WO2023217360A1

WO2023217360A1 - Method for producing a preform, preform, method for forming a composite fibre component and composite fibre component

Info

Publication number: WO2023217360A1
Application number: PCT/EP2022/062734
Authority: WO
Inventors: Florian REICHERT; Tim KROOSS
Original assignee: Schunk Kohlenstofftechnik Gmbh
Priority date: 2022-05-11
Filing date: 2022-05-11
Publication date: 2023-11-16

Abstract

The invention relates to a method for producing a preform to form a composite fibre component for high-temperature applications, wherein a stack (10) of at least two fibre layers (11) formed from carbon fibres (12) is formed, wherein the carbon fibres are used in the form of dry continuous fibres, wherein the stack undergoes a needling treatment that joins the fibre layers to one another.

Description

Schunk Carbon Technology GmbH

Method for producing a preform and preform and method for forming a fiber composite component and fiber composite component

The invention relates to a method for producing a preform for forming a fiber composite component for high-temperature applications and a preform for forming a fiber composite component for high-temperature applications, wherein a stack is formed from at least two fiber layers made of carbon fibers. The invention further relates to a method for producing a fiber composite component for high-temperature applications and a fiber composite component for high-temperature applications.

It is known from the prior art to produce a preform for forming a fiber composite component for high-temperature applications by means of a wet winding process, whereby, as a result of impregnation with a resin, wet carbon fibers are used to form a stack of at least two fiber layers formed from the carbon fibers around a shaped body or winding mandrel Winding device can be wound. The carbon fibers are, for example, in the form of a fiber-matrix semi-finished product pre-impregnated with a resin, such as a prepreg, or in the form of a dry one means resin-free, fiber bundles, such as a roving, which is passed through a resin bath before winding. A phenolic resin is regularly used as the matrix-forming resin. The use of the resin makes it possible to connect the fiber layers to one another and thus prefix a defined geometric shape of the stack determined by the molded body. After the resin has hardened, the stack or preform is then removed from the mold core while maintaining the shape and, after final hardening of the resin, is then further processed into a fiber composite component, with the preform first being pyrolyzed or carnonized to form a carbon matrix or carbon grid and then graphitized and subsequently infiltrated with pyrolytic carbon in order to obtain a component made of carbon fiber reinforced carbon (CFC) that is particularly suitable for high temperature applications. However, the disadvantage of this manufacturing process is that the phenolic resin that is regularly used is harmful to health and its use therefore requires cost-intensive increased protective measures for workers at a manufacturing site. At the same time, solvents that are usually used to remove resin residues contaminating production facilities are generally not beneficial to the health of workers and therefore require increased protective measures. In addition, as a result of the use of a resin in the manufacturing process itself, the additional process steps of hardening the resin as well as pyrolysis or carbonization and graphitization are required, which are not least highly energy-intensive and sometimes also time-consuming. These factors as a whole cause a disadvantageous increase in manufacturing time and in particular also in manufacturing costs of the preform or fiber composite component produced using this manufacturing process.

In another method known from the prior art for producing a preform for forming a fiber composite structure Partly for high-temperature applications or processes for producing a fiber composite component for high-temperature applications, a preform is first formed by forming a random fiber or short fiber fleece semi-finished product made of carbon fibers, which is infiltrated with pyrolytic carbon, in particular subsequently, to form the fiber composite component. However, the disadvantage of this manufacturing process is that the preform formed from the random fibers or short fibers by forming the random fiber or short fiber nonwoven semi-finished product has a comparatively high porosity, so that when the preform is infiltrated with the pyrolytic carbon, a large number of pores are formed Fiber structure of the preform must be filled with the pyrolytic carbon. In addition, a fiber composite component produced in this way has a comparatively shorter service life or service life due to the comparatively poorer mechanical properties of the random fibers or short fibers used to produce the preform.

The present invention is therefore based on the object of proposing a method for producing a preform for forming a fiber composite component for high-temperature applications and a preform for forming a fiber composite component for high-temperature applications as well as a method for producing a fiber composite component for high-temperature applications and a fiber composite component for high-temperature applications, which one cost-optimized production of such a preform or fiber composite component is possible or can be produced comparatively inexpensively and is improved in terms of service life.

This object is achieved by a method for producing a preform for forming a fiber composite component for high-temperature applications with the features of claim 1 and a preform for forming a fiber composite component for high-temperature applications with the features of claim 16 and a method for Manufacture of a fiber composite component for high-temperature applications with the features of claim 14 and a fiber composite component for high-temperature applications with the features of claim 17 solved.

In the method according to the invention for producing a preform for forming a fiber composite component for high-temperature applications, a stack is formed from at least two fiber layers made of carbon fibers, the carbon fibers being used in the form of dry continuous fibers, the stack being subjected to a needling treatment that connects the fiber layers to one another.

According to the invention, it is provided to form a stack or a laminate from at least two fiber layers or fiber layers made of carbon fibers, wherein the fiber layers can be arranged or layered one above the other or next to one another. Advantageously, the stack can comprise a plurality of such fiber layers. The stack can basically be designed to have any geometric shape, for example rotationally symmetrical. The fiber layers are made of carbon fibers. However, it is in principle also conceivable to transfer the process to other types of fibers, such as oxide ceramic fibers, silicon carbide fibers, pitch fibers, glass fibers or natural fibers.

According to the invention, it is further provided that when forming the stack, only dry, i.e. resin-free, carbon fibers are used, from which the fiber layers are or will be formed as dry, i.e. resin-free, fiber layers. In other words, in the method according to the invention, impregnation or pre-impregnation of the carbon fibers with a resin, in particular with a harmful phenolic resin, is completely dispensed with, so that as a result there are no cost-intensive increased protective measures for workers at a manufacturing site required are. The use of harmful solvents is also unnecessary, since it is not necessary to remove resin residues that contaminate production facilities because the carbon fibers are not impregnated or pre-impregnated with a resin. In addition, the use of dry carbon fibers eliminates at least the additional energy-intensive and time-consuming process step of hardening the resin. Depending on the intended further processing of the preform, the additional energy-intensive process steps of pyrolysis or carbonization and subsequent graphitization are completely eliminated. The method according to the invention therefore requires not only a comparatively reduced use of raw materials, but also a comparatively reduced number of process steps. Overall, the use of dry carbon fibers therefore enables time-optimized and, in particular, cost-optimized production of the preform or a fiber composite component made from the preform, in particular carbon fiber-reinforced carbon (CFC).

According to the invention it is further provided that the carbon fibers are used in the form of continuous fibers. Compared to random fibers or short fibers, continuous fibers have significantly improved mechanical properties, in particular stiffness and strength, so that the preform can in principle be further processed into a fiber composite component with a comparatively increased service life or service life. In addition, the use of continuous fibers enables the preform to be formed with a comparatively low porosity, so that in the event of a possible subsequent coating or infiltration of the preform with pyrolytic carbon, comparatively few pores of a fiber structure of the preform need to be filled with the pyrolytic carbon. In addition, the use of continuous fibers makes it possible to form the stack or preform by winding or dry winding. According to the invention it is further provided that the stack is subjected to a needling treatment that connects the fiber layers to one another, i.e. the fiber layers are connected to one another by means of the needling treatment. In contrast to the wet winding process known from the prior art, the fiber layers are therefore not connected to one another by a resin, but rather by a needling treatment of the stack, whereby at least immediately adjacent fiber layers can be connected to one another. During the needling treatment, structuring needles or felting needles of an automatically operating needling device can penetrate into the stack and be brought into engagement with the carbon fibers or continuous fibers for needling of the carbon fibers or continuous fibers. This needling can lead to an advantageous felting of the stack or the fiber layers, whereby a structurally stable geometric shape of the stack or preform can be obtained.

A further advantage of the method according to the invention is that by using dry continuous fibers which are needled, a fiber volume fraction or fiber volume content of a fiber composite component produced from the preform can be increased, which can have an advantageous effect on the mechanical properties of the fiber composite component.

As a result, the method according to the invention enables a time-optimized and cost-optimized production of a preform or a fiber composite component produced from the preform, the fiber composite component having improved mechanical properties or an improved service life.

In one embodiment of the method according to the invention, after subjecting it to the needling treatment, at least one further fiber layer made of the carbon fibers in the form of dry continuous fibers can be added to the stack at least once, wherein the stack can be subjected to a further needling treatment. Dem- Accordingly, it can be provided to add at least one further fiber layer, which is or will be formed from the carbon fibers in the form of dry continuous fibers, to the stack after the needling treatment has been carried out. The stack expanded by the at least one further fiber layer can then be subjected to a further needling treatment. The process steps of adding at least one further fiber layer to the stack and subjecting the stack expanded by the at least one further fiber layer to a further needling treatment can be repeated as often as desired. By carrying out several needling treatments, an improved cohesion of the fiber layers and thus a higher structural strength of the stack or preform can advantageously be achieved. A penetration depth of the structuring needle into the stack or expanded stack can be adjusted so that it can penetrate essentially exclusively into the at least one further fiber layer and into a fiber layer formed or arranged immediately preceding this further fiber layer in order to move the carbon fibers into the remaining ones Do not needle the fiber layers further unnecessarily or damage them if necessary.

Advantageously, the stack can be formed exclusively from the fiber layers made from the carbon fibers in the form of dry continuous fibers. In this case, the stack then exclusively comprises fiber layers which are or are formed from the carbon fibers in the form of dry continuous fibers.

Advantageously, the stack can be formed with a defined geometric shape, wherein the shape can be fixed as a result of the needling treatment. The stack can form a fiber body or a fiber structure, which can have the shape. In principle, the shape can be chosen arbitrarily. The shape can be two-dimensional or flat, in particular rectangular, square or circular or round. Alternatively, the shape can be three-dimensional be. Preferably, the shape can be rotationally symmetrical, in particular cylindrical or conical. The shape can be chosen so that the preform can be further processed into a fiber composite component forming a tube, a crucible, a plate, a profile, a rod or a grid. The shape of the stack can be fixed by the needling treatment in such a way that the preform has the shape, i.e. is structurally stable with regard to this shape, so that the preform can be further processed into a fiber composite component while maintaining the shape, which then also has the shape can.

Advantageously, the fiber layers can be formed from a filament yarn or from rovings and/or a semi-finished fiber product. The filament yarn can be a bundle or strand made of the parallel endless fibers or filaments and can comprise, for example, 1K, 3K, 6K, 12K, 24K filaments. Furthermore, the semi-finished fiber product can in particular be a woven fabric, a scrim, a braid or a fleece or nonwoven material, which can be formed from the continuous fibers. The semi-finished fiber product can in turn be formed from a filament yarn. It is important that the carbon fibers contained in the filament yarn or semi-finished fiber product are dry continuous fibers, so that the preform can be produced without resin.

The fiber layers can be formed in such a way that the carbon fibers in a fiber layer run in a single direction and/or that a direction of a fiber course, viewed along a stacking direction, varies at least partially from fiber layer to fiber layer. As a result, the fiber layers can be designed as unidirectional layers. In principle, however, the carbon fibers in a fiber layer can also be oriented in different directions, i.e. have no preferred orientation. Furthermore, the carbon fibers can be arranged in the fiber layers in such a way that the fiber layers can be arranged in a cross position. Advantageously, the stack can be formed by winding using a winding device and/or laying using a laying device. In particular, the stack or the fiber layers can also be formed by winding or laying the filament yarn and/or the semi-finished fiber product, in particular nonwoven or nonwoven fabric. The winding device can have several axes, for example six axes.

The stack can be formed by arranging the fiber layers on a mandrel of the winding device or the laying device. The mold core can determine a geometric shape of the stack or preform through a geometric shape of the mold core. To form a rotationally symmetrical stack or preform, the mold core can then be designed, for example, with a rotationally symmetrical shape. The mold core can be a winding mandrel on or around which the fiber layers or carbon fibers or continuous fibers can be wound or wound to form the stack. The continuous fibers can be pre-fixed to the mold core using deflections and friction as well as using retaining pins. Furthermore, the mold core can be at least partially made of Styrofoam.

In one embodiment of the method according to the invention, the mold core can be rotated during the formation of the stack and/or during the needling treatment. The stack arranged on the mold core can then be rotated. However, rotation of the mold core or stack is not absolutely necessary. The needling treatment can advantageously be carried out with stacks arranged on the mold core.

Advantageously, the preform obtained by subjecting the stack to the needling treatment can be removed from the mold core after the needling treatment. The stack or preform can be separated and removed from the mold core. Since the preform has a structural can have a fixed geometric shape, the preform can be removed from the mold core and further processed while maintaining the shape, in particular coated or infiltrated with pyrolytic carbon.

Advantageously, as a result of the needling treatment, a fiber course of the carbon fibers can be partially deflected and/or the carbon fibers can be partially damaged and/or a, preferably continuous, fiber structure of the carbon fibers can be partially interrupted. By needling the endless fibers, for example by means of structuring needles or felting needles, the endless fibers or endless fiber bundles can be deflected from one fiber layer into fiber layers at least directly adjacent to the fiber layer, which also results in a solidification or felting of the fiber layers or the Stack can be achieved. The continuous fibers, in particular the continuous fibers made from different fiber layers, can be intertwined with one another. During needling, a continuous fiber structure of the continuous fibers can be interrupted. The continuous fibers can also be partially damaged, shortened or broken during needling. The interruption of the fiber structure or damage to the continuous fibers can only be permitted to the extent that this can be largely compensated for by the comparatively good mechanical properties of the continuous fibers. Overall, a structurally stable preform can be obtained.

Advantageously, the needling treatment can be carried out in a direction perpendicular to a direction of a fiber course of the carbon fibers. A needling direction can be selected parallel to a stacking direction. In the case of a rotationally symmetrical stack, the needling treatment can be carried out in a radial direction with respect to the stack. In principle, an angle between the Verna- However, the direction of delung and the direction of the grain of the carbon fibers can also be chosen arbitrarily or appropriately.

Advantageously, the needling treatment can be carried out by means of a needling device, preferably electrically or pneumatically driven, whereby at least one structuring needle or felting needle of the needling device can be brought into engagement with the carbon fibers by immersing it in the stack. The needling device can be a multi-axis robot. During the needling treatment, the needling device can carry out several hundred lifting movements per minute. The stack can be arranged on a table during the needling treatment. The structuring needle can be notched round or square. Furthermore, the needling device can be integrated with the winding device or laying device in a system.

In the method according to the invention for producing a fiber composite component for high-temperature applications, the preform produced according to the method according to the invention for producing a preform is coated with pyrolytic carbon, preferably infiltrated, to form the fiber composite component. Preferably, the preform is infiltrated with the pyrolytic carbon. The pyrolytic carbon can then penetrate into a fiber structure of the preform and at least partially, preferably completely, fill the spaces or pores of the fiber structure located between the carbon fibers and completely surround the carbon fibers. Nevertheless, it can be provided that only the preform is coated with the pyrolytic carbon, which can lead to the formation of a surface layer made of the pyrolytic carbon. Because a carbon matrix can be formed completely from the pyrolytic carbon without resin, the carbon matrix can be a comparative have improved quality, so that the fiber composite component has comparatively better mechanical properties.

Advantageously, the preform can be coated or infiltrated with the pyrolytic carbon by means of chemical vapor deposition (CVD) or chemical vapor phase infiltration (CVI). For this purpose, the preform can be arranged in a reaction chamber into which a reaction gas made of a hydrocarbon can be introduced, whereby the pyrolytic carbon can be separated from the gas phase due to a chemical reaction.

In the preform according to the invention for forming a fiber composite component for high-temperature applications, a stack is formed from at least two fiber layers made of carbon fibers, the carbon fibers being used in the form of dry continuous fibers, the stack being subjected to a needling treatment that connects the fiber layers to one another. Regarding the advantageous effects of the preform according to the invention, reference is made to the description of the advantages of the method according to the invention for producing the preform.

Further advantageous embodiments of the preform result from the feature descriptions of the subclaims relating to method claim 1.

In the fiber composite component according to the invention for high-temperature applications, the preform produced by the method according to the invention for producing a preform is coated with pyrolytic carbon, preferably infiltrated, to form the fiber composite component. The advantageous effects of the fiber composite component according to the invention are discussed in the description of the advantages Method according to the invention for producing the fiber composite component.

In an advantageous embodiment of the fiber composite component, the fiber composite component can be designed for use in a device for crystal growth, for example for silicon crystal growth, in particular as a crucible. The fiber composite component can also be designed as a tube, plate, profile, rod or grid.

A further advantageous embodiment of the fiber composite component results from the description of the features of the subclaim related to method claim 14.

Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings.

Show it:

1 shows a partial view of a stack of fiber layers in cross section during a needling treatment;

Fig. 2 is a side view of a needling device.

1 shows a stack 10, which is formed from a plurality of fiber layers 11 arranged one above the other made of carbon fibers 12 in the form of dry continuous fibers, during a needling treatment, a structuring needle 13 of a needling device, not shown here, being brought into engagement with the carbon fibers 12 is used to form a preform from the stack 10 by connecting the fiber layers 1 1 to form a fiber composite component. By needling the carbon fibers 12, they become Carbon fibers 12 are partially deflected and intertwined with one another, with the fiber layers 11 being felted. The fiber layers 11 are formed from a fleece.

2 shows a needling device 14, which is formed by a multi-axis robot 14, which includes a robot arm 15 with an end section 16, which has structuring needles, not shown here, in order to form a stack 17 of fiber layers made of carbon fibers, also not shown here of dry continuous fibers to undergo a needling treatment that connects the fiber layers to one another in order to form a preform for forming a fiber composite component. The rotationally symmetrical stack 17 is arranged on a table 18.

Claims

Claims Method for producing a preform for forming a fiber composite component for high-temperature applications, wherein a stack (10, 17) is formed from at least two fiber layers (11) made of carbon fibers (12), characterized in that the carbon fibers are used in the form of dry continuous fibers , whereby the stack is subjected to a needling treatment that connects the fiber layers to one another. Method according to claim 1, characterized in that after subjecting the stack (10, 17) to the needling treatment, at least one further fiber layer (11) made of the carbon fibers (12) in the form of dry continuous fibers is added at least once, the stack being subjected to a further needling treatment is subjected to. Method according to claim 1 or 2, characterized that the stack (10, 17) is formed exclusively from the fiber layers (11) from the carbon fibers (12) in the form of dry continuous fibers. Method according to one of the preceding claims, characterized in that the stack (10, 17) is formed with a defined geometric shape, the shape being fixed as a result of the needling treatment. Method according to one of the preceding claims, characterized in that the fiber layers (11) are formed from a filament yarn and/or a semi-finished fiber product. Method according to one of the preceding claims, characterized in that the fiber layers (11) are formed such that the carbon fibers (12) in a fiber layer run in a single direction and / or that a direction of a fiber course is viewed along a stacking direction from fiber layer to fiber layer varies at least partially. Method according to one of the preceding claims, characterized in that the stack (10, 17) is formed by winding using a winding device and/or laying using a laying device. Method according to claim 7, characterized in that the stack (10, 17) is arranged by arranging the fiber layers (11) on one Mold core of the winding device or the laying device is formed. Method according to claim 8, characterized in that the mold core is rotated during the formation of the stack (10, 17) and/or during the needling treatment. Method according to claim 7 or 8, characterized in that the preform obtained by subjecting the stack (10, 17) to the needling treatment is removed from the mold core after the needling treatment. Method according to one of the preceding claims, characterized in that as a result of the needling treatment a fiber course of the carbon fibers (12) is partially deflected and/or the carbon fibers are partially damaged and/or a, preferably continuous, fiber structure of the carbon fibers is partially interrupted. Method according to one of the preceding claims, characterized in that the needling treatment takes place in a direction perpendicular to a direction of a fiber course of the carbon fibers (12). Method according to one of the preceding claims, characterized in that the needling treatment is carried out by means of a needling device (14), preferably electrically or pneumatically driven. is carried out, at least one structuring needle (13) of the needling device being immersed in the stack (10, 17) and brought into engagement with the carbon fibers (12). Method for producing a fiber composite component for high-temperature applications, characterized in that to form the fiber composite component, the preform produced according to one of claims 1 to 13 is coated with pyrolytic carbon, preferably infiltrated. Method according to claim 14, characterized in that the coating or infiltration of the preform with the pyrolytic carbon takes place by means of chemical vapor deposition (CVD) or chemical vapor phase infiltration (CVI). Preform for forming a fiber composite component for high-temperature applications, wherein a stack (10, 17) is formed from at least two fiber layers (11) made of carbon fibers (12), characterized in that the carbon fibers are used in the form of dry continuous fibers, the stack being one the fiber layers are subjected to needling treatment connecting each other. Fiber composite component for high temperature applications, characterized in that to form the fiber composite component, the preform produced according to one of claims 1 to 13 is coated, preferably infiltrated, with pyrolytic carbon. Fiber composite component according to claim 17, characterized in that the fiber composite component is designed for use in a device for crystal growth, in particular as a crucible.