Method for forming a fiber preform for use in the manufacture of a component from a composite material

Abstract

A method of manufacturing a preform (48) for use in the manufacture of a component from a composite material, comprising: Sewing fibers onto a film (56) to form a fiber bed (58) in a two-dimensional shape; and Conforming the fiber bed (58) to a three-dimensional shape to form the preform (48); characterized in that the film (56) is removed from the fiber bed (58) before it is adapted to the three-dimensional shape.

Description

INTRODUCTION

[0001] The present invention relates to methods for forming a fiber preform for use in the manufacture of a component from a composite material.

[0002] A method according to the preamble of claim 1 is disclosed, for example, in DE 10 2015 223 364 A1. Further prior art can also be found in the publications US 2013 / 0 015 602 A1, DE 196 29 044 A1, and DE 10 2007 032 904 B3.

[0003] Composite materials are used for buildings, bridges, and structural components such as boat hulls, swimming pool elements, shower enclosures, bathtubs, storage tanks, sinks, and countertops. In the automotive industry, composite materials are used for interior trim parts, structural components, chassis parts, and closure components. Composite materials are also used for components of spacecraft and aircraft.

[0004] Composite components are manufactured from fiber preforms consisting of yarns or fiber strands formed into three-dimensional (3D) shapes. The fiber preforms are typically produced using a 3D weaving process, a 3D braiding process, or a 3D laying of short fibers. One or more fiber preforms are placed in a mold, a resin is applied to the fiber preform(s), and the fiber preform(s) and the resin are molded into a composite component. SUMMARY

[0005] According to the invention, a method for producing a preform for use in the production of a component from a composite material is presented. According to a first embodiment of the invention, the method comprises the features of claim 1.

[0006] In one aspect, the method further comprises determining an amount by which the fibers are deformed when the fiber bed is formed from the two-dimensional shape to the three-dimensional shape, and determining at least one of the following quantities based on the degree of fiber deformation: orientation of the fibers within a plane of the fiber bed, number of fibers per unit area of ​​the fiber bed, material of the stitches used to attach the fibers to the film, number of stitches per unit area of ​​the fiber bed, or length of the fibers between a pair of adjacent stitches.

[0007] In one aspect, the method further comprises determining a first region of the fiber bed in which the degree of fiber deformation is higher than the degree of fiber deformation in a second region of the fiber bed, and sewing the fibers onto the film such that the fiber length in the first region of the fiber bed is greater than the fiber length in the second region of the fiber bed.

[0008] In one aspect, the method further comprises placing a piece of foam onto the film in the first region of the fiber bed before sewing the fibers onto the film to increase the fiber length in the first region.

[0009] In one aspect, the method further comprises determining a first region of the fiber bed in which the degree of fiber deformation is higher than the degree of fiber deformation in a second region of the fiber bed, sewing the fibers to the film using a first set of stitches in the first region of the fiber bed, sewing the fibers to the film using a second set of stitches in the second region of the fiber bed, and melting the stitches in the first region of the fiber bed after removing the film from the fiber bed and before conforming the fiber bed to the three-dimensional shape. The stitches of the first set are made of a first material, and the stitches of the second set are made of a second material that has a higher melting point than the first material.

[0010] In one aspect, the method further comprises determining a first region of the fiber bed in which the degree of fiber deformation is higher than the degree of fiber deformation in a second region of the fiber bed, sewing the fibers to the film in the second region of the fiber bed, and not sewing the fibers to the film in the first region of the fiber bed.

[0011] In one aspect, the film is water-soluble, and the method further comprises removing the film from the fiber bed by dissolving the film.

[0012] In one aspect, the film is paper, and the method further comprises removing the film from the fiber bed by tearing the film.

[0013] According to a second embodiment of the invention, the method comprises the features of claim 9.

[0014] In one aspect, the method further comprises forming the lacing using the first fibers.

[0015] In one aspect, the method further comprises releasing the stitches securing the first fibers to the first film along the edges of the first dart after the lacing is formed and before the lacing is pulled.

[0016] In one aspect, the method further comprises removing the first film after sewing the first fibers to the first film and before pulling the lacing.

[0017] In one aspect, the method further comprises forming the first dart in the first two-dimensional shape of the first fiber bed by sewing the first fibers to the first film in an area surrounding the first dart without sewing the first fibers to the first film in an area of ​​the first dart.

[0018] In one aspect, the method further comprises determining a tension in the first fibers when the first fiber bed is formed from the first two-dimensional shape to the first three-dimensional shape, and forming the first dart in a region of the first fiber bed in which the fiber tension is greater than the fiber tension in another region of the first fiber bed.

[0019] In one aspect, the method further comprises sewing second fibers onto a second film to form a second fiber bed in a second two-dimensional shape with a second dart, closing the second dart in the second fiber bed to form the second fiber bed into a second three-dimensional shape, and overlaying the first and second fiber beds such that (i) the second fiber bed covers the first dart in the first fiber bed and (ii) the first fiber bed covers the second dart in the second fiber bed. The first and second fiber beds form the preform.

[0020] In a third example of a method for producing a preform for use in manufacturing a component from a composite material, the method comprises sewing fibers to a film to form a fiber bed having a two-dimensional shape and conforming the fiber bed to a three-dimensional shape to form the preform. Sewing the fibers to the film comprises sewing the fibers to the film with a first number of stitches per unit area in a first region of the fiber bed and sewing the fibers to the film with a second number of stitches per unit area in a second region of the fiber bed. The first number is less than the second number.

[0021] In one aspect, the method further comprises determining a tension in the fibers when the fiber bed is formed from the two-dimensional shape to the three-dimensional shape, and sewing the fibers to the film using the first and second numbers of stitches per unit area in the first and second regions of the fiber bed, respectively. The fiber tension in the first region is greater than the fiber tension in the second region.

[0022] In one aspect, the method further comprises sewing a third number of fibers per unit area to the film in the first region of the fiber bed and sewing a fourth number of fibers per unit area to the film in the second region of the fiber bed. The third number is less than the fourth number.

[0023] In one aspect, the method further comprises removing the film after sewing the fibers to the film and before conforming the fiber bed to the three-dimensional shape.

[0024] In one aspect, the first region of the fiber bed corresponds to a dart in the two-dimensional shape, and the method further comprises releasing the stitches along the edges of the dart after removing the film and pulling the fibers extending over the dart to close the dart and bring the fiber bed into the three-dimensional shape.

[0025] Further areas of applicability of the present invention will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are provided for illustrative purposes only. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be better understood from the detailed description and the accompanying drawings, in which: Fig. 1 is a flow diagram showing a first example of a method for forming a fiber preform according to the principles of the present invention; Fig. 2 to 7 are perspective and planar views of an example of a fiber preform or a mold thereof at various stages of the process of Fig. 1 are; Fig. 8 is a flow diagram showing a second example of a method for forming a fiber preform according to the principles of the present invention; Fig. 9 to 14 are perspective and planar views of an example of a fiber preform or a mold thereof at various stages of the process of Fig. 8 are; Fig. 15 is a flow chart showing a third example of a method for forming a fiber preform according to the principles of the present invention; Fig. 16 to 20 are perspective and planar views of an example of a fiber preform or a mold thereof at various stages of the process of Fig. 8 are; and Fig. 21 to 25 are perspective and planar views of an example of a fiber preform or mold thereof at various stages of a fourth example of a method of forming a fiber preform according to the principles of the present invention.

[0027] Reference symbols may be reused in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0028] Some fiber preforms are first formed in a two-dimensional (2D) shape by sewing the fiber strands to a stabilizing fabric to form a fiber bed, and then formed into a 3D shape. The stabilizing fabric serves as a base layer onto which the fiber strands are sewn. The stabilizing fabric is typically a simple woven or nonwoven fabric that cannot stretch to conform to the contours of a complex part. In addition, the multiple stitches used to attach the fiber strands to the fabric result in high shear force compared to conventional scrims or woven fabrics. In turn, it is difficult to shear the material to conform to the contours of a target part.

[0029] To solve this problem, it may be desirable to remove the stitches in an area that requires shearing. However, this task is difficult for an operator once the preform is manufactured because the stitches are located in multiple layers of the preform. Therefore, portions of the preform are cut out and replaced with larger, more formable pieces. This leads to inefficient use of reinforcement material and a racetracking effect during the molding process. In addition, preforms must be thicker than necessary, increasing the cost of the overall operation and slowing preform production. Racetracking occurs when a fiber preform does not fill a mold evenly, creating a gap into which the resin drains instead of filling the entire composite part.

[0030] A method for forming a fiber preform according to the present invention solves the above-mentioned problems in one or more ways. In one way, the method uses a water-soluble film or an easily tearable film (e.g., newsprint) as a base layer to which the fiber strands are sewn, so that the film can be dissolved or torn from the fiber bed after the fiber bed has been formed. Removing the film improves the formability of the fiber preform, allowing the fiber preform to be formed from its 2D shape into its 3D shape without damaging the fiber preform.

[0031] In another way, the method varies one or more parameters in regions of the fiber preform that are subject to high shear when the fiber preform is formed from its 2D shape to its 3D shape. In one example, the method minimizes the number of stitches used to attach the fiber strands to the base layer in the high shear regions, does not sew the fiber strands to the base layer in the high shear regions, and / or uses fusible stitches in the high shear regions. In another example, the method reduces the number of fiber strands that traverse the high shear regions or forms darts or gaps in the high shear regions so that the fiber strands do not extend across the high shear regions.

[0032] In another example, when darts are formed in the fiber preform, the process forms laces extending over the darts and pulls on the ends of the laces to close the darts and transform the fiber preform from its 2D shape to its 3D shape. The laces may be formed from the fiber strands. The fiber strands forming the laces may be sewn to the base layer along the edges of the darts using wider stitches with lower thread tension than the stitches in other areas to allow the fiber strands to slide.

[0033] Referring to Fig. 1 begins a process for the formation of a Fig. 6 in step 10. In step 12, the method analyzes the shape of the preform 48 to identify areas of severe fiber deformation. Briefly referring to Fig. 2 and Fig. 3, the method may determine, for example, a desired 3D shape 50 (e.g., a truncated pyramid) of the preform 48 as well as a 2D shape 52 (e.g., a square) of the preform 48, which may be adapted (e.g., folded, formed) to the desired 3D shape 50. The method may then determine the extent of fiber deformation in the preform 48 when the preform 48 is transformed from the 2D shape 52 into the 3D shape 50. The method may make this determination using the finite element method (finite element analysis, FEM).

[0034] With further reference to Fig. 1, in the method, in step 14, a desired orientation of the fibers forming the preform 48 and a desired length of the fibers are determined, for example, based on the fiber deformation when the preform 48 is brought from its 2D shape 52 to its 3D shape 50. With brief reference to Fig. 7, for example, to form the preform 48 into its 2D shape 52, the fiber strands 54 are sewn to a base 56, e.g., a stabilizing fabric or film, to form a fiber bed 58 within a plane defined by an x-axis 60 and a y-axis 62. Each fiber strand 54 comprises thousands of interconnected fibers.

[0035] The fibers in the fiber strands 54 can be made of E-glass, S-glass, basalt, carbon, Kevlar®, or a combination thereof. The backing 56 can be made of a water-soluble material such as polyvinyl alcohol, polyethylene glycol, polyvinyl alcohol acetates, polyethylene oxides, or a combination thereof, so that the backing 56 can be dissolved after the fiber bed 58 has been formed. Alternatively, the backing 56 can be made of a material such as newspaper, which is easy to tear but strong enough to serve as a support for the fiber strands 54. The backing 56 can, in turn, be torn from the fiber bed 58 after the fiber bed 58 has been formed. Removing the backing 56 improves the formability of the preform 48, allowing the preform 48 to be adapted from its 2D shape 52 to its 3D shape 50 without damaging the preform 48.

[0036] The method can determine the orientation of each fiber strand 54 within the plane of the fiber bed, as well as the length of each fiber strand 54 between adjacent stitches that secure the fiber strand 54 to the backing 56. In the example shown, the orientation of each individual fiber strand 54 is generally parallel to the y-axis 62. If each fiber strand 54 is also stitched to the backing 56 at the locations 64 where the path of the fiber strand 54 changes direction, the length of each fiber strand 54 corresponds to the distance 66 between the locations 64.

[0037] The method can determine the fiber stress associated with several possible orientations of each fiber strand 54, e.g., using FEM, and select the fiber strand orientation that minimizes fiber stress in regions of high fiber deformation. For example, if a central region 68 of the fiber bed 58 is to be confined or compressed within a recess in a tool to form the preform 48 into its 3D shape 50, the method can select the fiber orientation that minimizes fiber stress in the central region 68. Thus, orienting the fiber strands 54 parallel to the y-axis 62, as shown, can minimize fiber stress in the central region 68 of the fiber bed 58.

[0038] Likewise, the method may, for example, using FEM, determine the fiber stress associated with several possible lengths of each fiber strand 54 and select the fiber strand length that minimizes the fiber stress in regions of high fiber deformation. If the central region 68 of the fiber bed 58 is to be compressed to form the preform 48 into its 3D shape 50, the method may select the fiber strand length that minimizes the fiber stress in the central region 68. For example, the method may increase the fiber strand length in the central region 68 of the fiber bed 58 relative to the fiber strand length in other regions of the fiber bed 58, as shown, which may minimize the fiber stress in the central region 68.

[0039] With reference to Fig. 1 and Fig. 4, the method identifies high-shear regions 70 in the fiber bed 58 in step 16, where sewing should be avoided or minimized. When the fiber bed 58 is transformed from the 2D shape 52 to the 3D shape 50, the degree of fiber deformation (e.g., the degree to which the fibers are bent) is greater in the high-shear regions 70 than in other regions of the fiber bed 58. The method may identify the high-shear regions 70 using FEM.

[0040] In step 18, the method may include placing a foam insert 72 on the base 56 in a region of the fiber bed 58 where additional fiber strand length is desired. As previously mentioned, the method may use a longer fiber strand length in regions of high fiber deformation than the fiber strand length in other regions of the fiber bed 58. Thus, the method may place the foam insert 72 in each of the high shear regions 70, as shown in Fig. 4 to increase the fiber strand length in the high shear regions 70. After the fiber strands 54 are sewn to the backing 56, the foam insert 72 is disposed between the fiber strands 54 and the backing 56, thus increasing the fiber strand length in the region(s) of the fiber bed 58 in which the foam insert 72 is disposed.

[0041] In step 20, the method sews the fiber strands 54 to the backing 56 to form the fiber bed 58, and in doing so, the method uses a different stitch density in the high shear regions 70 of the fiber bed 58. For example, the method may sew the fiber strands 54 to the backing 56 with a first number of stitches 74 per unit area in the high shear regions 70, while using a second number of stitches 76 per unit area in all other regions of the fiber bed 58. The first number is less than the second number. The first number may be zero. In this case, the method does not sew the fiber strands 54 to the backing 56 in the high shear regions 70 of the fiber bed 58.

[0042] In addition to or instead of adjusting the fiber strand length and / or stitch density in the high shear regions 70 of the fiber bed 58, the method may adjust the fiber strand orientation and / or the suture material and / or the fiber strand density (or all of these) in the high shear regions 70. For example, in the high shear regions 70, the method may align the fiber strands 54 perpendicular to the fold lines 78 about which the fiber bed 58 is folded when the fiber bed 58 is formed from the 2D shape 52 into the 3D shape 50. In the remaining portion of the fiber bed 58, the method may align the fiber strands 54 parallel to the vertical or horizontal edges of the fiber bed 58. Furthermore, the method may direct the fiber strands 54 in one layer in a different direction than the fiber strands 54 in another separate layer to accommodate part complexity.

[0043] In another example, the method may form the stitches 74 in the high shear regions 70 of the fiber bed 58 from a first material and the stitches 76 in all other regions of the fiber bed 58 from a second material. The first material may have a lower melting point than the second material such that the stitches 74 can be melted without melting the stitches 76. The first material may be low-density polyethylene, poly(ethylene adipate), poly(1-butene), poly(trans-1,4-butadiene), or a combination thereof. The second material may be polyester, polyamide 6, polyamide 66, glass, basalt, carbon, or a combination thereof.

[0044] In another example, the method may sew a third number of fiber strands 54 per unit area to the backing 56 in the high shear regions 70 and a fourth number of fiber strands 54 per unit area to the backing 56 in all other regions of the fiber bed 58. The third number is less than the fourth number. This concept is in Fig. 7, which shows a lower number of fiber strands 54 per unit area in the central region 68 of the fiber bed 58 than the number of fiber strands 54 in the remaining fiber bed 58. By reducing the fiber strand density in the central region 68 of the fiber bed 58, the fiber strands 54 can be spaced further apart in the compression direction before they become dense. As a result, the mechanical properties of the finished part in the central region 68 are not impaired.

[0045] With reference to Fig. 1 and Fig. 5, in the process, in step 22, the backing 56 is removed from the preform 48 and, if the foam insert 72 is placed on the backing 56, the foam insert 72 is removed from the preform 48. In the process, the backing 56 is removed from the preform 48 by dissolving the backing 56 in water or tearing it off from the fiber bed 58. In step 24, the process dries the preform 48 if the backing 56 has been removed by dissolving it.

[0046] In step 26, the process melts all stitches, such as stitches 74, in the high shear regions 70 of the fiber bed 58. In step 28, the process adds a binder to the preform 48. The binder may be an epoxy-based material or a urethane-based material.

[0047] In step 30, the method places the preform 48 into a preforming tool. In step 32, the method forms the preform 48 into its final 3D shape, which is Fig. 6. Once the preform 48 has its final 3D shape, the preform 48 can be placed into a final mold and formed into a composite part, e.g., using high-pressure resin transfer molding (HP-RTM). Instead of adding binder to the preform 48 and placing the preform 48 into the preform, the process can also simply place the preform 48 into the final mold. The process ends with step 34.

[0048] Referring to Fig. 8 begins a process for the formation of a Fig. 14 in step 100. In step 102, the method determines a 2D shape, e.g., a rectangle, corresponding to the Fig. 10 shown 2D shape 152 without darts 154, which can be converted into a desired 3D shape 156 of the Fig. 9. For example, the method can flatten the 3D shape 156 into the 2D shape 152 by computer modeling.

[0049] In step 104, the method analyzes the stress in the preform 150 as the preform 150 is formed from its 2D shape to its 3D shape 156 and removes material in areas of high stress to form the darts 154 in the 2D shape 152, as shown in Fig. 10. For example, the method may form the darts 154 in the region of the fiber bed 164 where the fiber tension is greater than the fiber tension in other regions of the fiber bed 164. While the darts 154 have a triangular shape in the example shown, the darts 154 may also have other shapes, such as another polygonal shape or a shape with curved sides. The darts 154 improve the formability of the preform 150, allowing the preform 150 to be adapted from its 2D shape 152 to its 3D shape 156 without damaging the preform 150.

[0050] If multiple preforms 150 are required to close gaps, the darts 154 can be aligned in different directions in the process in step 106. Briefly referring to Fig. 23, the method may orientate approximately two of the darts 154 in each preform 150 in a first direction 158 and two of the darts 154 in each preform 150 in a second direction 160 that is perpendicular to the first direction 158. If the preforms 150 are positioned one above the other, as in Fig. 24, the material of one of the preforms 150 again covers the darts 154 in the other of the preforms 150.

[0051] With reference to Fig. 8 and Fig. 11, in the process in step 108, fiber strands such as those shown in Fig. 7, are sewn to a removable stabilizing film 162 to form a fiber bed 164 in the 2D shape 152. In the Fig. In the example shown in Figure 11, the method places and sews the fiber strands on the stabilizing film 162 in areas surrounding the darts 154, without placing or sewing the fiber strands on the stabilizing film 162 in the areas of the darts 154. Alternatively, the method may place and sew the fiber strands on the stabilizing film 162 in the areas of the darts 154, but reduce the density of the fiber strands in the area of ​​the darts 154 compared to the fiber strand density in the remaining fiber bed 164.

[0052] The stabilizing film 162 can be made of a water-soluble material such as polyvinyl alcohol, polyethylene glycol, polyvinyl alcohol acetates, polyethylene oxides, or a combination thereof, so that the stabilizing film 162 can be dissolved after the fiber bed 164 has been formed. Alternatively, the stabilizing film 162 can also be made of a material such as newspaper, which is easy to tear but strong enough to serve as a support for the fiber strands. The stabilizing film 162 can, in turn, be torn from the fiber bed 164 after the fiber bed 164 has been formed. Removing the stabilizing film 162 improves the formability of the preform 150, allowing the preform 150 to adapt from its 2D shape 152 to its 3D shape 156 without damaging the preform 150.

[0053] With reference to Fig. 8 and Fig. 12, in the method, in step 110, laces 166 are formed over the darts 154 using an adjusted stitch width and tension. The width of the stitches used to attach the laces 166 to the stabilizing film 162 may, for example, be 10% to 50% greater than the width of the stitches used to attach the fiber strands to the stabilizing film 162. In another example, the tension of the stitches used to attach the laces 166 to the stabilizing film 162 may be 10% to 50% less than the tension of the stitches used to attach the fiber strands to the stabilizing film 162. The stitches may be made of a suture material such as polyester, polyamide 6, polyamide 66, glass, basalt, carbon, or a combination thereof.

[0054] In the Fig. In the example shown in Figure 12, the lacings 166 are formed from the fiber strands in the process. This is achieved in the process by pulling the fiber strands over the darts 154 and attaching them to edges 170 ( Fig. 11) the dart 154 is sewn to the stabilizing film 162 without sewing the fiber strands to the stabilizing film 162 in the areas of the darts 154. The suture material is used only along the edges 170 of the darts 154 to establish fixed points through which the lacings (fiber strands) can slide. In this method, the fiber strands are not sewn to the stabilizing film 162 in the areas of the darts 154, since the stabilizing film 162 is to be removed and then only the lacings are located in the dart areas, as in Fig. 13 shown.

[0055] With reference to Fig. 8, Fig. 12 and Fig. 13, in the method, in step 112, the stabilizing film 162 is removed from the preform 150. In the method, the stabilizing film 162 is removed from the preform 150 by dissolving the stabilizing film 162 in water or by tearing the stabilizing film 162 from the fiber bed 164. The preform 150 is dried in the method after the stabilizing film 162 has been removed by dissolving.

[0056] With reference to Fig. 8, Fig. 13 and Fig. 14, in the method in step 114, the darts 154 are closed by pulling on the ends 168 of the lacings 166 to form edges 170 ( Fig. 11) the darts 154 to be pulled together or overlapped. By pulling on the lacings 166, the preform 150 can also be pulled out of its Fig. 13 shown 2D shape 152 into the Fig. 14. The process may then involve joining the ends 168 of the laces 166 together to maintain the 3D shape 156 of the preform 150. After forming the laces 166 and before pulling the laces 166 to close the darts 154, the process may involve loosening the stitches securing the laces 166 to the fiber bed 164 along the edges 170 of the darts 154 to allow the laces 166 to slide through the stitches.

[0057] In step 116, the method adds a binder to the preform 150. The binder may be an epoxy-based material or a urethane-based material. In step 118, the method places the preform 150 into a preforming tool. In step 120, the method forms the preform 150 into its final 3D shape, which is shown in Fig. 14. Once the preform 150 has its final 3D shape, the preform 150 can be placed into a final mold and formed into a composite part, e.g., using HP-RTM. Instead of adding binder to the preform 150 and placing the preform 150 into the preform, the process can also simply place the preform 150 into the final mold. The process ends with step 122.

[0058] Referring to Fig. 15, a method for producing a Fig. 20. In step 202, the method determines a 2D shape, e.g., a rectangle, corresponding to a Fig. 17 shown 2D shape 252 without darts 254, which can be converted into a desired 3D shape 256 of the Fig. 16. In the process, the 3D shape 256 can be flattened into the 2D shape 252, for example, by computer modeling.

[0059] In step 204, the method analyzes the stress in the preform 250 as the preform 250 is formed from its 2D shape to its 3D shape 256 and removes material in areas of high stress to form the darts 254 in the 2D shape 252, as shown in Fig. 17. For example, the method may form the darts 254 in the region of the fiber bed 264 where the fiber tension is greater than the fiber tension in other regions of the fiber bed 264. While the darts 254 have a triangular shape in the example shown, the darts 254 may also have other shapes, such as another polygonal shape or a shape with curved sides. The darts 254 improve the formability of the preform 250, allowing the preform 250 to be adapted from its 2D shape 252 to its 3D shape 256 without damaging the preform 250.

[0060] If multiple preforms 250 are required to close gaps, the darts 254 can be aligned in different directions in the process in step 206. Briefly referring to Fig. 23, for example, two of the darts 254 in the preform 250 can be aligned in a first direction 258 and two of the darts 254 in the preform 250 can be aligned in a second direction 260, which is perpendicular to the first direction 258. If the preforms 250 are located one above the other, as in Fig. 24, the material of one of the preforms 250 again covers the darts 254 in the other of the preforms 250.

[0061] With reference to Fig. 15 and Fig. 18, in the process in step 208, fiber strands 266 are sewn to a removable stabilizing film 262 to form a fiber bed 264 in the 2D shape 252. In the Fig. 18, the method of sewing the fiber strands 266 to the stabilizing film 262 uses fewer stitches per unit area in the area of ​​the darts 254 than the number of stitches per unit area in the remaining fiber bed 264. Furthermore, the method uses fewer fiber strands 266 per unit area in the area of ​​the darts 254 than the number of fiber strands 266 in the remaining fiber bed 264. Each fiber strand 266 comprises thousands of interconnected fibers.

[0062] The fibers in the fiber strands 266 can be made of E-glass, S-glass, basalt, carbon, Kevlar®, or a combination thereof. The stabilizing film 262 can be made of a water-soluble material such as polyvinyl alcohol, polyethylene glycol, polyvinyl alcohol acetates, polyethylene oxides, or a combination thereof, so that the stabilizing film 262 can be dissolved after the fiber bed 264 has been formed. Alternatively, the stabilizing film 262 can also be made of a material such as newspaper, which is easy to tear but strong enough to serve as a support for the fiber strands. The stabilizing film 262 can, in turn, be torn from the fiber bed 264 after the fiber bed 264 has been formed. Removing the stabilizing film 262 improves the formability of the preform 250, allowing the preform 250 to adapt from its 2D shape 252 to its 3D shape 256 without damaging the preform 250.

[0063] Those of the fiber strands 266 that extend over the darts 254 form lacings over the darts 254. The fiber strands 266 that form the lacings are arranged along edges 270 ( Fig. 18) the darts 254 are sewn to the stabilizing film 262. The fiber strand density and the stitch density in the areas of the darts 254 can be 50% to 90% lower than the fiber strand density or the stitch density in all other areas of the fiber bed 264.

[0064] With reference to the Fig. 15, Fig. 18 and Fig. 19, in the method, in step 210, the stabilizing film 262 is removed from the preform 250. In the method, the stabilizing film 262 is removed from the preform 250 by dissolving the stabilizing film 262 in water or by tearing the stabilizing film 262 from the fiber bed 264. In the method, the preform 250 is dried after the stabilizing film 262 has been removed by dissolving. In step 212, the method undoes the stitches securing the laces 266 along the edges 270 of the darts 254 to the stabilizing film 262 so that the laces 266 can slide through the stitches.

[0065] With reference to Fig. 15, Fig. 19 and Fig. 20, in the method, in step 214, the darts 254 are closed by pulling on the ends 268 of the laces 266 to gather or overlap the edges 170 of the darts 154. The ends 268 of the laces 266 are formed by cutting the fiber strands forming the laces 266 on one side of each dart 254 along cutting lines 269 ( Fig. 18). This formation of the ends 268 of the lacings 266 ensures that after removal of the stabilizing film 262, the parts of the lacings 266 adjacent to the ends 268 can slide, while the parts of the lacings 266 on the other sides of the darts 254 are fixed. By pulling on the lacings 266, the preform 250 can also be removed from its Fig. 19 shown 2D shape 252 into the Fig. 20 shown 3D shape 256. Then, the lacings 266 can be connected to each other to maintain the 3D shape 256 of the preform 250. After forming the lacings 266 and before pulling the lacings 266 to close the darts 254, the method can include the stitches with which the lacings 266 are fastened along the edges 270 ( Fig. 18) the darts 254 are attached to the stabilizing foil 262, are loosened so that the lacings 266 can slide through the stitches.

[0066] In the method, in step 216, a binder is added to the preform 250. The binder may be an epoxy-based material or a urethane-based material. In step 218, the method places the preform 250 into a preforming tool. In step 220, the method forms the preform 250 into its final 3D shape, which is shown in Fig. 20. Once the preform 250 has its final 3D shape, the preform 250 can be placed into a final mold and formed into a composite part, e.g., using HP-RTM. Instead of adding binder to the preform 250 and placing the preform 250 into the preform, the method can also simply place the preform 250 into the final mold. The method ends with step 222.

[0067] With reference to the Fig. 21 to 25 is a process for the formation of the Fig. 25 shown fiber preform 300. The process of Fig. 21 to 25 is shown using preforms similar in shape to those shown in Fig. 9 to 12 shown preform 150 and the Fig. 15 to 20. Therefore, the reference numerals of these two preforms and their features are used to describe the process of Fig. 21 to 25 reused.

[0068] Fig. 21 shows the desired 3D shape 156 or 256 of the preform 300. Fig. 22 shows the 2D shape 152 or 252, which can be brought into the 3D shape 156 or 256. The method can determine the 2D shape 152 or 252 and specify where and how the darts 154 or 254 are to be formed therein, as described above with reference to steps 102, 104 and 106 of Fig. 8 or steps 202, 204 and 206 of Fig. 15. Once the 2D shape 152 or 252 is determined, the method involves transferring the preform 150 or 250 to the position described with reference to steps 108, 110 and 112 of Fig. 8 or with reference to steps 208, 210 and 212 of Fig. 15 described manner.

[0069] Fig. 23 shows two of the preforms 150, two of the preforms 250, or one of the preforms 150 and one of the preforms 250. As already mentioned, the preforms 150 and 250 have complementary patterns (e.g., the darts 154, 254 in the preforms 150 and 250 point in different directions). Fig. 24 shows two of the preforms 150 overlaid, two of the preforms 250 overlaid, and the preform 150 and the preform 250 overlaid. Because the preforms 150 and 250 have complementary patterns, the material in one of the preforms 150 or 250 covers the gaps (e.g., the darts 154, 254) in the other of the preforms 150 or 250 when the preforms 150 or 250 are overlaid. In the process, the preforms 150 or 250 may be formed into their 3D shapes 156, 256, for example, by pulling on the lacings 166 or 266, before the preforms 150 are arranged to overlaid.

[0070] Fig.25 shows two of the preforms 150, two of the preforms 250, or the preform 150 and the preform 250, which together form the preform 300 in its 3D shape 156 or 256. To form the preform 300, the method may include adding binder to the preforms 150 or 250, placing the preforms 150 or 250 into a preforming tool so that the preforms 150 or 250 lie on top of one another, and then forming the preform 150 or 250 into the preform 300. The preform 300 may be placed into a final forming tool and formed into a composite part, e.g., using HP-RTM.

Claims

[1] A method of manufacturing a preform (48) for use in the manufacture of a component from a composite material, comprising: Sewing fibers onto a film (56) to form a fiber bed (58) in a two-dimensional shape; and Conforming the fiber bed (58) to a three-dimensional shape to form the preform (48); characterized by , that the film (56) is removed from the fiber bed (58) before it is adapted to the three-dimensional shape. [2] The method of claim 1, further comprising: Determining an amount by which the fibers are deformed when the fiber bed (58) is brought from the two-dimensional shape to the three-dimensional shape, and Determining at least one of the following variables based on the degree of fiber deformation: orientation of the fibers within a plane of the fiber bed (58), number of fibers per unit area of ​​the fiber bed (58), material of the stitches with which the fibers are attached to the film (56), number of stitches per unit area of ​​the fiber bed (58) or length of the fibers between a pair of adjacent stitches. [3] The method of claim 2, further comprising: Determining a first region of the fiber bed (58) in which the degree of fiber deformation is higher than the degree of fiber deformation in a second region of the fiber bed (58), and Sewing the fibers onto the film (56) so that the fiber length in the first region of the fiber bed (58) is greater than the fiber length in the second region of the fiber bed (58). [4] The method of claim 3, further comprising placing a piece of foam (72) on the film (56) in the first region of the fiber bed (58) before sewing the fibers to the film (56) to increase the fiber length in the first region. [5] The method of claim 2, further comprising: Determining a first region of the fiber bed (58) in which the degree of fiber deformation is higher than the degree of fiber deformation in a second region of the fiber bed (58), Sewing the fibers onto the film (56) using a first set of stitches in the first region of the fiber bed (58), the stitches of the first set being made of a first material, Sewing the fibers onto the film (56) using a second set of stitches in the second region of the fiber bed (58), wherein the stitches of the second set consist of a second material having a higher melting point than the first material, and Melting the stitches in the first area of ​​the fiber bed (58) after removing the film (56) from the fiber bed (58) and before adapting the fiber bed (58) to the three-dimensional shape. [6] The method of claim 2, further comprising: Determining a first region of the fiber bed (58) in which the degree of fiber deformation is higher than the degree of fiber deformation in a second region of the fiber bed (58), Sewing the fibers onto the film (56) in the second area of ​​the fiber bed (58), and Not sewing the fibers onto the film (56) in the first area of ​​the fiber bed (58). [7] The method of claim 1, wherein the film (56) is water-soluble and the method further comprises removing the film (56) from the fiber bed (58) by dissolving the film (56). [8] The method of claim 1, wherein the film (56) is paper, and the method further comprises removing the film (56) from the fiber bed (58) by tearing the film (56). [9] A method of manufacturing a preform (150) for use in the manufacture of a component from a composite material, the method comprising: Sewing first fibers onto a first film (162) to form a first fiber bed (164) in a first two-dimensional shape with a first dart (154), Forming a lacing (166) extending over the first dart (154), and Pulling the lacing (166) to close the first dart (154) and to bring the first fiber bed (164) into a first three-dimensional shape. [10] The method of claim 9, further comprising forming the lacing (166) using the first fibers.

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