Method for producing a fiber composite component with integrated load introduction element, load introduction element and pressing tool

Abstract

Method for producing a fiber composite component (23) with an integrated load introduction element (10), comprising at least the following steps: ▪ Providing a pressing tool (20) with a first tool part (22) and a second tool part (21), wherein the first tool part (22) and the second tool part (21) form a cavity (24) for the shaping reception of the fiber composite component (23) in a closed state of the pressing tool (20), ▪ Positioning a first sub-element (11) of the load introduction element (10) in a first receptacle (22a) of the first tool part (22), wherein the first sub-element (11) comprises a connecting portion (12) which is connected at a first end (12a) to a first disc element (13), wherein the first disc element (13) is arranged facing a tool surface (22b) of the first tool part (22) and the connecting portion (12) is arranged facing away from this, ▪ Positioning a second sub-element of the load introduction element (10) in a second receptacle (21a) of the second tool part (21), wherein the second sub-element comprises a second disc element (15) which has a concentric recess (15a), ▪ Arranging a semi-finished fiber product (23) between the first (22) and the second tool part (21), and ▪ Closing the pressing tool (20) and pressing the semi-finished fiber product (23), wherein the connecting section (12) is at least partially pressed into the recess (15a) of the second disc element (15).

Description

[0001] The invention relates to a method for producing a fiber composite component with an integrated load introduction element, a load introduction element and a pressing tool for carrying out the method.

[0002] To connect fiber composite components to other components, especially metal components, it is known to provide load introduction elements (so-called inserts) in the fiber components. These load introduction elements locally reinforce the fiber composite component by ensuring a flat force introduction and thus preventing damage to the fiber structure. The load introduction elements typically also include fasteners such as bolts, screws, nuts, or simply recesses or holes to enable connection to the other components.

[0003] The load introduction elements are typically applied in subsequent steps to already finished and cured fiber composite components, resulting in considerable additional effort for preparing the joining surfaces by milling, grinding, and cleaning, as well as for the actual joining by surface bonding. In this case, the connection is provided solely by the material bond and is therefore limited in its strength.

[0004] Furthermore, methods are known for attaching the load introduction elements to the fiber composite component during its manufacturing process. This is achieved by inserting the load introduction element into the pressing tool and then wet pressing, whereby a semi-finished fiber product is formed into the component under high pressure and cross-linked. In this process, the load introduction elements are simultaneously bonded to a surface of the produced fiber composite component.

[0005] Due to the superficial connection provided in both cases, a load introduction element arranged in this way can only be used for limited loads. In particular, loading with higher shear stresses is difficult to represent.

[0006] WO 2015 / 039828 A1 discloses an assembly for producing a particularly fiber-reinforced plastic component with a particularly metallic connecting element, which has an anchoring section cast into the plastic component and a holding section protruding from the plastic component with a holding geometry. The assembly has at least one protective element, which has an inner geometry corresponding to the outer geometry of the holding section and can be placed onto the holding section of the connecting element, wherein the protective element in particular has a standardized outer geometry, and a mold for the plastic component, wherein at least one receptacle for the at least one protective element is provided in the mold.

[0007] DE 10 2011 116 300 A1 discloses a fiber composite component and a composite component manufactured therefrom. The fiber composite component comprises at least one thermally bondable metallic connector for joining the fiber composite component to another component. The metallic connector is an insert with a flat joining section surrounded by an edge. The edge is accommodated between fiber layers in the fiber composite component, and one side of the joining section is exposed on a surface of the fiber composite component, providing a joining point.

[0008] The object of the invention is therefore to design a load introduction element and to connect it to a fiber composite component in such a way that it can be used for high loads and can also be manufactured and integrated simply and as cost-effectively as possible.

[0009] This object is achieved by a method according to patent claim 1, as well as a load introduction element with the features of patent claim 6 and a pressing device according to patent claim 9.

[0010] Accordingly, a method for producing a fiber composite component with an integrated load introduction element is presented with at least the following steps: ▪ Providing a pressing tool with a first tool part and a second tool part, wherein the first tool part and the second tool part form a cavity for the shaping reception of the fiber composite component in a closed state of the pressing tool, ▪ Positioning a first sub-element of the load introduction element in a first receptacle of the first tool part, wherein the first sub-element comprises a connecting portion which is connected at a first end to a first disc element, wherein the first disc element is arranged facing a tool surface of the first tool part and the connecting portion is arranged facing away from this, ▪ Positioning a second sub-element of the load introduction element in a second receptacle of the second tool part, wherein the second sub-element comprises a second disc element which has a concentric recess, ▪ Arranging a semi-finished fiber product between the first and the second tool part, and ▪ Closing the pressing tool and pressing the semi-finished fiber product, wherein the connecting section is at least partially pressed into the recess of the second disc element.

[0011] The process involves producing a fiber composite component into which a load introduction element is integrated during production. The load introduction element is constructed in several parts and will be described in detail later. In any case, the load introduction element essentially comprises two sub-elements that are inserted into the fiber semi-finished product from opposite sides and joined together to form a single, common load introduction element.

[0012] For this purpose, the first sub-element is positioned in the first receptacle of the first tool part, and the second sub-element is positioned in the second receptacle of the second tool part. The semi-finished fiber product is then inserted into the pressing tool and thus between the two sub-elements. The sequence of steps can be performed sequentially or in parallel.

[0013] When the tool is subsequently closed, the semi-finished fiber product is pressed and the two sub-elements are simultaneously pressed together. The connecting section is pressed through the semi-finished fiber product in the closing direction of the pressing tool and into the recess of the second disc element, which is arranged on the opposite side of the semi-finished fiber product.

[0014] The first tool part can preferably be formed by an upper tool, and the second tool part by a lower tool of the pressing tool. Alternatively, however, the first tool part can also be designed as a lower tool and the second tool part as an upper tool. It is understood that in each case, the first and / or second tool part can each be manufactured from one or more pieces.

[0015] Preferably, the pressing step is carried out in such a way that clamping of the semi-finished fiber product and the associated local compression of the semi-finished fiber product are substantially avoided, in order to avoid local weakening of the fiber composite component produced in this way. Ideally, the first and second disc elements rest only flat on the semi-finished fiber product and are bonded to the semi-finished fiber product or to the fiber composite component produced therefrom by means of the matrix.

[0016] Semi-finished fiber products include, in particular, flat semi-finished products such as woven fabrics, non-crimp fabrics, multi-axial fabrics, embroideries, braids, mats, nonwovens, and knitted fabrics. Suitable fiber materials include glass fibers, carbon fibers, aramid fibers, and / or suitable natural fibers, as well as any combination thereof.

[0017] The described process thus eliminates the need for complex reworking of contact points and subsequent bonding of the load introduction element. Instead, the double-sided bonding and contacting achieves the best possible integration of the load introduction element into the fiber composite component. Compared to conventional manufacturing processes, this creates a fiber composite component whose load introduction element can withstand even high loads, especially high shear loads. Furthermore, the double-sided design prevents the fiber composite component from clamping during subsequent screwing.

[0018] For the sake of simplicity, the invention is always illustrated using only a single load introduction element. However, it is understood that more than one load introduction element can be integrated into the fiber composite component in the same way within the scope of the method. To do so, the corresponding steps simply need to be repeated for the corresponding number of sub-elements or performed simultaneously.

[0019] According to a further embodiment, the method may comprise the step of arranging a first seal between the first disc element and the first receptacle of the first tool part, and / or the step of arranging a second seal between the second disc element and the second receptacle of the second tool part.

[0020] The steps of arranging the first or second seal can either be performed before positioning the respective first or second sub-element. Alternatively, the first and / or second seal can be inserted into the respective recess together with the first or second sub-element. This means that the steps of arranging the respective seal and positioning the respective sub-element occur simultaneously.

[0021] The seals can be used, for example, to seal the respective recess or mechanically movable components arranged therein, such as the retaining elements described in detail below. The seals make it possible to seal these components against contamination caused by penetrating matrix. The seals are loosely applied and can be removed during or after removal of the produced fiber composite component.

[0022] Preferably, the method can comprise locally cutting the fiber semi-finished product prior to arranging the fiber semi-finished product to allow the connecting section to pass through the fiber semi-finished product. By means of the cutting, a fiber structure of the fiber semi-finished product is locally severed to facilitate the local passage of the connecting section. Cutting out a complete hole (for the passage of the connecting section) is possible, but not absolutely necessary, since the excess fiber material can be displaced laterally by the connecting section. Of course, it is still possible to provide a complete recess in the form of a hole in the fiber semi-finished product. For the sake of simplicity, the cutting or the provision of the hole can preferably take place before insertion into the pressing tool.

[0023] According to a further embodiment, the step of pressing in the connecting portion comprises coaxially inserting the connecting portion into a cylindrical extension of the second disk element. The correspondingly designed second disk element forms a sleeve-shaped receptacle with the cylindrical extension, wherein the connecting portion is inserted at least partially and coaxially into the cylindrical extension and clamped therein. The cylindrical extension can, for example, be produced in a sleeve-shaped manner by flanging the second disk element. The cylindrical extension is preferably formed concentrically on the second disk element. The geometries and tolerances of the connecting portion and the receiving cylindrical extension must be coordinated accordingly to provide a clamping connection between the two components.In any case, this creates a particularly resilient connection between the two sub-elements, so that the entire load introduction element can withstand high loads.

[0024] Furthermore, the method can comprise impregnating the semi-finished fiber product with a matrix, in particular by means of a liquid impregnation process, an injection process, and / or an infusion process, before, during, or after the step of arranging the semi-finished fiber product. Known methods are suitable for this purpose. Accordingly, the matrix is ​​preferably applied to the semi-finished fiber product before or during the step of arranging the semi-finished fiber product in the pressing tool. The semi-finished fiber product can thus be used, for example, as a prepreg, i.e., in a pre-impregnated state, or pressed into the fiber composite component in the pressing tool during what is known as "wet pressing."

[0025] Alternatively, it is possible to first place the semi-finished fiber product into the mold in a dry, non-impregnated state and then inject the matrix. For example, the matrix can be injected after the mold has closed using the resin transfer molding (RTM) process. Depending on the process, the mold is designed as a wet mold or an RTM mold.

[0026] Furthermore, a load introduction element for integration into a fiber composite component is presented, comprising a first sub-element comprising a substantially cylindrical connecting portion connected at a first end to a first disc element. Furthermore, the load introduction element comprises a second sub-element comprising a second disc element with a concentric recess, wherein the connecting portion is designed to be at least partially pressed into the recess of the second disc element.

[0027] For example, a connection between the cylindrical connecting section and the first disc element can be designed as a material fit, a force fit, and / or a form fit. The first end is understood to be an end arranged in the axial direction of the cylindrical body in the region of the end face there.

[0028] The material connection can be achieved, in particular, by welding the connecting section to the first disc element. In contrast, a positive connection can be achieved, for example, via a collar provided at the first end of the connecting section, which protrudes from this end in the axial direction. The first disc element is placed onto this collar with a concentric recess, wherein the concentric recess has an (inner) diameter equal to or larger than an outer diameter of the collar. The collar is then formed to fasten the sliding element to the first end in a positive fit. A screw connection is also possible to provide the connection.

[0029] The connecting section is preferably designed for connection to other components, in particular for plugging, screwing, or receiving a connecting means, wherein the connecting section may, for example, have a through-hole. The connecting section can be designed as a bushing, in particular as a stamped bushing, as a bolt, as a threaded bushing with an internal or external thread, or as a nut. A metallic material, a plastic, or a fiber-reinforced plastic is particularly suitable as a material for the entire load introduction element and its individual parts.

[0030] According to a further embodiment, the first sub-element may comprise a first seal which is arranged on a side of the first sliding element facing away from the second disc element.

[0031] Alternatively or additionally, the second sub-element may comprise a second seal arranged on a side of the second disc element facing away from the first disc element.

[0032] The first and / or second seals can, in particular, be detachably attached to the first and second sub-elements, respectively. Suitable seals include flat discs made of metal, rubber, or silicone, as well as O-rings made of rubber or silicone.

[0033] Preferably, the second disc element optionally has a cylindrical extension for coaxially receiving the connecting portion pressed into the second disc element. The cylindrical extension can, for example, be produced in a sleeve-like manner by flanging the second disc element. Preferably, the cylindrical extension is formed concentrically on the second disc element.

[0034] A further embodiment provides, only optionally, that the first disc element has a circumferential bevel on its outer edge facing the second disc element and / or that the second disc element has a circumferential bevel on its outer edge facing the first disc element. During impregnation with a matrix, an accumulation of the matrix can be generated in the cavity created by the bevel. This prevents contact between the disc material and the fiber material of the semi-finished fiber product, which at the same time is accessible to air and electrolytes, so that the corrosion formation otherwise caused by this can be prevented particularly easily and effectively.

[0035] The first and / or second disc elements can be made of metal (especially sheet metal), plastic, or fiber-reinforced plastic, for example. The geometry of the disc elements must generally be adapted to the loads to be absorbed. However, disc elements with a small thickness compared to their diameter, due to their flexibility, prevent advantageous adaptability to deformations of the fiber composite component, which can prevent damage.

[0036] In addition, a pressing tool for carrying out the described method for producing a fiber composite component is proposed, comprising a second tool part and a first tool part which, in a closed state (of the pressing tool), form a cavity for shaping the fiber composite component to be produced, wherein the first tool part comprises a first receptacle which is designed to receive a first partial element of a load introduction element, and the second tool part comprises a second receptacle which is designed to receive a second partial element of the load introduction element.

[0037] In the closed state of the pressing tool, the second receptacle can be arranged opposite and aligned with the first receptacle.

[0038] Preferably, the first and / or second receptacle each comprises a holding means, in particular a magnetic holder or a vacuum holder. The purpose of the holding means is to securely fix the respective sub-element while still allowing it to be releasably removed for removal of the fiber composite component.

[0039] Furthermore, the second receptacle can have a conical section to center the load introduction element. This can be achieved, in particular, by a conical section of the second receptacle, into which the punching bolt of the first sub-element engages during pressing into the second disc element and is guided accordingly into the desired position and thus centered. This allows for very tight manufacturing tolerances to be maintained. Accordingly, the punching bolt can have a chamfer or a conical section on its (second) end facing the second receptacle, which supports the centering process when pressing in the punching bolt.

[0040] Only optionally, the first receptacle of the first tool part and / or the second receptacle of the second tool part can comprise a mechanical ejector for removing the produced fiber composite component from the pressing tool. This can be designed, for example, as a mechanically movable lifting cylinder that presses the fiber composite component out of the first and / or second tool part.

[0041] The invention is explained in more detail below using an exemplary embodiment with reference to the figures. They show: Fig. 1a and Fig. 1b a load introduction element according to the description, Fig. 2 a side sectional view of a pressing tool with inserted fiber composite component and integrated load introduction element according to the description, Fig. 3 a flow chart of the process for the production of the fiber composite component from Fig. 1a and Fig. 1b according to the description.

[0042] Fig. 1a shows a load introduction element 10 for integration into a fiber composite component (20, see Fig. 2) with a first sub-element 11, which comprises a substantially cylindrical connecting section 12, which is connected at a first end 12a to a first disc element 13. Furthermore, the load introduction element 10 comprises a second sub-element, which comprises at least one second disc element 15 with a concentric recess 15a, wherein the connecting section 12 is designed to be at least partially pressed into the recess 15a of the second disc element 15. The connecting section 12 is designed to be connected to another component, for example as a bushing, punched bushing, bolt, screw or nut, or to connect other connecting means. Alternatively, a through-hole 16 can be included in the connecting section 12, which is designed to receive a connecting means, for example a screw for screwing to the other component.

[0043] Optionally (and therefore shown in dashed lines), the second disc element 15 can have a cylindrical extension 15b for coaxially receiving the connecting portion 12 pressed into the second disc element 15. The extension 15b can preferably be designed to clamp the connecting portion 12.

[0044] Also optional and therefore only shown in dashed lines, the first disc element 13 can have a circumferential chamfer 13c on its outer edge facing the second disc element 15. Alternatively or additionally, the second disc element 15 can comprise a circumferential chamfer 15c on its outer edge facing the first disc element 13. As can be seen from Fig. As can be seen in Figure 2, the chamfers can be used to create circumferential cavities 29, in which an accumulation of the matrix forms during impregnation. These cavities prevent corrosion by sealing the contact point between the disc elements 13, 15 and the fiber material in an airtight and fluid-tight manner, preventing access to air and electrolytes.

[0045] In Fig. 1b, the individual parts of the load introduction element 10 shown in view 1a are shown separately. The positive connection of the connecting section 12 and the first disk element 13 can be achieved, for example, via a collar 12b provided on the first end 12a of the connecting section 12, which protrudes from this first end 12a in the axial direction. The first disk element 13 is placed onto this collar 12b with a concentric recess 13a, wherein the concentric recess 13a has an (inner) diameter equal to or slightly larger than an outer diameter of the collar 12b. The collar 12b is then formed, and the sliding element 13 is fastened to the first end 12a in a positive-locking manner.

[0046] In Fig. 2 shows a pressing tool 20 for carrying out a method for producing a fiber composite component 23. The pressing tool 20 comprises a first tool part designed as an upper tool 22 and a second tool part designed as a lower tool 21, which in the Fig. 2, form a cavity 24 for receiving the fiber composite component 23 to be produced. The upper tool 22 comprises a first receptacle 22a, which is designed to receive the first sub-element 11 of the Fig. 1a and Fig. 1b. The lower tool 21 provides a second receptacle 21a, which is designed to receive the second sub-element of the load introduction element 10. In the closed state of the pressing tool 20, the second receptacle 21a is arranged opposite the first receptacle 22a.

[0047] In the illustrated embodiment, the first receptacle 22a comprises a holding means 25, which can be designed, for example, as a magnetic holder or vacuum holder, to hold the first sub-element 11 in position after positioning. Also possible (but not shown) is the arrangement of a corresponding holding means in the second receptacle 21a.

[0048] The second receptacle 21a may, for example, have a cone-shaped section 21b in the bottom region of the second receptacle 21a in order to center the load introduction element 10 for the pressing process.

[0049] Furthermore, the second receptacle 21a of the lower tool 21 optionally comprises a mechanical ejector 26 movable in the demolding direction E for removing the produced fiber composite component 23 from the pressing tool 20.

[0050] In Fig.3 shows a flow chart for a corresponding method for producing the fiber composite component 23 with the integrated load introduction element 10 and comprises at least the following steps: Step a: Prepare the pressing tool 20, Step b1: Positioning the first sub-element 11 of the load introduction element 10 in the first receptacle 22a of the upper tool 22, wherein the first sub-element 11 comprises the connecting section 12 which is connected at its first end 12a to the first disc element 13, and wherein the first sub-element 11 is arranged such that the first disc element 13 faces a tool surface 22b of the upper tool 22 and the connecting section 12 is arranged facing away from this. Step c1: Positioning the second sub-element of the load introduction element 10 in the second receptacle 21a of the lower tool 21, wherein the second sub-element comprises the second disc element 15, which has the concentric recess 15a.

[0051] Subsequent step c2: Arranging the semi-finished fiber product 23 on the lower tool 21 and on the second sub-element.

[0052] It should be noted that steps b1, c1 and c2 can be performed sequentially in any order or simultaneously.

[0053] Preferably, after steps b1, c1 and c2, the semi-finished fiber product is impregnated with a matrix in an impregnation step (step d) in order to subsequently press the fiber composite component, for example in the context of the so-called wet pressing process.

[0054] Step e: This is subsequently carried out as part of closing the pressing tool and pressing the semi-finished fiber product 23, wherein the connecting section 12 is at least partially pressed into the recess 15a of the second disc element 15.

[0055] Optionally, the method may include step b0 of arranging a first seal 27 between the first disk element 13 and the first receptacle 22a of the upper tool 22. This should occur before or simultaneously with step b1. Alternatively or additionally, a step c0 of arranging a second seal 28 between the second disk element 15 and the second receptacle of the lower tool 21a may be provided. This step may occur before or simultaneously with step c1.

[0056] Also optionally, the method may comprise, prior to arranging the semi-finished fiber product (step c2), a step a1 for providing and preparing the semi-finished fiber product 23 and locally cutting the semi-finished fiber product 23 for a passage of the connecting section 12 through the semi-finished fiber product 23.

Claims

[1] Method for producing a fiber composite component (23) with an integrated load introduction element (10), comprising at least the following steps: ▪ Providing a pressing tool (20) with a first tool part (22) and a second tool part (21), wherein the first tool part (22) and the second tool part (21) form a cavity (24) for receiving the fiber composite component (23) in a closed state of the pressing tool (20), ▪ Positioning a first sub-element (11) of the load introduction element (10) in a first receptacle (22a) of the first tool part (22), wherein the first sub-element (11) comprises a connecting portion (12) which is connected at a first end (12a) to a first disc element (13), wherein the first disc element (13) is arranged facing a tool surface (22b) of the first tool part (22) and the connecting portion (12) is arranged facing away from this, ▪ Positioning a second sub-element of the load introduction element (10) in a second receptacle (21a) of the second tool part (21), wherein the second sub-element comprises a second disc element (15) which has a concentric recess (15a), ▪ Arranging a semi-finished fiber product (23) between the first (22) and the second tool part (21), and ▪ Closing the pressing tool (20) and pressing the semi-finished fiber product (23), wherein the connecting section (12) is at least partially pressed into the recess (15a) of the second disc element (15). [2] Method according to claim 1, wherein the method comprises the step of arranging a first seal (27) between the first disc element (13) and the first receptacle (22a) of the first tool part (22), and / or the step of arranging a second seal (28) between the second disc element (15) and the second receptacle (21a) of the second tool part (21). [3] Method according to claim 1 or 2, wherein the method comprises, prior to arranging the semi-finished fiber product (23), locally cutting the semi-finished fiber product (23) for a passage of the connecting section (12) through the semi-finished fiber product (23). [4] Method according to one of claims 1 to 3, wherein the step of pressing in the connecting portion (12) comprises coaxially inserting the connecting portion (12) into a cylindrical extension (15b) of the second disc element (15). [5] Method according to one of claims 1 to 4, wherein the method comprises, before, during or after the step of arranging the semi-finished fiber product, impregnating the semi-finished fiber product with a matrix, in particular by means of a liquid impregnation method, an injection method and / or an infusion method. [6] Load introduction element for integration into a fiber composite component with a first partial element (11) which comprises a substantially cylindrical connecting section (12) which is connected at a first end (12a) to a first disc element (13), and a second partial element which comprises a second disc element (15) with a concentric recess (15a), wherein the connecting section (12) is designed to be at least partially pressed into the recess (15a) of the second disc element (15). [7] Load introduction element according to claim 6, wherein the second disc element (15) has a cylindrical extension (15b) for coaxially receiving the connecting section (12) pressed into the second disc element (15). [8] Load introduction element according to one of claims 6 to 7, wherein the first disc element (13) has a circumferential chamfer (13c) on its outer edge facing the second disc element (15) and / or the second disc element (15) has a circumferential chamfer (15c) on its outer edge facing the first disc element (13). [9] Pressing tool for carrying out a method for producing a fiber composite component according to claims 1 to 5, with a second tool part (21) and a first tool part (22), which in a closed state of the pressing tool (20) form a cavity (24) for the shaping reception of the fiber composite component (23) to be produced, wherein the first tool part (22) comprises a first receptacle (22a) which is designed to receive a first partial element (11) of a load introduction element (10), and the second tool part (21) comprises a second receptacle (21a) which is designed to receive a second partial element of the load introduction element (10). [10] Pressing tool according to claim 9, wherein the second receptacle (21a) is arranged opposite the first receptacle (22a) in the closed state of the pressing tool (10). [11] Press tool according to one of claims 9 to 10, wherein the first (22a) and / or the second receptacle (21a) each comprises holding means (25), in particular a magnetic holder or a vacuum holder. [12] Press tool according to one of claims 9 to 11, wherein the second receptacle (21a) has a cone-shaped portion (21b) to center the load introduction element (10). [13] Pressing tool according to one of claims 9 to 12, wherein the first receptacle of the first tool part (22) and / or the second receptacle (21a) of the second tool part (21) comprise a mechanical ejector (26) for removing the produced fiber composite component (23) from the pressing tool (20).

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