METHOD FOR PRODUCING A FIBER COMPOSITE COMPONENT AND FIBER COMPOSITE COMPONENT THEREFOR

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. The invention also relates to a fiber composite component for this purpose.

[0002] Due to the weight-specific strength and stiffness of fiber composite components made from fiber composite materials, such components have become indispensable in aerospace and many other applications, such as the automotive sector. During the production of a fiber composite component, a matrix material embedding the fiber material is usually cured under heat and pressure. After curing, it forms an integral unit with the fiber material. This forces the reinforcing fibers of the fiber material into their specified direction and allows them to transfer the loads that occur in the specified direction.

[0003] Fiber composite materials from which such fiber composite components are manufactured generally have two main components: a fiber material and a matrix material. The fiber material and matrix material can be separate or already embedded. In addition, other secondary components can be used, such as binder materials or additional functional elements to be integrated into the component. If dry fiber materials are provided for production, the matrix material of the fiber composite is infused into the fiber material during the manufacturing process using an infusion process through which the dry fiber material is impregnated with the matrix material. This usually occurs due to a pressure difference between the matrix material and the fiber material, for example, by evacuating the fiber material using a vacuum pump.In contrast, fiber composite materials are also known in which the fiber material is already pre-impregnated with the matrix material (so-called prepregs), so that when they are used, further impregnation of the fiber material is generally not necessary.

[0004] Carbon fibers or glass fibers are particularly used as fiber materials, while thermoplastic and thermosetting matrix plastics and resins are particularly used as matrix materials.

[0005] Before the matrix material cures, the fiber material is usually introduced into a mold or forced into a predetermined shape so that the final component shape is replicated with the mold's shaping surface. Both dry and pre-impregnated fiber materials can be deposited or introduced into the mold. For the production of large-scale structural components, such as the wing shells of commercial aircraft or rotor blades of wind turbines, automated fiber deposition processes are used to optimize the deposition process. A production system and at least one fiber deposition head are used to deposit a virtually continuous fiber material fed to the fiber deposition head onto the tool.

[0006] Such an automated fiber laying system is known, for example, from DE 10 2010 015 027 B4, in which several robots are guided on a rotating rail system, each with a laying head as the end effector. A fiber feeder continuously feeds fiber material from a fiber magazine to the laying heads, while the individual robots, with their laying heads, deposit the supplied fiber material onto a forming tool located in the center of the rotating rail system.

[0007] In addition to the linear deposition of fiber material on a tool, winding processes are also known in which the fiber material is continuously deposited on the surface of a tool that rotates around its own longitudinal axis. The rotational movement draws the fiber material from the material reservoir and winds it onto the rotating tool surface. One such winding process is known, for example, from DE 102014 112 311 A1, in which the winding core is designed to be flexible so that a process pressure can be exerted on the wound fiber material by adjusting pressures in the winding core (also called the liner or winding tool).

[0008] DE 10 2015 113 686 A1 discloses a winding process in which cracks in the surface are to be created. These cracks in the surface have concave areas that would normally be spanned by the wound fiber material. It is proposed to use a fixing thread that presses the fiber material radially into the concave recess.

[0009] DE 10 2015 102 440 A1 discloses a winding method for producing a hollow body with an internal thread, wherein here too the fiber material is pressed into the thread groove as a concave depression by a thread or a correspondingly shaped upper tool.

[0010] Finally, DE 41 22 785 A1 also discloses a winding process, whereby concave surface shapes are to be realized. The winding process shown here comprises two different windings. A first main winding is essentially longitudinal to the rotation axis, while a fixing winding crosses the thread of the main winding at a certain angle and presses it into the concave surface shape.

[0011] If web-like or strand-like fiber materials are laid down on multiply curved tool surfaces using an automated fiber laying system, as is the case, for example, in the production of hollow bodies in the area of ​​the end caps (poles), the individual web-like or strand-like fiber materials must be shortened in width, which is usually done by cutting off one of the outer strands or bands. However, since such cutting is currently only possible orthogonally to the laying direction, a material gap is created at these points between the adjacent fiber materials, which is repeated several times in each material layer of the preform to be produced. This often results in a weakened component, since these material gaps can lead to fiber undulations, which have a direct reduction, for example, in the compressive and tensile properties. Furthermore, it has been shown that such material gaps in pressure accumulators, e.g.Hydrogen tanks (LH2), can lead to a reduction in permeation properties.

[0012] Furthermore, the design of such fiber composite components often includes gaps during the automatic fiber placement process to prevent overlapping of adjacent fiber materials due to manufacturing tolerances. The web-shaped or strand-shaped fiber materials are thus already deposited with a deliberate material gap between the adjacent fiber materials, which - as already described - can also have a negative impact on the component and its properties. Additional fiber material layers are often used to compensate for these negative effects, which, however, runs counter to the core concept of lightweight construction using fiber composites.

[0013] DE 10 2011 054 650 A1 discloses a method and device for constructing a preform made from a plurality of cut mats of fiber material. The mats are gripped by a robot unit and placed in a corresponding position, with any resulting gaps being detected and filled with cut-to-size mold elements.

[0014] US 2007 / 0229805 A1 discloses a manufacturing system for the optical inspection of deposited fiber materials using a laser light section sensor. This sensor projects a laser line onto the surface to be inspected, which is then recorded by a camera. Deviations from the straight line result from surface irregularities, allowing gaps or steps to be detected.

[0015] WO 2012 / 022972 A1 discloses a method for creating a fiber preform using individual fiber mats (so-called sheets). These are placed on a surface, with positioning taking place depending on a sensor signal.

[0016] US 2020 / 0324474 A1 discloses an additive manufacturing process using "Fused Filament Fabrication (FFF)," in which a plastic material is fed into a print head, melted, and then dispensed in individual strands. A first group of strands is initially dispensed, spaced apart from each other, while these gaps are subsequently filled by a second group.

[0017] Finally, EP 3 957 471 A1 discloses the production of a complex component that is to be reinforced by a reinforcement element. A cavity is created at the interface between the first component and the second component, which is to be filled by a gusset.

[0018] It is therefore an object of the present invention to provide an improved method for producing a fiber composite component, in particular with a complex, multiply curved geometry, in which the disadvantages known from the prior art can be avoided.

[0019] The object is achieved according to the invention with the method according to claim 1. Advantageous embodiments of the invention can then be found in the corresponding subclaims.

[0020] 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, which method comprises the following steps Providing a web-shaped or strand-shaped, quasi-endless fiber material, depositing the band-shaped or strand-shaped, quasi-endless fiber material on a shaping, multiply curved tool surface of a provided forming tool in such a way that the individual fiber webs or fiber strands of the band-shaped or strand-shaped, quasi-endless fiber material are deposited next to one another, detecting at least one material gap between two adjacent fiber webs or fiber strands of the band-shaped or strand-shaped, quasi-endless fiber material deposited on the tool surface and their dimensions by means of a detection device, providing a filling material in order to fill the detected material gaps between adjacent fiber webs or fiber strands, and introducing the filling material into the detected material gaps depending on their dimensions.

[0021] Accordingly, a ribbon-like or strand-like fiber material is first provided, which is intended in the form of a quasi-continuous fiber material, particularly for automated deposition. This ribbon-like or strand-like fiber material is then deposited, preferably automatically, onto a forming tool surface of a provided forming tool using a fiber-laying system, with individual fiber webs or fiber strands being deposited side by side in a fiber layer and then several fiber layers being deposited one on top of the other.

[0022] During each pass, a plurality of individual fiber webs or fiber strands can be deposited, for example, 8, 16, or 32 individual fiber webs or fiber strands. At the end of such a weighing process, the depositing head of the fiber laying system can be realigned, with new fiber webs and fiber strands being deposited adjacent to the previously deposited fiber webs or fiber strands on the tool or on an already deposited fiber material layer.

[0023] During or after the deposition of a complete fiber material layer, material gaps between adjacent fiber webs or fiber strands are detected using a detection device. Detecting such material gaps involves not only detecting the presence of such a material gap, but also, in particular, the exact position relative to the component and / or its respective dimensions.

[0024] After at least one material gap has been detected and, if necessary, the exact position and dimensions of this material gap have been determined, a pre-determined filler material is inserted into this material gap to fill the detected material gaps between adjacent fiber webs or fiber strands. Preferably, the filler material is inserted not after the preform has been completed, which is also conceivable, but after each deposited fiber layer, i.e., before new fiber material is applied to the already deposited fiber material.

[0025] The fiber composite component is then manufactured by consolidating, i.e., hardening, or curing, the matrix material embedded in the fiber material. Consolidation occurs primarily by tempering the fiber preform with the embedded matrix material to the required process temperature, for example, to at least 180 °C. The term "consolidation" also refers to curing, particularly of reactive resins or thermosets.

[0026] The present invention makes it possible to close the design-related material gaps in the production of fiber composite components with multiply curved geometries, thereby improving the strength, stability, and permeation properties of the component. The present process can be fully automated, thereby improving component quality.

[0027] Both dry and pre-impregnated fiber materials can be used in the process according to the invention. If dry fiber materials are used, the dry fiber material must be infused with a matrix material in an infusion process.

[0028] Plastics and resins similar to the matrix material used and suitable for permanently closing the material gaps are particularly used as filler materials. The filler material should have a similar thermal expansion coefficient to the fiber composite material and preferably chemically create a bond within the material gap to the surrounding materials. Alternatively, a special embodiment provides for the filler material to consist of the matrix material of the fiber composite material or to contain such a matrix material. The filler material can also additionally contain fibers or fiber materials.

[0029] If dry fiber materials are used to produce the preform, it is advantageous if the filler material is also a dry fiber material, which may be binder-bound. After the dry fiber material has been introduced into the corresponding material gap and the preform has been completely produced, the infusion process is started so that both the deposited fiber material and the dry fiber material inserted into the material gaps are infused with the matrix material. The dry fiber material used as filler material is pre-cut separately depending on the dimensions of the respective material gap so that it can precisely fill the space of the material gap.

[0030] According to one embodiment, it is provided that the fiber material surface of the web-shaped or strand-shaped fiber material deposited on the tool surface is recorded contactlessly by means of a camera of the detection device and material gaps between two adjacent fiber webs or fiber strands are automatically detected by a digital evaluation of the recorded fiber material surface by means of an evaluation unit of the detection device.

[0031] The camera of the detection device records the fiber material surface and generates digital image data depicting the fiber material surface. Image analysis can be used to detect defects, such as material gaps. The digital image data can be displayed as a false-color image, with each color encoding a height of the fiber material surface. Through digital analysis, particularly image analysis, the material gaps, including their position and dimensions, can be recorded, and the filler material can then be inserted based on this.

[0032] According to one embodiment, it is provided that a height profile of the fiber material surface of the web-shaped or strand-shaped fiber material deposited on the tool surface is created by means of a light projection method in which a light line is projected onto the fiber material surface from a first direction by means of a light source of the detection device, the projected light line is recorded by means of a camera of the detection device from a second direction different from the first direction, while the light line is moved over the fiber material surface, and the height profile is created as a function of a detected deformation of the recorded light lines by means of a computing unit of the detection device, wherein material gaps between two adjacent fiber webs or fiber strands are automatically detected as a function of the created height profile by means of an evaluation unit of the detection device.

[0033] Such a light projection process can be carried out using a laser light section sensor (LLSS), which projects a laser line onto the fiber material surface and then records the laser line projected onto the surface from a different angle. If the surface exhibits unevenness, the projected laser line is deformed from its strict straightness, allowing conclusions to be drawn about the surface height at this projected position. The laser line is then moved across the entire component, with corresponding images of the laser line being taken at discrete times, allowing a height profile to be created for the entire component surface. Based on this height profile, material gaps can then be detected.

[0034] Here, too, it is conceivable that the height profile is created in the form of a false-color image, which is then subjected to image analysis in order to detect the material gaps based on the false-color image.

[0035] According to one embodiment, it is provided that the deposition of the web-shaped or strand-shaped fiber material on the shaping tool surface is first simulated by means of a simulation unit of the detection device based on production data and / or design data, wherein the material gaps between two adjacent fiber webs or fiber strands are detected depending on the simulated deposition of the web-shaped or strand-shaped fiber material.

[0036] In this embodiment, the component is not completely scanned to detect material gaps; instead, the material gaps are statically extracted from the manufacturing or design data. For this purpose, the deposition of the fiber material is simulated according to the manufacturing or design data, with the resulting material gaps—intentional or unintentional—recognizable in the simulation.

[0037] It has been shown that in many cases this is sufficient to reliably insert the filling material into the detected material gaps.

[0038] According to one embodiment, a prefabricated filler patch is separately produced from the filler material for at least one detected material gap based on the dimensions of the respective material gap. The produced filler patch is then inserted into the respective material gap of the deposited fiber material. The filler patch is produced from the filler material (e.g., dry fiber material, pre-impregnated fiber material, (elastic) plastic material without fiber material, or others) in such a way that the filler patch can precisely occupy and fill the space of the material gap within tolerances.

[0039] In a separate process step, a prefabricated filler patch is produced from the filler material that corresponds to the detected dimensions of the respective material gap. This separately produced, prefabricated filler patch can be inserted into the respective material gap after its production. This can be done manually, for example, by inserting the filler patch into the material gap. It is also conceivable that the filler patch is automatically picked up by a robot unit using a pick-and-place process and inserted into the respective material gap.

[0040] According to one embodiment, the prefabricated filling patch is produced from the filling material using a 3D printing device. The detected dimensions of the material gap into which the filling patch is to be inserted serve as the basis for the production of the filling patch.

[0041] According to one embodiment, the filling material is automatically introduced into at least one material gap in the deposited fiber material by means of an application device to which the filling material is continuously fed. Such an application device can, for example, be a printing device that continuously dispenses the filling material and introduces it into the material gap. In this embodiment, the filling patch to be produced is printed or produced directly in the material gap, so that an additional introduction of a separately produced filling patch is no longer necessary. The application device can be attached to a robot, which automatically positions the application device at the detected material gap and then prints the filling material into the material gap (e.g. by pressing it into the material gap) so that the entire space of the material gap is filled.

[0042] This can, for example, be done in parallel with the deposition of fiber materials in the downstream section if more than one robot has access to the tool. In this case, there is no need to wait until a complete layer of fiber material has been created, so the process times for filling the material gaps can be significantly reduced.

[0043] A further aspect of the present invention is a fiber composite component produced from a fiber composite material according to the method described above. Such a fiber composite component can, for example, be a hollow component.

[0044] The ribbon-like or strand-like fiber material can be laid down in the form of material webs consisting of a plurality of individual strands or individual webs or fiber strands or fiber webs. For example, a material web can be formed from 8, 16, or 32 individual strands or fiber strands, whereby individual strands or individual webs of a material web can be cut off and disconnected. After a material web has been laid down, additional material webs are laid down adjacent to it.

[0045] The present invention is explained by way of example with reference to the accompanying figures. They show: Figure 1: Schematic representation of a deposition head with a laser light section sensor in the downstream section; Figure 2: Representation of a component with complex geometry in the form of a pressure tank; Figure 3: Detailed representation of the individual fiber webs with material gaps.

[0046] Figure 1shows part of a fiber laying system for recording a height profile image 10 (shown as an example in Figure 2 ) by means of a laser light section sensor 5 in the downstream section of a deposition head 1, which has a pressure roller 2 at its lower end, with which a flat fiber material 3 is to be deposited onto a forming tool surface 4. The fiber materials 3 to be deposited can be dry rovings or tows, but also pre-impregnated prepregs. Usually, several rovings or tows are deposited simultaneously.

[0047] A laser light section sensor 5 is arranged in the downstream section of the deposition head 1. A laser light source 6 projects a laser light line 7 onto the already deposited portion of the semi-finished fiber product 3. The laser light is projected in the form of a laser light line 7 onto the fiber material 3 from a first direction.

[0048] The laser light section sensor 5 further comprises a camera 8 which is arranged at a defined distance from the laser light source 6 and records the laser light line 7 projected onto the semi-finished fiber product 3 from a different second direction at a predetermined and defined angle.

[0049] The camera 8 of the light section sensor 5 is connected to an image evaluation unit 9, which receives the line-by-line image data from the camera 8 via a data interface. The line-by-line image data is then analyzed to produce a one-dimensional height profile along the laser light line 7. For this purpose, height information is determined at a plurality of points along the laser light line 7, with all height information along this laser light line 7 ultimately resulting in the linear height profile.

[0050] This linear height profile with the individual height information along the laser light line 7 is now fed to a data processing system 10, for example with a machine learning system, in order to identify the material gaps to be filled.

[0051] Since the deposition head 1 is continuously moved on the tool surface 4 together with the light section sensor 5, a large number of linear height profiles are produced, which are continuously created by the image evaluation unit 9 and then provided to the data processing system 10 for defect classification.

[0052] Figure 2shows a pressure tank 20 formed layer by layer by laying down individual webs 21 of a strand-like or ribbon-like fiber material, wherein the fiber material can be applied to an internal liner. The forming tool, in this case the liner, has a cylindrical main part 22, at each of which two ends are provided with end caps 23. These end caps 23 extend from the cylindrical main part 22 to the poles 24 of the liner, with the surface in this transition region being curved several times.

[0053] In this multiply curved transition area, the parallel webs 21 of the strand-like or ribbon-like fiber material must be tapered so that each individual web receives an increasingly smaller width the closer it comes to the poles 24. However, since the webs 21 consisting of several individual strands can only be cut orthogonally to the laying direction, material gaps 30 arise from the adjacent webs, as shown in Figure 3 is presented in detail.

[0054] The Figure 3 The material gap 30 shown is created by the outer single strand 31 of web 21 being severed and then not laid down any further, causing web 21 to taper abruptly as it continues. This taper creates a material gap 30 that forms in the form of a gap along the laying direction until web 21 meets the adjacent material web again.

[0055] Were the individual material webs 21 with a fiber laying system, as exemplified in Figure 1 As shown, the already deposited fiber materials were scanned using the laser light section sensor, and a height profile was created. After depositing a single layer of fiber material consisting of a plurality of material webs 21, it is known at which positions on the fiber material surface the corresponding material gaps 30 with their respective dimensions exist.

[0056] A filler patch can now be created separately for each of these material gaps 30 to close these material gaps 30 in the deposited individual layer. Once this has been done, the individually produced filler patches (not shown) are inserted into the respective material layer 30, after which another layer of fiber material can be deposited as described above. This process is repeated until all layers of fiber material have been deposited. List of reference symbols

[0057] 1Deposition head 2Pressure roller 3Fiber material 4Tool surface 5Laser light section sensor 6Laser light source 7Laser light line 8Camera 9Image evaluation unit 10Digital data processing system 20Pressure tank 21Fiber material webs 22Cylindrical main part 23End cap 24Pole 30Material gap 31Single strand

Claims

1. Method for manufacturing a fiber composite component from a fiber composite material comprising a fiber material and a matrix material embedding the fiber material, wherein the method comprises the following steps: - providing a ribbon-shaped or strand-shaped, quasi-endless fiber material (3), - Depositing the ribbon-shaped or strand-shaped, quasi-endless fiber material (3) on a shaping, multiply curved tool surface (4) of a provided forming tool in such a manner that the individual fiber tracks or fiber strands of the ribbon-shaped or strand-shaped, quasi-endless fiber material (3) are deposited next to one another, - detecting at least one material gap (30) between two adjacent fiber tracks or fiber strands of the ribbon-shaped or strand-shaped, quasi-endless fiber material deposited on the tool surface and their dimensions by means of a detection device (8, 9, 10), - providing a filling material to fill the detected material gaps (30) between adjacent fiber tracks or fiber strands, and - introducing the filling material into the detected material gaps depending on their dimensions.

2. Method according to claim 1, characterized in that the fiber material surface of the ribbon-shaped or strand-shaped fiber material deposited on the tool surface is recorded without contact by means of a camera of the detection device, and material gaps between two adjacent fiber tracks or fiber strands are automatically detected by digital evaluation of the recorded fiber material surface by means of an evaluation unit of the detection device.

3. Method according to claim 1 or 2, characterized in that a elevation profile of the fiber material surface of the ribbon-shaped or strand-shaped fiber material deposited on the tool surface is created by means of a light projection method, in that a light line is projected onto the fiber material surface from a first direction by means of a light source of the detection device, the projected light line is recorded by means of a camera of the detection device from a second direction different from the first direction, while the light line is moved over the fiber material surface, and the elevation profile is created as a function of a detected deformation of the recorded light lines by means of a computing unit of the detection device, wherein material gaps between two adjacent fiber tracks or fiber strands are automatically detected as a function of the created elevation profile by means of an evaluation unit of the detection device.

4. Method according to one of the preceding claims, characterized in that the deposition of the ribbon-shaped or strand-shaped fiber material on the shaping tool surface is first simulated by means of a simulation unit of the detection device based on production data and / or design data, wherein, depending on the simulated deposition of the ribbon-shaped or strand-shaped fiber material, the material gaps between two adjacent fiber webs or fiber strands are detected.

5. Method according to one of the preceding claims, characterized in that a pre-assembled filling patch is produced separately from the filling material based on the dimensions of the relevant material gap for at least one detected material gap, wherein the pre-assembled filling patch is then inserted into the relevant material gap of the deposited fiber material.

6. Method according to claim 5, characterized in that the pre-assembled filling patch is produced from the filling material by means of a 3D printing device.

7. Method according to one of the preceding claims, characterized in that the filling material is automatically introduced into at least one material gap of the deposited fiber material by means of an application device to which the filling material is continuously supplied.

8. Method according to one of the preceding claims, characterized in that the filling material consists of the matrix material of the fiber composite material or contains such a matrix material, or that the filling material consists of a fiber composite material with matrix material and fiber material or contains such a fiber composite material, or that the filling material is a dry fiber material.

9. Method according to one of the preceding claims, characterized in that after the filling material has been introduced into at least one of the detected material gaps, the matrix material is consolidated.

10. Fiber composite component made of a fiber composite material obtainable by the method according to one of the preceding claims.

11. Fiber composite component according to claim 10, characterized in that the fiber composite component is a hollow component.