Semipreg with matrix coating

Abstract

The invention relates to a semipreg made of UD layers, wherein one or both outer layers of the semipreg has / have 30 to 45 wt.% of matrix material, based on the total weight of the semipreg. At least 60 wt.% of the matrix material (based on the total weight of the semipreg) penetrates less than 100 µm of the semipreg (measured in the thickness direction of the semipreg). The invention additionally relates to a method for producing the semipreg and to a method for producing a fiber-reinforced composite component made of the semipreg.

Description

[0001] Semi-prepreg with matrix coating

[0002] Description:

[0003] The invention relates to a semi-prepreg with at least two unidirectional fiber layers and a matrix coating according to the preamble of claim 1.

[0004] Unidirectional fiber layers (UD layers) are well known. UD layers are also known, which are impregnated with a matrix material to form a prepreg. In a prepreg, the matrix material is usually located within the fiber material. Preferably, the matrix material is evenly distributed throughout the fiber material in a prepreg, meaning the matrix material is present in approximately equal proportions throughout the fiber material.

[0005] Document US 2009 / 0068428 describes a type of fabric with an adhesive layer on at least one side. A plurality of fabric layers are bonded together by the adhesive layer. The fabric has reinforcing fibers in one direction and interwoven auxiliary threads. The adhesive content on at least one surface of the fabric should not exceed 40 g / m 2 and the resulting material is then impregnated with a matrix material.

[0006] DE 10 2011 084 626 discloses a fiber-reinforced composite material intended for use as a clutch disc. The composite material comprises at least two superimposed carbon fiber layers, with the layers said to be impregnated with a matrix.

[0007] Document US 2012 / 0100354 describes a fiber-reinforced material to be formed from NCFs and containing carbon fibers. The material is to be subsequently processed with a matrix material, and the NCF layers are to be sewn together.

[0008] EP 3 705215 describes a process for impregnating textiles to form a prepreg, where the textile can be, for example, a UD material. In this process, the process parameters—such as the contact pressure—can be adapted to the different fabrics and the different matrix materials used, so that optimal impregnation or full impregnation can be achieved. Impregnation can be carried out on one or both sides.

[0009] A disadvantage of these materials is that matrix material usually has to be added to the material if a component (e.g., a fiber-reinforced composite component) is to be produced from it. If the material already contains the required matrix material (in the form of a prepreg), the matrix material is integrated within the fiber layer, and the material is generally difficult to drape as a prepreg.

[0010] Document US 2022 / 0388274 further describes the use of fiber layers, for example in the form of nonwovens or UD fiber layers. A matrix layer is provided on one side in direct contact with the fiber layers, which is intended to bond the superimposed fiber layers to each other. The matrix layer is intended to bond the two fiber layers by impregnating the two fiber layers. Consequently, the matrix material of the matrix layer must penetrate into both fiber layers and (based on the arrangement of the matrix layer) at least completely penetrate the adjacent fiber layer in order to also at least partially penetrate the more distant fiber layer. According to the document, the material can contain 20 to 50 wt% matrix material.

[0011] The Japanese document JP 2018065999 proposes a reinforcing fiber material that may also comprise a matrix material. The reinforcing fibers can be present in a fiber aggregate, whereby, among other things, a sewn UD structure is also taught here. According to Figure 1, a matrix material is provided on one side of the fiber aggregate. The matrix material should preferably remain on the surface of the fiber aggregate at a concentration of 50 to 70 wt.%. Depending on the selected shape of the fiber aggregate and the selected matrix material, the matrix material should not impregnate more than 15 to 97 pm into the fiber aggregate. The matrix material content should be between 1 and 20 wt.% and improve the dimensional stability as well as the impregnability of the material.

[0012] A disadvantage of this state of the art is that a corresponding amount of matrix material still has to be added during the component production process.

[0013] The aim of the present idea was therefore to provide a semi-prepreg that already has the necessary matrix content for component production, but which should still be easy to drape.

[0014] This object is achieved by a semi-prepreg with the features of claim 1. According to claim 1, the semi-prepreg has at least two fiber layers, each fiber layer being a so-called UD fiber layer (and thus not a woven fabric). In a UD fiber layer, the fibers within the fiber layer lie parallel next to one another and against one another (without gaps). The at least two fiber layers form the outer layers of the semi-prepreg, so that each fiber layer has an outer side. The at least two fiber layers can be laid on top of one another in such a way that the fiber orientation of both fiber layers is essentially parallel to one another or the fiber orientations of the different fiber layers are at an angle other than 0° to one another. Furthermore, the fiber layers are sewn together, the sewing taking place perpendicular to the plane in which the reinforcing fibers of a fiber layer lie.The stitching therefore takes place in the thickness direction of the semi-prepreg to be formed, or rather the at least two fiber layers. The semi-prepreg has a matrix content of 30 to 45 wt.% matrix material based on the total weight of the semi-prepreg. Preferably, the semi-prepreg therefore has a matrix content (of 30 to 45 wt.%) based on the total weight of the fiber layers - formed from reinforcing fibers. The matrix material content is thus sufficient to produce a fiber-reinforced composite component (component) from the semi-prepreg without the need for additional (and often complex and time-consuming) matrix impregnation (e.g. in the form of matrix infusion) (during component production). However, the matrix material content is only located on an upper side and / or an underside of the semi-prepreg (i.e. on the outer surface(s) of the fiber layers). Furthermore, the matrix material hardly penetrates into the semi-prepreg. At least 60 wt.% of the total matrix material penetrates less than 100 pm into the semi-prepreg, with the penetration depth being measured essentially perpendicular (at an angle between 80° and 95°) to the direction of propagation of the reinforcing fibers in the fiber layers and in the thickness direction of the semi-prepreg. Therefore, the fiber material does not completely penetrate the matrix material within the semi-prepreg; rather, only a small weight fraction (less than 40 wt.%) of the matrix material penetrates deeper than 100 pm into the semi-prepreg. It should be clear that in a semi-prepreg in which at least 60 wt% of the matrix material penetrates less than 100 pm deep into the semi-prepreg, 60 wt% of the matrix material penetrates less than 100 pm deep into the fiber layer forming the outer layer or - in the case of a double-sided application of the matrix material to both outer surfaces - into both fiber layers forming the outer layers.This advantageously allows the semi-prepreg to remain drapable, as the fiber layers remain flexible relative to each other. It was extremely surprising that, even with such a shallow penetration depth, such a high proportion of the matrix can be bonded to the semi-prepreg via the fiber layers. When using more than two fiber layers, at least two fiber layers form the outer layers of the semi-prepreg, and the remaining fiber layers are located within the semi-prepreg. The remaining fiber layers within the semi-prepreg are preferably free of matrix material.

[0015] If the fiber layers were completely penetrated with matrix material, the semi-prepreg would essentially contain no air and would have a porosity of less than 10% (preferably less than 4% to 2%).

[0016] The semi-prepreg having the features of claim 1 should preferably have a porosity which is greater than 10%, preferably greater than 15%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 70%, greater than 80%, greater than 90%.

[0017] The semi-prepreg with the matrix material content mentioned in claim 1 can be referred to as a so-called non-crimp fabric (NCF) semi-prepreg.

[0018] A semi-prepreg is understood to be a textile fiber material, preferably in the form of UD fiber layers, that contains between 25% and a maximum of 60% matrix material, based on the total weight of the semi-prepreg. The matrix material is not evenly distributed throughout the fiber material (i.e., the fiber layers), but rather the majority of the fiber material is free of matrix material. The outer surfaces of the semi-prepreg are formed by the outer surfaces of the fiber material, i.e., the fiber layers.

[0019] In one embodiment of the semi-prepreg, the matrix material is applied to the semi-prepreg by means of coating (for example by dipping, powdering and / or melting).

[0020] Preferably, at least 60 wt.% of the total matrix material penetrates less than 70 pm, preferably less than 50 pm, preferably less than 40 pm, preferably less than 30 pm, preferably less than 25 pm, more preferably less than 20 pm into the fiber layer, wherein the penetration depth is measured approximately perpendicular (at an angle between 80° and 95°) to the direction of propagation of the reinforcing fibers in the fiber layers. In one embodiment of the semi-prepreg, at least 90 wt.% of the total matrix material penetrates less than 70 pm, preferably less than 50 pm, preferably less than 40 pm, preferably less than 30 pm, preferably less than 25 pm, more preferably less than 20 pm into the fiber layer of the semi-prepreg, wherein the penetration depth is measured approximately perpendicular (at an angle between 80° and 95°) to the direction of propagation of the reinforcing fibers in the fiber layers.

[0021] In an embodiment in which both outer surfaces of the semi-prepreg comprise the matrix material, in one embodiment what has just been disclosed regarding the penetration depth of the matrix material and the proportion of the penetrating matrix material should apply to each individual outer surface of the corresponding fiber layer. The different outer surfaces of the different fiber layers can have the same penetration depth and proportion of penetrating matrix material or different penetration depths and proportions. As explained, the semi-prepreg therefore comprises a matrix material proportion that is sufficient for component production without the matrix material having completely penetrated the semi-prepreg prior to component production. In the semi-prepreg according to claim 1, which is not completely penetrated by a matrix material, only one or both outer sides comprise the matrix material.In particular, the center of the semi-prepreg – i.e., the area where the two fiber layers touch (in a structure with only two fiber layers) – is free of matrix material. This enables a high degree of mobility between the at least two fiber layers, thereby increasing the drapability and formability of the semi-prepreg. In a semi-prepreg with more than two fiber layers, the fiber layers located in the middle in the thickness direction should be free of matrix material. For example, in a semi-prepreg formed from four fiber layers laid on top of one another, the second and third fiber layers are preferably free of matrix material (and the area between the second and third fiber layers is also free). The semi-prepreg therefore always contains fiber material that is free of matrix material. The term "free of matrix material" in this context does not mean that the fibers of the fiber layer cannot exhibit so-called sizing (from the outset).Sizing is used especially for carbon fibers to facilitate fiber processing and amounts to a maximum of 6 wt.%, preferably only 3 wt.%, and even more preferably only 1.5 wt.% of the total weight of the fiber layer. For example, an epoxy or a thermoplastic, or a mixture of both, is used as sizing material.

[0022] In one embodiment, the entire matrix material is provided on the outer surface(s) over a continuous area. "Consistent area" means that essentially no surface portions of the corresponding outer surface (which are intended to contain matrix material) are free of matrix material. Preferably, at least 80%, preferably at least 90%, and most preferably 100% of a coated outer surface is coated with the matrix material. Due to the full-surface coating, the semi-prepreg can slide particularly well with the coating side over other or similarly constructed semi-prepregs or adhere to them (depending on the properties of the matrix material used).

[0023] In another embodiment, the entire matrix material is distributed discontinuously on the outer surface(s) of the semi-prepreg. Discontinuous distribution occurs particularly when the matrix material is not distributed over the entire outer surface(s). For example, the matrix material can be distributed in the form of islands or conglomerates on the outer surfaces, with the vast majority of the islands or conglomerates not interconnected (achievable, for example, with powder impregnation). Such a matrix distribution has the advantage that the semi-prepreg remains more flexible overall, so that its drapability can be further increased.

[0024] In one embodiment, the matrix material is not present as a grid, mesh or nonwoven material on one of the outer surfaces.

[0025] In one embodiment, both outer surfaces of the semi-prepreg are provided with a matrix material, wherein the amount of matrix material on the first outer surface is preferably equal to the amount of matrix material on the second outer surface. This advantageously results in a homogeneous structure of the semi-prepreg, which can simplify the production of the fiber-reinforced composite component from the semi-prepreg. For example, the fiber composite component can be produced from the semi-prepreg by joining the semi-prepreg to the fiber composite component under pressure and heat in a mold (e.g. a mold), whereby the existing matrix material flows evenly through the semi-prepreg and completely impregnates the semi-prepreg. With a homogeneous structure, the direction in which the semi-prepreg is inserted into the mold for component production is irrelevant. This advantageously prevents manufacturing errors and reduces scrap.

[0026] In another embodiment, both outer surfaces comprise the matrix material, but the amount of matrix material on the first outer surface is different from the amount of matrix material on the second outer surface. With such a design, for example, gravity can be utilized for component production if the outer surface with the high matrix material content is placed at the top of the mold, allowing the matrix material to flow downwards (also) with the aid of gravity to produce the component.

[0027] The matrix material for coating one or both outer sides of the semi-prepreg can be, for example, a thermoplastic, a thermoset, or a mixture of thermoplastic and thermoset. In one embodiment, the matrix material comprises polyetheretherketone, or preferably, polyetheretherketone is used exclusively as the matrix material. In one embodiment, the matrix material comprises polyphenylene sulfide (PPS), or preferably, polyphenylene sulfide is used exclusively as the matrix material. In one embodiment, the matrix material comprises polyetherimide (PEI), or preferably, polyetherimide is used exclusively as the matrix material. In one embodiment, the matrix material comprises polyaryletherketone (PAEK), or preferably, polyaryletherketone is used exclusively as the matrix material.If one of the mentioned matrix materials is used exclusively, this means that 95 to 100%, preferably 100%, of the matrix material is the mentioned material.

[0028] In one embodiment, the matrix material for coating one or both outer sides is either a thermoplastic or a thermoset, wherein both the thermoplastic and the thermoset consist of less than six, less than four, less than three individual components.

[0029] In one embodiment, the matrix material is applied as a powder to one or both outer sides of the semi-prepreg, onto the corresponding outer sides of the fiber layers. The powder preferably has an average particle size of 20 to 100 μm, preferably 25-50 μm. In another embodiment, the matrix material is applied using an immersion bath, wherein the average particle size of the matrix material in the immersion bath is also between 20 to 100 μm, preferably between 25-50 μm. In another embodiment, the matrix material can also be applied to one or both outer surfaces of the semi-prepreg using a combination of powder coating and immersion bath, wherein a matrix material with an average particle size of the matrix material—as stated above—is used.

[0030] In a further embodiment, the semi-prepreg comprises additional unidirectional fiber layers and / or nonwoven layers between the outer layers. For example, the semi-prepreg can comprise four fiber layers, with a nonwoven layer being deposited between every two fiber layers (i.e., in the example with four fiber layers, three nonwoven layers). The nonwoven layers are preferably random-fiber nonwoven layers made of a thermoplastic fiber material with a basis weight of less than 5 g / m 2 . The fiber layers can preferably be arranged symmetrically in the semi-prepreg, for example having the following layer structure: 907 -45 7 +45790°.

[0031] In another embodiment of the semi-prepreg, the carbon fibers of the at least two fiber layers are essentially undulating within the fiber layers. Accordingly, the stitching of the fiber layers to each other is selected so that no waviness occurs between the fiber layers. The skilled person is aware, among other things, from document EP 2547816, that the stitch length and stitch width must be adjusted to take into account the fineness of the reinforcing fibers, the angle of the reinforcing fibers within the layers, and the linear density of the sewing thread.

[0032] According to a further embodiment of the semi-prepreg, the at least two fiber layers within the semi-prepreg have an angle of 0790°, +457135°, 307150° or 20760° to each other, or the at least two fiber layers are laid at a combination of the said angles to each other within the semi-prepreg.

[0033] A further subject matter of the present invention relates to a method for producing the semi-prepreg having the features of claim 1. Therefore, statements regarding the semi-prepreg should also apply to the method, where appropriate. On the other hand, statements regarding the method should also apply to the semi-prepreg, where appropriate.

[0034] In the method for producing the semi-prepreg, preferably, at least two fiber layers of reinforcing fibers are first formed, wherein the reinforcing fibers within each layer are arranged unidirectionally and parallel to one another. The UD layers (unidirectional layers) of reinforcing fibers are then deposited on top of one another, wherein the main propagation direction of the fibers of different fiber layers can form an angle of equal or different from 0° to one another. A nonwoven material can be provided between the at least two fiber layers of reinforcing fibers. In one embodiment of the method for producing the semi-prepreg, the at least two fiber layers of reinforcing fibers are sewn together (in the thickness direction) before the matrix material is applied. The sewing is preferably carried out such that the sewing thread forms loops beneath the superimposed fiber layers.In one embodiment of the method, the reinforcing fibers of each fiber layer are additionally sewn within the fiber layer, so that the reinforcing fibers of a fiber layer are resistant to displacement relative to one another within the fiber layer. In one embodiment, the sewing threads are made of a material that either dissolves in the matrix material used during subsequent processing of the semi-prepreg into the component (without forming a separate phase) or of a material that has a melting temperature higher than that of the matrix material and therefore predominantly remains intact during impregnation. In one embodiment, the sewing threads can be made of the same material as the matrix material to be applied. The matrix material is preferably applied to the first and / or second outer surface of the semi-prepreg thus formed by powder impregnation, powder coating, padding, doctor blade, and / or film transfer.

[0035] In one embodiment of the method for producing the semi-prepreg, the matrix material is first applied to a first and / or a second of the at least two fiber layers, and then the at least two fiber layers are stacked on top of each other, thus forming the semi-prepreg. In this case, the layers are arranged such that the matrix material forms the outer surface of the semi-prepreg. The different fiber layers are then sewn together (and also penetrate the matrix layer).

[0036] Another object of the present invention relates to a manufacturing method for a fiber-reinforced composite material. The fiber-reinforced composite material (component) is preferably formed solely from the semi-prepreg or a plurality of semi-prepregs, as described here. Statements regarding the semi-prepreg or the production of the semi-prepreg also apply accordingly to the method for producing the fiber-reinforced composite component, where appropriate. Preferably, the fiber-reinforced composite material is produced from the semi-prepreg (or a plurality of semi-prepregs) without the addition of any further matrix material, wherein the semi-prepreg (or a plurality of semi-prepregs) are formed into the fiber-reinforced composite material under pressure and heat.The matrix material required for component production (fiber-reinforced composite component) is therefore provided solely by the semi-prepreg and does not need to be introduced in a further process step, for example, by matrix injection. This simplifies the manufacturing process and shortens processing times.

[0037] Preferably, the component is formed from a single semi-prepreg. The semi-prepreg comprises a plurality of UD fiber layers. Depending on the component, the number of UD fiber layers can vary, and thus also the proportion of matrix material on one or both outer sides of the semi-prepreg.

[0038] When forming the component from two semi-prepregs, it is preferable to arrange the two semi-prepregs for the production of the composite material in such a way that the matrix material lies on the outer surfaces of the finished composite. In this example, semi-prepregs are used that each have the matrix material on only one outer surface.

[0039] When forming the component from more than two semi-prepregs or when using exactly two semi-prepregs, in one embodiment the semi-prepregs can also be arranged in the composite material to be produced such that one or more matrix material layers lie within the composite material to be produced. For this purpose, for example, when using more than two semi-prepregs, one (or more) semi-prepreg(s) with matrix material on the outer surface can be arranged between two or more semi-prepregs with matrix material on the outer surface and processed to form the composite material. The invention is explained in more detail below with reference to figures and examples, wherein the figures and examples only show exemplary embodiments of the idea. This is not intended to limit the scope of protection of the present idea.

[0040] Figure 1 shows a schematic representation of a semi-prepreg with a matrix coating, where the matrix coating is only present on an outer surface of the semi-prepreg.

[0041] Figure 2 shows a microscopic image of the semi-prepreg with a powder coating.

[0042] Figure 3 also shows a microscopic image of the semi-prepreg at a different magnification than Figure 2.

[0043] Figure 1 schematically shows a semi-prepreg 1 constructed from five UD fiber layers made of multifilament reinforcing fibers. Within each UD fiber layer, the reinforcing fibers lie parallel to one another, and fiber-free regions within a UD layer are essentially non-existent. The semi-prepreg 1 has two outer surfaces that run parallel to the main extension plane of the UD fiber layers. On one of the outer surfaces, the semi-prepreg in Figure 1 has a matrix material 2. In the embodiment of Figure 1, the matrix material 2 has been applied as a powder to the outer surface of the semi-prepreg 1. The application takes place such that the matrix material is applied to an outer surface of a UD fiber layer, which then forms the outer surface of the semi-prepreg 1. 30 to 45 wt.% of matrix material, based on the total weight of the semi-prepreg, is applied.If the semi-prepreg consists only of the UD fiber layers and the matrix material, the weight specification (30 to 45 wt.% based on the semi-prepreg) also corresponds to the specification 30 to 45 wt.% based on the total weight of the fiber layers. The matrix material 2 hardly penetrates into the UD fiber layer that forms the outer surface. Advantageously, the matrix material is therefore predominantly located only on the surface of the outer surface. Preferably, less than 40 wt.% of the total matrix material penetrates deeper than 100 pm in the thickness direction into the fiber layer of the semi-prepreg 1. Preferably, at least 60 wt.% of the total matrix material penetrates less than 20 pm in the thickness direction into the fiber layer of the semi-prepreg 1. Preferably, at least 90 wt.% of the total matrix material penetrates less than 100 pm in the thickness direction into the fiber layer of the semi-prepreg. Preferably at least 90 wt.% of the total matrix material penetrates less than 20 pm deep in the thickness direction into the fiber layer of the semi-prepreg. In one embodiment, at least 90 wt% of the total matrix material penetrates less than 10 pm deep in the thickness direction into the fiber layer of the semi-prepreg. The fiber layer of the semi-prepreg that comprises the matrix material is an outer layer of the semi-prepreg. For example, if 90 wt% of the total matrix material penetrates less than 20 pm deep in the thickness direction into the fiber layer of the semi-prepreg, then 90 wt% of the total matrix material also penetrates less than 20 pm deep in the thickness direction into the semi-prepreg. The matrix material 2 is therefore only located superficially on the fiber layer of the semi-prepreg 1 in the area of ​​the outer surfaces and the middle fiber layers are essentially completely free of the matrix material 2. This improves the mobility of the fiber layers among each other and increases the drapability of the semi-prepreg 1.The matrix material in the semi-prepreg therefore has no stabilizing functions within the semi-prepreg, such as ensuring the cohesion of different (fiber) layers.

[0044] Figure 2 shows a microscopic image of the semi-prepreg 1 with matrix material 2. The matrix material 2 is located primarily on an outer surface of the semi-prepreg 1 and barely penetrates the fiber layers 3 of the semi-prepreg 1. In the exemplary embodiment shown in Figure 2, the semi-prepreg 1 was impregnated with the matrix material 2 by powder binding. The polymer powder agglomerated during the impediment and was present as a kind of matrix material conglomerate on the outer surface of a fiber layer 3 of the semi-prepreg.

[0045] Figure 3 shows a microscopic image of the same material as in Figure 2 at a higher resolution. The matrix material 2 lies on top of the fiber layer 3 and barely penetrates the fiber layer 3.

[0046] Examples:

[0047] A multiaxial non-crimp fabric based on carbon fibers was produced on a multiaxial system (Karl Mayer Holding GmbH & Co. KG). First, individual layers in the form of fiber layers were produced from parallel, adjacent, and touching carbon fiber yarns of the type HTS45 E13 12K 800tex (Teijin Carbon Europe GmbH). Two of these fiber layers were stacked on top of each other such that the lower layer had an angle α of +45° and the upper layer an angle α of -45° with respect to the production direction of the multiaxial non-crimp fabric. The fiber layers arranged on top of each other in this way were knitted together using a sewing thread in a tricot weave in the thickness direction of the non-crimp fabric. In this example, the sewing threads used consisted of a co-polyamide and had a fineness of 33 dtex. The stitch length was 3.6 mm, the stitch width was 5 mm.

[0048] Example 1

[0049] The fabric produced in this way (multiaxial fabric) was then impregnated with a matrix material on a single outer side of the fabric. In Example 1, the fabric was impregnated using a powder scattering system (Machinesfabrik Herbert Meyer GmbH). The fabric was fed to the powder coating area via deflection rollers. The polymer used was PEEK 150 with an average particle size of between 10 and 100 μm (Victrex Manufacturing Limited). During the powder coating step, the polymer was evenly scattered and then melted using infrared heating fields. The powder coating step was carried out twice so that the fabric received a uniform coating on both sides. After powder coating was complete, the material was wound onto a cardboard tube, wrapped in film, and prepared for further processing for component production. The semi-prepreg produced in this way had a matrix content of 42% by weight.% with respect to the total weight of the semi-prepreg, whereby 60 wt.% of the matrix material has penetrated no deeper than 25 pm into the fiber layers of the semi-prepreg, measured from the outer surfaces with matrix material.

[0050] Example 2

[0051] In Example 2, the fabric produced as described above was impregnated with the matrix material by means of a dip impregnation process. The fabric was fed into the impregnation area via rollers. The polymer used was PEEK 150 with an average particle size between 10 and 50 pm (Victrex Manufacturing Limited). During the impregnation step, the fabric was passed through a dispersion of carrier liquid (organic solvent, preferably an alcohol or water) and the polymer powder and then dried until the material was free of carrier liquid. The polymer was then melted using infrared heating fields. The semi-prepreg was then wound onto a cardboard tube, wrapped in film, and prepared for further processing into components. The semi-prepreg had a matrix content of 42 wt.% based on the total weight of the semi-prepreg.The matrix material was located on both outer surfaces of the fiber layers of the semi-prepreg and about 60 wt% of the total matrix material penetrated no deeper than 25 pm into the semi-prepreg from the outer surfaces of the semi-prepreg (thus, about 60 wt% of the total matrix material penetrated no deeper than 25 pm into the fiber layers forming the outer surfaces of the semi-prepreg).

Claims

Semi-prepreg with matrix coating Claims:

1. Semi-prepreg (1) comprising at least two unidirectional fiber layers (3) made of carbon fibers, wherein the carbon fibers within each of the unidirectional fiber layers (3) are provided parallel to one another and adjacent to one another and the carbon fibers of adjacent unidirectional fiber layers (3) are laid at an angle between 0 and 180° to one another, wherein the semi-prepreg (1) contains 30 to 45 wt.% matrix material (2) based on the total weight of the semi-prepreg (1), wherein one of the at least two unidirectional fiber layers (3) forms a first outer layer of the semi-prepreg (1) and a first surface of this fiber layer is a first outer surface of the semi-prepreg (1), wherein the at least one other unidirectional fiber layer forms a second outer layer of the semi-prepreg (1) and a second surface of this fiber layer is a second outer surface of the semi-prepreg (1), wherein the first surface and the first outer surface lie approximately parallel to the second surface and the second outer surface, wherein the at least two unidirectional fiber layers (3) made of carbon fibers are sewn to one another perpendicular to the main propagation direction of the carbon fibers of the unidirectional fiber layers (3), characterized in that the entire matrix material (2) is provided on the first and / or the second outer surface, wherein at least 60 wt.% of the total. Matrix material (2) penetrates from this or these outer surface(s) less than 100 pm perpendicular to the main propagation direction of the carbon fibers of the unidirectional fiber layers (3) into the semi-prepreg (1).

2. Semi-prepreg (1) according to claim 1, wherein 90 wt.% of the total matrix material (2) penetrates into the semi-prepreg (1) starting from this or these outer surface(s) of the semi-prepreg (1) less than 20 pm, preferably less than 10 pm, perpendicular to the main propagation direction of the carbon fibers of the unidirectional fiber layers (3).

3. Semi-prepreg (1) according to claim 1 or 2, wherein the matrix material (2) is distributed on the outer surface(s) continuously and / or discontinuously.

4. Semi-prepreg (1) according to at least one of the preceding claims, wherein the amount of matrix material (2) on the first outer surface is equal to the amount of matrix material on the second outer surface or the amount of matrix material (2) on the first outer surface is not equal to the amount of matrix material (2) on the second outer surface.

5. Semi-prepreg (1) according to at least one of the preceding claims, wherein the matrix material (2) is a thermoplastic, a thermoset or a mixture thereof.

6. Semi-prepreg (1) according to at least one of the preceding claims, wherein the semi-prepreg (1) has further unidirectional fiber layers (3) and / or nonwoven layers between the outer layers.

7. Semi-prepreg (1) according to at least one of the preceding claims, wherein the carbon fibers of the at least two fiber layers (3) undulation-free in the fiber layers (3).

8. Semi-prepreg (1) according to at least one of the preceding claims, wherein the at least two fiber layers (3) are laid at an angle of 0790°, +457135°, 20760°, 307150° or in a combination of said angles to one another within the semi-prepreg (1).

9. A method for producing a semi-prepreg (1) according to at least one of claims 1 to 8, wherein the matrix material (2) is applied to the first and / or the second outer surface by powder impregnation, powder coating, padding, doctor blade and / or film transfer.

10. The method according to claim 9, wherein firstly the at least two unidirectional fiber layers (3) made of carbon fibers are laid down at an angle other than 0° to each other and then the matrix material (2) is applied.

11. Method according to claim 10, wherein before applying the matrix material (2) the at least two fiber layers (3) are sewn together perpendicular to the main propagation direction of the carbon fibers of the unidirectional fiber layers (3).

12. The method according to claim 10, wherein firstly the matrix material (2) is applied to a first and / or a second of the at least two fiber layers (3) and then the at least two fiber layers (3) are arranged to form the semi-prepreg (1) such that the matrix material (2) is present as the outer surface of the semi-prepreg (1).

13. Manufacturing process for a fiber-reinforced composite material, comprising at least one semi-prepreg (1) according to at least one of the Claims 1 to 8, wherein the at least one semi-prepreg (1) becomes the fiber-reinforced composite material under pressure and heat without the addition of a further matrix material.

14. Manufacturing method according to claim 13, wherein when using more than two semi-prepregs (1), these are arranged in the structure for the production of the composite material such that the matrix material lies on the outer surfaces of the composite material to be finished.

15. Manufacturing method according to claim 13, wherein for the production of the composite material, a single semi-prepreg (1 ) is used. a. Manufacturing method according to claim 14, wherein the semi-prepreg (1 ) has more than two fiber layers (3) and / or nonwoven material.

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