Device and method for producing a fibre composite component

Abstract

The invention relates to a method for producing a fiber composite component from a fiber composite material comprising a fiber material and a matrix material embedding the fiber material by means of an injection method, wherein the method comprises the following steps: - providing a molding tool with a shaping tool surface, - introducing the dry fiber material into the molding tool, and - injecting the matrix material into the dry fiber material introduced into the molding tool in an injection method, characterized in that - during the injection of the matrix material into the fiber material, one or more pressure waves are generated in the matrix material.

Description

[0001] The invention relates to a method for producing a fiber composite component from a fiber composite material comprising a fiber material and a matrix material embedding the fiber material by means of an injection method. The invention also relates to a device for this purpose.

[0002] Due to the high strength-to-weight ratio and stiffness of fiber-reinforced composite components, these components are now indispensable in the aerospace and automotive industries. In the production of a fiber-reinforced composite component, a matrix material injected into a fiber material is typically cured or consolidated under temperature and pressure, forming an integral unit with the fiber material after curing. This forces the reinforcing fibers of the fiber material into the specified direction, enabling them to transfer the applied loads in that direction.

[0003] Fiber-reinforced composite materials, from which such fiber-reinforced composite components are manufactured, generally have two main components: a fiber material and a matrix material. In addition, further secondary components can be used, such as binder materials or additional functional elements that are to be integrated into the component.

[0004] In addition to dry fiber materials, which require subsequent injection with the matrix material, pre-impregnated fiber materials (so-called prepregs) are also used, in which the fiber material is already pre-impregnated with the matrix material. A subsequent injection process is then generally unnecessary. Before the matrix material cures, the fiber material is usually placed in a mold whose surface replicates the shape of the final component.

[0005] When using dry fiber material, a (vacuum) injection process is often employed to inject the matrix material into the fiber material. In this process, the fiber material is typically placed on a mold and sealed vacuum-tight using a vacuum setup. The vacuum-tight sealed fiber material is then evacuated, causing the matrix material to be injected into the fiber material due to the pressure gradient between the fiber material and the external environment. The matrix material can then be cured, for example, in an autoclave, thus producing the component.

[0006] In addition, it is also known to use closed molds consisting of two or more mold halves, which, when closed, form a component cavity into which the fiber material is introduced. After closing the mold, the resulting component cavity can then be evacuated to inject the matrix material. The tight sealing of the mold allows for the application of high pressure, which is crucial for both the injection and curing of the matrix material. This feature enables rapid production and adherence to high quality standards.

[0007] The RTM process (vacuum injection molding) has established itself as a significant method for manufacturing high-quality fiber-reinforced composite (FRC) components, particularly in the field of carbon fiber reinforced polymer (CFRP) applications in aircraft construction. This process enables the integral fabrication of complex structures with integrated elements such as stringers, flanges, and frames. This makes the method particularly suitable for the mass production of components, which is why it is so attractive.

[0008] The RTM process involves injecting liquid matrix material, which is typically heated to the required injection temperature. In practice, two main methods are available. The first method involves introducing the matrix material into a pressure pot, from which it is injected into the mold via lines using compressed air. This method is characterized by its robustness and requires few components, thus minimizing cleaning effort. The second method uses a fluid pump to enable more precise pressure control and higher pressure. However, this method requires more extensive cleaning, especially when using single-component matrix systems.

[0009] The aim of the injection process is always to reduce, minimize, or completely eliminate dry spots or pores within the fiber material, as such unimpregnated areas, where the fiber material is not fully impregnated with the matrix material, can negatively affect the component quality.

[0010] Although the matrix material is typically degassed in a heated matrix reservoir before being injected into the fiber material to remove air bubbles and any dissolved gases, the formation of air bubbles during the injection process cannot be completely prevented. These bubbles inevitably enter the component sooner or later. They then become trapped in the fibers of the structure, forming pores or dry areas where the fiber material is not impregnated with the matrix material.

[0011] It is therefore an object of the present invention to provide an improved injection method for the production of fiber composite components with which the formation of pores or dry areas can be reduced.

[0012] The problem is solved according to the invention using the method according to claim 1. Advantageous embodiments of the invention are described in the corresponding dependent claims.

[0013] According to claim 1, a method for producing a fiber composite component from a fiber composite material comprising a fiber material and a matrix material embedding the fiber material is proposed by means of an injection method, which according to the generics comprises the following steps: Providing a molding tool with a shaping tool surface, introducing the dry fiber material into the molding tool, and injecting the matrix material into the dry fiber material introduced into the molding tool using an injection process.

[0014] According to the invention, it is now provided that one or more pressure waves are generated in the matrix material during the injection of the matrix material into the fiber material.

[0015] It has been shown that such pressure waves within the matrix material, which are generated during the injection of the matrix material into the fiber material, can loosen and remove the air bubbles hanging on the fibers, thus reducing or even completely avoiding the number of pores and dry areas within the component.

[0016] Such a pressure wave is generated, in particular, by first increasing the pressure of the matrix material in a piping system for transporting the matrix material and / or in the component cavity of the mold itself, and then suddenly or rapidly releasing it. This creates a pressure wave in the matrix material, which propagates through the piping system for transporting the matrix material and into the already impregnated areas of the component cavity. This pressure wave detaches the air bubbles that are attached to the fibers of the fibrous material and carries them out of the component by the further transport of the matrix material.

[0017] The pressure waves are preferably generated periodically, so that a plurality of such pressure waves propagate through the matrix material within a given period.

[0018] The generation of pressure waves can begin as soon as the matrix material flows into the component or component cavity. However, it is also conceivable that the pressure waves are generated even when the fiber material is almost completely impregnated with the matrix material and a kind of flushing process is carried out to impregnate the remaining areas of the fiber material.

[0019] The pressure waves are preferably generated in a pulsed manner, i.e., the pressure of the matrix material increases and is released very quickly to create a pressure wave with a steep flank.

[0020] Such a device, with which the fiber material is to be injected with the matrix material, comprises in particular a matrix reservoir in which the matrix material to be injected is stored, and a piping system that has at least one supply line from the matrix reservoir to an inlet on the mold, in order to inject the matrix material from the matrix reservoir into the fiber material that has been introduced into the mold. Additionally, the piping system may have at least one return line, which is arranged at an outlet of the mold and is operatively connected to a resin trap and a vacuum pump. It is conceivable that the return line also opens into the supply line or the matrix reservoir, thus creating a kind of circuit. A fluid pump may preferably be integrated into this piping system to transport the matrix material within the system.

[0021] According to one embodiment, the pressure waves are generated by reducing or interrupting the flow at least once in a flexible hose line for transporting the matrix material, while a fluid pump connected to the flexible hose line builds up fluid pressure in the conveying direction upstream of the at least one hose clamp, which is then released by opening the at least one hose clamp.

[0022] In this embodiment, the previously described piping system has, at least in sections, a flexible hose that is not only flexible but can also be compressed. The hose clamp can reduce or completely stop the flow in this flexible hose, causing the matrix material to back up in the direction of flow of the peristaltic pump upstream of the hose clamp, thus increasing the pressure. If the hose clamp is then suddenly opened—that is, quickly, abruptly, or jerkily—the fluid pressure upstream of the hose clamp drops abruptly, resulting in a pressure wave within the matrix material. This pressure wave then propagates through the piping system and, potentially, also and especially, through the impregnated fiber material.While the hose clamp reduces or completely interrupts the flow, the fluid pump continues to run continuously in order to create the corresponding back pressure at the hose clamp.

[0023] The hose clamp can be electrically actuated, preferably being directly connected to a process control system. This system is configured to cyclically or periodically actuate the hose clamp during injection, reducing or completely interrupting the flow and then abruptly opening it to generate pressure waves. This allows this part of the injection process to be integrated into the overall process control system.

[0024] According to one embodiment, the flow is reduced or interrupted by means of at least one hose clamp in a supply line which is arranged at an inlet on the molding tool.

[0025] Such a supply line is provided in the piping system as a conduit for transporting the matrix material from the matrix reservoir to an inlet on the mold. The hose clamp is arranged in a section within which the supply line is designed as a flexible hose. In principle, such a supply line can be designed as a continuous, particularly one-piece, flexible hose. The hose clamp is positioned between the matrix reservoir and the inlet on the mold. The fluid pump is located between the matrix reservoir and the hose clamp.

[0026] According to one embodiment, the flow is reduced or interrupted by means of at least one hose clamp in a return line which is arranged at an outlet on the molding tool.

[0027] Such a return line is provided in the piping system as a conduit for transporting the matrix material, which exits as excess material at an outlet on the mold and is typically collected in a resin trap. This resin trap is connected to a vacuum pump, preventing the vacuum pump from becoming contaminated with matrix material when the component is evacuated via this return line. At least one section of this return line, preferably the entire return line, is designed as a flexible hose, allowing for the inclusion of a hose clamp to reduce or interrupt the flow. If the flow in this return line is reduced or interrupted while the fluid pump continues to convey or pump matrix material, overpressure builds up in the return line upstream of the hose clamp in the conveying direction. This overpressure is then also generated in the mold and thus in the component cavity.If this hose clamp is now released abruptly, the pressure also drops abruptly, creating a corresponding pressure wave (negative) directly in the component cavity.

[0028] It may be provided that such a hose clamp is provided in both the supply line and the return line, whereby these periodically and alternately reduce or interrupt their flow accordingly, so that different pressure waves form within the component cavity and the piping system.

[0029] According to one embodiment, the pressure waves are generated by means of at least one peristaltic pump, which is arranged in a flexible hose line for transporting the matrix material.

[0030] A peristaltic pump of this type consists of at least a rotor, a stator, and conveying elements (usually in the form of rollers) that are arranged on the rotor and clamp a flexible hose line against the stator. This clamping point is moved in the conveying direction by the rotation of the rotor, thus transporting the matrix material. Depending on the speed and delivery volume, such a peristaltic pump is capable of generating a pressure wave, as an overpressure is generated in front of the clamping point, while a vacuum is created behind it. When the conveying element leaves the stator's effective range, these pressure conditions are abruptly released.

[0031] Such a peristaltic pump can be arranged in a flexible hose section in the supply line and / or in the return line.

[0032] According to one embodiment, the pressure waves are generated by means of at least one diaphragm pump, which is arranged in a supply line and / or in a return line for transporting the matrix material.

[0033] In a diaphragm pump of this type, a flexible diaphragm is in contact with the fluid, in this case the matrix material, and can be moved from a suction position to a pumping position, thereby exerting a pump pressure that transports the matrix material in the conveying direction. This change in the position of the diaphragm can generate a pressure wave in the matrix material.

[0034] According to one embodiment, the pressure waves are generated by a first fluid pump, arranged in a supply line on the molding tool, and a second fluid pump, arranged in a return line on the molding tool, simultaneously generating a fluid pressure in the conveying direction towards the molding tool, so that the matrix material pressure in the fiber material introduced into the molding tool is increased, and subsequently, after the matrix material pressure has increased, the conveying direction of the second fluid pump is reversed.

[0035] In this embodiment, the two fluid pumps, arranged so that the mold with the component cavity lies between them, are controlled such that the matrix material is conveyed in the direction of the mold. This increases the internal pressure in the component cavity, whereupon the delivery direction of the second fluid pump in the return line is abruptly reversed, causing the internal pressure to decrease and generating the pressure wave.

[0036] According to one embodiment, a closed mold tool with at least two mold tool halves is provided, which in the closed state forms a component cavity for the fiber material, wherein during the injection of the matrix material into the fiber material in the component cavity the mold tool halves are cyclically moved towards and away from each other, so that pressure waves are generated in the matrix material injected into the fiber material.

[0037] By cyclically, and especially impulsively, moving the two mold halves towards and away from each other, a pressure change can be generated within the component cavity. This pressure change also creates a pressure wave, which can be used to expel air bubbles. A flexible seal can be positioned between the two mold halves to compensate for the cyclical movement of the two mold halves and thus create a vacuum-tight seal within the component cavity.

[0038] According to one embodiment, the matrix material is conveyed from a matrix reservoir via a feed line into the fiber material and from there via a return line back into the matrix reservoir and / or the feed line.

[0039] This allows for a kind of flushing process in which the fiber material continues to be injected with matrix material over a certain period, even though the fiber material is largely impregnated with the matrix material. Since the return line leads back into the matrix reservoir, and thus the matrix material coming from the outlet returns to the matrix reservoir, the fiber material can be continuously flushed with the matrix material over an extended period. This flushing process, in conjunction with the pressure waves, ensures that as many air bubbles as possible are transported out of the fiber material, thus largely preventing the formation of pores.

[0040] Therefore, in this embodiment, a flushing circuit is established by continuously pumping the matrix material from the matrix reservoir, in which excess matrix material from the return line is fed back into the matrix reservoir.

[0041] The problem is also solved by a corresponding device for producing a fiber composite component from a fiber composite material comprising a fiber material and a matrix material embedding the fiber material, set up for carrying out an injection process in which the dry fiber material introduced into a mold is injected with the matrix material, wherein the device according to the invention has at least one pressure wave generator which is set up to generate pressure waves in the matrix material during the injection of the matrix material into the fiber material.

[0042] According to one embodiment, the device is designed to carry out the procedure described above.

[0043] According to one embodiment, at least one pressure storage volume is provided in a piping system for transporting the matrix material.

[0044] The invention is explained in more detail using the accompanying figure as an example. It shows: Figure 1 schematic representation of a system according to the invention for carrying out the method.

[0045] Figure 1 Figure 10 schematically shows a device 10 with which a fiber material 12 is to be injected into a mold 14 with a matrix material 16. In the exemplary embodiment, the mold is a Figure 1 a closed mold tool consisting of 2 halves, in the closed state forming a component cavity in which the fiber material 12 to be injected is located.

[0046] The device 10 comprises a matrix reservoir 18 containing the matrix material 16. The mold 14 also has an inlet 20, also called a sprue, through which the matrix material 16 to be injected is directed into the component cavity and thus transported into the fiber material 12.

[0047] From the matrix reservoir 18 to the inlet 20 on the mold 14, there is a supply line for the matrix material 16, which is designed as a flexible hose 22. In the exemplary embodiment of the Figure 1 This flexible hose line 22 is continuous and one-piece, so that it can be used as a segment in the preparation of the device 10.

[0048] The flexible hose line 22 also contains a fluid pump in the form of a peristaltic pump 24, which draws the matrix material 16 from the matrix reservoir 18 by means of negative pressure and pushes it into the component cavity with the fiber material 12.

[0049] Between the peristaltic pump 24 and the inlet 20 a forming tool 14, a pressure sensor 26 is located in the flexible hose line, which measures the internal pressure P1 of the matrix material 16 without contact on the outer shell surface of the flexible hose line 22.

[0050] In the exemplary embodiment of the Figure 1 At the opposite end of the inlet 20, there is an outlet 28 on the molding tool 14, to which a second flexible hose line 30 is arranged.

[0051] This second flexible hose line 30 leads into a resin trap 32, which is evacuated using a vacuum pump 34. It is also conceivable that the second flexible hose line 30 is routed back into the matrix reservoir 18 or the first flexible hose line 22 to create a flushing cycle. It is also conceivable that a peristaltic pump is provided in the second flexible hose line 30 to assist in this process.

[0052] In the first flexible hose line 22, shortly before the inlet 20, between pressure sensor 26 and inlet 20, there is a first hose clamp 36, which is designed to clamp the flexible hose line 22 at this point in order to reduce or interrupt the flow.

[0053] In the second flexible hose line 30, behind the outlet 28, there is also a second step clamp 38, which is also designed to clamp the flexible hose line 30 at this point in order to reduce or interrupt the flow.

[0054] To generate a pressure wave in the piping system comprising the first flexible hose 22 and the second flexible hose 30, as well as in the component cavity containing the fiber material 12, the hose clamps 36 and 38 are cyclically or periodically closed alternately, while the peristaltic pump 24 continues to pump the matrix material 16. The sudden opening of the closed hose clamp releases the accumulated pressure abruptly, and a corresponding pressure wave forms in the matrix material.

[0055] For example, if the first hose clamp 36 is closed while the peristaltic pump 24 continues to pump the matrix material 16, the pressure sensor 26 can detect that the internal pressure within the flexible hose 22 is rising. Once the desired internal pressure is reached, the first hose clamp 36 is opened abruptly, causing the internal pressure to suddenly release and a corresponding pressure wave to propagate through the matrix material in the already impregnated areas of the fiber material 12. If this process is repeated cyclically or periodically, air bubbles that have become attached to the fiber material can be released and carried away, thereby reducing the formation of pores in the subsequently manufactured component.

[0056] The same applies to the second hose clamp 38, which interrupts the return line at the outlet 28. This causes an internal pressure to build up, particularly in the fiber material 12 of the component cavity, which is suddenly released by the abrupt opening of the hose clamp. Here, too, a pressure wave travels through the fiber material 12 in a negative direction.

[0057] The hose clamps 36 and 38 can be controlled via a higher-level process control (not shown), which is part of the general plant control system. Reference symbol list

[0058] 10 Device 12 Fiber material 14 Molding tool 16 Matrix material 18 Matrix reservoir 20 Inlet 22 Flexible hose (first) 24 Peristaltic pump 26 Pressure sensor 28 Outlet 30 Second flexible hose 32 Resin trap 34 Vacuum pump 36 First hose clamp (supply) 38 Second hose clamp (return)

Claims

1. A method for producing a fiber composite component from a fiber composite material comprising a fiber material (12) and a matrix material (16) embedding the fiber material (12) by means of an injection method, wherein the method comprises the following steps: - providing a mold (14) with a shaping tool surface, - introducing the dry fiber material (12) into the mold (14), and - injecting the matrix material (16) into the dry fiber material (12) introduced into the mold (14) in an injection process. characterized by the fact that - during the injection of the matrix material (16) into the fiber material (12), one or more pressure waves are generated in the matrix material (16).

2. Method according to claim 1, characterized by the fact thatThe pressure waves are generated by reducing or interrupting the flow at least once by a hose clamp (36, 38) arranged in a flexible hose line (22, 30) for transporting the matrix material (16), while a fluid pump connected to the flexible hose line (22, 30) builds up fluid pressure in the conveying direction upstream of the at least one hose clamp (36, 38), which is then released by opening the at least one hose clamp (36, 38).

3. Method according to claim 2, characterized by the fact that the flow is reduced or interrupted by means of at least one hose clamp (36, 38) in a supply line which is arranged at an inlet (20) on the molding tool (14).

4. Method according to claim 2 or 3, characterized by the fact thatthe flow is reduced or interrupted by means of the at least one hose clamp (36, 38) in a return line which is arranged at an outlet (28) on the forming tool (14).

5. Method according to any one of the preceding claims, characterized by the fact that the pressure waves are generated by means of at least one peristaltic pump (24) which is arranged in a flexible hose line (22, 30) for transporting the matrix material (16).

6. Method according to any one of the preceding claims, characterized by the fact that the pressure waves are generated by means of at least one diaphragm pump which is arranged in a supply line and / or in a return line for the transport of the matrix material (16).

7. Method according to any of the preceding claims, characterized by the fact thatThe pressure waves are generated by a first fluid pump, which is arranged in a supply line on the molding tool (14), and a second fluid pump, which is arranged in a return line on the molding tool (14), simultaneously generating a fluid pressure in the conveying direction towards the molding tool (14), so that the matrix material pressure in the fiber material (12) which is introduced into the molding tool (14) is increased, wherein the conveying direction of the second fluid pump is then reversed after the increase in the matrix material pressure.

8. Method according to any one of the preceding claims, characterized by the fact thatA closed mold tool (14) with at least two mold tool halves is provided, which in the closed state forms a component cavity for the fiber material (12), wherein during the injection of the matrix material (16) into the fiber material (12) in the component cavity the mold tool halves are cyclically moved towards and away from each other, so that pressure waves are generated in the matrix material (16) injected into the fiber material (12).

9. Method according to any one of the preceding claims, characterized by the fact that the matrix material (16) is conveyed from a matrix reservoir (18) via a feed line into the fiber material (12) and from there via a return line back into the matrix reservoir (18) and / or the feed line.

10. Device (10) for producing a fiber composite component from a fiber composite material comprising a fiber material (12) and a matrix material (16) embedding the fiber material (12) configured for carrying out an injection process in which the dry fiber material (12) introduced into a mold tool (14) is injected with the matrix material (16), characterized by the fact that the device (10) has at least one pressure wave generator which is configured to generate pressure waves in the matrix material (16) during the injection of the matrix material (16) into the fiber material (12).

11. Device (10) according to claim 10, characterized by the fact that the device (10) is set up to carry out the method according to one of claims 1 to 9.

12. Device (10) according to claim 10 or 11, characterized by the fact that in a piping system for transporting the matrix material (16) at least one pressure storage volume is provided.

13. Device (10) according to one of claims 10 to 12, characterized by the fact that a conduit system for transporting the matrix material (16) is provided, which has a supply line from a matrix reservoir (18) to the molding tool (14) and a return line that leads from the molding tool (14) to the matrix reservoir (18) and / or the supply line.

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