A method for preparing a high-strength composite material screw preform

Abstract

A hollow screw is prepared by winding fiber cloth around a core mold, and the excess part is cut into a skirt to prepare a part of the screw head. The fibers on both sides of the weft direction of the fiber cloth are removed and threaded fibers are prepared by bundling the fibers. The bundled fibers are sewn to the hollow screw. The threaded fibers are sewn to the hollow screw, and each point of the prepared thread is riveted by the screw body. The threaded fibers are tightly combined with the body and are more firmly filled to fill the hollow part of the hollow screw. Another part of the screw head is prepared and is sewn to a part of the screw head.

Description

Technical Field

[0001] The present invention relates to the technical field of high-stability bonding of composite materials, and in particular to a method for preparing a high-strength composite material screw preform. Background Art

[0002] In the aerospace field, screws are frequently used for connecting structures. However, how to prepare lightweight, high-strength composite screws has always been a pain point in the industry. The existing high-strength technology is to prepare the screws by stacking carbon fiber cloth layers to the thickness of the screw length, densifying them with silicon carbide, and finally machining them to make thread machines. The threads prepared by this processing method will destroy the continuity of the fibers, leaving some of the fibers in the threads exposed, affecting the strength and service life of the components. Moreover, the machined threads are easily worn out by the broken fibers under the action of shear and tensile forces for a long time, causing the threads to loosen.

[0003] Patent No. 2021113431509 discloses a method of preparing threads by wrapping bundled fibers around axial fibers, and then preparing threads by calendering with a graphite mold; this method can indeed prepare threads quickly, but the prepared threaded fibers are independent of the main fiber structure of the screw rod, and the threaded fibers are easy to fall off after being subjected to a relatively strong tensile force. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides a method for preparing a high-strength composite material screw preform.

[0005] S1. Preparation of a hollow screw (1) and a portion of a screw head (3): The hollow screw (1) is formed by winding a complete fiber cloth around a hollow core mold. When the fiber cloth is wound, the cloth layers are already bonded together. The bonding method includes but is not limited to needle punching and organic adhesive bonding. The length of the hollow screw (1) is greater than the length of the screw. The excess portion is cut out to form a skirt, and a portion of the screw head (3) is prepared.

[0006] S2. Preparation of threaded fibers (2): The threaded fibers (2) are prepared by removing fibers on both sides of the warp direction of the fiber cloth, releasing fibers in the weft direction, and bundling the multiple fibers left in the middle into a bundle as threaded fibers (2). The fibers on both sides of the weft direction of the fiber cloth are removed, and the warp direction fibers are released as processing allowances. n fibers are taken from the left and right sides of the fiber cloth to form a bundle of fibers (6), where n is a positive integer. The bundled fibers (6) on the left and right sides are interlaced with each other, and the left and right sides of the bundled fibers (6) are folded with the threaded fibers (2) as fold lines.

[0007] S3, threaded fibers (2) and hollow screw (1) are sewn together: thread positions are marked on the surface of the hollow screw (1); the threaded fibers (2) are sequentially sewn along the thread positions marked on the surface of the hollow screw (1) using the bundled fibers (6) as suture lines; during the suturing process, the threaded fibers (2) are ensured to be in a tight state; the bundled fibers (6) penetrate the hollow screw (1) through the suture needle and are pierced out from the other end of the hollow screw (1), and the suture line passes through the hollow part; a special barb is inserted into the hollow screw (1) to hook out the bundled fibers (6). The special barb hooks out the bundled fibers (6), and the mth bundled fibers (6) are brought out from one side of the hollow screw (1), and the m+1th bundled fibers (6) are brought out from the other side of the hollow screw (1), where m is a positive integer.

[0008] S4. Filling the hollow part of the hollow screw (1): After the threaded fibers (2) are sewn onto the surface of the hollow screw (1), the fiber bundles are sewn into the hollow part to fill it until it is full.

[0009] S5, preparing another part of the screw head (4) and suturing it to the other part of the screw head (3); preparing a mold to clamp and shape the thread before performing post-processing.

[0010] The technical highlight of the present invention is that the integrity of the threaded fibers (2) is maintained, and the screw prepared is more stable and durable in harsh environments, and each point of the prepared thread is riveted by the screw body, and the threaded fibers (2) are tightly combined with the body and are more secure. The present invention adopts the hollow screw (1) preparation technology to eliminate the influence of knotting caused by the suture process; and the direction of the fibers filled in the hollow part of the present invention is vertical, and the tensile strength is higher; the bundled fibers (6) of the present invention are all transversely sutured to the screw, and the screw structure is more compact and the shear strength is also higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of the structure of a screw;

[0012] Figure 2 Top view of the skirt cut out for the screw head;

[0013] Figure 3 Preparation of threaded fibers for threaded fiber cloth Step 1;

[0014] Figure 4 Preparation of threaded fibers for threaded fiber cloth Step 2;

[0015] Figure 5 Step 3 of preparing threaded fibers for threaded fiber cloth;

[0016] Figure 6 A schematic diagram of sewing bundled fibers on a threaded fiber to a hollow screw;

[0017] Figure 7 A schematic diagram of the bundled fiber being hooked out of the hollow part of the screw by a special barb;

[0018] Figure 8 This is a schematic diagram of the screw after it is prepared and is limited by the mold. Specific implementation plan

[0019] A core mold with a diameter of 1.2 cm is prepared, and a carbon fiber plain cloth with a width of 7 cm and a length of 27.3 cm is prepared and wound on the core mold. Organic glue is used for bonding during the winding process. The core mold is pulled out to obtain a cylinder with an outer diameter of 2 cm and an inner diameter of 1.2 cm. A 2 cm piece of fiber cloth is cut at one end of the cylinder and cut into 6 pieces evenly. The transverse fibers are removed, leaving the longitudinal fibers. The longitudinal fibers are evenly spread out, and the hollow screw (1) is prepared.

[0020] The carbon fiber plain weave is cut to a width of 8 cm and a length of 28 cm. The fiber bundles on both sides are removed to leave 12 strands of carbon fiber with a length of 28 cm. The 12 strands of fiber are twisted into a single strand of coarse fiber. The 4 side fibers of the single strand of coarse fiber are twisted into a bundle of fibers (6). The bundle of fibers (6) is staggered left and right and folded with the single strand of coarse fiber as the center line. The preparation of the threaded fiber (2) is completed.

[0021] A thread line is drawn on the prepared hollow screw (1), and the bundled fibers (6) on the threaded fibers (2) are vertically sewn onto the threaded line track. After sewing in two bundles of bundled fibers (6), the two bundles of fibers are hooked out from the upper part with a special crochet needle, and then two bundles of fibers are sewn in, and the two bundles of fibers are hooked out from the lower part with a crochet needle, until the threaded fibers (2) are all sewn onto the hollow screw (1); after the sewing is completed, the hollow part of the hollow screw (1) is filled with vertical fibers.

[0022] Cut the regular hexagonal carbon fiber plain weave cloth and stack it to a thickness of 0.5 cm. Use the skirt prepared by the hollow screw (1) as a suture line to wrap the regular hexagonal carbon fiber plain weave cloth and then sew it.

Claims

1. A method for preparing a high-strength composite material screw preform, characterized in that: The steps are: S1. Preparation of a hollow screw (1): the hollow screw (1) is formed by winding a complete fiber cloth around a hollow core mold; when the hollow screw (1) is wound, the cloth layers are already adhered to each other; S2, cutting out the excess part to form a skirt and preparing a part of the screw head (3); S3, preparing a threaded fiber (2), wherein the threaded fiber (2) is obtained by removing fibers on both sides of the warp direction of the fiber cloth, releasing fibers in the weft direction, and bundling multiple fibers left in the middle into a bundle as the threaded fiber (2); removing fibers on both sides of the weft direction of the fiber cloth, and releasing fibers in the warp direction as processing allowance; taking n fibers on the left and right sides of the fiber cloth as a bundled fiber (6), where n is a positive integer; the bundled fibers (6) on the left and right sides are interlaced with each other, and the left and right sides of the bundled fibers (6) are folded with the threaded fiber (2) as a fold line; S4, the threaded fibers (2) are sewn together with the hollow screw (1); the thread positions are marked on the surface of the hollow screw (1); Using the bundled fibers (6) as suture lines, the threaded fibers (2) are sequentially sutured along the threaded positions marked on the surface of the hollow screw (1); during the suture process, the threaded fibers (2) are ensured to be in a taut state; S5, filling the hollow part of the hollow screw (1); The bundled fibers (6) penetrate the hollow screw (1) through a suture needle and come out from the other end of the hollow screw (1), and the suture thread passes through the hollow part; a special barb is inserted into the hollow screw (1) to hook out the bundled fibers (6); the special barb hooks out the bundled fibers (6), and the mth bundled fibers (6) are brought out from one side of the hollow screw (1), and the m+1th bundled fibers (6) are brought out from the other side of the hollow screw (1), where m is a positive integer; after the threaded fibers (2) are sutured on the surface of the hollow screw (1), the fiber bundles are sewn into the hollow part to fill it until it is full; S6. Prepare another part of the screw head (4), sew it to another part of the screw head (3), and complete the preparation of the high-strength composite material screw preform. After the preparation of the high-strength composite material screw preform is completed, prepare a half-type internal thread mold to clamp and limit the thread fiber (2).

2. The method for preparing a high-strength composite material screw preform according to claim 1, characterized in that: The bonding method in step S1 is needle punching or organic adhesive bonding.

3. The method for preparing a high-strength composite material screw preform according to claim 1, characterized in that: In step S1, the length of the hollow screw (1) is greater than the length of the screw.

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