Method for forming a fiber composite preform

Abstract

A method for forming a fiber composite preform is disclosed, the preform including a web, a flange and a bent portion, the method comprising the following steps: laying a laminate on a tool, the laminate including a longitudinal edge and a transverse edge, and the tool including a convex portion, the convex portion including a surface and a lateral wall, the web being configured to be positioned on the surface of the convex portion, and the flange being configured to be positioned on the lateral wall of the convex portion; forming the preform on the convex portion; clamping the transverse edges of the laminate to the tool so that the web and flange of the laid-up laminate are maintained under a tensile load; and bending the longitudinal portion of the convex portion.

Description

Technical Field

[0001] The present invention relates to a method for forming a composite preform having strong raised and / or kinked regions to allow the preform to bend. Background Art

[0002] When conventional forming methods are used to make curved preforms (eg, having strongly convex or curved shapes and / or kinked areas), wrinkles may occur.

[0003] A problem with forming a raised flange from a flat laminate (for example, in a curved, raised structure like a frame) is that the laminate is flat when laid. The flat laminate is then formed into, for example, an L-shape. Consequently, due to its curved, convex shape, there is excess material in the area of the L-shaped flange relative to the web of the preform. This excess material must be flushed to the sides of the preform to avoid wrinkling. This is difficult to achieve using conventional forming methods, so wrinkles can occur.

[0004] This effect is even more critical when the part includes a kink area. Wrinkles appear in the kink area due to excess material, as shown in the previous example. The current method to eliminate wrinkles is to cut the flange and separate it into two separate flanges without continuous fiber between them. Summary of the Invention

[0005] The present invention relates to a method of forming a preform from a wrinkle-free laid-up laminate.

[0006] The method of the present invention aims to enable the formation of complex geometries without wrinkles on those geometries having the following characteristics:

[0007] • The geometry of the raised flange can result in excess material in the formed flange, thereby causing wrinkles and / or kinks that would result in excess material in the formed flange with conventional forming methods.

[0008] • Double curvature preforms for laminates that cannot be developed from three-dimensional (3D) geometries.

[0009] The method of the present invention utilizes the concept of a neutral axis. The neutral axis is the axis in a beam (bending member) or cross section along which there is no longitudinal stress or strain. If the cross section is symmetrical, isotropic, and free of bending before bending occurs, the neutral axis lies at the geometric centroid. All fibers on one side of the neutral axis are in tension, while those on the other side are in compression.

[0010] The forming method of the present invention can shift the neutral axis below the flange. In this way, the method can form the preform with the fibers of the entire web and flange under tension and without wrinkling.

[0011] The method for forming a fiber composite material preform of the present invention is applicable to a preform comprising a web and at least one flange, a longitudinal axis, and at least one bend relative to said longitudinal axis.

[0012] The method comprises the following steps:

[0013] Laying a laminate onto a tool, the laminate including longitudinal and transverse edges. The tool includes a male portion including a surface, which may be flat, and at least one lateral wall. The web of the preform is configured to be positioned on the surface of the male portion, and the flange is configured to be positioned on the lateral wall of the male portion.

[0014] • Forming the preform on the convex portion.

[0015] • Clamping the transverse edges of the laminate to the tool so that the web and flanges of the laid-up laminate are held under tensile load.

[0016] • Bending the convex portion relative to the longitudinal axis of the preform such that a curved portion of the preform is achieved.

[0017] The claimed invention allows for the formation of complex geometries without wrinkles. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To complete the description and to facilitate a better understanding of the present invention, the accompanying drawings are provided. The accompanying drawings form an integral part of the specification and illustrate preferred embodiments of the present invention. The accompanying drawings include the following figures.

[0019] Figure 1 A schematic perspective view of a C-shaped preform positioned on the male portion of an embodiment of a tool is shown.

[0020] Figure 2 Shown in final bending position Figure 1 Schematic perspective view of a C-shaped preform.

[0021] Figure 3 Shown positioned over the male portion in the clamped position Figure 1 Cross-sectional view of a C-shaped preform.

[0022] Figure 4 A perspective view of an embodiment of a tool is shown.

[0023] Figures 5 to 9 The following steps of an embodiment of the method object of the present invention are shown Figure 4 Cross-sectional view of the tool.

[0024] Figure 10 The final bending step of the method is shown Figure 4 perspective view of the tools.

[0025] Figure 11 Schematic plan views of a C-shaped preform are shown in two positions, a first position in which the preform is not bent and a second position in which the preform is bent about an axis transverse to the plane of the flange.

[0026] Figure 12 Schematic plan views of a C-shaped preform are shown in two positions, a first position in which the preform is not bent and a second position in which the preform is bent about an axis transverse to the plane of the web. DETAILED DESCRIPTION

[0027] Figure 1 A C-shaped preform is disclosed. Alternatively, an L-shaped preform can also be formed using the present method. Although the concepts presented herein can be applied to other structural parts of aircraft components besides C-shaped or L-shaped preforms, this description will focus on C-shaped preforms.

[0028] The C-shaped preform 1 is positioned on the tool 5. The laminate 4 comprises longitudinal edges 4.1 and transverse edges 4.2. The longitudinal edges 4.1 are the edges of the laminate 4 positioned in its longitudinal boundaries and comprising the C-shape. The transverse edges 4.2 are the transverse boundaries of the laminate 4 extending along the edges of the flange 3.

[0029] The tool 5 shown comprises a male portion 7 comprising a surface 7.1 and two lateral walls 7.2. The web 2 of the preform 1 is positioned on the surface 7.1 of the male portion 7, while the flange 3 is positioned on the lateral walls 7.2 of the male portion 7. In the embodiment shown, the surface 7.1 of the male portion 7 is flat, and the lateral walls 7.2 are also flat.

[0030] Figure 2 Disclosed is a device having a curved portion 2.1 Figure 1 The preform 1 of the embodiment. Specifically, Figure 2 In the disclosed embodiment, the bent portion 2.1 is bent about an axis transverse to the plane of the flange 3, so that the preform 1 comprises a kink.

[0031] Figure 3An embodiment of a clamping system for the transverse edge 4.2 of the laminate 4 is disclosed. Specifically, the flange 3 comprises an extra-length region 3.1 that is clamped against the convex portion 7. In the embodiment shown, this is achieved by two clamping members 10 that extend along the transverse edge 4.2 of the laminate 4 and press the extra-length region 3.1 against the convex portion 7. The web 2 and the flange 3 of the laid-up laminate 4 are thereby held under tensile load.

[0032] Figure 11 and Figure 12 Two embodiments of the curved preform 1 are disclosed. Figure 11 An embodiment is disclosed in which the preform 1 is bent about an axis transverse to the plane of the web 2. It relates to curved convex geometries, for example frames.

[0033] In the embodiment shown, the male part 7 comprises a first part 7.3 and at least one second part 7.4 articulated relative to the first part 7.3, such that the step of bending the male part 7 is performed by moving the second articulated part 7.4 relative to the first part 7.3.

[0034] The first portion 7.3 and the second hinged portion 7.4 comprise surfaces configured to receive the laid-up laminate, said surfaces being positioned without any curvature between them in the longitudinal direction during the laying step of the laminate 4.

[0035] Thus, in a first position, the laid-up laminate 4 is laminated such that the longitudinal axes 20 of the two parts 7.3, 7.4 form a straight line. In a final step of the process, the hinged part 7.4 is moved relative to the first part 7.3 and the curved part 2.1 is created.

[0036] Figure 12 A side view of a preform 1 is disclosed, which is bent about an axis transverse to the plane of the flange 3 , such that a kink is created in the C-shaped preform 1 .

[0037] Likewise, the first portion 7.3 and the second hinged portion 7.4 comprise surfaces configured to receive the laid-up laminate, these surfaces being positioned without any curvature between them in the longitudinal direction during the laying step of the laminate 4.

[0038] In particular, in the first position, the surfaces of the first portion 7.3 and the second portion 7.4 are positioned in a flush manner. In a final step of the process, the hinged portion 7.4 is moved relative to the first portion 7.3 and the curved portion 2.1 is created.

[0039] Figures 4 to 10Another embodiment of a tool 5 is disclosed. This embodiment includes, in addition to a male portion 7, a base portion 6 comprising a surface 6.1, which may be flat. The male portion 7 is movable relative to the base portion 6. Specifically, the male portion 7 is displaced in a direction perpendicular to the surface 6.1 of the base portion 6. Specifically, the male portion 7 is positioned on a base plate 12 that slides relative to a set of posts 13.

[0040] according to Figures 4 to 10 , laying the laminate 4 onto the tool 5 comprises the following steps:

[0041] • Laying the laminate 4 on the surfaces 6.1, 7.1 of the base part 6 and the male part 7. Again, in the embodiment shown in the figures, said surfaces 6.1, 7.1 are flat.

[0042] • Moving the male part 7 of the tool 5 relative to the base part 6 so that the flange 3 is moulded from the laid-up laminate 4 into the lateral walls 7 . 2 of the male part 7 .

[0043] The laid-up laminate 4 is a flat laminate comprising the web 2 and the flange 3 .

[0044] In particular, if Figure 4 As disclosed in , the male portion 7 comprises a first portion 7.3 and at least one second portion 7.4 articulated relative to the first portion 7.3. Thus, the step of bending the preform 1 is performed by moving the second articulated portion 7.4 relative to the first portion 7.3. Specifically, the tool 5 shown in the embodiment comprises two articulated portions 7.4.

[0045] The two parts 7 . 3 , 7 . 4 are displaceable relative to the base part 6 of the tool 5 .

[0046] As in Figures 5 to 10 As can be seen in the drawing, both the first part 7.3 and the second hinged part 7.4 comprise flat surfaces which are configured to receive the laid-up laminate 4 positioned in a flush manner during the laying step of the laminate 4, e.g. as in Figure 5 Can be seen in.

[0047] The forming process of this embodiment is performed by bagging. Specifically, a membrane 11 is positioned on the laminate 4 and sealed to the tool 5. The membrane 11 covers the surfaces 7.1 and 6.1 of the male portion 7 and the base portion 6. The tool 5 is also capable of varying the pressure under the membrane 11 to form the preform. To this end, the tool 5 must ensure an airtight condition when actuated.

[0048] Additionally, the tool 5 may be self-heating to allow heating under vacuum to activate the adhesive. Temperature sensitive devices or components should be properly insulated to avoid damage during heating.

[0049] Other alternatives to the forming process are also possible, for example applying pressure to the web 2 and flange 3 of the preform by means of a tool rather than by means of a bag.

[0050] Figure 6 The step of raising the male part 7 relative to the base part 6 is disclosed. As a result, the membrane 11 is stretched due to the push of the male part 7 on the membrane 11. The flange 3 of the laid-up laminate 4 is then deposited on the lateral wall 7.2 of the male part 7.

[0051] Figure 7 represents a forming step, in which the air pressure under the membrane 11 is reduced to form the preform 1. Thus, the membrane 11 is sucked in such a way that it is fixed on the convex portion 7, and the laminate 4 is formed.

[0052] exist Figure 8 In the step shown, the air pressure is increased from the pressure at which the preform 1 is formed, the diaphragm 11 is released, and then, as in Figure 9 As can be seen in FIG, the convex portion 7 is lowered.

[0053] The transverse edges 4.2 of the laminate 4 are clamped to the tool 5 so that the web 2 and the flange 3 of the laid-up laminate 4 are held under a tensile load. In particular, the tool 5 comprises clamps 10, such as in Figure 9 Can be seen in.

[0054] The longitudinal edges 4.1 may also be clamped at this stage, or alternatively they may be clamped before the forming step, or they may not be clamped during the entire process.

[0055] Finally, the articulated portion 7.4 of the tool 5 is moved relative to the first portion 7.2 and the C-shaped preform 1 is twisted.

[0056] The laid-up laminate 4 comprises a plurality of layers. The method may include a step of cutting at least one layer of the laid-up laminate 4 in the region of the bend 2.1 in a direction transverse to the longitudinal axis 20 of the preform 1. This is known as slicing or inter-layer cutting. In other words, one or more layers of the laminate 4 are completely or partially cut at a point to allow the unidirectional fibers to open. In this way, gaps are introduced between the layers, particularly in the 0-direction of the laminate.

[0057] These consecutive cut layers may be placed adjacent to each other before bending the preform 1 so that there is a gap between them after bending the preform 1. Alternatively, the consecutive cut layers may overlap so that there is no gap between them after bending the preform 1. In another embodiment, the consecutive cut layers may overlap so that there is a certain degree of overlap between two adjacent layers after bending the preform 1.

[0058] An advantage of the method of the invention is that it allows including cuts to improve the discontinuity of the flange 3, thus avoiding tension and fiber breakage.

Claims

1. A method for forming a fiber composite material preform, the preform (1) comprising a web (2) and at least one flange (3), a longitudinal axis (20) and at least one bend (2.1) relative to the longitudinal axis (20), the method comprising the steps of: laying a laminate (4) on a tool (5), the laminate (4) comprising longitudinal edges (4.1) and transverse edges (4.2), and the tool (5) comprising a convex portion (7), the convex portion comprising a surface (7.1) and at least one lateral wall (7.2), the web (2) of the preform (1) being configured to be positioned on the surface (7.1) of the convex portion (7), and the flange (3) being configured to be positioned on the lateral wall (7.2) of the convex portion (7), forming said preform (1) on said convex portion (7), clamping the transverse edges (4.2) of the laminate (4) to the tool (5) so that the web (2) and flanges (3) of the laid-up laminate (4) are held under tensile load, bending the longitudinal portion of the convex portion (7) relative to the longitudinal axis (20) of the preform (1) so as to complete the bent portion (2.1) of the preform (1), wherein the convex portion (7) comprises a first portion (7.3) and at least one second portion (7.4) articulated relative to the first portion (7.3), such that the step of bending the convex portion (7) is performed by moving the second articulated portion (7.4) relative to the first portion (7.3).

2. The method for forming a fiber composite material preform according to claim 1, wherein: The tool (5) comprises a base portion (6) comprising a surface (6.1), the convex portion (7) being movable relative to the base portion (6) in a direction perpendicular to the surface (6.1) of the base portion (6), the step of laying the laminate (4) comprising the following steps: Laying a laminate (4) on the surface (6.1) of the base portion (6) and the surface (7.1) of the male portion (7), • Moving the male part (7) relative to the base part (6) such that the flange (3) is positioned in the lateral wall (7.2) of the male part (7).

3. The method for forming a fiber composite material preform according to claim 2, wherein: When the laminate is laid on the surface (6.1) of the base part (6) and the surface (7.1) of the male part (7), the surface of the base part and the surface of the male part are positioned in a flush manner.

4. A method for forming a fiber composite material preform according to any one of claims 1 to 3, wherein: The laid-up laminate (4) is a flat laminate comprising the web (2) and the flange (3).

5. A method for forming a fiber composite material preform according to any one of claims 1 to 3, wherein: The method comprises the step of clamping the longitudinal edges (4.1) of the laminate (4) to the tool (5).

6. A method for forming a fiber composite material preform according to any one of claims 1 to 3, wherein: The preform (1) is bent about an axis transverse to the plane of the flange (3).

7. The method for forming a fiber composite material preform according to claim 1, wherein: The preform (1) is bent about an axis transverse to the plane of the web (2).

8. The method for forming a fiber composite material preform according to claim 1, wherein: The first portion (7.3) and the second articulated portion (7.4) comprise surfaces configured to receive the laid-up laminate, said surfaces being positioned without any bending therebetween in the longitudinal direction during the laying step of the laminate (4).

9. A method for forming a fiber composite material preform according to any one of claims 1 to 3, wherein: The laid-up laminate (4) comprises a plurality of layers, and the method comprises the step of cutting at least one layer of the laid-up laminate (4) in the region of the curved portion (2.1) in a direction transverse to the longitudinal axis (20) of the preform (1).

10. A method for forming a fiber composite material preform according to any one of claims 1 to 3, wherein: The method comprises the steps of providing an extra length region (3.1) of the flange (3) and clamping the extra length region (3.1) against the male portion (7).

11. A method for forming a fiber composite material preform according to any one of claims 1 to 3, wherein: The forming process is performed by bagging.

12. The method for forming a fiber composite material preform according to claim 11, wherein: The step of forming the preform (1) comprises the following sub-steps: providing a membrane (11) on said laminate (4), Sealing the diaphragm (11) against the tool (5), • Reducing the pressure under the membrane (11) to form the preform (1).

13. The method for forming a fiber composite material preform according to claim 12, wherein: After the forming step and before clamping the transverse edges (4.2), the pressure under the membrane (11) is increased from the pressure at which the preform (1) was formed.

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