A composite material cylinder preform structure and a method of making the same

Abstract

The composite thin-walled shell is not firm enough because of its thinness and the added connecting structure, and the preparation method disclosed by the present application overcomes the problem of insufficient connecting strength of the composite thin-walled shell. A piece of rectangular warp-weft interlaced fiber cloth is cut, and the warp fibers on two sides are symmetrically removed to release the weft fibers, and the width of the remaining warp fibers in the direction perpendicular to the warp fibers is 2 times the height of the column; the length of the released weft fibers is greater than the wall thickness of the thin-walled shell, the cut fiber cloth is symmetrically folded in the warp direction, the cut fiber cloth after symmetric folding is folded in a wave shape starting from one side of the weft as a starting point, and a rectangular column is prepared. One side of the folded column is in a hair shape, and a plurality of hair-shaped fibers are bundled into a bundle as a suture line and sewn into the thin-walled shell preform, and after sewing, a certain thickness of carbon fiber cloth is sewn in by needling as a processing allowance.

Description

Technical Field

[0001] This application relates to the field of aerospace technology, and in particular to a composite material column preform structure and its preparation method. Background Technology

[0002] In the aerospace field, thin-walled components are widely used due to their lightweight characteristics. In certain environments, it is necessary to connect thin-walled components with screws. However, due to their thinness, thin-walled components have too few threads, resulting in poor engagement with screws and a tendency to detach. Existing technology involves adding composite material cylinders to the thin-walled components and then machining threads onto these cylinders to obtain the threads.

[0003] In the field of composite materials, the fiber structure arrangement often determines the strength and toughness of the component, and the connection method between the prefabricated column and the thin-walled component plays a decisive role in the final connection strength of the structure. Summary of the Invention

[0004] To address the above reasons, this application proposes a composite material column prefabricated structure and its preparation method, characterized in that: S1. Preparation of the column; S2. Prepare a partial thin-walled shell; S3, connecting column and part of thin-walled shell; S4. Complete the thin-walled shell.

[0005] Preferably, a rectangular piece of interwoven warp and weft fiber fabric is cut, and the warp fibers on both sides are symmetrically removed to release the weft fibers. The width of the retained warp fibers in the direction perpendicular to the warp fibers is twice the height of the column; the length of the released weft fibers is greater than the wall thickness of the thin-walled shell. Furthermore, the cut fiber fabric is symmetrically folded along the warp direction; the symmetrically folded cut fiber fabric is then folded starting from one side of the weft line in a wavy pattern, and the folded surfaces are tightened and sewn together to prepare a rectangular column.

[0006] Preferably, after the fiber cloth is folded into a column, the released weft threads are also folded into a columnar cross-section resembling hair; the adjacent hair-like fibers n strands are bundled into single fibers (n is a positive integer) until all fibers are bundled into single fibers.

[0007] Preferably, a partially thin-walled shell is prepared, wherein the partially thin-walled shell is made of fiber cloth laid up to 20% to 95% of the required thickness, and is prepared by a sewing process; Furthermore, the column and the thin-walled shell are connected by inserting a special needle into part of the thin-walled shell. The special needle brings out a single strand of fiber. After the special needle is pulled out, the single strand of fiber penetrates the thin-walled shell.

[0008] Furthermore, the specially designed needle has a hole in the middle, through which a fiber ring passes. After the specially designed needle penetrates the thin-walled shell, it brings out the fiber ring, inserts a single fiber into the fiber ring, and pulls out the specially designed needle to bring out the single fiber.

[0009] Preferably, after all the single fibers have penetrated the thin-walled shell, traction force is applied to all the single fibers in sequence to ensure that the column is in contact with the thin-walled shell; the single fibers are then evenly spread on part of the thin-walled shell surface. Furthermore, after the single fiber is evenly spread on part of the thin-walled shell, it is sewn into the thin-walled shell in sequence by stitching. Furthermore, the single-stranded fibers are sewn out on one side of the back of the column, and when the last stitch is sewn, the single-stranded fibers are unraveled and laid flat on part of the thin-walled shell. All single-stranded fibers have completed this step.

[0010] Preferably, a fiber cloth is further covered on a portion of the thin-walled shell to achieve a final thin-walled shell thickness of 70% to 99%. The newly covered portion of the thin-walled shell is then sewn together using a double-strand bidirectional sewing process. The sewing dot pattern is 2mm×2mm to 8mm×8mm. The mesh and fiber cloth are then covered sequentially, and this process is repeated multiple times to achieve a final thin-walled shell thickness of 101% to 120%. The shell is then connected using a needle-punching method. Attached Figure Description

[0011] Figure 1 A plan view of the unfolded fiber cloth for preparing the column preform; Figure 2 A diagram of a specially designed needle structure; Figure 3 A structural diagram of a columnar bundled fiber used for stitching thin-walled shells; Figure 4 This is a cross-sectional view of the fiber arrangement after the column and thin-walled shell are combined. Detailed Implementation

[0012] To better understand this patent, a detailed description of the patent will be provided in conjunction with the accompanying drawings.

[0013] S1. Preparation of the column: Cut a rectangular piece of T300-3K carbon fiber fabric, such as... Figure 1 As shown, the horizontal direction represents the length, which is 600mm, and the vertical direction represents the width, which is 680mm. The thickness of the T300-3K carbon fiber cloth is 0.3mm. The vertical fibers on both sides are removed when the cloth is stacked horizontally, leaving a vertical fiber length of 100mm.

[0014] Fold along the vertical symmetrical line as the center line, starting from the horizontal direction. The fold width is 20mm. Fold in a wavy pattern until the diameter of the column reaches 20mm. At this point, there should be a little excess in the width. Trim off the excess and sew the folded carbon fiber cloth together.

[0015] After completing the above steps, a square column with a base of 20mm x 20mm and a height of 50mm is obtained, and one side of the square face of the column is covered with 250mm long carbon fiber "hairs". Adjacent "hairs" are bundled into a single bundle of 2-6 strands, and the ends of the "hairs" are bundled together by twisting.

[0016] S2. Preparation of a partial thin-walled shell: Cut 25 rectangular pieces of T300-3K carbon fiber fabric of the same shape, each 300mm*300mm in size and 0.3mm thick. Take 15 pieces of carbon fiber fabric from the 25 pieces, align them, and stack them. Use a double-strand, two-way stitching process to sew them together. The stitching dot pattern is 20mm×20mm temporary stitches. This step yields a square thin sheet preform of 300mm×300mm×4.5mm.

[0017] S3, connecting the column and part of the thin-walled shell: Determine the connection points between the column and the thin-walled shell section, and mark the connection points with a marker. Prepare a high-strength flat mold with a square hole, the diameter of which is slightly larger than the square base of the column. Place the thin-walled shell section onto the flat mold, ensuring the hole on the mold coincides with the connection point marked by the marker on the thin-walled shell. Place the flat mold on a support frame, with the column vertically positioned directly below the square hole of the mold, the "hair" of the column at the top.

[0018] Use a special needle to vertically insert it into the mold from the marked position on the other side. The special needle is like... Figure 2 As shown, there is a thread hole 5mm from the needle tip. A 10mm long polyester thread is threaded through the hole and connected end to end. A thickened section is 10mm above the thread hole for easier handling. A specially designed needle is inserted until it pierces the thickened section and partially adheres to the thin-walled shell, pulling out some of the polyester thread. A corresponding column "hair" is selected, and the end of the "hair" is inserted into the polyester thread about 20mm. The needle is then withdrawn, and the "hair" penetrates the thin-walled shell and is pulled out. This step is repeated until all "hairs" have penetrated the thin-walled shell. All "hairs" are tightened sequentially, at least twice, to ensure the column adheres to the thin-walled shell.

[0019] After all the "hairs" pierce through the thin-walled shell, they spread out in a flower-like pattern on the shell. The previously twisted bundled fibers are untied, the mold is removed, and 6-10 adjacent fibers are taken as a new bundle. This new bundle is used as a suture fiber to sew into the thin-walled shell. All new bundles are sutured into the thin-walled shell. To ensure uniformity and aesthetics of the suture, a dot matrix is ​​pre-drawn, and each bundle is sewn into the thin-walled shell according to the dot matrix. The prefabricated body is sewn using a double-strand, bidirectional suture technique, with a suture dot matrix of 4mm × 4mm.

[0020] S4. Complete the thin-walled shell: Three layers of carbon fiber cloth of the same size are stacked on the non-column side of the thin-walled shell, achieving a wall thickness of 5.4 mm. The shell is then sewn together using the stitching fibers from the column end of the thin-walled shell, employing a double-strand bidirectional stitching process with a stitch dot matrix of 4 mm × 4 mm. A mesh is then laid on the non-column side surface, followed by carbon fiber cloth of the same size. This step is repeated at least five times until the wall thickness reaches at least 6.9 mm. The final layer of carbon fiber cloth is then needle-punched to bond with the remaining thin-walled shell, completing the thin-walled shell structure. This invention describes a prefabricated structure and its preparation method, not the final product. The final product in this embodiment requires a wall thickness of 6 mm; therefore, the prefabricated structure prepared in this embodiment has a wall thickness greater than the final product, allowing sufficient processing allowance.

Claims

1. A method for preparing a composite material column prefabricated structure, characterized in that: S1. Cut a rectangular piece of warp and weft interwoven fiber fabric, symmetrically remove the warp fibers on both sides, and release the weft fibers. The width of the retained warp fibers in the direction perpendicular to the warp fibers is twice the height of the column; the length of the released weft fibers is greater than the wall thickness of the thin-walled shell; fold the cut fiber fabric symmetrically in the warp direction; after symmetrical folding, start folding the cut fiber fabric from one side of the weft thread in a wavy pattern, tighten and sew the folded surface to prepare a rectangular column; after folding the fiber fabric into a column, the released weft threads are also folded into a hair-like cross-section of the column; bundle adjacent hair-like fibers n strands into single fibers (n is a positive integer) until all fibers are bundled into single fibers; S2. Prepare a partial thin-walled shell, which is made of fiber cloth laid up to 20%~95% of the required thickness and is prepared by sewing process; connect the column and the thin-walled shell, insert a special needle into the partial thin-walled shell, the special needle brings out a single strand of fiber, pull out the special needle, and the single strand of fiber penetrates the thin-walled shell. S3. Connect the column and the thin-walled shell. After all the single fibers have penetrated the thin-walled shell, apply traction force to all the single fibers in sequence to ensure that the column is in contact with part of the thin-walled shell; spread the single fibers evenly on the surface of part of the thin-walled shell. S4. Complete the thin-walled shell by covering part of the thin-walled shell with fiber cloth to achieve a final thin-walled shell thickness of 70% to 99%. Sew the newly covered part of the thin-walled shell together using a double-strand bidirectional stitching process. The stitching dot matrix is ​​2mm×2mm to 8mm×8mm. Cover the mesh and fiber cloth in sequence, repeating the steps multiple times to achieve a final thin-walled shell thickness of 101% to 120%. Needle-punch the newly covered fiber cloth to complete the preparation of the thin-walled shell preform.

2. The method for preparing a composite material column prefabricated structure according to claim 1, characterized in that: The specially designed needle has a hole in the middle, through which a fiber ring passes. After the specially designed needle penetrates the thin-walled shell, it brings out the fiber ring. A single fiber is inserted into the fiber ring, and pulling out the specially designed needle can bring out the single fiber.

3. The method for preparing a composite material column prefabricated structure according to claim 1, characterized in that: After the single fiber is evenly spread on a portion of the thin-walled shell, it is sequentially sewn into the portion of the thin-walled shell by stitching.

4. The method for preparing a composite material column prefabricated structure according to claim 1, characterized in that: When the single fiber is sewn out on one side of the back of the column, and it is the last stitch, the single fiber is unraveled and laid flat on part of the thin-walled shell; when all the single fibers are sewn out on one side of the back of the column, and it is the last stitch, the single fiber is unraveled and laid flat on part of the thin-walled shell.

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