SE509503C2 - Arrangement, procedure and hollow body when forming plastic parts - Google Patents

Abstract

The 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, 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. 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 moulded according to the method. The invention can be applied within many different areas where there is a need for hollow bodies which comprise reinforced plastic, for example within the area of the manufacture of vehicle components made of reinforced plastic. Among particularly preferred applications, there is the use of hollow bodies according to the invention for load-bearing elements, such as pillars and beams in motor vehicles.

Description

15 20 25 30 35 509 503 2 manufacture of hollow reinforced plastic parts in. Large series. The printing bag method involves placing reinforcing material in the form of cut pieces of fabric, mat, SMC or preformed glass fiber reinforcement in a two-part mold. Inside the mold, a pressure bag or the like of a soft, flexible material is placed, inside the reinforcing material, after which the mold halves are brought together. Thereafter, matrix material in the form of curing-initiated ester resin is injected into the mold to impregnate the reinforcing material, the pressure bag being pressurized with a pressure of the order of 0.5 - 1 MPa. Thereby, the reinforcing material, which is now impregnated with hardening matrix material, is pressed against the mold. After a sufficient matrix material has been made, the mold halves and the hollow body of fiberglass-reinforced polyester plastic are removed. inside. hardening of openings A modified variant of the pressure bag method is used in the manufacture of elongated hollow bodies such as masts and flagpoles. The reinforcing material is then cut or cut and placed on a foil which will serve both as an external shape and as a release layer. On top of the reinforcement material, a bladder of soft and flexible material is placed, which in an inflated condition will approximately have the inner dimensions of the finished product.

Then the bladder is put under a slight pressure at the same time as the reinforcing material is folded around the inflated bladder and fixed in this position. The fixation can be done with the help of clamping rulers or the like. Polymerization-initiated ester resin with hardener, or other similar curable matrix material, is then poured into the "mold" formed between the folded foil on the outside and the inflated bladder on the inside, the reinforcing material being impregnated with the matrix material. The "shape" is maintained in this position until sufficient curing of the matrix material has been achieved for demolding to take place. Another known manufacturing process for reinforced plastic parts involves the use of a core of expanding thermoplastic. This process is mainly suitable for the manufacture of minor details such as guitar necks and canoe paddles. In this process, reinforcing material is placed in a split mold, after which a core of the heat-expanding thermoplastic is placed inside the reinforcing material, the mold halves are compressed while heating, the thermoplastic expanding and filling the cavity inside the mold while the molten thermoplastic impregnates the reinforcing material. After cooling, a plastic part is obtained with a core of expanded thermoplastic with reinforcing material enclosed in the matrix material at the surfaces of the part.

Through a previously known hollow bodies are manufactured using rigid cores, which other forming process can either be removable or remain as a permanent part of the finished plastic part. This process can also be used to make hollow bodies of reinforced plastic, the reinforcing material being applied to the core in the form of a pre-woven sock which is threaded over the core or in the form of cut pieces of reinforcing material draped around the core, after which the core and reinforcing material are placed inside an open mold. then closes around the core and reinforcement material. Thereafter, under pressure, a curing-initiated ester resin matrix material is injected into the closed-end mold, or the like as to impregnate the reinforcement material. The matrix material can also be sucked in by means of a vacuum or by a combination of pressure and vacuum.

This previously known process type is called Resin Transfer Molding or RTM molding. The most common material for permanent cores in RTM molding is different types of urethane foam. In the case of materials for removable cores, there may be mentioned wax, paraffin, sand with binder, and metal alloys with low melting point.

Another previously known manufacturing process for simpler hollow bodies of reinforced plastic is so-called winding.

In this process, rigid hollow bodies can be used as a permanent core, whereby resin-impregnated reinforcing material in the form of so-called roving or fabric is wound around the core in a defined pattern and then cured.

The previously known manufacturing processes for manufacturing hollow bodies of reinforced plastic can be perceived to have certain disadvantages.

In manufacturing processes using an inflatable hose, bladder, or the like as a soft membrane and as a "core", the application of reinforcing material outside the core may be perceived as cumbersome, since the "core" does not provide a stable support when the reinforcing material is applied thereto.

Processes that utilize cores of expanding thermoplastic often produce expensive end products and can, in applications where low weight is significant, cause problems with overweight of the end product compared to hollow hollow bodies.

Solid cores of the conventional type certainly offer an excellent support when applying reinforcement material, which requires that the pressing pressure during the forming is applied from the outside.

This can process the effect. complicating the tool design and processes Processes that use conventional solid cores can also cause problems with the reinforcing material not being pressed into full contact with the inner walls of the mold tool. SUMMARY OF THE INVENTION: Thus, the present invention has as its first object to provide an arrangement, intended for use in forming hollow bodies comprising reinforced plastic, which eliminates the previously mentioned difficulties which may be experienced with known technique.

This first object of the invention is achieved in that the arrangement, according to the following claim 1, comprises a preformed core which, is self-supporting, a material set, and a divisible molding tool, and that flexible pressurizing connection and an arrangement therefrom comprises a pressurizing membrane, a pressurizing means, and the pressurizing membrane is adapted to be able to enclose the preformed core at the same time as the material set is applied to the outside of the pressure membrane, and that the pressurizing means is arranged to pressurize the pressurizing connection when the mold is in an internal pressure membrane via the closed position.

Furthermore, the present invention has as its second object to provide a method of forming hollow bodies comprising reinforced plastic, the method utilizing the arrangement according to the invention.

This is achieved, claim 11, in that the method comprises using another object of the invention according to a preformed core which is self-supporting, a set of material, and a divisible molding tool, and that the method thereby comprises flexible pressure membrane on top of the preformed core, then subsequently applying a applying the batch of material to the outside of the pressure membrane to form a blank for forming a hollow body, to insert the blank into the mold tool in an open position and then to bring the mold tool into a closed position around the blank, and to pressurize the internal pressure of the pressure membrane internally of the blank located inside the forming tool in its closed position, to thereby shape and consolidate the material set.

Finally, the present invention has as its third object to provide a hollow body with high rigidity and load-bearing capacity produced by the method according to the invention, and using the arrangement according to the invention.

This third object of the invention is achieved, according to claim 20, in that the hollow body comprises a first layer with a reinforcing material and a matrix material, and that the main part of the reinforcing fibers contained in the reinforcing material follows the stress direction of the loads the hollow body is expected to be subjected to when loading. .

DESCRIPTION OF THE DRAWINGS: The invention will be described in the following with reference to the accompanying drawings, in which Fig. 1 schematically shows a method which utilizes an arrangement according to the invention to form a hollow body, and Fig. 2 schematically in sub-figures 2A and 2B shows two different sectional views of a hollow body according to the invention, wherein 2A shows a cross section and 2B a longitudinal section.

Before-: DRAWN Urrönmcsrommn: 10 15 20 25 30 35 505? 505, P 7 In a first preferred embodiment, the arrangement according to the invention comprises a preformed core 1, 1 ', 1 ", which is self-supporting. In the described embodiment the core 1, 1', 1" consists of a porous material. Furthermore, according to the invention, the arrangement comprises material set 3, 3 ', and a divisible forming tool 8.

In addition, the arrangement in the first embodiment comprises a flexible pressure membrane 2, 2 ', a pressurizing connection 12, the pressure membrane 2' being adapted to be able to enclose the preformed core 1 'while the sonar material set 3' is applied to the outside of the pressure membrane 2 '.

The pressurizing means 13 is in the described embodiment arranged to be able to pressurize the internal pressure membrane internally via the pressurizing connection 12, and via the porous core 1 ', when the forming tool 8 is in a closed position.

The preformed core 1, 1 ', 1 ", which is self-supporting, consists in the first embodiment of a porous foam core of polyurethane foam.

However, the preformed core 1, 1 ', 1 "can be made of other materials, for example by methods well known to those skilled in the art for foam or cellular plastic parts, as long as the core 1, 1', 1" offers sufficient rigidity and otherwise suitable properties for application. Thus, the choice of material for the core 1, 1 ', 1 "is also relatively flexible. However, the core 1, 1', 1" is preferably made of a porous material to facilitate pressurization.

The outer dimensions of the preformed core 1, 1 ', 1 "are made slightly smaller than the internal dimensions of the cavity (not shown) in the divisible mold tool 8 where the molding is to take place, i.e. slightly smaller than the finished mold. the outer dimensions of the hollow body 16.

In the embodiment described here, the outer dimensions of the preformed core 1, 1 ', 1 "are made about 5 mm smaller than the internal cavity (not shown) of the forming tool 8, i.e. with 5 m" offset ". However, this so-called "offset" is adapted based on the thickness of the material set 3, 3 'and other process conditions, for example the nature of the pressure membrane 2, 2', and the shape of the hollow body 16 to be formed.

The preformed core 1, 1 ', 1 "used in the invention thus has a shape which substantially adheres to the shape of the internal cavity of the previously mentioned mold tool 8, and thereby also to the shape of the hollow body 16 to be formed.

The pressure membrane 2, 2 'consists in the described embodiment of one of a thin, flexible foil of polyamide plastic, nylon 6-66, in the form of a bag.

However, many other materials are conceivable for use in the pressure membrane 2, 2 'as long as the soul material offers sufficient flexibility and extensibility, and is able to function as a non-permeable membrane for the pressurizing medium to be used in pressurizing the pressure membrane 2, 2'. Likewise, 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 to be formed.

The pressure membrane 2 is intended to be applied to the outside of the preformed core 1 so that it substantially encloses it.

In the described embodiment, the pressure membrane 2 is in the form of a bag with a closed "bottom" and an open end. This enables the pressure membrane 2 'to be stepped on the outside of the preformed core 1' and that the pressure membrane 2 'with its enclosing material set 3' is pressurized internally via a pressurizing connection 12 which runs through one end of the mold tool 8.

During molding, the molding tool 8 is fixed in a closed position around the preformed core 1 'with enclosing pressure membrane 2' and material set 3 ', the internal pressure supplied' via the pressurizing connection 12 being passed to all areas inside the pressure membrane 2 'via the preformed core 1'. since this is of course porous in the described embodiment.

However, embodiments are also conceivable in which the preformed core 1, 1 ', 1 "is not porous. In such cases the pressure distribution takes place entirely via the space between the core 1' and the pressure membrane 2 '.

In the described embodiment, one end of the tubular pressurizing connection 12 is attached to the open end of the "bag-shaped" pressure membrane 2, 2 'by means of a tape or the like, so that a sufficiently tight connection is obtained to enable pressurization of the pressure membrane 2, 2 '. The pressurizing connection 12 is threaded through a hole at the other end of one end 14 of the molding tool 8 and is connected by means of a coupling according to the prior art via a pressure line to the pressurizing means 13.

The pressure membrane 2, 2 'can, however, be designed in many different ways.

Thus, it is possible to use a pressure membrane which has the shape of a sack with a prepared valve in the "bottom" of the sack, and an open end which is used to be able to pull the sack on top of the porous core, thereby closing the open end of the pressure diaphragm at one the "end" of the porous core in a suitable manner, for example by means of a tape or by heat sealing or the like. A large number of different types of connections and seals according to the prior art are conceivable which enable all pressurization of the pressure diaphragm 2, 2 'in the practice of the invention.

The material set 3, 3 'according to the first embodiment of the invention comprises both reinforcement material and a thermoplastic matrix material.

In the first embodiment, the material set 3 comprises approximately 50% by volume of continuous glass fiber as reinforcement material and 50% by volume of thermoplastic polyester fibers as matrix material. However, the levels of reinforcement material and matrix material can be varied within the level, preferably within wide limits depending on the application. reinforcement material, however, is in the range of 25 to 60% by volume.

The material in the material set 3, 3 'in the described embodiment consists of an inner layer facing the pressure membrane and an outer layer which, when molded, faces the inner surfaces of the forming tool.

The inner layer (not shown in detail) of the material batch 3, 3 'consists in the first embodiment of a warp knit, in which the fibers in one direction consist of so-called hybrid yarns of continuous glass fibers and continuous polyester fibers, respectively, while the fibers in the other direction only consists of continuous polyester fibers.

In the described embodiment, a seam or piece of the warp knit material is wound around the preformed core 1, 1 'and thereby fixed with tape, yarn stubs or other fixing means 6 so that the hybrid yarn, and thereby the continuous reinforcing fibers, essentially follows the 509 503 11 the longitudinal direction of the finished hollow body 16 and thus form angles in the vicinity of 0 ° compared with said longitudinal direction.

On the outside of this inner layer of the material batch then follows in the described embodiment 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 advantageously takes place directly on the preformed core 1 'with the pressure membrane 2', and the pressure membrane enclosing the inner layer of reinforcing material enclosing (not shown). In this case, the braiding can be effected, for example, by means of a braiding device according to a long-known technique, of the type which is still used, for example, in the manufacture of braided shoelaces. In the described embodiment, the braiding has the consequence that the hybrid yarn and thus also the reinforcing fibers in the described embodiment will form angles between approximately 20 and 70 ° in relation to the longitudinal direction of the finished hollow body 16.

The material set 3, 3 'is thus provided in the first embodiment partly in the form of a first layer of warp knit which is draped around the pressure membrane 2' enclosing the preformed core, partly in the form of a second layer which is braided on top of the first layer.

It is also conceivable that the material set 3, 3 'is provided in the form of a nonwoven sheet or the like, with a suitable structure and composition, which is draped around the porous core 1' with its pressure membrane 2 '.

If desired, the layer of the material set 3, 3 'which during the molding is intended to be in contact with can be designed as a release layer 10, 20 20 25 30 35 509 503 12 of the mold tool, i.e. a layer of low adhesion to the surfaces of the mold tool. This can be done by modifying the chemical composition of the outermost layer, for example by using fibers or filaments of a chemically inert material in the outermost layer.

Embodiments are also conceivable where the material set 3, 3 'consists of more than two layers. the structures of the material set 3, 3 'and the angles indicated above, should only be seen as approximate indications make it easy for a person skilled in the art to understand. Thus, many other embodiments are intended for the invention. conceivable within the scope of the invention.

Typical of preferred embodiments of hollow bodies according to the invention. is that the main part. of the reinforcing fibers included in the material set run in the tension direction for the loads that are expected to occur on the finished hollow body in its use, and that the reinforcing fibers are continuous.

The divisible mold tool 8 included in the arrangement according to the invention can have a construction well known to the person skilled in the art, comprising at least two mold halves 9, 9 ', and some form of moving means (not shown) operating with, for example, pneumatics or hydraulics, which are arranged in a known manner. to be able to place the forming tool 8 in both an open (not shown) and a closed, fixed position (shown in Fig. 1).

In the first embodiment of the invention, the divisible mold tool 8 has two mold halves 9 and 9 ', a pressurizing connection 12 running through the end of one half 9' 14. The inner surfaces of the mold tool 8 can be treated. to provide a release effect when in contact with a material set. Such a so-called "non-stick" treatment can for instance consist of a plasma coating with Teflon or the like.

A pressurizing means 13 is arranged to be suitably connected to the pressurizing connection 12, which in the described embodiment forwards the pressure created by the pressurizing means 13 to the interior of the pressure membrane. In the described embodiment, the pressurizing means 13 is a compressed air compressor according to the prior art.

However, the pressurizing means 13 can also consist of, for example, an oil pump or of a device as a high-pressure steam. Thus, the internal pressurization of the pressure diaphragm can take place both by pneumatics and hydraulics. As will be appreciated by those skilled in the art, the choice of pressurization method may affect the pressure membrane 2, 2 ', which, of course, must be substantially non-permeable to the pressurizing medium used. The choice of material for the porous core 1, 1 ', 1 "can also be influenced to some extent by the chosen pressurization method. Obviously for the choice of material for In the following, the most important sub-steps of a preferred embodiment of the method according to the invention will be briefly described.

On top of a preformed core 1 which is self-supporting, a flexible pressure membrane 2 is threaded. On the outside of the flexible pressure membrane 2 and the preformed core 1 a set of material 3 is applied, to form 4 a blank 5 for forming a hollow body 16. 10 15 20 25 30 35 509 503 14 In this case, the material set has a structure as previously described herein.

Due to the fact that the core 1, 1 'is self-supporting, it constitutes a stable support when applying the pressure membrane 2, 2' and the material set 3, 3 'thereon.

In addition, in that the core 1, 1 'is preformed into a shape which substantially adheres to the shape of the hollow body 16 to be formed, and to the internal dimensions of the mold tool 8, an even distribution of the material set 3, 3' in different portions of the walls in the finished hollow body 16 is secured. In addition, a certain control of the wall thickness in different wall portions of the shaped hollow body 16 is made possible.

In the described embodiment, the application of the pressure membrane 2 and the material batch 3, respectively, on the outside of the preformed core 1 takes place mainly manually, but it is quite possible to achieve a higher degree of automation of these components with techniques well known to those skilled in the art.

As previously mentioned, the batch of material 3 ', applied to the outside of the preformed core 1' with its enclosing pressure membrane 2 ', forms a blank 5 for forming a hollow body 16. The blank 5 is placed inside a divisible forming tool 8 which is in an open position (not shown). ). Thereafter, the tool parts or mold halves 9, 9 'of the mold tool 8 are closed around the blank 5 and locked in the closed position (as shown in Fig. 1).

The pressurizing connection 12 is connected to the pressurizing means 13 and the pressurizing membrane 2 'is pressurized internally by the pressurizing membrane 2', via the pressurizing connection 12, being connected to. the pressurizing agent 13. In a first pressurizing step, the pressurizing membrane 2 'is pressurized internally to about 2 bar overpressure.

In connection with the first pressurizing step, the inner walls of the mold 8 are heated by means of heating means 11, which in the described first embodiment function by means of hot oil which is circulated in channels inside the walls of the mold 8.

The reason why in the described embodiment the first pressurization step is carried out is that one wants to counteract the shrinkage which often occurs with the thermoplastic matrix material in the vicinity of the glass conversion temperature of the polyester.

However, embodiments are also conceivable in which the pressurization takes place so that full forming pressure is applied already at the beginning of the heating phase and is maintained at this level until formation and consolidation of the batch of material has taken place. In the described, preferred embodiment, the heating takes place by means of heating means 11 in the walls of the mold tool 8, but one could also imagine embodiments of the invention where the heating of the material set 3 'takes place before the blank 5 is placed in the mold tool 8.

In the described embodiment, the oil circulation for heating the heating means 11 is arranged with an oil pump (not shown) suitable for the purpose. The oil is heated with an external device (not shown) which includes electrical resistors for heating. In this case, the external device (not shown) also comprises cooling means for cooling the circulating oil. In the described embodiment, these (not shown) consist of cooling means pipe loops for cold water circulation which are immersed in the oil. However, it is also conceivable that the shaping tool could be heated using superheated steam or another medium, or that the cooling could take place in another suitable manner than described herein.

The inner walls of the mold 8 and the material set 3 'inside the mold 8 are heated in the described embodiment by means of the heating means 11 to the softening temperature of the thermoplastic matrix material, which in the described embodiment is approximately 250 ° C.

Then, in a second pressurization step, the internal pressure inside the pressure diaphragm 2 'is raised to about 6 bar and maintained at this level for about 5 minutes.

During heating, the thermoplastic matrix material of the material batch 3 'melts which, thanks to the internal pressure in the inner pressure membrane 2', is pressed into a tight contact against the inner walls of the molded tool 8 locked in a closed position to be consolidated and formed into an external shape. adheres to the shape of the inner walls of the mold tool 8.

In addition to effecting consolidation and shaping of the material set 3 ', the pressurization of the pressure membrane ensures that air bubbles enclosed in the material set 3' are displaced. optionally, After this forming process, the forming tool 8, and thereby also the material set 3 ', is cooled to a temperature in the vicinity of room temperature using the previously mentioned cooling means of the oil circulation (not shown).

In industrial production, it is not practical or economically defensible to cool the mold to a temperature close to room temperature after each molding. In such cases, therefore, the cooling is interrupted at the highest possible temperature which, in experiments in the present process, has been found to give sufficient solidification and rigidity of the thermoplastic matrix material for the shaped hollow body 16 to be removed from the mold 8 in an open position, without that the shaped hollow body 16 is deformed or adheres to the molding tool 8G. After cooling the molding tool 8, the internal pressure of the pressure membrane is released and the pressurizing means 13 is released. After the divisible connection 12 to the forming tool 8 has been opened, the shaped hollow body 16 can be removed 15.

In cases where this is desirable and possible, in view of the shapes of the hollow body 16 and the preformed core 1 ", the core 1" is removed from the hollow body 16. This has been indicated in the appended Fig. 1 which shows a shaped hollow body 16 with a partially extended core 1 ".

Otherwise, i.e. if it is not desirable or possible to remove the core 1 ", it may remain as a more or less integral part of the shaped hollow body 16. In such cases, polyurethane foam or the like may advantageously be injected into the gap formed between the core and the pressure membrane during shaping to prevent the partially loose core from "rattling" in the finished hollow body.

After forming, the hollow body 16 can be machined in various ways according to the prior art, for example by cutting off end pieces, by external grinding or varnishing.

Heretofore, a first preferred embodiment of the invention has been described. The first embodiment utilizes, as previously stated, a thermoplastic matrix material which forms an integral part of the material set used.

In a second preferred embodiment of the invention only matrix material material set 3, 3 'substantially reinforcing material is hardenably supplied into the closed forming tool through a therefore included while an injection means 10 (Fig. 1) is provided to thereby impregnate the reinforcing material.

The second embodiment can be said to be similar to RTM technology to some extent, but with the fundamental difference that a molding pressure, according to the present invention, is applied from the inside by means of the pressure membrane 2 'applied to the outside of the preformed core 1' inside the material set 3 '.

In forming hollow bodies according to the second preferred embodiment of the invention, the material set 3, 3 'consists of a textile material as in the first embodiment, but with the difference that the thermoplastic matrix material is eliminated and the material set similarly therefore essentially only comprises continuous reinforcing fibers.

The curable matrix material in the second embodiment of the invention is curable vinyl ester resin, but many other matrix materials of the type used for conventional RTM technology are conceivable.

The matrix material is injected in the second embodiment in hardening-initiated form, but embodiments of the invention are also conceivable where the initiation takes place inside the mold tool.

The second preferred embodiment of the invention provides significant advantages over the prior art. In addition to the advantages of the invention which have previously emerged, it may be mentioned that, in the second embodiment of the invention, the porous core 1, 1 ', 1 "is made substantially smaller than the internal cavity of the molding tool. 8 can facilitate the impregnation of the reinforcing material with injected matrix material and thereby shorten the process time.

In practicing the invention according to the second preferred embodiment, the various process settings are adapted to what the embodiment requires. Such an adaptation can be performed by the person skilled in the art in a detailed description and with knowledge of conventional RTM technology. from the present It is to be understood that the temperatures, times, pressures and other process settings set forth in the foregoing description should only be considered as guidelines for those skilled in the art to understand enabling the invention.

When practicing the invention in industrial production, of course, process settings and material selection must be optimized in relation to the type of hollow bodies to be economically and manufactured, as well as outgoing production technical considerations, etc.

In the following, a preferred embodiment of a hollow body according to the invention will be described with reference to Figures 2A and 2B.

Fig. 2A schematically shows a cross-section of a portion of a hollow body according to the invention, while Fig. 2B schematically shows a longitudinal sectional view seen from the side of the same hollow body, in a similar portion as in Fig. 2A. The hollow body shown in Figures 2A and 2B is of a type in which the porous core remains. The hollow body 20 is intended to be used for a load-bearing element, more particularly a load-bearing post in a lightweight motor vehicle.

The hollow body 20 according to the described embodiment comprises, from the outside and inwards, a first layer of reinforced plastic 21, 21 'comprising reinforcing material and cohesive thermoplastic matrix material, two reinforcing elements 24 and 25, a second layer 22, 22' derived from the previously discussed the pressure membrane, and a porous core 23.

The reinforcing elements 24, 25 are intended to constitute a reinforcement when, for example, mounting of hinge hinges and the like on the hollow body 20 by means of a screw 26 (indicated by dashed lines). The reinforcing elements 24, 25 are advantageously constituted by carbon fiber-reinforced epoxy plates which have been inserted on the outside of the pressure membrane 22, 22 'in millings in the porous core 23 before the molding. After the molding, the reinforcing elements 24, 25 constitute integral parts in the hollow body 20, which in the described embodiment is of course intended for a load-bearing post of composite material for a motor vehicle.

By giving the reinforcing elements 24, 25 sufficiently large surfaces, stresses on a screw 26 which have been screwed through or into the reinforcing elements 24, 25 can be distributed in the walls 21, 21 'of the hollow body 20.

In Figures 2A and 2B it has been indicated that the reinforcing fibers run mainly in the longitudinal direction of the hollow body 20. This is of great importance in order to obtain maximum load-bearing capacity in the current application, i.e. a load-bearing post for a motor vehicle. In load-bearing elements, the main part 10 15 20 25 30 35 509 sooo 21 of the reinforcing fibers should substantially follow the tension direction of the loads that may arise.

The material set of the hollow body in the described embodiment has the structure and composition previously described with an inner layer of warp tricot of hybrid yarn and an outer layer of braided hybrid yarn.

In the molding, the thermoplastic matrix material, i.e. polyester filament of the hybrid yarn, fused to form a cohesive matrix material in the finished hollow body 20.

Reinforcing materials containing continuous fibers have 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 posts or beams for motor vehicles.

The invention has been described above with reference to the accompanying figures and by means of preferred embodiments. It is to be understood that the invention is in no way limited by these examples, but that its scope is limited by the appended claims.

The reinforcing material included in the material set does not, of course, have to be provided in the form of a material with a warp knit layer and a braided layer of hybrid yarns, but can be provided in many different forms, as long as the bulk of the reinforcing fibers follow the stresses of the finished hollow body. .

Thus, the reinforcing material can also be provided in the form of roving, in the form of a nonwoven material or in the form of individual reinforcing fibers. Various types of reinforcement which have been preformed, for example by blowing or spraying reinforcement fibers on mesh molds or the like, can also be used.

However, as previously mentioned, continuous reinforcing fibers are preferred in the practice of the invention. The fiber dimensions in general can vary within a very large area depending on the application. reinforcing fibers or various In addition to synthetic mineral fibers, such as glass fibers, the use of natural fibers, such as flax or ramie, is conceivable. Mixtures of different reinforcing fibers can also be used in the material batch.

The reinforcing material does not necessarily have to be made of glass fiber but can be made of any suitable fiber which has, or can be given, a sufficiently high adhesion and wettability to the matrix material used, and which is able to give desired properties to the finished hollow body.

In order to increase the adhesion to the matrix material used, the reinforcing fibers or the reinforcing material may be subjected to various chemical or physical treatment methods. Examples of such methods are oxidation with chemical oxidizing agents, corona and plasma treatment.

The application of a batch of material or a reinforcing material need not, as previously mentioned, be done by manually draping and fixing a fabric or a nonwoven sheet around the porous core with its enclosing pressure membrane, but can also be done, for example, by winding or a fabric of roving of reinforcing material reinforcement material around the core and the pressure membrane. 10 15 20 25 30 35 509 soš fl 23 As previously mentioned, the application of a set of materials can advantageously be automated in various ways according to known techniques.

In the case of thermoplastic matrix material, the matrix material included in the material batch can be selected from a large number of thermoplastic polymers as long as the softening point is at a suitable level. At their appropriate level is meant that the softening point should be at a sufficiently high level to meet the requirements of the finished hollow body in terms of heat resistance, and at the same time at a sufficiently low level for melting to be -realistic in an industrial manufacturing process. Examples of polymers which may meet these requirements and which also require a realistic price are thermoplastic polyester and polypropylene, but there are many other possible polymers which are suitable for use with matrix materials in the practice of the invention.

In embodiments of the invention that utilize injection of hardenable or polymerizable resins and the like, there are a large number of chemical compounds that can be used as matrix materials. Examples of such thermosets are polyester, vinyl ester and epoxy. In applications of the invention where thermosets are used, in addition to the addition of harder ones, other additives can also be added, for example flame retardants, UV stabilizers and color pigments. Such an addition preferably takes place before the curable matrix material is added to the reinforcement material, but can also take place inside the mold tool. Also with regard to embodiments with thermoplastic matrix material, various additives can be imagined in the matrix material, for example color pigments.

Claims (27)

10 15 20 25 30 35 509 503 24 PATENT REQUIREMENTS: Arrangement for forming hollow bodies comprising reinforced plastic, said arrangement comprising a preformed core (1) which is self-supporting, a set of material (3), and a divisible forming tool (8), characterized in that the arrangement comprises a flexible pressure membrane (2), a connection (12) and a pressurizing means (13), and that the pressure membrane (2 ') is thereby adapted to be able to pressurize enclose the preformed core (1'), at the same time as the material set (3 ') is a pressure membrane ( 2 '), and that the pressurizing means (13) is arranged to internally pressurize said pressure membrane applied to the outside of said (2') via the pressurizing connection (13) when the mold tool (8) is in a closed position. Arrangement according to claim 1, characterized in that the preformed core (1, 1 ', 1 ") consists of a porous material which enables pressure applied via the pressurizing connection (12) to be distributed in whole or in part via said preformed core (1'). when pressurizing the pressure diaphragm (2 '). Arrangement according to claim 1 or 2, characterized in that the material set (3, 3 ') comprises both a thermoplastic matrix material, and that the arrangement comprises reinforcement material and one comprises heating means (11) which are arranged to heat the thermoplastic matrix material to its softening point when the mold (8) is in a closed position. 10 15 20 25 30 35 509 505 25 Arrangement according to one of the preceding claims, characterized in that the reinforcing material comprises glass fibers and that the matrix material comprises thermoplastic polyester fibers. Arrangement according to claim 1 or 2, characterized in that the material set (3, 3 ') comprises a reinforcing material and that the molding tool (8) comprises an injection means (10) for injecting curable matrix material. Arrangement according to claim 5, characterized in that the reinforcing material in the material set (3, 3 ') comprises glass fiber and that the curable matrix material comprises vinyl ester. Arrangement according to one of the preceding claims, characterized in that the reinforcing material in the material set (3, 3 ') comprises continuous reinforcing fibers, and that the main part of the reinforcing fibers is arranged to follow the stress direction of the loads expected to occur on a hollow body (16) formed using the arrangement. Arrangement according to any one of the preceding claims, characterized in that the batch of material (3, 3 ') is provided in the form of an inner layer of warp knitwear, and an outer layer made by braiding, and that the arrangement comprises a braiding device for braiding said outer layer on top of the preformed core. Arrangement according to one of the preceding claims, characterized in that the material set (3, 3 ') is shaped as a sock or as a continuous tube. 10 15 20 25 30 35 509 503 26 Arrangement according to any one of the preceding claims, characterized in that the preformed core (1, 1 ', 1 ") is provided with reinforcing elements of a material other than said core recesses inside which (1') are arranged on the outside of the pressure membrane (2 '). ) enclosing the core (1 ') and said recesses. 11. ll. A method of forming hollow bodies comprising reinforced plastic, comprising using a preformed core (1) which is self-supporting, a set of material (3), and a divisible forming tool (8), characterized in that the method comprises enclosing a flexible pressure membrane ( 2, 2 ') on top of the preformed core (1, 1'), then applying the batch of material (3, 3 ') to the outside of the pressure membrane (2') to form a blank (5) for forming a hollow body, to introduce the blank ( 5) in the mold tool (8) in an open position to then bring the mold tool (8) into a closed position around the blank (5), and that the pressure membrane (2 ') of the blank (5) the mold tool (8) in its closed position, to thereby shape and consolidate the material set (3 '). internal pressurized located inside Method according to claim 11, characterized in that the preformed core (1 ') consists of a pressure applied to the pressurizing connection (13) is wholly or partly distributed via said preformed core (1') during pressurization of the pressure membrane (2 '). porous material, and that via Method according to claim 11 or 12, characterized in that the material set (3, 3 ') used in the method comprises both a reinforcing material and a thermoplastic matrix material, and that heating means (11), when the molding tool (8) is in In its closed position, the thermoplastic matrix material heats to a temperature higher than the softening point of the matrix material. A method according to any one of claims 11 to 13, characterized in that the reinforcing material in the material set (3, 3 ') used in the method comprises glass fiber and that the thermoplastic matrix material in the material set (3, 3') comprises polyester. Method according to claim 11 or 12, characterized in that the material batch (3, 3 ') used in the method comprises a reinforcing material and that the mold tool (8) comprises an injection means (10) into which the mold tool (8) is hardenable matrix material. to impregnate said reinforcement material. A method according to claim 15, characterized in that the reinforcing material in the material batch (3, 3 ') used in the method comprises glass fiber and that the curable matrix material comprises vinyl ester. Method according to any one of claims 11 to 16, characterized in that the reinforcing material of the material batch (3, 3 ') used in the method comprises continuous reinforcing fibers, and that the main part of the reinforcing fibers is arranged to follow the stress direction of the loads expected to occur on a hollow body (16) formed by the method. Method according to one of Claims 11 to 17, characterized in that the set of material (3, 3 ') is provided in the form of an inner layer of warp knitwear, and an outer layer produced by braiding, and in that The method comprises braiding said outer layer in a braiding device. Method according to one of Claims 11 to 18, characterized in that the preformed core (1, 1 ') is provided with recesses inside which reinforcing elements of a material other than the core (1, 1') are placed before forming. Hollow body, comprising a first layer (21, 21 ') with a reinforcing material and a matrix material, characterized by the main part of the reinforcing fibers as. included in the reinforcement material follows the direction of stress of the loads the sunroof body (20) is expected to be subjected to when loading. A hollow body according to claim 20, characterized in that the reinforcing fibers comprise continuous fibers. Hollow body according to claim 20 or 21, characterized in that the hollow body (20) comprises a preformed core (23), and that a second layer (22, 22 ') of the hollow body (20) is located inside the first layer (21, 21). ') but outside the core (23), and that said second layer (22, 22') originates from a pressure membrane. Hollow body according to claim 22, characterized in that the preformed core (23) comprises recesses, and that reinforcing elements (24, 25) are located 5. said recesses in the first (21, 21 ') and second layer (22, 22). '). A hollow body according to any one of claims 20 to 23, characterized in that the matrix material in the first layer (21, 21 ') comprises a thermoplastic. 10 509 5o3 "l 29 A hollow body according to any one of claims 20 to 24, characterized in that the reinforcing material comprises glass fiber and the matrix material polyester. A hollow body according to any one of claims 20 to 25, characterized in that the first layer comprises reinforcing material in the form of warp knitwear and / or in the form of braided reinforcing material. Hollow body according to one of Claims 20 to 26, characterized in that the hollow body (20) is designed as a load-bearing element for a motor vehicle.