Method for producing a component from a composite material with locally different thicknesses

Abstract

A method for manufacturing a component from a composite material with locally varying thicknesses comprises the steps of providing a first laminate arrangement, providing a separating layer on at least one parting section of a first surface of the first laminate arrangement, providing a second laminate arrangement having a second surface corresponding to the first surface of the first laminate arrangement, placing the second laminate arrangement with its second surface onto the first surface of the first laminate arrangement so that the at least one parting section is enclosed, joining the first laminate arrangement to the second laminate arrangement by heating and / or pressure, and guiding a cutting tool along at least one contour on the second laminate arrangement corresponding to the at least one parting section.so that at least part of the second laminate arrangement detaches completely, and remove the detached part, leaving a depression in each case.

Description

Technical field

[0001] The present description relates to a method for manufacturing a component from a complex composite material with locally varying thicknesses. Technical background

[0002] Numerous manufacturing processes are known for producing assemblies and complex structures from composite materials, such as fiber-reinforced plastics. Components with a uniform thickness are generally easier to produce than those with depressions, pockets, or locally varying thicknesses. To create pockets in composite components, it is known to manufacture the components with a uniform thickness and then remove material across the surface using cutting tools. However, with modern, high-strength composites, this process places significant stress on the cutting tool, leading to wear and tear, and is time-consuming. While varying thicknesses are known for components manufactured using RTM (Research Tomography) or from prepregs, these can result in problematic resin flow fronts or uneven temperature gradients.Pronounced thickness ratios of 1:2 or 1:3 are therefore problematic. Consequently, the costs for manufacturing a component with pockets or depressions from a composite material are high. WO2016 / 003983 A1 and US2012 / 228005 A1 disclose methods and systems for manufacturing a component from a composite material with locally varying thickness. EP0065765 A1 discloses a method for manufacturing a component from a composite material with locally varying thickness.

[0003] It is therefore an object of the invention to propose a method or system for manufacturing a component from a composite material with locally varying thicknesses, which is cost-effective and can be implemented quickly.

[0004] The problem is solved by a method for manufacturing a component from a complex composite material with locally varying thicknesses, having the features of independent claim 1. Advantageous embodiments and further developments of the invention can be found in the dependent claims and the following description.

[0005] A method according to claim 1 is proposed.

[0006] The component can be manufactured using various fiber-matrix systems, in which unidirectional fibers, preferably continuous, woven fabrics, and / or non-woven fabrics in the form of multiple layers are embedded in a matrix material, thus forming a composite material. The fibers and the matrix material can be selected according to the application and the expected mechanical and thermal stresses.

[0007] In one embodiment, for example, reactive resins could be used that cure under pressure and heat to form thermosets. The two laminate arrangements could then be produced using prepregs and, if necessary, pre-cured. However, resin-infiltrable layer structures are also conceivable, which can be infiltrated using an RTM or vacuum infusion process. The first laminate arrangement can include a preform.

[0008] However, thermoplastic matrix materials are also conceivable, such as PPS, PEEK, PEKK, PEI, PAEK, and others. The two laminate arrangements are then preferably already fully impregnated subcomponents, which can be bonded together by stacking and heating. Furthermore, such laminate arrangements can be thermoformed. During thermoforming, the two laminate arrangements can be joined together, thus enclosing the separating layer between them.

[0009] The first laminate arrangement could be a simple, flat surface with a uniform thickness. This flat shape can be curved once or multiple times. It has a first surface that bonds with the second surface of the second laminate arrangement.

[0010] The second laminate arrangement could be manufactured in the same way and comprise a continuous arrangement of several layers of unidirectional fibers, a woven fabric, and / or a non-woven fabric. In principle, the second laminate arrangement could also include fibers that are distributed or oriented differently than in the first laminate arrangement. The second surface of the second laminate arrangement must be designed so that it can be laid flush with the first surface.

[0011] The two laminate arrangements each have a thickness that together determines the thickness of the desired component. A key aspect of the invention lies in providing a separating layer locally between the two laminate arrangements where a recess, pocket, or arbitrarily reduced thickness is desired. The separating layer is designed to prevent the two laminate arrangements from bonding in the relevant separation section.

[0012] To produce a closed component from the composite material, the two laminate arrangements are joined together by applying heat and / or pressure to the two overlapping components. Depending on the matrix material used, the two laminate arrangements could either harden together or fuse at the interface between the first and second surfaces due to softening or melting of the matrix material. However, because a separating layer is locally present, this joining process is prevented locally, so that the two laminate arrangements remain separate in the separation zone defined by the separating layer even after being joined. By guiding the cutting tool along a contour corresponding to the separating layer, the second laminate arrangement is locally separated.Due to the lack of connection to the underlying first laminate layer, simply cutting out the contour is sufficient to completely detach the intended section of the second laminate layer from the first. After removing the section, for example by hand or using a suction cup, the desired recess in the component is created.

[0013] By guiding the cutting tool along a single, closed contour, tool wear can be reduced, and the time required to create the recess can be significantly reduced compared to conventional methods. Tooling costs are also considerably lowered. Furthermore, the separating layer prevents damage to the fiber structure of the first laminate layer, or to the portion of fibers remaining in the component at the point of reduced thickness, by the cutting tool.

[0014] In an advantageous embodiment, the first laminate arrangement and the second laminate arrangement comprise a fiber-reinforced plastic comprising fibers from a group of fibers, the group comprising carbon fibers, glass fibers, aramid fibers, and mixtures thereof. The fibers run in at least one direction and preferably in several directions intersecting at an angle to one another. In particular, the fibers are formed in the form of fiber bundles, woven fabrics, or non-woven fabrics, which are formed as individual sheets. The particular advantages of the method are especially evident with continuous fibers, since the separating layer arranged according to the invention reliably prevents damage to fibers of a remaining layer. Instead of continuous fibers, short fibers and / or non-woven fiber material, as well as woven material, could also be used.

[0015] In an advantageous embodiment, the separating layer is incorporated into the first or second laminate arrangement so that it is flush with the adjacent material of the first or second laminate arrangement on the first or second surface, respectively. The first or second laminate arrangement could be prefabricated and already equipped with the separating layer. In this case, the separating layer is not applied to the relevant surface of the first or second laminate arrangement, but rather integrated directly into the layer structure of the first or second laminate arrangement. The outward-facing surface of the respective laminate arrangement then is flush with the adjacent material.

[0016] In an advantageous embodiment, the separating layer has a thickness corresponding to that of a layer of the laminate arrangement adjacent to the first or second surface. The separating layer can be selectively combined with an outermost layer of fibers adjacent to the first or second surface. In this outermost layer, fibers are locally removed and replaced by the separating layer. Consequently, the fibers within the separation section are interrupted at the contour of the separating layer. The separating layer preferably abuts the fiber ends as precisely as possible. A gap of less than one-tenth of a millimeter could be tolerated between the fiber ends and the separating layer. Protrusion of the fiber ends into the separation section should be avoided as far as possible, so that when cutting out the contour of the separation section, a tensile force on the fiber ends by the guided tool is prevented.

[0017] In an advantageous embodiment, the separating layer comprises a plastic that is dimensionally stable, at least temporarily, at temperatures up to 250°C, preferably up to 275°C, more preferably up to 330°C, and particularly preferably up to 400°C. This corresponds to a temperature to which the first laminate arrangement and the second laminate arrangement could be exposed in order to create a bond between the two laminate arrangements. To counteract thermally induced deterioration, the material of the separating layer is adapted accordingly.

[0018] In an advantageous embodiment, the separating layer comprises an aluminum layer. No special mechanical requirements are placed on the aluminum layer, and ordinary alloys containing, for example, magnesium, manganese, silicon, and / or other elements could be used. The aluminum layer reliably prevents adhesion while simultaneously ensuring sufficient thermal stability. This also facilitates the precise penetration and guidance of the cutting tool up to the separating layer, resulting in improved corrosion resistance in the remaining underlying layers. The aluminum layer can be implemented as a foil and preferably as a thin sheet with a thickness of more than one-tenth of a millimeter, for example, approximately 0.3 mm. Aluminum is a relatively soft material and is very easy to machine.When using such aluminum layers, it is easily possible to mill to the correct depth without damaging fibers of an underlying layer that will later be on the outside of the finished component. The fibers of this layer are therefore not severed and are completely covered with resin. The mechanical properties remain unchanged, and the component remains electrically insulated due to the resin coating. This prevents galvanic corrosion of surrounding aluminum components during subsequent use.

[0019] However, other metallic materials are also conceivable for this purpose.

[0020] In an advantageous embodiment, the separating layer comprises polyimide. Separating films are commercially available in the form of polyimide-containing adhesive tapes or films. This plastic is particularly temperature-resistant and permanently withstands temperatures up to approximately 230°C and can be briefly exposed to temperatures up to 400°C. This consequently enables effective separation of the two laminate arrangements. A further advantage of such a polyimide film is that, with a thin film, in the case of consolidation of the component in a tool with a fixed cavity, i.e., an upper and lower tool made of steel, the additional film does not impair the surrounding consolidation of the two laminate arrangements before the process is carried out.

[0021] The separating layer can be made of a plastic that is temperature-resistant up to approximately 330°C, at least for short periods. This is useful when processing PPS. When processing materials such as PEEK, a higher temperature resistance is necessary, and the separating layer should be temperature-resistant up to 400°C or slightly above for short periods.

[0022] In an advantageous embodiment, the at least one separation section is spaced apart from the edges of the first and second laminate arrangements. Consequently, the pocket or recess to be produced does not project into an edge region of the component being manufactured, but is completely surrounded on all sides by material from adjacent areas. It is therefore necessary to approach the composite of the two laminate arrangements transversely to the first and second surfaces, plunge it into the material of the second laminate arrangement, and then guide it along the contour. The plunge depth must be adapted to the installation depth of the separation layer so that the layer structure of the first laminate arrangement is not damaged.

[0023] In an advantageous embodiment, the first laminate arrangement is joined to the second laminate arrangement during a thermoforming process. In a thermoforming process, a blank is created from a sheet of thermoplastic material, heated to melting temperature in an oven, and then formed into a three-dimensional shape using a mold with two matching molds. According to the invention, both laminate arrangements, which consist, for example, of a fiber-reinforced thermoplastic material, are provided with the separating layer and heated. The laminate arrangements rest on one of the first molds. After reaching the melting temperature, the second mold is pressed onto the laminate arrangements in the direction of the first mold. Both laminate arrangements bond together and enclose the separating layer.The three-dimensionally shaped component can then be removed from the mold after appropriate cooling and solidification.

[0024] As mentioned above, in an advantageous embodiment of the inventive method, this method comprises forming by thermoforming using a mold. The mold consists of two molds, one of which can be referred to as the male mold and the other as the female mold, wherein both molds are adapted to each other such that the laminate arrangements, including the two laminate arrangements, are brought into a desired shape by pressing the two molds together.

[0025] The invention further relates to a system according to claim 11.

[0026] The system is designed to carry out the method according to the invention. The mold serves as a base for the first laminate arrangement, and the contact surface is adapted to the shape of the first laminate arrangement. The first laminate arrangement can be placed flush with the contact surface. During the execution of the method, the second laminate arrangement can be placed on the first surface of the first laminate arrangement. As explained above, the first surface can comprise at least one separation section in which a separating layer, referred to here as the separating material, is provided for separating the two laminate arrangements from each other. As also explained above, the separating material can be placed after the first laminate arrangement has been laid or integrated directly into a layer adjacent to the first surface during the production of the first laminate arrangement.The joining device is designed to connect the two arrangements. It is particularly advantageous if the joining device can be removed from the forming tool after joining, so that the cutting tool can then be moved freely to cut out the contour(s) in question from the second laminate arrangement.

[0027] In an advantageous embodiment, the joining device is designed to exert heat and pressure directed at the contact surface on the laminate arrangements. Depending on the fiber-matrix system used, the joining device can be designed differently. Essentially, suitable joining devices for common fiber-matrix systems include the capability to apply pressure or temperature to achieve melting or curing.

[0028] In an advantageous embodiment, the joining device can be configured to perform a thermoforming process. The joining device is therefore realized by the forming tool, which has a first and a second form that are adapted to each other and can perform a joining and, if necessary, a forming process by pressing the two forms together, including the laminate arrangements with an intermediate separating layer.

[0029] In an advantageous embodiment, the cutting tool comprises a milling tool. The cutting tool could be movably arranged above the forming tool via a 2-axis guide. The plunge groove of the milling tool is also preferably controllable. It is conceivable to enable the axis of the milling tool to tilt in the case of curved components or curved laminate arrangements, so that it always runs perpendicular to the local surface tangent of the outer surface of the second laminate arrangement facing away from the first.

[0030] According to the invention, the joining device has a cover which, together with the contact surface, forms a closed chamber for resin infusion as required. The cover could be flexible or rigid. A flexible cover could, for example, be a vacuum film that can be sealed to the contact surface. By applying a vacuum, pressure is exerted on the composite of the two laminate arrangements, and simultaneously, resin infusion, i.e., vacuum infusion, is carried out. Alternatively, the cover could also be rigid, and resin could be forced into the layer structure by means of overpressure. This method is also known as the RTM process. This embodiment relates in particular to fiber-matrix systems based on a reaction-curing resin. Additional flow aids could optionally be provided to enable better distribution of the reaction resin.

[0031] In an advantageous embodiment, the contact surface is heatable. The contact surface could thus form part of the joining device. A cover or similar element for exerting pressure on the laminate assembly could therefore be designed more simply, since the heating effect primarily originates from the forming tool. Brief description of the characters

[0032] The following section describes exemplary embodiments with reference to the accompanying drawings. The illustrations are schematic and not to scale. Identical reference numerals refer to identical or similar elements. The drawings show: Fig. 1a-1e shows a schematic representation of a system with which a method for manufacturing a component from a composite material with locally varying thicknesses is produced. Fig. 2 shows a schematic representation of the method. Detailed description of implementation examples

[0033] In Fig. 1a bis 1e A process for manufacturing a component from a composite material with locally varying thicknesses, as well as a system for manufacturing such a component, is presented. Fig. 1a A forming tool 2 is shown, which has a support surface 4. A first laminate arrangement 6 is arranged on this surface, which has a first surface 8 that faces away from the forming tool 2.

[0034] A separating layer 10 is placed on the first surface 8. The separating layer 10 then extends only over a separation section 12 and is designed to prevent a material-bonded connection with a second laminate arrangement 14, which is subsequently placed on the first separating layer 10. Of course, it is also possible to integrate the separating layer 10 directly into the first laminate arrangement 6, so that it preferably terminates flush with the first surface 8.

[0035] The second laminate arrangement 14 has a second surface 16 facing the first laminate arrangement 6. It is placed on the first surface 8 so that both laminate arrangements 6 and 14 enclose the separating layer 10.

[0036] Fig. 1b Figure 1 shows the two laminate arrangements 6 and 14 in planar contact with the separating layer 10 between them. A cover 18 is positioned on the second laminate arrangement 14 and exerts pressure on the laminate arrangements 6 and 14 in the direction of the mold 2. In this example, the cover 18 is rigid and is subjected to a force by an external device (not shown).

[0037] It could additionally be provided that the mold 2 and / or the cover 18 are heatable. The cover 18, together with the mold 2, forms a joining device 20. In this example, the two laminate assemblies 6 and 14 are fiber-reinforced plastics in which reinforcing fibers are embedded in a thermoplastic matrix material. To join the two laminate assemblies 6 and 14, heating is carried out under a specific pressure so that the matrix material of the two laminate assemblies 6 and 14 melts or softens, and a bond is formed at the interface between the first surface 8 and the second surface 16.

[0038] In Fig. 1c The cover 18 is removed. The two laminate arrangements 6 and 14 are connected. A cutting tool 22 with a milling cutter 26 driven by a motor 24 is guided along a contour 28 on the second laminate arrangement 14. The contour 28 corresponds to the edge contour of the separating layer 10. The milling cutter 26 plunges to a depth corresponding to the thickness of the second laminate arrangement 14. Since the separating layer 10 prevents a connection between the first laminate arrangement 6 and the second laminate arrangement 14, a section 30 is cut out of the second laminate arrangement 14. Fig. 1d This is illustrated in a top view of the second laminate arrangement 14. This illustration also makes it clear that the contour 28 can be positioned completely within the first laminate arrangement 6. The relevant separation section 12 is therefore spaced apart from all edges 29 of the first laminate arrangement 6 and the second laminate arrangement 14.

[0039] After removal of the section 30, a recess 32 is created in the second laminate arrangement 14, or a component 34 is formed from the two laminate arrangements 6 and 14. This is in Fig. 1e shown in a top view. Consequently, this procedure results in a component 34 which has a locally reduced thickness.

[0040] Fig. 2 Figure 36 shows the process of method 36 in a schematic block diagram. Method 36 comprises the steps of providing 38 the first laminate arrangement 6, arranging 40 the separating layer 10 on at least one separation section 12 of the first surface 8 of the first laminate arrangement 6, providing 42 the second laminate arrangement 14, which has the second surface 16 that correlates with the first surface 8 of the first laminate arrangement 6, placing 44 the second laminate arrangement 14 with the second surface 16 onto the first surface 8 of the first laminate arrangement 6, such that the at least one separation section 12 is enclosed, joining 46 the first laminate arrangement 6 with the second laminate arrangement 14 by heating and / or pressing, and optionally forming 47 by means of a thermoforming process.the guiding 48 of the cutting tool 22 along at least one contour 28 corresponding to the at least one separation section 12 in the second laminate arrangement, such that at least one section 30 of the second laminate arrangement 14 is completely detached, and the removal 50 of the at least one detached section 30, so that a recess 32 is formed in each case. The arrangement 40 of the separation layer 10 can already be carried out when the first laminate arrangement 6 is provided 38, as shown by a dashed box around the two blocks 38 and 40. The provision 38 of the first laminate arrangement 6 or the second laminate arrangement 14 can include the provision of a fiber mold body,which is to be infiltrated with a resin. This can be done by vacuum infusion or an RTM process when joining 46. Alternatively, the first laminate arrangement 6 and the second laminate arrangement 14 can be pre-impregnated or designed as cured components with a thermoplastic matrix. In the latter case, the laminate arrangements 6 and 14 could be thermoformed from a planar shape to a three-dimensional shape if required.

[0041] In Fig. 3a A detailed representation shows a separating layer 10 integrated into the layer structure of the first laminate arrangement 4. Here, the separating layer 10 has a thickness d1 that corresponds to a thickness d2 of the outermost layer 52 located on the first surface 8. Thus, the outermost layer 52 and the separating layer 10 are flush with each other on the first surface. The outermost layer 52 therefore has a correspondingly dimensioned cutout into which the separating layer 10 is integrated.

[0042] In Fig. 3b The separating layer 10 is located on the outermost layer 52. This can be done very easily and flexibly, especially for experimental purposes.

[0043] It should also be noted that "comprehensive" or "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps of other embodiments described above, provided this is covered by the scope of the claims. Reference numerals in the claims are not to be considered as a limitation. Reference symbol list

[0044] 2 Forming tool 4 Support surface 6 First laminate arrangement 8 First surface 10 Separation layer 12 Separation section 14 Second laminate arrangement 16 Second surface 18 Cover 20 Joining device 22 Cutting tool 24 Motor 26 Cutter 28 Contour 29 Edge 30 Section 32 Recess 34 Component with locally reduced thickness 36 Process 38 Providing the first laminate arrangement 40 Arranging the separation layer 42 Providing the second laminate arrangement 44 Applying the second laminate arrangement 46 Joining the laminate arrangements 47 Forming 48 Guiding the cutting tool 50 Removing the section 52 Outermost layer

Claims

1. A method (26) for manufacturing a component (34) from a composite material with locally varying thicknesses, comprising the steps of: providing (38) a first laminate assembly (6), arranging (40) a separating layer (10) at at least one separating section (12) of a first surface (8) of the first laminate assembly (6), providing (42) a second laminate assembly (14) having a second surface (16) that correlates with the first surface (8) of the first laminate assembly (6), placing (44) the second laminate assembly (14) with the second surface (16) on the first surface (8) of the first laminate assembly (6) so that the at least one separating section (12) is enclosed, joining (46) the first laminate assembly (6) to the second laminate assembly (14) by heating and / or pressing on a joining device (20) designed to join the superimposed first laminate assembly (6) and second laminate assembly (14) with the separating material enclosed by applying pressure and / or heat, wherein the bonding device (20) has a cover (18) which, together with the support surface (4), forms a closed chamber for resin infusion as required; guiding (48) a cutting tool (22) along at least one contour (28) in the second laminate assembly (14) that correlates with the at least one separating section (12), so that at least one section (30) of the second laminate assembly (14) is completely detached, and removing (50) the at least one detached section (30) so that a recess (32) is created in each case.

2. Method (26) according to claim 1, wherein the first laminate assembly (6) and the second laminate assembly (14) comprise a fiber-reinforced plastic comprising fibers from a group of fibers, the group comprising: - carbon fibers, - glass fibers, - Aramid fibers, and - blends thereof.

3. Method (26) according to claim 1 or 2, wherein the separating layer (10) is incorporated into the first laminate assembly (6) or the second laminate assembly (14) so that it is flush with the adjacent material of the first laminate assembly (6) at the first surface (8) or second surface (16), respectively.

4. Method (26) according to claim 3, wherein the separating layer (10) has a strength corresponding to a strength of a layer of the respective laminate assembly (6, 14) adjacent to the first surface (8) or the second surface (16), respectively.

5. Method (26) according to one of the preceding claims, wherein the separating layer (10) comprises a plastic which is dimensionally stable at least for a short time at temperatures up to 250°C, preferably up to 275°C, more preferably up to 330°C, and particularly preferably up to 400°C.

6. Method (26) according to one of the preceding claims, wherein the separating layer (10) comprises an aluminum foil.

7. Method (26) according to one of the preceding claims, wherein the separating layer (10) comprises polyimide.

8. Method (26) according to one of the preceding claims, wherein the at least one separating section (12) is spaced apart from edges of the first laminate assembly (6) and the second laminate assembly (14).

9. Method (26) according to one of the preceding claims, wherein the joining (46) of the first laminate assembly (6) to the second laminate assembly (14) is performed in a thermoforming process.

10. Method (26) according to claim 9, further comprising the step of: forming (47) by means of the thermoforming process using a forming tool (2).

11. System for manufacturing a component (34) from a composite material with locally varying thicknesses, comprising: a forming tool (2) with a support surface (4) for receiving a first laminate assembly (6) having a first surface (8) and a second laminate assembly (14) with a second surface (16) located thereon, a separating material that can be applied as a separating layer (10) to at least one separating section (12) of the first surface (8) of the first laminate assembly (6), a joining device (20) designed to join the superimposed first laminate assembly (6) and second laminate assembly (14) with the enclosed separating material by applying pressure and / or heat, and a cutting tool (22) which is movably arranged relative to the support surface (4) and is designed to be guided along at least one contour (28) correlating with the at least one separating section (12) in the second laminate assembly (14) with a predeterminable immersion depth, so that at least one section (30) of the second laminate assembly (14) is completely detached, characterized in that the connection device (20) has a cover (18) which, together with the support surface (4), forms a closed chamber for resin infusion as required.

12. System according to claim 11, wherein the connecting device (20) is designed to apply heat and pressure directed at the support surface (4) to the laminate assemblies (6, 14).

13. System according to claim 11 or 12, wherein the connecting device (20) is adapted to perform a thermoforming process.

14. System according to any one of claims 11 to 13, wherein the cutting tool (22) comprises a milling tool.

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