Composite material screw, forming method thereof, and mold

Abstract

This invention discloses a composite material screw, comprising an integrated structure consisting of a metal disc, a metal screw body, and a composite material disc; it also provides a molding method and a molding die. This composite material screw eliminates the need for drilling holes in the connected parts, avoiding the difficulties of connection operations in confined spaces and the sealing issues in connections requiring sealing. The molding method involves assembling the composite material layup, the metal disc, and the pre-embedded screw body into a screw preform, which is then integrally molded to net dimensions. This avoids the difficulties of composite material processing while retaining the excellent properties of the composite material, shortening the production cycle, improving production efficiency, and making it suitable for mass production. The mold-molded composite material screw offers high operational efficiency, reduces heat loss during demolding, and ensures dimensional consistency of the parts through the molding process, achieving the effects of improving work efficiency, reducing costs, and ensuring product dimensional accuracy and quality.

Description

Technical Field

[0001] This invention belongs to the field of screw technology, and more specifically, relates to a composite material screw, its molding method, and mold. Background Technology

[0002] Currently, screw connections primarily involve creating connecting holes in the structure, through which screws pass to connect the structural components. This method requires creating connecting holes in the main structure, which compromises the integrity of the original structure, necessitating localized reinforcement of the hole-making area in critical structural components. For aerospace structures with relatively confined and enclosed spaces and components requiring sealing, this type of connection with drilled holes is unsuitable.

[0003] Screws made of metal require specialized connecting tools, resulting in high overall costs. Furthermore, the heavy weight of metal screws is detrimental to the weight reduction requirements of aerospace structures.

[0004] Composite materials are widely used in the aerospace field due to their excellent properties such as high specific strength, high specific modulus, corrosion resistance, and high temperature resistance. A wide variety of composite material screws are available on the market, including C / C composite screws, graphite screws, ceramic matrix composite screws, and C / SiC screws. However, most of these are limited in their application because composite materials are brittle and have high hardness, making them difficult to process and prone to brittle fracture and tooth breakage during thread machining.

[0005] Composite screws, which are integrally formed from composite materials and embedded metal parts, have limited applications due to the challenges of protecting the metal parts and sealing the threads during the molding process. Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned shortcomings by providing a composite material screw, along with its molding method and molding die. This composite material screw eliminates the need for drilling holes in the connected parts, avoiding difficulties in connection operations in confined spaces and sealing issues in connections requiring sealing. The molding method employs a compression molding process to integrally form the screw within net dimensions, avoiding the difficulties in processing composite materials while retaining their excellent properties. This shortens the production cycle, improves production efficiency, and allows for mass production. The molded composite material screw reduces heat loss during demolding, and the compression molding process ensures dimensional consistency, thereby improving work efficiency, reducing costs, and guaranteeing product dimensional accuracy and quality.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] This invention provides a composite material screw compression molding die for producing composite material screws, comprising an upper die, a middle frame, and a lower die.

[0009] The upper and lower molds are arranged relative to each other;

[0010] The middle frame is detachably connected to the upper mold and the lower mold respectively, and the middle frame is provided with a number of detachable core molds;

[0011] The core mold has a mold cavity that conforms to the shape of the screw preform, and the upper mold has a number of protrusions, the position of each protrusion corresponding to the mold cavity of the core mold; when the upper mold is attached to the middle frame, each protrusion is located in the corresponding mold cavity of the core mold.

[0012] Furthermore, a guide post is fixed to the lower mold, the guide post passing through the middle frame and the upper mold but not fixedly connected to them, the middle frame being connected to the upper mold via a release plate and bolts. As the lower mold descends with the molding press, the middle frame automatically separates from the lower mold.

[0013] Furthermore, the upper part of the demolding module is connected to the upper mold via round holes and bolts, while the lower part is connected to the middle frame via oblong holes and bolts. After the lower mold descends, under the action of gravity, the middle frame and the upper mold automatically separate through the oblong holes, and the demolding of the middle frame can be completed simply by removing the bolts in the oblong holes.

[0014] Furthermore, the middle frame is provided with several recessed holes that fit with the outer wall of the core mold, and the outer wall of the core mold is engaged with the recessed holes on the middle frame. Preferably, 2 to 100 core molds are arranged in one middle frame.

[0015] Furthermore, the mold cavity of the core mold conforms to the composite material screw, including a first disc cavity, a second disc cavity, and a through hole arranged sequentially and connected. The first disc cavity is used to place the composite material disc portion of the screw preform, the second disc cavity is used to place the metal disc portion of the screw preform, and the through hole is used to place the threaded section of the screw preform and to position the screw preform. The screw preform of the present invention refers to a preform in which a screw body is embedded in a composite material layup and combined with a metal disc, and its composition and shape are basically consistent with the composite material screw after compression molding.

[0016] Furthermore, a gasket is provided at the bottom of the second disc cavity. The gasket can reduce the damage of the metal disc to the core mold while adjusting the product thickness, and at the same time prevent direct impact damage to the product when demolding.

[0017] Furthermore, the top of the mold cavity of the core mold is provided with an circumferential overflow groove, and the bottom of the mold cavity is provided with a cylindrical overflow groove, which is used to contain the resin overflowing when the mold is closed, to prevent the extruded resin from affecting the opening and closing of the mold and the product accuracy. At the same time, the cylindrical overflow groove is also used as a demolding channel for the product.

[0018] Furthermore, the outer edge of the upper mold protrusion forms a gap of a certain thickness between the mold and the core mold in the middle frame when the mold is closed. This facilitates resin flow and extrusion, and also allows the flash to be squeezed into the gap, preventing the upper mold and the middle frame from not being able to close completely due to the flash, thus avoiding the product thickness exceeding the tolerance due to the presence of flash.

[0019] Furthermore, the upper mold protrusion is also provided with micro protrusions, which are located in the middle part of the contact surface between the protrusion and the core mold cavity. These micro protrusions are used to form a conical recess on the back of the composite material disc during compression molding.

[0020] The present invention also provides a composite material screw produced using the above-mentioned mold, comprising a screw body, a metal disc, and a composite material disc; the screw body is made of metal and includes a columnar threaded section and a plurality of feet circumferentially distributed at the bottom of the threaded section; the composite material disc is formed by hot pressing and curing of a composite material layup assembly; the threaded section of the screw body passes through the metal disc, the metal disc is in contact with the composite material disc, and the feet of the screw body are sandwiched between the composite material layup assemblies.

[0021] Furthermore, the metal disc and the composite material disc are bonded together by molding, so that the composite material screw forms an integral structure, thereby improving the connection strength.

[0022] Furthermore, the metal disc has multiple elongated, waist-shaped protrusions evenly distributed around it, which helps to increase the rigidity of the metal disc, improve the tensile deformation resistance of the composite material screw, and thus improve the tensile breaking strength. These protrusions can be set to 3-8. The metal disc also has multiple overflow holes evenly distributed around it, and the composite material disc also has multiple overflow holes at corresponding positions to the metal disc. The overflow holes on the metal disc are used for drilling and positioning guidance of the overflow holes on the composite material disc, ensuring that the overflow holes on the metal disc and the composite material disc are aligned. The overflow holes on both the metal disc and the composite material disc are also used for venting and removing excess adhesive when the composite material disc is bonded to the connected component. The number of through holes can be set to 1-4.

[0023] Furthermore, the back of the composite material disc is also provided with a conical recessed structure, which is used to store adhesive in the adhesive layer of the composite material disc when it is bonded to the connected parts, so as to ensure the effective strength of the adhesive connection.

[0024] Furthermore, the screw body has a variable thickness base structure, with the base thickness gradually decreasing radially along the columnar thread section. This design ensures both the deformation strength and stiffness of the base under tensile load and achieves a weight reduction design for the metal screw body. The number of bases can be set to 3 to 8.

[0025] Furthermore, the composite material layup is a (+ / -45°) / (0°, 90°) quasi-isotropic layup formed by alternating layers of composite prepreg, which can ensure that it is subjected to balanced forces in all directions.

[0026] Preferably, the resin matrix of the composite prepreg is a thermoplastic resin or a thermosetting resin, and the reinforcing fiber is one or more hybrid reinforcing fibers selected from carbon fiber, glass fiber, aramid fiber or basalt fiber.

[0027] Furthermore, the ratio of the number of composite prepreg layers in the composite material layup groups distributed on the upper and lower sides of the screw body is (1-5):(1-5), preferably 2:1, so that the mechanical properties and structural quality are more balanced.

[0028] The present invention also provides a method for forming the above-mentioned composite material screw, which involves sequentially laying and assembling the composite material layup group, the metal disc, and the screw body to form a screw preform, placing the screw preform into the above-mentioned mold, and then forming the whole through a molding process.

[0029] Furthermore, the molding method includes the following steps:

[0030] The composite material layup group located on the upper side of the screw body and the composite material layup group located on the lower side of the screw body are laid according to the layup ratio and fiber direction, respectively.

[0031] Apply a protective layer to the surface of the metal disk;

[0032] The metal disc, screw body, and composite material layup are assembled into a screw preform.

[0033] Place the sealing ring at the root of the threaded section of the screw body, and place the preform into the core mold cavity of the mold.

[0034] The upper mold, middle frame and lower mold of the mold are fixed on the molding machine. The molding machine is operated to make the molds fit together and the molds are heated to the curing temperature of the composite material.

[0035] Turn on the molding machine, install the core mold in the middle frame, and then close the mold to cure;

[0036] After curing, the part is demolded, completing the molding process.

[0037] Furthermore, after the part is formed, the overflow holes on the composite material disc are machined according to the position of the overflow holes on the metal disc.

[0038] Furthermore, the protective layer of the metal disc comprises three layers: the first and second layers, closest to the metal disc, are adhesive-backed auxiliary materials, while the third layer, furthest from the metal disc, is a highly elastic material. At different stages of the molding process (including the initial resin flow and mold closing), the combined auxiliary material protective layers provide protection for the surface of the metal disc. During the initial resin flow stage, the adhesive-backed auxiliary material protects the metal disc; during the mold closing stage, the highly elastic material is compressed to fill the cavity for protection.

[0039] Furthermore, the composite material layup on the upper side of the base and the protective layer on the surface of the metal disc need to be drilled at the corresponding threaded sections.

[0040] Furthermore, the sealing ring includes two lower sealing rings and one upper sealing ring. The lower sealing rings are fitted side-by-side within the two pitches at the root of the threaded section, filling the pitch recesses. The upper sealing ring is fitted between the two lower sealing rings. This multi-sealing ring combination ensures that the upper sealing ring will not be cut during movement, effectively achieving thread sealing.

[0041] Furthermore, after curing, once the core mold has cooled to room temperature, the product is ejected from the mold cavity. After demolding, the edges of the product are cleaned with sandpaper to remove burrs and flash, as well as the protective layer of the metal disc and the sealing ring.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] The composite material screw of this invention adopts an integrated structure composed of a metal disc, a metal screw body, and a composite material disc. The connection between the screw and the connected part is achieved through adhesive bonding of the composite material disc and the connected part. This eliminates the need for drilling holes in the connected part, avoiding the difficulties of connection operations in confined spaces and the sealing problems in connections requiring sealing. Operation is simple and operating costs are low. Its integrated structure results in high tensile strength and low weight for the entire composite material screw product, making it suitable for applications with high weight reduction requirements.

[0044] The molding die of this invention features a detachable middle frame structure, allowing the upper and lower dies to be fixed on the molding press. Demolding only requires replacing the core mold within the middle frame, ensuring both dies operate at a relatively high temperature and reducing heat loss during demolding. Furthermore, the multi-cavity design of the single mold guarantees consistent part dimensions, thus improving work efficiency, reducing costs, and ensuring product dimensional accuracy and quality stability. The middle frame is secured by a demolding module and bolts, and the design of the demolding module and its oblong hole facilitates easier demolding of the middle frame.

[0045] The method for forming composite screws described in this invention combines a composite material layup, a metal disc, and a pre-embedded metal screw body into a screw preform, which is then formed into a single, net-size assembly through a molding process. This method effectively achieves the integrated forming of the metal disc, the metal screw body, and the composite material layup, resulting in high forming efficiency and facilitating mass production.

[0046] The molding method described in this invention, based on the molding characteristics of compression molding, uses a combination of auxiliary materials to prevent resin in the composite material from overflowing onto the surface of the metal disc, thus protecting the metal disc. It also employs a dynamic sealing method with multiple sealing rings to achieve thread sealing protection, eliminating the need for post-processing steps such as resin cleaning and improving the appearance quality of the product. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of a composite material screw provided in Embodiment 1 of the present invention;

[0048] Figure 2 This is a schematic diagram of the metal disc structure of the composite material screw described in Example 1;

[0049] Figure 3 This is a schematic diagram of the screw body of the composite material screw described in Example 1;

[0050] Figure 4 This is a side view of the screw body of the composite material screw described in Example 1;

[0051] Figure 5 This is a schematic diagram of the back structure of the composite material disc of the composite material screw described in Example 1;

[0052] Figure 6 This is a top-view perspective structural diagram of the composite material screw described in Example 1;

[0053] Figure 7 This is a rotated cross-sectional view of the composite material screw described in Example 1;

[0054] Figure 8 This is a schematic diagram of the composite material screw compression molding die described in Example 2;

[0055] Figure 9 This is a cross-sectional view of the mold for molding composite screws described in Example 2 (including the molded composite screws).

[0056] Figure 10 This is a cross-sectional view of the core mold of the composite material screw compression molding die described in Example 2;

[0057] Figure 11 This is a schematic diagram of the middle frame structure of the composite material screw compression molding die described in Example 2;

[0058] Figure 12 This is a schematic diagram of the upper mold of the composite material screw compression molding die described in Example 2;

[0059] Figure 13 This is a schematic diagram showing the state of the composite material screw compression molding die when it is opened, as described in Example 2.

[0060] Figure 14 This is a schematic diagram of the preform laying combination in the molding method described in Example 3.

[0061] In the diagram: 1-Upper mold, 101-Protrusion, 102-Micro protrusion, 2-Middle frame, 201-Concave hole, 202-Handle, 3-Lower mold, 4-Core mold, 401-First cavity, 402-Second cavity, 403-Through hole, 404-Circumferential overflow groove, 405-Cylindrical overflow groove, 5-Removable module, 501-Oval hole, 6-Composite material screw, 61-Composite material disc, 611-Conical recess, 612-Overflowing adhesive Hole, 613-First composite material layup, 614-Second composite material layup, 62-Metal disc, 621-Raised rib, 63-Screw body, 631-Threaded section, 632-Foot, 7-Washer, 8-Sealing ring, 81-Lower sealing ring, 82-Upper sealing ring, 9-Guide post, 10-Hex socket head cap screw, 11-Protective layer, 111-First protective layer, 112-Second protective layer, 113-Third protective layer. Detailed Implementation

[0062] Preferred embodiments of the present invention will now be described in more detail with reference to the accompanying drawings and specific examples.

[0063] Example 1

[0064] like Figure 1 The illustrated composite material screw includes a screw body 63, a metal disc 62, and a composite material disc 61. The screw body 63 is made of metal and includes a columnar threaded section 631 and several feet 632 evenly distributed circumferentially at the bottom of the threaded section 631. The composite material disc 61 is formed by hot pressing and curing a composite material layup, and the back of the composite material disc 61 is also provided with a conical recess 611. The threaded section 631 of the screw body 63 passes through the metal disc 62, and the metal disc 62 and the composite material disc 61 are bonded together by molding. The feet 632 of the screw body 63 are sandwiched between the composite material layups.

[0065] like Figure 2 As shown, in this embodiment, the metal disc 62 has six elongated, waist-shaped protruding ribs 621 evenly distributed around it in a circumferential direction. This helps to increase the rigidity of the metal disc 62, improve the tensile deformation resistance of the composite material screw, and thus improve the tensile breaking strength. The metal disc 62 also has three overflow holes 612 evenly distributed around it in a circumferential direction. These holes are used for drilling and positioning guidance of the overflow holes 612 on the composite material disc 61, ensuring that the overflow holes 612 on the metal disc 62 and the overflow holes 612 on the composite material disc 61 are in the same position. They can also be used to release excess adhesive when the composite material disc 61 is bonded to the connected parts.

[0066] like Figure 3 and Figure 4As shown, the screw body 63 in this embodiment has 6 feet 632, and the thickness of the feet 632 gradually decreases along the radial direction of the columnar thread section 631. This design not only ensures the deformation strength and stiffness of the feet 632 under tensile load, but also achieves the weight reduction design of the metal screw body 63.

[0067] like Figure 5 and Figure 6 As shown, the composite material disk 61 is also provided with three overflow holes 612 at the corresponding positions of the metal disk 62, which are used to vent and overflow adhesive when the composite material disk 61 is bonded to the connected parts. The conical recess 611 structure provided on the back of the composite material disk 61 is used to store adhesive in the adhesive layer when the composite material disk 61 is bonded to the connected parts, so as to ensure the effective strength of the bonded connection.

[0068] The rotatable cross-sectional view of the composite material screw described in this embodiment is as follows: Figure 7 As shown, the base 632 of the screw body 63 is sandwiched between the composite material ply groups. The composite material ply groups described in this embodiment are (+ / -45°) / (0°, 90°) quasi-isotropic ply groups formed by alternating layers of composite material prepreg, which can ensure that the force is balanced in all directions. In this embodiment, the ratio of the number of composite material prepreg layers in the composite material ply groups distributed on the upper and lower sides of the base 632 of the screw body 63 is 2:1, which is more conducive to achieving a balance between mechanical properties and structural quality.

[0069] The resin matrix of the composite prepreg described in this embodiment can be a thermoplastic resin or a thermosetting resin, and the reinforcing fiber can be one or more hybrid reinforcing fibers selected from carbon fiber, glass fiber, aramid fiber or basalt fiber.

[0070] Example 2

[0071] like Figure 8 The diagram illustrates a composite material screw compression molding die for the composite material screw described in Example 1. It includes an upper mold 1, a middle frame 2, and a lower mold 3. The upper mold 1 and lower mold 3 are respectively fixed to a molding machine by bolts. The middle frame 2 is positioned above the lower mold 3 by guide posts 9 and is connected to the upper mold 1 by a release plate 5 and hexagonal socket head cap screws 10. The middle frame 2 contains several detachable core molds 4, each containing a mold cavity conforming to the shape of the screw preform to be molded. The guide posts 9 are precision-grade straight guide posts.

[0072] Based on the analysis of the shape of the composite screw 6, the threaded section 631 is chosen to face downwards for compression molding. The mold cross-section when the mold is closed is as follows. Figure 9 As shown in the diagram, the left side represents the area without products, while the right side represents the area containing products. The structure of core mold 4 is as follows: Figure 10As shown, the mold cavity of the core mold 4 includes a first disc cavity 401 and a second disc cavity 402. The first disc cavity 401 is used to place the composite material disc 61 of the screw preform, and the second disc cavity 402 is used to place the metal disc 62 of the screw preform. A through hole 403 is drilled at the bottom to place the threaded section 631 of the screw preform for positioning the screw preform. A sealing ring 8 is also provided at the root of the threaded section 631 to prevent glue overflow.

[0073] In this embodiment, the top of the mold cavity of the core mold 4 is provided with a circumferential overflow groove 404, and the bottom is provided with four cylindrical overflow grooves 405. By setting the circumferential overflow groove 404 and the cylindrical overflow grooves 405, the extruded resin can be prevented from affecting the mold opening and closing and the product precision. The bottom of the second cavity 402 of the core mold 4 is provided with a hole for placing the shim 7. During operation, the shim 7 is first placed in the hole of the core mold 4, and then the screw preform with the metal disc 62 is placed on the shim 7. The shim 7 is designed for three purposes: 1. To prevent the metal disc 62 from directly contacting the core mold 4, which would damage the core mold 4 itself after repeated molding; 2. By adjusting the thickness of the shim 7, the thickness of the product itself can be effectively controlled to ensure that it meets the required tolerance range; 3. When the product is demolded, the demolding force acts directly on the shim 7, and the product is pushed out of the core mold 4 through the shim 7, preventing the concentrated demolding force from causing impact damage to the product.

[0074] The middle frame 2 described in this embodiment is as follows: Figure 11 As shown, there are 12 recessed holes 201 that fit with the outer wall of the core mold 4. The outer wall of the core mold 4 is engaged with the recessed holes 201 on the middle frame 2, which facilitates the disassembly of the core mold 4.

[0075] The upper mold 1 described in this embodiment is as follows: Figure 12 As shown, the upper mold 1 is provided with a plurality of protrusions 101, the position of each protrusion 101 corresponding to the position of the mold cavity of the core mold 4, so that when the upper mold 1 and the middle frame 2 are fitted together, each protrusion 101 is located in the corresponding mold cavity of the core mold 4. The outer edge of the protrusion 101 forms a certain small gap with the corresponding core mold 4 in the middle frame 2 to ensure smooth glue flow, and at the same time leave a certain space for possible flash, to prevent the upper mold 1 and the middle frame 2 from not being able to be pressed tightly together, resulting in the product thickness not being guaranteed.

[0076] In this embodiment, the protrusion 101 is further provided with a micro protrusion 102, which is located in the middle part of the contact surface between the protrusion 101 and the mold cavity of the core mold 4, such as... Figure 9 and Figure 12 As shown, the micro protrusion 102 is used to form a conical recess 611 on the back of the composite material disk 61 during compression molding.

[0077] In this embodiment, the guide post 9 is fixed to the lower mold 3. The guide post 9 passes through the middle frame 2 and the upper mold 1 but is not fixedly connected to them. The demolding module 5 is connected to the upper mold 1 above through a round hole and an internal hex bolt 10, and connected to the middle frame 2 below through a waist-shaped hole 501 and an internal hex bolt 10. The middle frame 2 is also provided with a handle 202 for easy demolding.

[0078] The mold described in this embodiment uses a twelve-cavity molding process. During use, the screw preform is placed into the core mold 4 inside the middle frame 2. The upper mold 1 and lower mold 3 are fixed to the molding machine with bolts. The middle frame 2 is placed according to the above structure and connected to the upper mold 1 and lower mold 3 respectively. The lower mold 3 of the molding machine moves upward, and after pressing to the closed state, molding is performed, followed by heat preservation and curing to form the composite material screw 6. During demolding, the lower mold 3 moves downward with the molding machine, and the middle frame 2 automatically separates from the lower mold 3. After the lower mold 3 moves downward, under the action of gravity, the middle frame 2 automatically separates from the upper mold 1 through the oblong hole 501. Only the internal hex bolts 10 inside the oblong hole 501 need to be removed to complete the demolding of the middle frame 2. After demolding, the part is reinserted into the core mold 4 to continue molding, ensuring that the overall temperature of the mold remains high, reducing molding waiting time, and improving work efficiency.

[0079] Example 3

[0080] A method for forming a composite material screw according to Embodiment 1 involves sequentially laying and assembling a composite material layup group, a metal disc 62, and a screw body 63 to form a screw preform, placing the screw preform into a mold as described in Embodiment 2, and then forming the whole through a molding process.

[0081] The above molding method specifically includes the following steps:

[0082] (1) Cut out composite prepreg sheets and lay the first composite prepreg group 613 and the second composite prepreg group 614 by rotating 45° from top to bottom in the order of fiber direction in the composite prepreg (according to the isotropic layup). The first composite prepreg group 613 includes multiple layers of composite prepreg and the second composite prepreg group 614 includes multiple layers of composite prepreg.

[0083] (2) Complete the cutting of the first composite material layup group 613 and the second composite material layup group 614.

[0084] (3) Complete the cutting of protective layer 11, including the first protective layer 111, the second protective layer 112 and the third protective layer 113.

[0085] (4) According to Figure 14 In the order shown, attach the protective layer 11 of the metal disk 62 to the metal disk 62, and mark the position of the overflow hole 612 on the metal disk 62 on the upper surface of the protective layer 11 for positioning during subsequent assembly.

[0086] (5) According to Figure 14 As shown, the threaded section 631 of the screw body 63 is passed through the first composite material layup 613 and then through the metal disc 62. The metal disc 62 is adjusted so that the overflow hole 612 on the metal disc 62 is positioned at the corresponding position of the gap in the base 632. Then, the second composite material layup 614 is placed below the base 632 and stacked together with the first composite material layup 613 above the base 632. The fiber direction of the composite prepreg at the bottom layer of the first composite material layup 613 intersects the fiber direction of the prepreg at the top layer of the second composite material layup 614 at a 45° angle, thus completing the screw prefabrication assembly.

[0087] (6) Place the sealing ring 8 on the root of the threaded section 631 of the screw body 63, and place the screw preform in the mold cavity of the core mold 4. The outer edge of the screw preform should be flush with the edge of the mold cavity. The sealing ring 8 includes two lower sealing rings 81 and one upper sealing ring 82. The lower sealing rings 81 are placed side by side in the two pitches at the root of the threaded section 631 to fill the pitch recess. The upper sealing ring 82 is placed between the two lower sealing rings.

[0088] (7) Fix the upper mold 1, middle frame 2 and lower mold 3 of the mold onto the molding machine, operate the molding machine to make the molds fit together, and heat the mold to the curing temperature of the composite material.

[0089] (8) Open the molding machine, install the core mold 4 in the middle frame 2, and then close the mold.

[0090] (9) Lock the mold and raise the temperature of the mold containing the core mold 4 to the curing temperature.

[0091] (10) Curing and molding are carried out in accordance with the standard curing system of the material.

[0092] (11) After curing, wait for the core mold 4 to cool to room temperature, then eject the product from the mold cavity to complete the demolding.

[0093] (12) Use sandpaper to remove the burrs and rough edges of the product, and remove the protective layer 11 and sealing ring 8 of the metal disc 62.

[0094] (13) Based on the position of the overflow hole 612 on the metal disk 62, use a carbide drill bit to drill a through hole on the composite material disk 61, which is the overflow hole 612, and clean the burrs on the edge of the hole.

[0095] In steps (3) and (4) above, the protective layer 11, during the initial flow stage of the composite material, is not fully bonded to the metal disk 62 due to the high-elasticity protective material of the third protective layer 113. It primarily protects the metal disk 62 by adhering to the adhesive auxiliary materials of the first and second protective layers 111 and resisting resin overflow from the composite material onto the surface of the metal disk 62. During the gradual mold closing process, the resin flow within the composite material generates strong penetrating force. To resist this force, the adhesive auxiliary materials are pushed apart from the surface of the metal disk 62. A second protective layer 112 is then applied over the adhesive auxiliary material of the first protective layer 111, providing reinforcement. The adhesive auxiliary materials of the first and second protective layers 111 and 112 are mainly responsible for protecting the metal disk 62 during the early stages of mold closing. Among the three auxiliary materials, the third protective layer 113 is a high-elasticity material that plays a major protective role. As the mold gradually closes, the high-elasticity material fills the cavity between the mold gasket 7 and the metal disk 62, completely blocking the resin in the composite material from penetrating into the surface of the metal disk 62, thus achieving a seal on the surface of the metal disk 62.

[0096] In step (6) above, a multi-seal ring combination is used for thread sealing. Thread sealing is a dynamic process. During the molding process, as the mold gradually closes, the threads at the root of the screw body 3 will be slowly exposed (the composite material layup of the screw preform is gradually thinned). The seal ring 8 needs to move to the root of the exposed threads to achieve resin sealing. A single seal ring cannot achieve effective sealing. When a single seal ring is placed on the screw, it will be pushed across two pitches. Half of the single seal ring is within the upper pitch and half is within the lower pitch. The threads are relatively sharp and will cut the single seal ring during the molding process, making it impossible to effectively achieve resin sealing of the threads. In this embodiment, two lower seal rings 81 are used to fill the adjacent pits of the threads, and then an upper seal ring 82 is placed between the two lower seal rings 81. With this multi-seal ring combination, the upper seal ring 82 will not be cut during the movement, and resin sealing of the threads can be effectively achieved.

[0097] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and principles of the described embodiments, and these modifications and variations should also be considered within the scope of protection of the present invention.

Claims

1. A composite material screw compression molding die, characterized in that, Includes the upper mold, middle frame, and lower mold. The upper and lower molds are arranged relative to each other; The middle frame is detachably connected to the upper mold and the lower mold respectively, and the middle frame is provided with a number of detachable core molds; The core mold has a cavity that conforms to the shape of the screw preform, and the upper mold has a number of protrusions, the position of each protrusion corresponding to the cavity of the core mold; when the upper mold is attached to the middle frame, each protrusion is located in the cavity of the corresponding core mold; the outer edge of the protrusion of the upper mold forms a gap of a set thickness between it and the core mold in the middle frame in the mold-closed state. The core mold cavity includes a first disc cavity, a second disc cavity, and a through hole for placing the threaded section of the screw preform, which are arranged and connected in sequence.

2. The composite material screw compression molding die according to claim 1, characterized in that, The top of the core mold cavity is provided with a circumferential overflow groove, and the bottom of the core mold cavity is provided with a cylindrical overflow groove.

3. A composite material screw, formed by a composite material screw compression molding die as described in claim 1 or 2, characterized in that, It includes a screw body, a metal disc, and a composite material disc; the screw body is made of metal and includes a columnar threaded section and several feet distributed circumferentially at the bottom of the threaded section; the composite material disc is formed by hot pressing and curing of a composite material layup; the threaded section of the screw body passes through the metal disc, the metal disc is attached to the composite material disc, and the feet of the screw body are placed between the composite material layups.

4. The composite material screw according to claim 3, characterized in that, The metal disk has multiple elongated waist-shaped protrusions evenly distributed around its circumference, and multiple overflow holes are also evenly distributed around its circumference. The composite material disk has multiple overflow holes at positions corresponding to those on the metal disk. The back of the composite material disk also has a conical recessed structure.

5. The composite material screw according to claim 3, characterized in that, The screw body has a variable thickness base, with the base thickness gradually decreasing radially along the columnar thread section.

6. The composite material screw according to claim 3, characterized in that, The composite material layup group is a (+ / -45°) / (0°, 90°) quasi-isotropic layup formed by alternating layers of composite prepreg.

7. The composite material screw according to claim 3, characterized in that, The ratio of the number of prepreg layers in the composite material layup group distributed on the upper and lower sides of the screw body is (1-5):(1-5).

8. A method for molding a composite material screw according to any one of claims 3-7, characterized in that, Includes the following steps: The composite material layup group located on the upper side of the screw body and the composite material layup group located on the lower side of the screw body are laid according to the layup ratio and fiber direction, respectively. Apply a protective layer to the surface of the metal disk; The metal disc, screw body, and composite material layup are assembled into a screw preform. Place the sealing ring at the root of the threaded section of the screw body, and place the preform into the core mold cavity of the mold. Install the mold onto the molding machine, and then close and solidify it. After curing, the part is demolded, completing the molding process.

9. The method for forming composite material screws according to claim 8, characterized in that, The protective layer of the metal disk consists of three layers: the first and second layers, which are close to the metal disk, are adhesive auxiliary materials, and the third layer, which is far from the metal disk, is a highly elastic material.

10. The method for forming composite material screws according to claim 8, characterized in that, The sealing ring includes two lower sealing rings and one upper sealing ring. The lower sealing rings are fitted side by side within two pitches at the root of the threaded section, and the upper sealing ring is fitted between the two lower sealing rings.

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