Mould for producing a hot-formed fibre composite component

Abstract

The invention proposes a mould for producing a hot-formed fibre composite component, having a forming tub with a base, a peripheral edge and a tub opening which faces away from the base and is delimited by the edge, having a forming mould, which is arranged in the forming tub, for applying a preform, and having a clamping frame which supports an elastic membrane and has a lower boundary surface for application on an upper boundary surface of the edge, wherein the edge and the clamping frame are designed to establish a fluid-tight connection with each other, so that the forming tub with the applied clamping frame can be evacuated by removal of air by suction through a suction connection arranged in the forming tub, wherein the membrane is designed to cling to a preform located in the forming tub and adjacent, free base regions when the forming tub is evacuated in the direction of the base of the forming tub, so that the preform is pressed onto the forming mould, and wherein the mould is heat-resistant up to a curing temperature of at least 200°C.

Description

[0001] Tool for producing a hot-formed fiber composite component

[0002] Technical area

[0003] The present description relates to a tool for producing a hot-formed fiber composite component and a method for producing a hot-formed fiber composite component.

[0004] Technical background

[0005] When manufacturing an aircraft structure, flat components are often combined with stiffening elements that have a highly curved profile. If the structure in question is made of a fiber composite material, such as CFRP, various manufacturing processes can be used to produce the stiffening elements.

[0006] One well-known process is hot forming, in which a preform with a fiber layer structure in an uncured matrix is ​​mechanically formed at a suitable forming temperature, and the formed preform is subsequently cured in an autoclave. Removing the formed preform from a forming tool and inserting it into a curing tool is complex, as damage and positioning deviations must be avoided. Manufacturing a tool system with a laying tool, a forming tool, and a curing tool also results in high costs. Description

[0007] The task can be considered to propose an alternative tool system that is more cost-effective and involves less manual effort.

[0008] This object is achieved by the subject matter of independent claim 1. Further embodiments emerge from the dependent claims and from the following description.

[0009] A tool for producing a hot-formed fiber composite component is proposed, comprising a forming trough with a bottom, a circumferential rim, and a trough opening facing away from the bottom and delimited by the rim, a forming tool arranged in the forming trough for placing a preform, and a clamping frame carrying an elastic membrane with a lower boundary surface for placing on an upper boundary surface of the rim, wherein the rim and the clamping frame are designed to establish a fluid-tight connection with one another, so that the forming trough with the clamping frame placed thereon can be evacuated by sucking air through a suction connection arranged in the forming trough, wherein the membrane is designed to nestle against a preform located in the forming trough and adjacent, free bottom regions during evacuation of the forming trough in the direction of the bottom of the forming trough,so that the preform is pressed onto the forming tool, and the tool is temperature-resistant up to a curing temperature of at least 200°C.

[0010] The forming trough has a base, which preferably includes a flat inner base surface. The base is surrounded by the circumferential rim, wherein the rim preferably runs perpendicular to the inner base surface and completely surrounds the base. It may be advisable to realize the forming trough as a single, integral component. This could be done by casting and subsequent surface treatment; by machining; or by additive manufacturing processes. However, it is also conceivable to produce the base separately from the rim and then connect the two components with a form-fitting or force-fitting connection. When manufacturing the forming trough, a fluid-tight connection between the base and the rim is required. The forming trough could be made of a metallic material, ceramic, or other appropriately temperature-resistant materials.

[0011] The edge has an upper boundary surface, which could, for example, be parallel to the base. The upper boundary surface serves to support the clamping frame so that it completely covers the tub opening. As explained below, at least one seal can be arranged on the upper boundary surface, or the upper boundary surface is designed to establish a fluid-tight connection with a seal arranged on the clamping frame.

[0012] The clamping frame has a shape adapted to the shape of the rim. The clamping frame preferably has a lower boundary surface that can be placed flush with the upper boundary surface of the rim. The clamping frame could have a continuous profile component whose profile cross-section has a width adapted to the material thickness of the rim. The profile component thus encloses a membrane opening that corresponds to the tub opening. This membrane opening is completely spanned by the elastic membrane.

[0013] The elastic membrane could be made of silicone or be based on a silicone-like material or another suitable elastomer. The elastic membrane has an elongation at break that is preferably at least 200%, so that the membrane is sufficiently flexible during evacuation, as described below. It is preferable to select a material for the membrane that returns as far as possible to its original unstretched state.

[0014] The forming trough can include a suction port on the edge, particularly a lower portion of the edge, or on a portion of the bottom near the edge, which can be connected to an air extraction device. This suction port extracts air from the cavity between the forming trough and the clamping frame with the membrane arranged thereon, causing the membrane to move toward the bottom due to the negative pressure.

[0015] The forming tool is arranged on the base and has a predetermined shape that determines the forming of a preform made of a fiber composite material. The forming tool could, for example, be placed centrally on the base and protrude from the base towards the tank opening. The preform is placed on a support surface of the forming tool, which faces away from the base and towards the tank opening. When the cavity is evacuated, the elastic membrane moves continuously towards the base and thus the preform arranged on the forming tool. As a result, the membrane exerts increasing pressure on the preform, which is thereby pressed against the forming tool.

[0016] If the tool according to the invention is located in an oven, an autoclave or similar, or is heated by an integrated or external heating device, the tool can reach a predetermined forming temperature. Once this temperature is reached, evacuating the cavity of the forming trough causes the preform to be pressed onto the forming tool by the pressure of the elastic membrane, thereby assuming the shape predetermined by the forming tool. Once the cavity is evacuated as far as possible, the membrane lies flush with a surface of the preform facing the membrane. The preform can be held in this state for subsequent curing. Curing could be carried out in the same oven or autoclave, which is then heated to a predetermined curing temperature. In addition, increased pressure can also act on the tool during curing, for example in a typical pressure range of up to 8 bar.The tool according to the invention is suitable for tolerating the curing temperature through the use of suitable materials, for example, metallic materials and a silicone membrane. Consequently, the tool according to the invention allows at least the forming tool and the curing tool to be combined, significantly reducing the costs of the required tools and simultaneously avoiding highly accurate placement by eliminating the step of removing the tool from a forming tool and inserting it into a curing tool.

[0017] In an advantageous embodiment, the edge is higher than the combined height of the forming tool and the intended preform. Buckling of the preform due to mechanical stress generated by the membrane directly after the tool closes can be avoided. Furthermore, it is also possible to produce profiles with a double curve or an omega geometry. This allows the membrane to initially rest gently and evenly on the preform, and then continuously press the preform onto the surface of the forming tool facing the membrane.

[0018] In an advantageous embodiment, the tool further comprises at least one circumferential seal arranged on the upper boundary surface and / or the lower boundary surface, wherein the circumferential seal is designed to seal the upper boundary surface and the lower boundary surface against one another in a fluid-tight manner. The circumferential seal could preferably be designed as a single piece or as a ring, so that there are no free ends of the seal that enclose a gap between them and lead to leaks. It may be advisable to use two or more seals that surround one another, thus improving reliability and increasing pressure resistance. The seals serve to create an insulated atmosphere beneath the membrane. The seals could be made of the same or a similar material as the membrane.Temperature-resistant, permanently elastic polymers, natural or synthetic rubbers and the like may also be suitable.

[0019] In an advantageous embodiment, the suction connection is arranged in the floor or on a base section of the edge facing the floor. When arranged on the floor, the forming tool can be easily replaced because it rests on the floor surface and can be directly coupled to the suction connection. As explained further below, the forming tool can have a base that can be placed on the floor and extends there to the edge. A positive or non-positive connection to the suction connection could be made directly. Suction channels leading to several suction openings distributed over the floor could be connected to the suction connection on the floor. The suction channels could also be arranged in the forming tool. The adapted arrangement of suction openings improves the overall suction.If the suction connection is arranged on the edge, air can be sucked out of the cavity at the edge, whereby the edge can also have suction channels that can lead to several suction openings arranged on the edge.

[0020] In an advantageous embodiment, the suction port is fluidly connected to several suction openings arranged in the base or in the forming tool. The suction openings could be distributed over a large area of ​​the base or the forming tool, so that even different forming tool shapes lead to reliable extraction of air from the cavity. If, for example, the membrane lies over some of the suction openings during the evacuation process, these are closed by the membrane. Other suction openings, however, could remain open and allow continued extraction.

[0021] In an advantageous embodiment, the forming tool can be detachably inserted into the forming trough. The tool can therefore be used modularly to produce a wide variety of profiles.

[0022] In an advantageous embodiment, the forming tool has a base body which can be placed on the base guided by the edge and / or guide elements. The base and the forming tool could preferably be adapted to one another in terms of their dimensions such that the forming tool completely fills the base after insertion into the forming trough and is thus firmly positioned on the tool. The edge or separate guide means could be used to guide the forming tool, for example positioning pins or positioning holes in the base, grooves or tongues on the edge, or the like. It is also conceivable that the suction connection, if arranged in the base, projects into an opening in the forming tool and can be used to guide and fix the forming tool. Suction openings could be provided in the base body and connected to the suction opening.For this purpose, the base body could have suction channels extending from the suction opening to the extraction openings. The position and number of the extraction openings could be adapted to the respective forming tool.

[0023] In an advantageous embodiment, the tool further comprises a lower release film and an upper release film that can be overlapped with the lower release film for enclosing a preform to simplify placing the preform on the forming tool and to prevent contamination. The lower release film could have an area that is slightly smaller than the area of ​​the base but larger than the preform. The preform could be arranged on the lower release film and then covered with the upper release film. Particularly with a somewhat larger lower release film, the lower release film could be gripped at the edge to move the preform. Overall, contamination of the preform when moving it onto the forming tool can be prevented and, at the same time, positioning can be improved.

[0024] In an advantageous embodiment, the tool further comprises a laying tool with a depositing surface for depositing the preform, wherein the depositing surface is smaller than the area of ​​the base. The laying tool could have a surface approximately corresponding to the area of ​​the base. The depositing surface located thereon could be provided for receiving the lower release film, on which the layered structure of the preform is created. It is conceivable to pre-cure the preform slightly; for this purpose, the laying tool could be placed in the forming trough. However, this is not necessary within the scope of the invention.

[0025] The invention further relates to a method for producing a hot-formed fiber composite component, comprising the steps of providing a preform; placing the preform on a forming tool arranged on a bottom of a forming trough which comprises a peripheral edge and a trough opening facing away from the bottom and delimited by the edge; placing a lower boundary surface of a clamping frame carrying an elastic membrane on an upper boundary surface of the edge, wherein the edge and the clamping frame are designed to establish a fluid-tight connection with one another; heating the arrangement to a forming temperature; sucking air out through a suction connection arranged in the forming trough so that the membrane nestles against the preform and adjacent, free bottom regions towards the bottom of the forming trough, so that the preform is pressed onto the forming tool and is thereby deformed;Heating the assembly to a curing temperature and curing the formed preform to produce the component; and removing the clamping frame with the membrane and removing the component. In an advantageous embodiment, providing the preform comprises placing the preform on a laying tool and / or cutting a prepreg.

[0026] In an advantageous embodiment, the preform is arranged on a lower release film before being placed on the forming tool and is covered by an upper release film.

[0027] In an advantageous embodiment, before the formed preform is cured, the arrangement is arranged in an atmosphere with an increased pressure in a usual pressure range of up to 8 bar.

[0028] Short description of the characters

[0029] The following examples are described in more detail with reference to the accompanying drawings. The illustrations are schematic and not to scale. Like reference numerals refer to like or similar elements. They show:

[0030] Fig. 1 is a schematic view of a laying tool.

[0031] Fig. 2 is a schematic view of a forming tank with a

[0032] Forming tool and a preform that is placed on the forming tool.

[0033] Fig. 3 shows the forming trough with a clamping frame with an elastic membrane mounted on it. Fig. 4 shows a process of forming the preform using the membrane by suctioning off air.

[0034] Fig. 5 a process of removing the clamping frame and the membrane to remove a cured component.

[0035] Detailed description of implementation examples

[0036] Fig. 1 shows a laying tool 2 with a bottom side 4 and a top side 6, with a laying surface 8 arranged on the top side 6. A preform 10 can be produced there, for example, by cutting a prepreg, by stacking pre-impregnated fiber fabrics or non-crimp fabrics, or the like. A lower release film 12 is arranged on the laying surface 8, for example, onto which the preform 10 is placed to prevent adhesion to the laying surface 8 and contamination of the preform 10, as well as to improve transportability.

[0037] The lower release film 12 has a surface area that significantly exceeds the base area of ​​the preform 10 and consequently includes a peripheral edge strip 14 that could be gripped. This could be done, for example, with suction cups of a lifting device. The preform 10 is covered, for example, by an upper release film 16, which creates an overlap 18 with the lower release film 12. This completely encloses the preform 10.

[0038] On outer edges 20 of the laying tool 2, recesses 22 are arranged, for example, which can establish a positive connection with a fixing frame (not shown) or the like in order to fix the laying tool 2.

[0039] The preform 10, which in the form shown could also be delivered ready-made by a supplier, is to be formed to produce a curved profile component. For example, the preform 10 can be used to produce a stringer or a similar element for an aircraft structure. For this purpose, Fig. 2 shows a forming trough 24 which comprises a base 26 and an edge 28 running around the base 26. The base 26 has a base surface 30 which, for example, is completely flat and extends to the edge 28. The edge 28 runs perpendicular to the base surface 30 and has a trough opening 32 facing away from the base 26. An upper boundary surface 34 of the edge 28, which runs parallel to the base surface 30, has two circumferential seals 36 which, for example, are annular in design and each run gap-free on the upper boundary surface 34.

[0040] A forming tool 38 is arranged on the bottom 26 and comprises a base 40 and a forming body 42. The base 40 extends essentially over the entire bottom surface 30 and runs as far as the edge 28. A suction connection 44 is provided on the bottom 26, which extends, for example, vertically through the bottom 26 into the base 40 and is there in fluid communication with a suction channel 46. The suction channel 46 is in fluid communication with a plurality of suction openings 48 distributed over the base 40. The suction connection 44 can be coupled to an external suction device (not shown here), which applies a vacuum to the suction connection 44 and conveys air through it into the suction device. This illustration also shows the preform 10 with the release films 12 and 16, as it is placed on a support surface 50 of the forming body 42.

[0041] Fig. 3 further shows a clamping frame 51, which has a lower boundary surface 52 that largely corresponds to the upper boundary surface 34 of the forming tub 24. At this point, it should be noted that the forming tub 24 can, for example, have a square, rectangular or round, in particular circular, cross-section, and the surrounding edge 28 and the clamping frame 51 are shaped accordingly. Furthermore, an elastic membrane 54 is shown, which is carried by the clamping frame 51 and extends completely over the tub opening 32. The clamping frame 51 can be placed on the upper boundary surface 54 in such a way that the seals 36 create a fluid-tight connection between the clamping frame 51 and the edge 28, and consequently a cavity 56 in the tool 58 formed by the elements shown is sealed off from the surrounding atmosphere.

[0042] Before the actual forming process, the tool 58 is heated to a forming temperature, and the components forming the tool 58 are designed to be temperature-resistant. The forming temperature could, for example, be in a range of 80°C to 120°C. Heating can be carried out in a furnace or autoclave (not shown here) or by heating elements integrated into the tool 58 or externally.

[0043] Fig. 4 shows an evacuation of the cavity 56 by suctioning air through the suction port 44. As a result, the membrane 54 rests on the preform 10 and presses it onto the forming tool 40. This deforms the preform 10 such that it takes on the shape of the forming tool 42. Curing can occur in this state.

[0044] Curing occurs by heating the tool 58 to a curing temperature, which could, for example, be in a range of 150°C to 200°C. During the curing process, the preform 10 is additionally mechanically fixed by placing the tool 58 in an atmosphere with a pressure of up to 8 bar.

[0045] Subsequently, as shown in Fig. 5, the clamping frame 51 together with the membrane 54 are removed from the edge 28, and the manufactured component 60 can be removed from the tool 58. The release films 12 and 16 still present on the component 60 allow the component 60 to be easily detached from the forming body 42.

[0046] Additionally, it should be noted that "comprising" or "having" 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. Reference signs in the claims are not to be considered as limitations.

[0047] List of reference symbols

[0048] 2 laying tools

[0049] 4 Bottom

[0050] 6 Top

[0051] 8 storage area

[0052] 10 preforms

[0053] 12 lower release film

[0054] 14 surrounding edge strip

[0055] 16 upper release film

[0056] 18 Overlap

[0057] 20 outer edge

[0058] 22 Deepening

[0059] 24 forming tank

[0060] 26 Floor

[0061] 28 Rand

[0062] 30 floor space

[0063] 32 tub opening

[0064] 34 upper boundary surface

[0065] 36 Seal

[0066] 38 Forming tool

[0067] 40 Base

[0068] 42 forming bodies

[0069] 44 Suction connection

[0070] 46 Suction channel

[0071] 48 Suction opening

[0072] 50 contact surface

[0073] 51 clamping frames

[0074] 52 lower boundary surface

[0075] 54 Membrane 56 Cavity

[0076] 58 tools

[0077] 60 components

Claims

Patent claims 1 . Tool (58) for producing a hot-formed fiber composite component (60), comprising: a forming trough (24) with a bottom (26), a circumferential edge (28) and a trough opening (32) facing away from the bottom (26) and delimited by the edge (28), a forming tool (38) arranged in the forming trough (24) for placing a preform (10), and a clamping frame (51) carrying an elastic membrane (54) with a lower boundary surface (52) for placing on an upper boundary surface (34) of the edge (28), wherein the edge (28) and the clamping frame (51) are designed to establish a fluid-tight connection with one another, so that the forming trough (24) with the clamping frame (51) placed thereon can be evacuated by sucking off air through a suction connection (44) arranged in the forming trough (24), wherein the membrane (54) is designed toto nestle against a preform (10) located in the forming trough (24) and adjacent, free bottom areas when evacuating the forming trough (24) in the direction of the bottom (26) of the forming trough (24), so that the preform (10) is pressed onto the forming tool (38), and wherein the tool (58) is temperature-resistant up to a curing temperature of at least 200°C.

2. Tool (58) according to claim 1, wherein the edge (28) is higher than the common height of the forming tool (38) and an intended preform (10).

3. Tool (58) according to one of the preceding claims, further comprising at least one circumferential seal (36) which is arranged on the upper boundary surface (34) and / or the lower boundary surface (52) is arranged, wherein the circumferential seal (36) is designed to seal the upper boundary surface (34) and the lower boundary surface (52) against each other in a fluid-tight manner.

4. Tool (58) according to one of the preceding claims, wherein the suction connection (44) is arranged in the base (26) or on a base portion of the edge (28) facing the base (26).

5. Tool (58) according to one of the preceding claims, wherein the suction connection (44) is in fluid communication with a plurality of suction openings (48) arranged in the base (26) or in the forming tool (38).

6. Tool (58) according to one of the preceding claims, wherein the forming tool (38) is detachably insertable into the forming trough (24).

7. Tool (58) according to claim 6, wherein the forming tool (38) has a base body (40) which can be placed on the base (26) guided at the edge (28) and / or at guide elements.

8. Tool (58) according to one of the preceding claims, further comprising a lower release film (12) and an upper release film (16) which can be overlapped with the lower release film (12) for enclosing a preform (10) to simplify the placing of the preform (10) on the forming tool (38) and to prevent contamination.

9. Tool (58) according to one of the preceding claims, further comprising a laying tool (2) with a laying surface (8) for Depositing the preform (10), whereby the depositing surface (8) is smaller than the surface of the base (26).

10. A method for producing a hot-formed fiber composite component (60), comprising the steps: Providing a preform (10), Placing the preform on a forming tool (38) arranged on a bottom (26) of a forming trough (24) comprising a peripheral edge (28) and a trough opening (32) facing away from the bottom (26) and delimited by the edge (28), Placing a lower boundary surface (52) of a clamping frame (51) carrying an elastic membrane (54) onto an upper boundary surface (34) of the edge (28), wherein the edge (28) and the clamping frame (51) are designed to establish a fluid-tight connection with one another, Heating the assembly to a forming temperature, Suction of air through a suction connection (44) arranged in the forming trough (24) so ​​that the membrane (54) nestles towards the bottom (26) of the forming trough (24) onto the preform (10) and adjacent, free bottom areas, so that the preform (10) is pressed onto the forming tool (38) and is thereby deformed, Heating the arrangement to a curing temperature and curing the formed preform (10) to produce the component (60), and Remove the clamping frame (51) with the membrane (54) and remove the component (60).

11. Method according to claim 10, wherein providing the preform (10) comprises laying the preform on a laying tool and / or cutting a prepreg.

12. The method according to claim 10 or 11, wherein the preform (10) is placed on the forming tool (38) before being placed on a lower separating film (12) and is covered by an upper separating film (16).

13. Method according to one of claims 10 to 12, wherein before curing of the formed preform (10) the arrangement is arranged in an atmosphere with an increased pressure of up to 8 bar.

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