using the previously mentioned cooling members of the oil circulation (not shown) .
• the core 1'' is removed from the hollow body 16. This has been indicated on attached Fig. 1 which shows a moulded hollow body 16 with a partly removed core 1 ' ' .
• the latter can be left in place as a more or less integral part of the moulded hollow body 16.
• polyurethane foam or the like can advantageously be injected into the gap which has formed between the core and the pressure membrane during moulding in order to prevent the partially loosened core from "rattling" in the finished hollow body.
• the hollow body 16 can be worked in different ways according to the state of the art, for example by cutting off end pieces, by external grinding or painting.
• thermo-plastic matrix material which constitutes an integrated part of the material charge which is used.
• the material charge 3, 3' essentially comprises only reinforcement material, while a hardenable matrix material is delivered to the closed moulding tool by means of an injection member 10 (Fig. 1) provided for this purpose, in order to impregnate the reinforcement material.
• the second embodiment may be said to be similar to the RTM technique to some extent, but with the fundamental difference that a moulding pressure, according to the present invention, is applied from the inside with the aid of the pressure membrane 2 ' arranged on the preformed core 1 ' and lying to the inside of the material charge 3'.
• the material charge 3, 3' consists of a similar textile material as in the first embodiment, but with the difference that the thermoplastic matrix material is omitted and the material charge therefore essentially only comprises continuous reinforcement fibres.
• the hardenable matrix material consists of hardenable vinyl ester resin, although many other matrix materials of the type used for conventional RTM techniques are conceivable.
• the matrix material is injected in hardening-initiated form, but embodiments of the invention are also conceivable in which the initiation takes place inside the moulding tool.
• the second preferred embodiment of the invention affords considerable advantages over the prior art. Apart from the advantages of the invention which have already become apparent, mention may be made of the fact that in the second embodiment of the invention, because the porous core 1, 1', 1'' is made considerably smaller than the internal cavity of the moulding tool 8, it is possible to facilitate the impregnation of the reinforcement material with injected matrix material and thereby to shorten the process time.
• the various process parameters are adjusted according to the requirements of the embodiment. Such adjustments can be made by the skilled person on the basis of the present description and with the knowledge of conventional RTM techniques.
• Fig. 2A shows a diagrammatic transverse section of an area of a hollow body according to the invention
• Figure 2B shows a diagrammatic longitudinal section, seen from the side of the same hollow body, in a similar area to Fig. 2A.
• the hollow body shown in Figures 2A and 2B is of a type in which the porous core is left in place.
• the hollow body 20 is intended to be used for a load-bearing element, more especially a load-bearing pillar in a motor vehicle with low weight.
• the hollow body 20 comprises, from the outside inwards, a first layer of reinforced plastic 21, 21' which comprises reinforcement material and binding thermoplastic matrix material, two strengthening elements 24 and 25, a second layer 22, 22' originating from the previously discussed pressure membrane, and a porous core 23.
• the strengthening elements 24, 25 are intended to provide strengthening when, for example, mounting door hinges and the like on the hollow body 20 with the aid of a screw 26 (indicated by dashed lines).
• the strengthening elements 24, 25 advantageously consist of carbon fibre-reinforced epoxy plates which have been inlaid, on the outside of the pressure membrane 22, 22', in recesses in the porous core 23 prior to moulding. After moulding, the strengthening elements 24, 25 constitute integrated parts of the hollow body 20 which, in the described embodiment, is of course intended for a load-bearing pillar of composite material for a motor vehicle.
• the material charge of the hollow body in the described embodiment has the structure and composition already described, with an inner layer of warp knit fabric of hybrid yarn and an outer layer of braided hybrid yarn.
• thermoplastic matrix material i.e. polyester filaments of the hybrid yarn
• the thermoplastic matrix material has melted in order to form a contiguous matrix material in the finished hollow body 20.
• Reinforcement material containing continuous fibres has been found to be most advantageous for use in hollow bodies according to the invention which are intended to be used in load-bearing structures, for example in load- bearing pillars or beams for motor vehicles.
• the reinforcement material included in the matrix material does not of course have to be in the form of a material with a warp knit fabric layer and a braided layer of hybrid yarn, and instead it can be in many different forms, as long as most of the reinforcement fibres follow the stressing direction of the loads which may occur on the finished hollow body.
• the reinforcement material can also be in the form of roving, in the form of a nonwoven material or in the form of individual reinforcement fibres. It is also possible to use different types of reinforcement which have been preformed, for example by blowing or injecting reinforcement fibres onto preforming screens or the like.
• continuous reinforcement fibres are preferred for implementing the invention.
• the fibre dimensions can also vary within a very wide range depending on the application.
• the reinforcement material need not necessarily consist of glass fibre, and instead it can consist of any suitable fibre which has, or can be given, sufficiently great adhesion and wettability to the matrix material used, and which is able to confer the desired properties on the finished hollow body.
• the reinforcement fibres or the reinforcement material can be exposed to different chemical or physical treatment methods.
• Examples of such methods are oxidation with chemical oxidizing agents, corona treatment and plasma treatment.
• the application of a material charge or of a reinforcement material need not be carried out by manually by draping and fixing a woven fabric or a nonwoven sheet round the porous core with its surrounding pressure membrane, but can instead also be done, for example, by winding a roving of reinforcement material or a woven fabric of reinforcement material round the core and the pressure membrane.
• the matrix material included in the material charge can, in the case of thermoplastic matrix material, be chosen from a large number of thermoplastic polymers, as long as their softening point lies at a suitable level.
• Suitable level means that the softening point should lie at a sufficiently high level to satisfy the heat resistance requirements placed on the finished hollow body, and at the same time at a sufficiently low level to ensure realistic melting in an industrial manufacturing process.
• polymers which may satisfy these requirements and which also entail a realistic price are thermoplastic polyester and polypropylene, but there are many other possible polymers suitable for use as matrix material in implementing the invention.
• thermosetting plastics are polyester, vinyl ester and epoxy.
• flame retardants for example flame retardants, UV stabilizers and colouring pigments.
• Such addition is preferably carried out before the hardenable matrix material is added to the reinforcement material, although it can also take place inside the moulding tool.
• thermoplastic matrix material it is also possible to provide various additives in the matrix material, for example colouring pigments.

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• Composite Materials (AREA)
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• Casting Or Compression Moulding Of Plastics Or The Like (AREA)

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Cited By (16)

Citations (6)

• 1997
  • 1997-05-12 SE SE9701755A patent/SE509503C2/sv unknown
• 1998
  • 1998-04-28 WO PCT/SE1998/000770 patent/WO1998051481A1/sv active Application Filing

Patent Citations (6)

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