METHOD FOR PRODUCE A FIBER-CONTAINING LAYER AND PREPREG

Description

[0001] The invention relates to a method for producing a layer containing impregnated and unidirectionally arranged fibers for use as a prepreg or for a prepreg intended for the manufacture of a fiber-reinforced object, wherein fibers are cut in several mutually opposed areas after production of the layer and wherein the cuts thus formed run within boundaries of the prepreg.

[0002] The invention also refers to a prepreg.

[0003] Fiber-reinforced components have the advantage over monolithic objects that quasi-ductile compressive behavior can be achieved. High flexural strengths can also be attained.

[0004] Prepregs, which can be single- or multi-layered, are used for ceramic composite materials. To produce prepregs, it is known to use high-temperature-resistant continuous fiber bundles, so-called rovings, which can consist of up to 50,000 individual fibers or filaments. Suitable fibers include, in particular, ceramic fibers such as silicon carbide, aluminum oxide, carbon, and mullite, which are embedded in a ceramic matrix, e.g., made of silicon carbide, aluminum oxide, carbon, or mullite.

[0005] Short fibers can also be used, which are combined by spraying with a suspension consisting of ceramic particles, water, an alcoholic compound and a dispersant to impregnate the short fibers (see e.g. EP 3 450 128 A1).

[0006] EP 2 848 599 B1 describes a process for producing an oxide ceramic composite material in which fiber bundles are arranged with a random orientation of their longitudinal axis of at least two dimensions.

[0007] A disadvantage of such fiber-reinforced composite materials is that it is often difficult to produce complex shapes, especially those with small radii of curvature and / or thick wall thicknesses, due to the build-up of internal stresses and the risk of delamination.

[0008] Oxide ceramic prepregs are also known, in which the fibers are available in the form of a woven or non-woven fabric. Disadvantages include fiber loss when cutting the prepregs to size.

[0009] Documents EP 2 127 840 A1, JP 2009-286817 A, JP 2008-207545 A, JP 2008-207544 A, and EP 3 369 768 A1 each describe a method for producing a layer containing impregnated and unidirectionally arranged fibers, intended for use in prepregs. In this process, the fibers are cut in several spaced-apart areas after the layer has been manufactured.

[0010] The present invention is based on the objective of further developing a method for producing a layer for the manufacture of fiber-reinforced objects and an intermediate product for a fiber-reinforced object in such a way that even complex objects can be manufactured, whereby the build-up of residual stress is avoided and the risk of delamination is prevented.

[0011] The objects made from the layers should have a high modulus of elasticity and low elongation at break.

[0012] The layers should be able to be draped without any problems.

[0013] The production of large-volume, complex, curved components should be just as possible as the production of thin-walled objects.

[0014] The problem is solved by the measures derived from claim 1. Further developments result from the dependent claims.

[0015] The layers can be produced, for example, using winding technology, by winding a previously impregnated roving, i.e., bundles of fibers (fiber filaments), onto a core, on the surface of which, for example, a carrier film is previously arranged.

[0016] The roving formed by continuous fibers is impregnated by first passing the roving through a suspension or slurry consisting of ceramic particles, water and an alcoholic compound, in particular in the form of glycerin, as well as possibly a dispersing agent and / or possibly an organic binder.

[0017] To ensure that the fibers are completely and homogeneously impregnated with the slurry, the suspension or slurry preferably has a viscosity of < 1000 Pa·s, preferably less than 100 Pa·s, and particularly less than 50 Pa·s, at a shear rate of 100 1 / s. The viscosity can be determined, for example, at a shear rate of < 100 s⁻¹ and a temperature of 20 °C using a coaxial cylindrical rotational viscometer.

[0018] Alternative methods for impregnating the fibers are also possible, such as spraying the slip or pouring the slip onto the unidirectionally arranged roving, to name just a few examples.

[0019] The layer formed by unidirectionally running, i.e., parallel to each other oriented, fiber filaments, which are surrounded by the slurry also known as matrix precursor, constitutes the layer in which, according to the invention, fibers have been cut in predetermined areas.

[0020] The pre-assembled unidirectional fiber filament layer is fixed in place by a carrier film.

[0021] The fibers are cut in the areas of the layer that lie within the prepreg(s) formed from that layer; because a layer can be cut into one or more prepregs. Naturally, the layer itself can also be used as a prepreg.

[0022] According to the invention, prepregs consisting of layers or sections of layers made of parallel oriented fiber filaments surrounded by slurry, which in turn have been cut in desired areas after the formation of the layer, can be placed on shaped carriers which in turn define the negative geometry of the fiber-reinforced object or component to be produced.

[0023] Preferably, at least two or more layers according to the invention or prepregs produced from them are placed on top of each other beforehand, wherein the orientation of the fibers of one layer to that of the subsequent layer includes an angle α > 0°, in particular α > 10°, preferably 45°≤ α ≤ 90°, particularly preferably α = 90°, so that a bi- or multidirectional fiber architecture results.

[0024] The cuts are not continuous, and it is particularly intended that the fibers are cut at a cutting angle β to the longitudinal direction of the fibers, where 45° ≤ β ≤ 90°, preferably 60° ≤ β < 86°, and in particular β = 75° or β approximately equal to 75°.

[0025] Furthermore, the invention is characterized in that, viewed in the longitudinal direction of the fibers, the distance a between successive cuts is in particular 5 mm ≤ a ≤ 75 mm, preferably 20 mm ≤ a ≤ 40 mm, particularly preferably a is equal to 30 mm or approximately equal to 30 mm.

[0026] The length L of a cut can be 5 mm ≤ L ≤ 100 mm, preferably 10 mm ≤ L ≤ 30 mm, and particularly preferably L equal to or approximately equal to 25 mm. The cuts can have a straight course without this limiting the teaching according to the invention.

[0027] In particular, the cuts, viewed from above, may have a geometry of a straight line, a wave segment, or a polygonal section.

[0028] Different cutting geometries can also be used for a single layer.

[0029] Cutting can be done using suitable tools such as knives, cutters, stamps or without tools (water jet, laser).

[0030] In particular, it is intended that fibers from the group consisting of glass fibers, carbon fibers, ceramic fibers, or combinations of one or more of these fibers will be used.

[0031] The invention is also characterized in particular by the fact that oxides, mixed oxides, nitrides, carbonitrides, in particular of the elements Al, Si, Zr, Y, Mg, Ca or carbon, in particular fibers from the group Al 2 O 3 , SiO 2 , ZrO 2 , Y 2 O 3 , Y 2 O 3 stabilized ZrO 2 , yttrium aluminum garnet , mullite , Si 3 N 4 , SiC, SiCN , SiBNC or combinations of two or more of these materials are used as materials for the fibers.

[0032] Preferably, ceramic particles from the group consisting of Al 2 O 3 , SiO 2 , ZrO 2 , Y 2 O 3 , Y 2 O 3 stabilized ZrO 2 , yttrium aluminum garnet , mullite , Si 3 N 4 , SiC , SiCN , SiBNC or carbon or silicon or combinations of two or more such materials are used as matrix precursor components.

[0033] The ceramic particles should have a bimodal size distribution, i.e., a particle size distribution with two non-overlapping peaks. One peak can be between 0.05 µm and 0.3 µm, preferably between 0.08 µm and 0.2 µm, and the other between 0.5 µm and 3 µm, preferably between 0.7 µm and 1.2 µm. The first fraction is the fine fraction, and the second the coarse fraction. The volume fraction of the fine particles can be between 3 vol% and 25 vol% of the total particles, and the volume fraction of the coarse particles between 75 vol% and 77 vol% of the total particles. The particle size can be determined, for example, by laser scattering.

[0034] The proportion of ceramic particles can range from 10% to 50% by volume based on the total volume of the slurry. The proportion of organic additives, e.g., alcoholic compounds, particularly in the form of glycerol, can range from 10% to 35% by weight based on the total weight of the ceramic particles in the slurry.

[0035] The remainder should be water, with the possible addition of a dispersant and / or binder, pressing aid.

[0036] After layering two or more corresponding planar fiber sheets, where the orientation of the fiber filaments of the superimposed layers differs from one another, in particular where the orientation of one layer forms an angle of 90° to that of the subsequent layer, they can then be draped as prepreg (pre-impregnated fibers, pre-impregnated fiber matrix semi-finished products), e.g., by placing them on a mold. This is followed by pressure treatment and simultaneous drying, e.g., in an autoclave. Sintering then takes place, e.g., at temperatures between 1,000 °C and 1,300 °C for composites with oxide ceramic fibers and at temperatures between 1,400 °C and 1,600 °C for composites with non-oxide ceramic fibers.

[0037] The invention also relates to the production of ceramic composite materials using prepreg technology, wherein fiber rovings and a liquid matrix precursor component containing a ceramic filler are used. This provides ceramic composite materials with a fiber architecture suitable for manufacturing and material properties, exhibiting damage-tolerant fracture behavior and good mechanical properties.

[0038] The layers according to the invention, which form the fiber architecture of the prepregs, offer the advantage that the lamination process, i.e., the joining of the individual layers or the prepregs produced from the layers, is considerably facilitated, since internal stresses are avoided or reduced, which otherwise can lead to delamination during processing in chemical and thermal processes (sintering).

[0039] It is possible to supply large-volume components with both thin and thick walls. Thick walls are feasible because they prevent internal stresses. Avoiding these stresses is particularly important when thick-walled sections are additionally bent or curved multiple times. Thin walls are possible because they allow for precise placement of the individual layers.

[0040] It is also possible to deep-draw the layers. This allows for the forming of radii with small diameters or complex, multi-curved structures.

[0041] According to the invention, it is generally provided that at least two unidirectionally arranged and impregnated fiber layers are arranged one above the other to form a bi- or multidirectional fiber architecture.

[0042] The thickness of each fiber layer should be in the range between 0.20 and 0.5 mm, preferably 0.4 mm.

[0043] A fiber diameter of approximately 10 µm is preferred. The fiber volume fraction in each layer should be approximately 30 to 42 vol%.

[0044] The individual layers are aligned at an angle of more than 10°, preferably 90°, with respect to the orientation of the parallel fibers of each layer.

[0045] Independently of this and according to the invention, the fibers within the unidirectional fiber layer are cut according to a special or desired cutting pattern before the layers are laid on top of each other.

[0046] In other words, the fibers, which are aligned parallel to each other, are aligned without being cut, in order to then be selectively cut within the area of ​​the layer used for a prepreg.

[0047] According to the invention, a multidirectional prepreg is provided, consisting of individual prepreg layers as the layers according to the invention, which in turn have a unidirectional arrangement of the fibers. Furthermore, the fibers are pre-cut, i.e., cut within the respective fiber layer. These cuts are not continuous, but rather several spaced-apart cuts are made, each of which can have a length of 10 to 30 mm.

[0048] The cut following a cut in the longitudinal direction of the fibers can be offset, for example by an offset of 10 to 30 mm. The cuts should be made in such a way that they can overlap when viewed in the longitudinal direction of the fibers.

[0049] While straight cuts are preferred, other geometries are also possible.

[0050] After cutting the fibers of a layer, at least two unidirectional and impregnated or infiltrated fiber layers are joined together with correspondingly cut, i.e., pre-assembled, fiber filaments. Prepregs formed in this way hold together without any additional support, regardless of the fiber cuts, because the orientations of the unidirectional layers form an angle between them that is greater than 0°, preferably 90°. These multidirectional prepregs can then be draped onto a mold to the desired extent and pressed onto it, for example, in an autoclave.

[0051] This is followed by drying and sintering, as is well known in the production of ceramic composite materials.

[0052] Surprisingly, despite the severed fibers, good mechanical values ​​are achieved, comparable to conventional fabric-reinforced composites.

[0053] Another advantage is that automated manufacturing and processing of the layers into prepregs is possible.

[0054] The manufacturing process is carried out as follows. First, a unidirectional fiber filament layer is produced, for example, using a winding or laying machine (prepreg machine for unidirectional tapes). For this purpose, one or more rovings are used, which can consist of, for example, 50,000 individual filaments with filament diameters in the range of 10 µm. The roving is then impregnated by passing it through a slurry containing, as previously described, ceramic particles, an alcoholic compound (especially glycerin), water, and optionally a dispersant and / or a binder such as an organic polymer binder. The impregnated roving can then be wound onto a core.

[0055] Rovings of any denier and length can be processed. There is no waste, unlike in textile processing.

[0056] The layer of parallel, infiltrated fibers, removed from the core after winding and arranged on a release film, is processed by cutting the fibers according to a desired pattern, i.e., by assembling them. The film is then removed, and at least two assembled unidirectional fiber filament layers are layered on top of each other. The orientation of the fibers in the layers to each other includes an angle α with α > 10°, in particular an angle of 90°, in order to provide a bi- or multidirectional prepreg.

[0057] The invention is of particular interest for materials in which high-modulus fibers with low elongation at break are used and the matrix also has a high modulus of elasticity and low elongation at break. This applies especially to ceramic composites. Furthermore, the process is advantageous for filler-containing liquid matrix precursors.

[0058] The production of unidirectional fiber filament layers ensures infiltration of the fiber bundle. The fiber filaments are arranged parallel, straight, and non-wavy. This offers the advantage that the ceramic particles of the matrix precursor, i.e., the slurry, remain within the fiber bundle during processing, e.g., in the autoclave process, so that the individual filaments do not touch each other.

[0059] The invention results in prepregs with a fiber volume content of 30 to 42 vol.%. Load-adapted fiber alignment is enabled.

[0060] A composite material can be reproducibly provided in which bi- or multidirectional prepregs with cut unidirectional fiber filament layers are used, thus enabling simplified draping.

[0061] Residual stress and distortion of the component are avoided, an advantage that is particularly important for high-modulus fibers and matrices with low elongation at break. The limitations associated with thick-walled curved structures are essentially eliminated.

[0062] Complex geometries with radii of up to 1 mm, e.g. by deep drawing, are possible.

[0063] Thin-walled sheets can be produced because the prepregs can be laid down accurately and precisely.

[0064] According to the invention, a ceramic composite material is produced using prepregs that are suitable for manufacturing and material properties. The fiber architecture of the prepregs provides ceramic composite materials with damage-tolerant fracture behavior, while distortion and internal stress are avoided or reduced. Deep drawing is made possible.

[0065] Furthermore, the fiber architecture prevents or reduces particle migration into fiber bundle areas. The fiber filaments are completely surrounded by the matrix filler and therefore essentially have no contact points.

[0066] Further details, advantages and features of the invention will become apparent not only from the claims and the features to be derived therefrom - individually and / or in combination - but also from the following description of preferred embodiments to be derived from the drawings.

[0067] They show: Fig. 1 a schematic representation of a layer according to the invention with a first type of cuts, Fig. 2 a layer according to the invention with a second type of cuts, Fig. 3 a layer according to the invention with cutting templates, Fig. 4 a multiply curved structure and Fig. 5 an arc-shaped structure.

[0068] Further details and advantages of the teaching according to the invention become apparent from the figure, which relate to the production of a layer intended for a prepreg, by means of which a ceramic composite material is produced, which can be used, for example, for a casting trough, for a charging aid for, for example, aluminium casting, for walls and linings for aircraft gas turbines, for nozzles for burner technology, for shaped parts for the heat treatment of metals.

[0069] The objects or components in question can, by way of example, have lengths between 10 mm and 3,000 mm, wall thicknesses in the range of 0.5 mm and 10 mm, and radii of curvature that can be up to 1 mm.

[0070] In particular, several of the layers according to the invention are arranged one above the other, in order to then - if necessary after cutting to the desired geometry - be placed or draped onto a carrier which defines the negative shape of an object to be manufactured, in order to subsequently be subjected to a vacuum pressing process and a sintering process in the usual manner.

[0071] Draping without supports is also possible.

[0072] In Fig. 1 A unidirectional layer 10 according to the invention is shown in principle, consisting of parallel fibers or fiber filaments 12, 14 which have been impregnated beforehand - as is known in the manufacture of fiber-reinforced components.

[0073] For this purpose, for example, a fiber bundle (roving), which can consist of 500 to 50,000 individual filaments, can be wound onto a core, whereby the roving has been infiltrated, i.e. impregnated, with a slurry before being laid down.

[0074] The fibers 12, 14 can consist of one or more of the oxides, mixed oxides, nitrides, carbonitrides, in particular of the elements Al, Si, Zr, Y, Mg, Ca or carbon, in particular of fibers from the group Al 2 O 3 , SiO 2 , ZrO 2 , Y 2 O 3 , Y 2 O 3 stabilized ZrO 2 , yttrium aluminum garnet , mullite , Si3N4 , SiC , SiCN , SiBNC or combinations of two or more of these materials.

[0075] For impregnation, a slurry is used which contains ceramic particles, in particular those from the group oxides, mixed oxides, nitrides, carbonitrides, especially of the elements Al, Si, Zr, Y, Mg, Ca or carbon, in particular Al 2 O 3 , SiO 2 , ZrO 2 , Y 2 O 3 , Y 2 O 3 stabilized ZrO 2 , yttrium aluminum garnet , mullite , Si 3 N 4 , SiC, SiCN, SiBNC or carbon or silicon or combinations of two or more such materials.

[0076] In particular, a slurry is used which preferably contains 10 vol.% to 40 vol.%, based on the total volume of the slurry, ceramic particles and 10 wt.% to 35 wt.%, based on the total weight of the ceramic particles in the slurry, glycerin, an organic binder, up to 2 wt.%, based on the total solids content of the slurry, and water.

[0077] After removing the infiltrated roving wound onto the core, layer 10 is obtained with the parallel fiber filaments 12, 14, whereby the fiber bundles are no longer individually distinguishable.

[0078] The roving should be wound around the core in such a way as to result in a layer thickness between 0.1 mm and 10 mm, preferably between 0.2 mm and 0.5 mm. Preferably, layer 10 should have a thickness of 0.4 mm. The layer thickness is determined by the denier of the rovings used and the settings, e.g., the winding process.

[0079] The impregnation and fiber layer density should be such that a fiber volume content between 20 vol.% and 60 vol.%, in particular between 30 vol.% and 42 vol.%, is achieved.

[0080] The corresponding fibers 12, 14 should be arranged on a separating film.

[0081] According to the invention, the fibers 12, 14 are partially cut. Corresponding cuts are identified by reference numerals 16, 18, 20, 22, 24, 26, 28.

[0082] The cuts 16, 18, 20, 22, 24, 26, 28 – hereinafter referred to simply as cuts – exhibit, as shown in the illustration in Fig. 4 The following arrangement is preferred.

[0083] In the exemplary embodiment, the sections of successive rows 30, 32 are oriented in opposite directions.

[0084] Furthermore, the cuts are made at an angle β to the longitudinal axis of the fibers 12, 14, which can be between 45° and 90°. A preferred angle β is 75°.

[0085] The length L of cuts 16, 18, 20, 22, 24, 26, 28 should be between 5 mm and 100 mm, preferably in the range of 25 mm.

[0086] The distance a between two similarly oriented cuts 20, 22 should be in the range between 5 mm and 75 mm, preferably in the range of 30 mm.

[0087] Furthermore, sections of successive rows 30 and 32 should overlap (double arrow U), as can be seen in the diagram. The overlap U in percent should be between 0% and 90%, particularly in the range of <16%, so that, according to the diagram, the Fig. 1 , according to which the cuts 16, 18, 20, 22, 24, 26, 28 cut the fibers 12, 14 at an angle of + / - 75°, the overlap is 5 mm.

[0088] If, in the exemplary embodiment, the sections 16, 18, 20, 22, 24, 26, 28 are straight, other section geometries, such as waves, polygons, wave segments or similar, are also possible.

[0089] Sections can also have irregular geometries, as can be seen from the Fig. 2 This is illustrated. Thus, fibers 12, 14 are severed by cuts 34, 36 exhibiting an irregular wave geometry.

[0090] After cutting the fibers 12, 14, appropriately prepared layers are placed on top of each other, wherein the orientation of the fibers of one layer to the orientation of the unidirectional fibers of the other layer includes an angle α which is greater than 10°, in particular should be 90°.

[0091] Prepregs can then be cut from a corresponding stack of layers, as is done in Fig. 3 This is shown in purely principle terms. From a corresponding stack of 200 layers, the topmost of which corresponds to layer 10 in terms of its cuts, prepregs 202, 204, and 206 can be cut and then draped, for example, by placing them on a form. Several corresponding prepregs can also be stacked on top of each other.

[0092] The fiber-severing cuts are clearly visible within the blanks for the prepregs 202, 204, 206.

[0093] Lamination then takes place in the usual way using vacuum pressing, with a residual pressure in the range of 2 kPa to 40 kPa. Vacuum drying can then be carried out at a temperature of, for example, 60 °C to 140 °C.

[0094] Finally, the resulting body is sintered, with temperatures in the range between 1,100 °C and 1,300 °C being preferred.

[0095] Based on the Fig. 4 and 5 The following are purely exemplary examples of shaped bodies produced from layers manufactured according to the invention or from prepregs formed therefrom.

[0096] Thus, in Fig. 4 A layer 300 of a multiply curved body is shown. In principle, the unidirectional layer 300 is shown with the parallel fiber filaments 312, 314, which in the simplified representation are cut by sections 318, 320 perpendicular to their longitudinal direction.

[0097] In Fig. 5 The figure shows a prepreg consisting of two layers 400 and 500, in which the parallel fibers 412 and 414 of layer 400 extend perpendicularly to the parallel fibers 512 and 514 of layer 500. The fibers 412, 414, 512, and 514 are also cut, as indicated by sections 418, 420, 518, and 520.

[0098] By forming corresponding layers 400, 500, a prepreg and thus a composite body can be produced that is strongly curved, with radii up to 1 mm possible.

Claims

1. A method for producing a layer (10, 300, 400, 500) containing impregnated and unidirectionally arranged fibres (12, 14, 312, 314, 412, 414, 512, 514) for use as a prepreg or for a prepreg (202, 204, 206) intended for the production of a fibre-reinforced object, wherein fibres are cut through after production of the layer in several areas at a distance to one another, and wherein cuts (16, 18, 20, 22, 24, 26, 28, 318, 320, 418, 420, 518, 520) formed in this way extend within limits of the prepreg, characterized by the method steps: - Impregnation of the fibres (12, 14, 312, 314, 412, 414, 512, 514) with a slip containing - 10 % v / v to 50 % v / v of ceramic particles, relative to the total volume of the slip, wherein the ceramic particles used are those from the group of oxides, mixed oxides, nitrides, carbonitrides of the elements Al, Si, Zr, Y, Mg, Ca, or carbon, - water, - 10 % v / v to 35 % v / v of alcoholic compound, such as glycerol, relative to the total weight of the ceramic particles in the slip, - Arrangement of the layer produced in this way on a carrier element and subsequent cutting through of the fibres.

2. The method according to claim 1, characterized in that the fibres (12, 14, 312, 314, 412, 414, 512, 514) are cut through at a cutting angle β, relative to the longitudinal axis of the fibres, of 45° ≤ β < 90°, preferably of 60° ≤ β < 86°, particularly preferably where β is equal to or approximately equal to 75°.

3. The method according to claim 1 or 2, characterized in that when viewed in the longitudinal direction of the fibres (12, 14, 312, 314, 412, 414, 512, 514), the distance a between consecutive cuts (16, 18, 20, 22, 24, 26, 28, 318, 320, 418, 420, 518, 520) is 5 mm ≤ a ≤ 75 mm, in particular 20 mm ≤ a ≤ 40 mm, preferably where a is equal to or approximately equal to 30 mm and / or that the length L of a cut is 5 mm ≤ L ≤ 100 mm, in particular 10 mm ≤ L ≤ 30 mm, preferably where L is equal to or approximately equal to 25 mm.

4. The method according to at least one of the preceding claims, characterized in that when viewed in the longitudinal direction of the fibres (12, 14, 312, 314, 412, 414, 512, 514), consecutive rows (30, 32) of cuts (16, 18, 20, 22, 24, 26, 28, 318, 320, 418, 420, 518, 520) are oppositely oriented and / or that when viewed in the longitudinal direction of the fibres, consecutive cuts overlap over a length U, in particular over a length in percent of 0 ≤ U ≤ 90, in particular of 0 ≤ U ≤ 20, particularly preferably where U is equal to or less than 16.

5. The method according to at least one of the preceding claims, characterized in that in a plan view onto the layer (10, 300, 400, 500), the cut (16, 18, 20, 22, 24, 26, 28, 318, 320, 418, 420, 518, 520) has the geometry of a straight line, of a wave section, of a polygonal chain section or of a combination of one or more of these elements.

6. The method according to at least one of the preceding claims, characterized in that the layer (10, 300, 400, 500) is arranged on a carrier film as the carrier element.

7. The method according to at least one of the preceding claims, characterized in that the fibres (12, 14, 312, 314, 412, 414, 512, 514) used are fibres of a fibre bundle, wherein the fibre bundle consists of 500 to 50,000, in particular of 3,000 to 7,000, particularly preferably of approximately 5,000 fibres.

8. The method according to at least one of the preceding claims, characterized in that the fibres (12, 14, 312, 314, 412, 414, 512, 514) used are fibres from the group of glass fibres, carbon fibres, ceramic fibres, or a combination of one or more of these fibres.

9. The method according to at least one of the preceding claims, characterized in that the materials used for the fibres (12, 14, 312, 314, 412, 414, 512, 514) are oxides, mixed oxides, nitrides, carbonitrides, in particular of the elements Al, Si, Zr, Y, Mg, Ca or carbon, in particular fibres from the group of Al2O3, SiO2, ZrO2, Y2O3, Y2O3 stabilized ZrO2, yttrium aluminium garnet, mullite, Si3N4, SiC, SiCN, SiBNC or combinations of two or more of these materials.

10. The method according to at least one of the preceding claims, characterized in that the ceramic particles used are those from the group of Al2O3, SiO2, ZrO2, Y2O3, Y2O3 stabilized ZrO2, yttrium aluminium garnet, mullite, Si3N4, SiC, SiCN, SiBNC or carbon or silicon or combinations of two or more of such materials.

11. A method for producing a prepreg (202, 204, 206) using several layers (10, 300, 400, 500) according to at least claim 6, wherein layers are laid one above the other such that the orientation of the unidirectional fibres of consecutive layers form an angle α of α > 0°, in particular of 30° ≤ α ≤ 90°, preferably of α = 90°, wherein the carrier films are removed prior to laying the layers one above the other.

12. A prepreg (202, 204, 206) consisting of one or more layers (10, 300, 400, 500) or containing such produced according to at least one of the preceding claims.

13. The prepreg according to claim 12, characterized in that the prepreg (10, 300, 400, 500) has several layers (10, 300, 400, 500), wherein the orientations of the unidirectional fibres (12, 14, 312, 314, 412, 414, 512, 514) of consecutive layers form an angle α of α > 0°, in particular of 30° ≤ α ≤ 90°, preferably of α = 90°, and the layers are preferably free of carrier films.

14. The prepreg according to claim 12 or 13, characterized in that the layer of the prepreg (10, 300, 400, 500) has a thickness d of 0.5 mm ≤ d ≤ 1 mm, in particular of 0.2 mm ≤ d ≤ 0.5 mm, particularly preferably where d is equal to or approximately equal to 0.4 mm.

15. The prepreg according to at least one of claims 12 to 14, characterized in that the fibres (12, 14, 312, 314, 412, 414, 512, 514) have a diameter D of 5 µm ≤ D ≤ 20 µm, in particular where D is equal to or approximately equal to 10 µm.