Method for producing a fiber-reinforced component

Abstract

Method for producing a fiber-reinforced component (10) containing recycled carbon fibers, comprising the following steps: a) providing a tool frame (20) by firmly connecting a circumferential frame part (22) and a base part (26) while providing a receiving space (24) for a tool (30) delimited by the tool frame (20), b) providing a tool (30) made of a pore-free and cavity-free plastic produced by 3D printing, wherein the tool (30) has at least one cavity (32) for shaping the component (10), and providing one or more predetermined breaking points on the tool (30), c) inserting the tool (30) into the receiving space (24) of the tool frame (20) in such a way that the tool (30) in the inserted state rests against the base part (26) and frame part (22) in such a way that support and force transmission takes place between the tool frame (20) and the tool (30), d) Providing a flowable molding compound which is a fiber-epoxy resin mixture containing recycled carbon fibers with a length of 50 µm to 150 µm with a fiber mass fraction of at least 30%, e) introducing the molding compound into the cavity (32) of the tool (30) by means of overpressure, f) curing the molding compound, and g) destroying the tool (30) after curing of the molding compound to expose the component (10).

Description

[0001] The invention relates to a method for producing a fiber-reinforced component.

[0002] DE 10 2012 212 610 A1 discloses a method for producing lightweight components from carbon fiber-reinforced thermoplastic. DE 10 2011 079 525 A1 relates to a method for producing a fiber-reinforced plastic semi-finished product. DE 10 2018 215 660 A1 relates to an injection mold for producing injection-molded components. DE 10 2016 221 390 A1 discloses an injection mold and a method for producing such a mold. DE 10 2014 001 445 A1 relates to a device for producing rotor blade shells. WO 2012 / 175 323 A1 relates to casting molds produced by generative processes. DE 10 34 844 A discloses destructible molds for producing molded bodies from meltable elastomers. EP 2 783 764 B1 discloses a pyrolysis system and a method for recovering carbon fibers from carbon fiber-containing plastics and recycled carbon fibers. EP 2 902 433 A1 discloses a method for producing carbon fiber pellets.

[0003] DE 10 2011 081 374 A1 discloses a method for producing a molded part made of carbon fiber-reinforced plastic, which can be used as a tool mold or lamination mold in the production of components made of carbon fiber-reinforced plastic (CFRP). Thus, several CFRP prepregs can be laminated on top of each other and cured and molded at a defined temperature and pressure. Due to the required rigidity, such tool molds are comparatively solid and are typically machined.

[0004] The object of the invention is to provide an improved method for producing a fiber-reinforced component.

[0005] The method for producing a fiber-reinforced component containing recycled carbon fibers comprises the steps described below.

[0006] A tool frame is provided by firmly connecting a surrounding frame part (limitation towards the sides, e.g. surrounding side wall) and a base part (limitation in the direction of gravity downwards) while providing a receiving space for a tool delimited by the tool frame (step a)).

[0007] Before, at the same time or thereafter, a tool made by 3D printing from a pore-free and cavity-free plastic is provided, wherein the tool has at least one cavity (negative mold) for shaping the component, and one or more predetermined breaking points are provided on the tool (step b)).

[0008] After the tool and the tool frame have been prepared, the tool is inserted into the receiving space of the tool frame in such a way that the tool, when inserted, rests against the base part and frame part in such a way that support and force transmission takes place between the tool frame and the tool (step c)).

[0009] Before, at the same time or after steps a) to c), a flowable casting compound or molding compound (material for producing the component) is provided, which is a fiber-epoxy resin mixture containing the recycled carbon fibers with a length of 50 µm to 150 µm with a fiber mass fraction of at least 30% (step d)).

[0010] The molding compound is then introduced into the cavity of the tool or the cavity of the tool is filled with the (flowable) molding compound by means of overpressure (step e)).

[0011] During and / or after the molding compound is introduced, it cures (step f). In other words, the (flowable) molding compound cools and hardens into the fiber-reinforced component.

[0012] After the molding compound has cured, the mold is destroyed to expose the fiber-reinforced component (step g). The component can then be removed from the receiving space and / or the mold. The component's shape (outer contour) corresponds to the cavity (inner contour) formed on or in the mold before the mold was destroyed.

[0013] By inserting or placing the tool into the receiving space of the tool frame, the tool frame can support or stabilize the tool, so that a comparatively high level of rigidity and strength can be achieved through the combination of tool and tool frame. This allows comparatively high pressures to be used during component production (step e)). Tools manufactured using conventional 3D printing, for example, from plastic, can be used as tools. By arranging the tool in the tool frame, the lower rigidity and strength of the tool materials (e.g., plastic) can be compensated or equalized. The tool frame is designed, in particular, as an inherently rigid frame.

[0014] The molding compound is preferably produced by stirring recycled carbon fibers into the epoxy resin. This makes it easy to create a flowable molding or casting compound.

[0015] According to the invention, the recycled carbon fibers have a length of 50 µm to 150 µm, in particular 100 µm (micrometers). This allows the carbon fibers to achieve a stabilizing effect on the component in the cured state, while the flowability of the molding compound is sufficiently maintained in the uncured (flowable) state.

[0016] The fiber mass fraction of recycled carbon fibers in the molding compound is at least 30%, preferably at least 40%, and more preferably at least 50%. This allows a high proportion of recycled carbon fibers and thus a high stabilizing effect for the component to be achieved with a sufficiently flowable molding compound.

[0017] Preferably, the tool (manufactured by 3D printing) can be made of plastic, in particular a thermoplastic (e.g., polylactide (PLA), etc.) or a thermoset. This contributes to a cost-effective and comparatively lightweight construction of the tool.

[0018] The plastics of the tool are designed without pores or unwanted cavities (the cavities described above are not unwanted cavities). The printed plastics and the printed tool behave particularly incompressibly under compressive stress.

[0019] The mold has one or more predetermined breaking points. These predetermined breaking points facilitate the exposure of the component contained in the cavity of the (still undamaged) mold.

[0020] The frame part and the base part of the tool frame are connected to each other, in particular by bolting. The frame part and the base part are firmly connected to each other. This facilitates the support of a tool arranged in the receiving space. The base part is particularly designed such that it completely closes the clear cross-section of the frame part. The base part and the frame part can have the same main dimensions (length and width).

[0021] Preferably, the tool can be designed such that it can be inserted into the receiving space of the tool frame. Thus, the outer contour of the tool and the inner contour of the frame part and the base part can largely, in particular completely, correspond to one another. When inserted, the tool rests against the base part and frame part in such a way that support and force transmission occur between the tool frame and the tool. This allows for particularly high pressures during component production.

[0022] Further advantageous embodiments will become apparent from the following description and the drawing. The drawing shows, schematically, Fig. 1 a tool frame used in the process in a plan view ( Fig. 1a) and in a Fig. 1a drawn sectional view ( Fig. 1b); and Fig. 2 the tool frame Fig. 1 with inserted tool and manufactured component in a top view ( Fig. 2a) and in a Fig. 2a drawn sectional view ( Fig. 2b).

[0023] The Fig. 1a and Fig. 1b shows a tool frame, designated overall by reference numeral 20. The tool frame 20 has a circumferential frame part 22, which defines a receiving space 24 for a tool on the sides. Furthermore, the tool frame 20 has a base part 26, which defines the receiving space 24 downwards in the direction of gravity g (see FIG. Fig. 1b).

[0024] The frame part 22 and the base part 26 of the tool frame 20 are connected to one another and, in the example, bolted together. In the example, the base part 26 is designed such that it completely closes the clear cross-section of the frame part 22. In the example, the base part 26 and the frame part 22 have the same main dimensions (same length and width; see Fig. 1a and Fig. 1b).

[0025] The Fig. 2a and Fig. 2b show the tool frame 20, wherein a tool 30 is inserted into the receiving space 24 and the fiber-reinforced component 10 is also shown.

[0026] The tool 30 is manufactured by 3D printing and, in the example, has a cavity 32 for shaping the component 10. The tool 30 is made of plastic, in particular a thermoplastic or a thermoset, as described above. The plastic is formed without pores and undesired cavities (the cavity 32 is not an undesired cavity).

[0027] In the example, the tool 30 is designed such that it can be inserted into the receiving space 24 of the tool frame 20. The outer contour 34 of the tool 30 and the inner contour 28 of the frame part 22 and the base part 26 correspond largely, in particular completely, to one another. In the inserted state, the tool 30 rests against the base part 26 and the frame part 22 in such a way that support or force transmission can occur between the tool frame 20 and the tool 30.

[0028] The tool 30 has one or more predetermined breaking points (not shown). These facilitate the release of the component 10 from the cavity 32 (release of the component 10 is shown in Fig. 2a and Fig. 2b has not yet been done).

[0029] As explained above, component 10 is formed from a cured fiber-resin mixture, namely a mixture or molding compound of recycled carbon fibers and epoxy resin (not shown in detail). The recycled carbon fibers are mixed with the epoxy resin, in particular, stirred into it. In the example, the recycled carbon fibers have a length of 50 µm to 150 µm. The fiber mass fraction of the recycled carbon fibers in the molding compound is at least 30% in the example.

[0030] The process for producing the fiber-reinforced component containing recycled carbon fibers can be as follows.

[0031] The tool frame 20 is provided, which delimits the receiving space 24 for the tool 30 by the surrounding frame part 22 and the base part 26 (cf. Fig. 1a and b). Before, simultaneously, or afterward, the tool 30 is manufactured and provided accordingly by 3D printing, wherein the tool 30 in the example has a cavity 32 (negative mold) for shaping the component 10.

[0032] After the tool 30 and the tool frame 20 have been prepared, the tool 30 is inserted into the receiving space 24 of the tool frame 20 (cf. Fig. 2a and b). Before, simultaneously, or after these steps, a flowable casting or molding compound (material for producing component 10) is provided, which is a fiber-epoxy resin mixture containing the recycled carbon fibers.

[0033] The molding compound is then introduced into the cavity 32 of the tool 30, or the cavity 32 of the tool 30 is filled with the (flowable) molding compound using overpressure. During and / or after the introduction of the molding compound, the molding compound hardens. In other words, the (flowable) molding compound cools and hardens to form the fiber-reinforced component 10 (see FIG. Fig. 2a and b).

[0034] After the molding compound has hardened, the tool 30 is destroyed to expose the fiber-reinforced component 10. The component 10 can thus be removed from the receiving space 24 and / or the tool 30. The component 10 corresponds in its shape (outer contour) to the cavity 32 (inner contour) arranged on or in the tool 30 before the tool 30 was destroyed.

[0035] The procedure can be further developed as described above.

Claims

[1] Method for producing a fiber-reinforced component (10) containing recycled carbon fibers, comprising the following steps: a) providing a tool frame (20) by firmly connecting a circumferential frame part (22) and a base part (26) while providing a receiving space (24) for a tool (30) delimited by the tool frame (20), b) providing a tool (30) made of a pore-free and cavity-free plastic produced by 3D printing, wherein the tool (30) has at least one cavity (32) for shaping the component (10), and providing one or more predetermined breaking points on the tool (30), c) inserting the tool (30) into the receiving space (24) of the tool frame (20) in such a way that the tool (30) in the inserted state rests against the base part (26) and frame part (22) in such a way that support and force transmission takes place between the tool frame (20) and the tool (30), d) Providing a flowable molding compound which is a fiber-epoxy resin mixture containing recycled carbon fibers with a length of 50 µm to 150 µm with a fiber mass fraction of at least 30%, e) introducing the molding compound into the cavity (32) of the tool (30) by means of overpressure, f) curing the molding compound, and g) destroying the tool (30) after curing of the molding compound to expose the component (10). [2] Method according to claim 1, characterized by Mixing the molding compound with the recycled carbon fibers with a fiber mass fraction of at least 40%. [3] Method according to claim 1, characterized by Mixing the molding compound with the recycled carbon fibers with a fiber mass fraction of at least 50%. [4] Method according to one of the preceding claims, characterized by Forming the tool (30) from a thermoplastic or a thermoset. [5] Method according to one of the preceding claims, characterized by Connecting the frame part (22) to the base part (26) of the tool frame (20) by bolting.

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