A woven composite flat sheet forming apparatus and a woven composite forming method

Abstract

This invention proposes a braided composite material flat sheet forming device and a braided composite material forming method, including a mandrel frame and a flexible and flattenable forming device. During braiding, the flexible forming device can be installed in a bent state within a slot in the mandrel frame, and after removal, it can return to a straight state to obtain a braided composite material preform with openings. The pre-embedded pins for the openings can be embedded in the flexible forming device according to design requirements. The mandrel frame can be clamped onto the traction mechanism of a braiding machine to obtain a multi-layered braided preform. This invention also includes a low-damage forming method for braided composite material flat sheets with openings. This invention has the advantages of high forming accuracy, minimal damage to the preform structure, low hole-making damage, and integrated forming.

Description

Technical Field

[0001] This invention relates to the field of porous composite material forming technology, specifically to a braided composite material flat sheet forming apparatus and a braided composite material forming method using the forming apparatus. Background Technology

[0002] Composite materials possess advantages such as superior specific performance, high designability, and lightweight properties, leading to their widespread application in aerospace, rail transportation, and other fields. Braided composite materials utilize woven preforms with interwoven structures as reinforcements, offering low manufacturing costs, high forming efficiency, and excellent overall mechanical properties. However, the woven preforms exhibit poor structural retention, and during the lamination and transfer processes of woven composite flat sheets, in-plane shear deformation, yarn slippage, and surface wrinkling are prone to occur, severely impacting the forming quality and mechanical properties of the woven composite flat sheets.

[0003] Mechanical connection is a major method for joining composite material components. However, composite materials are difficult to machine, and traditional machining drilling processes are complex, inefficient, and have low forming stability. Due to the anisotropy of composite materials, mechanical drilling disrupts the continuity of the internal fibers, leading to delamination, internal fragmentation, burrs, and other damage, which seriously affects the mechanical properties of the open area of ​​the component.

[0004] Therefore, a new technical solution is needed to solve the above problems. Summary of the Invention

[0005] Purpose of the invention: To solve the above problems, the present invention provides a braided composite material flat plate forming device, which solves the technical problems of structural damage caused by the stacking and transfer of preforms in the traditional forming process, and damage to the internal fibers of the composite material in the perforated area when manufacturing braided composite material flat plates with openings.

[0006] The present invention also provides a method for forming woven composite materials using the above-mentioned woven composite material flat sheet forming device, which also solves the above problems.

[0007] To achieve the above objectives, the technical solution of the braided composite material flat plate forming device provided by the present invention is as follows:

[0008] A woven composite material flat sheet forming device includes a mandrel frame and a bendable forming device. The mandrel frame is cylindrical, and a portion of its cylindrical surface has an inwardly recessed groove with an arc-shaped cross-section. The bendable forming device includes several bent plates arranged side-by-side and several bendable thin plates. Each bent plate has an arc-shaped cross-section. When the sides of every two adjacent bent plates are in close contact, the bottom surfaces of all bent plates form a continuous long arc surface, the curvature of which is the same as the curvature of the groove bottom surface, and the length and width of the long arc surface are also the same as the length and width of the groove bottom surface. The upper surfaces of two adjacent bent plates span a bendable thin plate, and the top surfaces of two adjacent bent plates are recessed with mutually facing and interconnecting grooves. The grooves are provided in which each flexible sheet is disposed in the groove on the top surface of two adjacent bent sheets, and one side edge of the flexible sheet is fixed to the inner side of the groove of one bent sheet, and the other side edge of the flexible sheet is fixed to the inner side of the groove of the other bent sheet; the thickness of the flexible sheet is the same as the depth of the groove, so that after the sides of every two adjacent bent sheets are in close contact, the top surface of all flexible sheets and the top surface of all bent sheets form a continuous arc surface; the upper surface of the bent sheet and / or the bent sheet is provided with a number of upwardly protruding openings for pre-embedded pins; when each flexible sheet is flattened from the bent state, the top surface of each flexible sheet and the top surface of the bent sheet portion between two adjacent flexible sheets form a continuous plane.

[0009] Furthermore, the pre-embedded pins with holes are all located on the outermost curved plates not in a row. The top surfaces of these curved plates are provided with grooves on both sides for accommodating the flexible thin plates, and the middle position is a rib that separates the two grooves. The pre-embedded pins with holes are installed on these ribs.

[0010] Furthermore, it also includes a curing plate (5), which has several holes that correspond one-to-one with the pre-embedded pins. When the curing plate (5) is used in conjunction with the bendable forming device, the pre-embedded pins are inserted into the holes.

[0011] Furthermore, the two outermost curved plates in the row have openings at both ends along their length, and fixing pins are provided in the openings. The core mold frame (3) has blind holes corresponding to the openings in its grooves, and mounting holes corresponding to the openings are also provided at the four corners of the curing plate (5). When the bendable forming device is located in the groove, the fixing pins are installed downwards in the blind holes in the openings. When the bendable forming device is engaged with the curing plate (5), the fixing pins extend upwards in the openings and are installed in the mounting holes.

[0012] Furthermore, the flexible sheet is made of rubber.

[0013] Furthermore, the bendable sheet is made of shape memory alloy. The bendable sheet is initially flat and can be restored to its initial flat state by heating after bending.

[0014] Beneficial effects: The woven composite material flat plate forming device provided by this invention provides a flexible forming device that can bend and flatten, so that during the weaving process of the preform, the woven composite material flat plate preform is always under the constraint of the flexible forming device, so that the woven composite material flat plate preform will not produce undesirable phenomena such as yarn slippage, in-plane shear deformation, and wrinkling due to steps such as stacking, transfer, and handling; at the same time, the pre-embedded hole pins provided on the flexible forming device are always positioned at the pre-designed opening position of the woven composite material flat plate preform, preserving the continuity of the fibers around the opening of the woven composite material flat plate preform during the forming process, and preventing shape and position movement during the transfer of the preform, thus ensuring the accuracy of the opening forming.

[0015] The braided composite material forming method using the above-mentioned braided composite material flat plate forming device provided by the present invention adopts the following technical solution, including the following steps:

[0016] S1, the bendable forming device is bent and installed in the slot reserved in the core mold frame to form a complete curved surface to be woven;

[0017] S2, use a braiding machine to braid the prefabricated body; during the braiding process, the yarn passes around the pre-embedded pins to form pre-embedded holes, and continues to braid until the preset number of layers of the prefabricated body is obtained;

[0018] S3, cut out the preform from the bendable forming device and fix the preform to the edge of the bendable forming device around the perimeter, and remove the bendable forming device of the bending mode from the core mold frame.

[0019] S4, the bendable forming device is restored to the flattened mode to obtain a woven composite material flat preform with openings.

[0020] Furthermore, a curing plate is provided, which has several holes corresponding to the pre-embedded pins. When the curing plate is used in conjunction with the flexible forming device, the pre-embedded pins are inserted into the holes. After step S4, the prefabricated woven composite material plate with holes and the pre-embedded pins are transferred from the flexible forming device to the curing plate for curing.

[0021] Furthermore, the preform curing process involves using epoxy resin vacuum bag curing molding technology to obtain a cured woven composite material flat sheet.

[0022] Furthermore, the pre-embedded pins with openings on the cured woven composite material plate are removed to obtain a woven composite material plate with openings.

[0023] Beneficial effects: In the braided composite material forming method provided by the present invention, a braided composite material flat plate preform with openings can be obtained by using a braided composite material flat plate forming device. The forming process of this method is simple and easy to operate. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the flexible forming mechanism in this invention;

[0025] Figure 2 This is a schematic diagram of the positioning block and support block in this invention;

[0026] Figure 3 This is a schematic diagram of the deformation of the bendable forming mechanism in this invention;

[0027] Figure 4 This is a schematic diagram of the core mold frame in this invention;

[0028] Figure 5 This is a schematic diagram of the preform weaving process in this invention;

[0029] Figure 6 This is a schematic diagram illustrating the transfer of a perforated woven composite material flat preform to a curing plate in this invention;

[0030] Figure 7 This is a schematic diagram of the curing of a perforated woven composite flat vacuum bag in this invention. Detailed Implementation

[0031] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0032] Please combine Figure 1 and Figure 2 As shown, the present invention discloses a woven composite material flat plate forming device, including a core mold frame 3 and a bendable forming device; the core mold frame 3 is cylindrical, and a portion of the cylindrical surface of the core mold frame 3 is recessed inward to provide a groove 31 with an arc-shaped cross-section.

[0033] The bendable forming device includes several bent plates arranged side by side and several bendable thin plates 13. Figure 1 It contains two types of bent plates. The two outermost bent plates in a row are numbered 11, and the other bent plates not on the outermost side are numbered 12. The cross-section of each bent plate is arc-shaped.

[0034] like Figure 3 As shown, the row of curved plates can change between a bent state and an open state. After the sides of every two adjacent curved plates are pressed together, the bottom surfaces of all the curved plates form a continuous long arc surface, and the curvature of this long arc surface is the same as the curvature of the bottom surface of the groove. The length and width of the long arc surface are also the same as the length and width of the bottom surface of the groove, so that the flexible forming device can be fitted into the groove of the core mold frame 3 in the bent state and form an integral cylindrical shape with the core mold frame 3. In this flexible forming device, the upper surface of two adjacent curved plates spans a flexible thin plate 13, and the top surfaces of two adjacent curved plates are recessed with mutually facing and communicating grooves 15. Each flexible thin plate 13 is disposed in the groove 15 on the top surface of the two adjacent curved plates, and one side edge of the flexible thin plate 13 is fixed to the inner side surface of one of the curved plate grooves, and the other side edge of the flexible thin plate 13 is fixed to the inner side surface of the other curved plate groove. The fixing method can be adhesive fixation. The thickness of the flexible sheet 13 is the same as the depth of the groove 15, so that after the sides of every two adjacent bent plates are in close contact, the top surfaces of all the flexible sheets 13 form a continuous arc surface with the top surfaces of all the bent plates. Simultaneously, the flexible sheets 13 also connect adjacent bent plates together, making the entire flexible forming device a whole through these flexible sheets 13. Furthermore, when each flexible sheet 13 is flattened from its bent state, the top surface of each flexible sheet 13 forms a continuous plane with the top surface of the bent portion between two adjacent flexible sheets 13. In the flexible forming device, a plurality of upwardly protruding pre-embedded pins 2 are provided on the upper surface of the bent plates and / or the bent sheets 13. In the accompanying drawings provided in this embodiment, the pre-embedded pins 2 are provided on the bent plates 12, and the pre-embedded pins 2 are all located on the bent plates that are not the outermost in a row, i.e. Figure 1 On the bent plates 12, the top surfaces of these bent plates 12 are provided with grooves 15 on both sides for receiving the bendable sheet, and the middle position is a rib 16 that separates the two grooves 15. The pre-embedded pins 2 are installed on these ribs 16, and the ribs 16 are provided with blind holes 21 for receiving the pre-embedded pins 2. The position of the pre-embedded pins 2 can be embedded in the preset position on the bendable forming device according to design requirements. The two outermost bent plates 11 in a row have openings 17 at both ends in the longitudinal direction, and fixing pins 14 are provided in the openings 17; such as Figure 4 As shown, the slot 31 of the core mold frame 3 is provided with a blind hole 32 corresponding to the opening 17. When the bendable forming device is located in the slot 31, the fixing pin 14 is installed downward in the opening 17 and fixed in the blind hole 32 so that the bendable forming device is fixed in the slot 31.

[0035] In this embodiment, the flexible sheet 13 can be made of rubber or shape memory alloy. When the flexible sheet 13 is made of rubber, bending or flattening of the flexible sheet is achieved passively. When the flexible sheet 13 is made of shape memory alloy, the flexible sheet 13 is initially in a flat state, and after bending, it returns to its initial flat state by heating. That is, flattening of the flexible sheet 13 can be actively achieved by heating.

[0036] To facilitate the removal of the woven composite preform obtained from the bendable forming device for subsequent curing, a curing plate 5 is further provided. The curing plate 5 has several holes 51 corresponding one-to-one with the pre-embedded pins 2 on the bending plate 12. When the curing plate 5 is engaged with the bendable forming device, the pre-embedded pins 2 are inserted into the holes 51. Mounting holes 52 corresponding to the openings 17 of the bending plate 11 are also provided at the four corners of the curing plate 5. When the bendable forming device is engaged with the curing plate 5, fixing pins 14 extend upwards from the openings 17 and are fixed in the mounting holes 52.

[0037] The method for forming braided composite materials using the above-mentioned braided composite material flat sheet forming device is as follows:

[0038] S1, the bendable forming device is bent and installed in the slot 31 reserved in the core mold frame 3 to form a complete curved surface to be woven;

[0039] S2, as Figure 5 As shown, a rotary braiding machine is used to braid the prefabricated body; during the braiding process, the yarn passes around the pre-embedded pin 2 to form a pre-embedded hole, and the braiding continues until the preset number of layers of the prefabricated body is obtained;

[0040] S3, cut out the preform from the bendable forming device and fix the preform to the edge of the bendable forming device around the perimeter, and remove the bendable forming device 1 of the bending mode from the core mold frame 3.

[0041] S4, the bendable forming device is restored to the flattened mode to obtain a woven composite material flat preform with openings. The bendable forming mechanism flattens the preform while restoring it to the flattened mode. Since the preform is fixed on all four sides, it can be ensured that the preform is flattened evenly, and openings have been formed on the woven composite material flat preform at this time.

[0042] Furthermore, after step S4, the following steps may also be included:

[0043] S5, then the perforated woven composite material flat preform and the perforated embedded pins 2 are transferred from the bendable forming device to the curing plate 5 for preform curing. Figure 5 As shown. Figure 6As shown, the preform curing process involves using epoxy resin vacuum bag curing technology to obtain a cured woven composite material plate 4. Then, the pre-embedded pins 2 with openings on the cured woven composite material plate 4 are removed to obtain a woven composite material plate with openings.

Claims

1. A braided composite material flat sheet forming device, characterized in that, It includes a core mold frame and a bendable forming device; the core mold frame is cylindrical, and a portion of the cylindrical surface of the core mold frame is recessed inward with a groove having an arc-shaped cross-section; The bendable forming device includes several bent plates arranged side by side and several bendable thin plates; each bent plate has an arc-shaped cross-section; after the sides of every two adjacent bent plates are pressed together, the bottom surfaces of all bent plates form a continuous long arc surface, and the curvature of the long arc surface is the same as the curvature of the bottom surface of the groove, and the length and width of the long arc surface are also the same as the length and width of the bottom surface of the groove; the upper surfaces of two adjacent bent plates span a bendable thin plate, and the top surfaces of two adjacent bent plates are recessed with mutually facing and communicating grooves; each bendable thin plate is disposed in the groove on the top surface of the two adjacent bent plates, and one side edge of the bendable thin plate is fixed to the inner side of the groove of one bent plate, and the other side edge of the bendable thin plate is fixed to the inner side of the groove of the other bent plate; the thickness of the bendable thin plate is the same as the depth of the groove, so that after the sides of every two adjacent bent plates are pressed together, the top surfaces of all bendable thin plates and the top surfaces of all bent plates form a continuous arc surface; the upper surface of the bent plates and / or the bendable thin plates are provided with several upwardly protruding pre-embedded pins. When each flexible sheet is flattened from its bent state, the top surface of each flexible sheet forms a continuous plane with the top surface of the bent portion between two adjacent flexible sheets.

2. The braided composite material flat plate forming device according to claim 1, characterized in that, The pre-embedded pins with holes are all located on the outermost curved plates not in a row. The top surfaces of these curved plates are provided with grooves on both sides for accommodating the flexible thin plates, and the middle position is a rib that separates the two grooves. The pre-embedded pins with holes are installed on these ribs.

3. The braided composite material flat plate forming device according to claim 2, characterized in that, It also includes a curing plate (5), which has several holes that correspond one-to-one with the pre-embedded pins. When the curing plate (5) is used in conjunction with the bendable forming device, the pre-embedded pins are inserted into the holes.

4. The braided composite material flat sheet forming device according to claim 3, characterized in that, The two outermost curved plates arranged side by side have openings at both ends along their length, and fixing pins are provided in the openings. The groove of the core mold frame (3) has blind holes corresponding to the openings, and the four corners of the curing plate (5) also have mounting holes corresponding to the openings. When the bendable forming device is located in the groove, the fixing pins are installed downward in the blind holes in the openings. When the bendable forming device is engaged with the curing plate (5), the fixing pins extend upward in the openings and are installed in the mounting holes.

5. The braided composite material flat plate forming device according to claim 1, characterized in that, The flexible sheet is made of rubber.

6. The braided composite material flat sheet forming device according to claim 1, characterized in that, The bendable sheet is made of shape memory alloy. The initial state of the bendable sheet is flat, and it can be restored to its initial flat state by heating after bending.

7. A method for forming a braided composite material using the braided composite material flat sheet forming apparatus as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1, the bendable forming device is bent and installed in the slot reserved in the core mold frame to form a complete curved surface to be woven; S2, use a braiding machine to braid the prefabricated body; during the braiding process, the yarn passes around the pre-embedded pins to form pre-embedded holes, and continues to braid until the preset number of layers of the prefabricated body is obtained; S3, cut out the preform from the bendable forming device and fix the preform to the edge of the bendable forming device around the perimeter, and remove the bendable forming device of the bending mode from the core mold frame. S4, the bendable forming device is restored to the flattened mode to obtain a woven composite material flat preform with openings.

8. The method for forming braided composite materials according to claim 7, characterized in that, A curing plate is provided, which has a plurality of holes corresponding to the pre-embedded pins. When the curing plate (5) is used in conjunction with the bendable forming device, the pre-embedded pins are inserted into the holes. After step S4, the woven composite material flat preform with holes and the pre-embedded pins are transferred from the bendable forming device to the curing plate for preform curing.

9. The method for forming braided composite materials according to claim 8, characterized in that, The preform curing process involves using epoxy resin vacuum bag curing molding technology to obtain a cured woven composite material flat sheet.

10. The method for forming braided composite materials according to claim 9, characterized in that, Remove the pre-embedded pins with openings from the cured braided composite material plate to obtain a braided composite material plate with openings.

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