Method for integrally forming a composite material hollow stent

Abstract

The application provides a preparation method of integrally forming a composite hollow support, a core mold rod is used as a backbone, a rubber layer is used as a skin to cover the periphery of the metal rod body of the core mold rod to form a forming core mold, the overall shape of the forming core mold is consistent with the shape of the composite hollow support to be prepared; a support skin is laid on the surface of the forming core mold to form a preform; the preform is placed in the internal cavity of a mold, is sent into a forming equipment to be solidified and formed, then the mold is removed, the metal rod constituting the core mold rod is disassembled and separated from the rubber layer, and finally the rubber layer in the channel is removed to obtain the hollow composite support. The forming process is simple in operation and good in repeatability, realizes the integrated forming of the design and manufacturing of the composite hollow support, and improves the production efficiency and forming performance.

Description

Technical Field

[0001] This invention belongs to the field of composite material processing and manufacturing technology, and in particular relates to a method and molding tooling for integrally molding a hollow, variable cross-section or even multiple-channel opening bracket made of composite material. Background Technology

[0002] Advanced composite materials are widely used in the aerospace field due to their excellent properties such as high specific strength, high specific modulus, excellent fatigue resistance and corrosion resistance, and good designability.

[0003] Some composite material components, especially hollow supports, need to be integrally cured and molded to meet the requirements of strength and lightweight. If separate connection technologies such as co-bonding, secondary bonding or mechanical connection are used, it is difficult for the final product to meet both the requirements of strength and lightweight at the same time.

[0004] For irregularly shaped hollow supports with variable cross-sections or even multiple openings, existing manufacturing methods mostly employ a modular connection approach. Individual composite material components are typically manufactured using an air-bag inflatable molding process. This involves laying a prepreg skin on a metal mold, applying pressure to the skin using an air compressor, and then performing processes such as thermosetting, demolding, and post-processing. However, air bag inflation can easily lead to problems such as slippage, tearing, wrinkling, and yarn trapping, and the quality of individually modular products also presents potential risks that are difficult to control. Summary of the Invention

[0005] In view of this, the present invention proposes a method for integrally molding a hollow scaffold with variable cross-section or even multiple pathways made of composite materials, specifically as follows:

[0006] A method for preparing a hollow composite material scaffold by integral molding, characterized in that it includes:

[0007] Step 1: Making the molding core mold: The molding core mold is composed of a core mold rod as the backbone, which is assembled and connected from at least one straight metal rod of equal diameter. A rubber layer is used to cover the outer periphery of the metal rod of the core mold rod. The overall shape of the molding core mold is consistent with the shape of the hollow support of the composite material to be prepared.

[0008] Step 2: Prefabrication: Thermosetting resin is used to impregnate fabric and fiber felt on the surface of the molding core mold to form a support skin and form a prefabricated body.

[0009] Step 3: Mold closing: Place the preform into the internal cavity enclosed by the mold. The shape of the internal cavity is consistent with the shape of the internal cavity of the mold used to make the core mold in Step 1. After closing and securing the mold, send it into the molding equipment to solidify and form.

[0010] Step 4: After curing and molding, first remove the mold, then disassemble the metal rods that make up the core mold rod and pull them out of the rubber layer. Finally, remove the rubber layer in the channel to obtain the hollow composite material bracket.

[0011] In step one, the mold for making the core mold consists of a metal forming female mold, a base, and a cover plate. The metal forming female mold creates an internal cavity that matches the shape of the hollow support of the composite material to be manufactured. The core mold rod is fixed in the internal cavity, and rubber is poured into the gap between the core mold rod and the internal cavity, thereby forming a core mold with the core mold rod as the backbone and a rubber layer covering the outer wall of the core mold rod.

[0012] When the hollow composite material support to be prepared is a variable cross-section straight segment, its internal channel is a single channel that can be passed through by a straight rod. Therefore, a single straight metal rod of equal diameter is selected as the core mold rod. An insert hole is opened on one end face of the metal rod. A positioning post matching the insert hole is fixed on the base. The two modules of the metal forming female mold have a through hole at one end for the positioning post to pass into the internal cavity. The two modules of the metal forming female mold have an inlet at the other end face. An inlet gap is formed between the inlet and the corresponding end of the metal rod fixed in the internal cavity. First, the insert hole at one end of the metal rod is nested with the guide post on the base. Then, the metal forming female mold is assembled so that the metal rod is fixed in the internal cavity of the metal forming female mold. Rubber is then injected from the inlet gap. The cover plate is then placed on top to completely seal the internal cavity. The mold is then tightened with bolts. After standing for 24 hours, the core mold is demolded.

[0013] The mandrel consists of a main rod and at least one branch rod that are intersected and fixed together. The main rod and the branch rod are straight metal rods of equal diameter. The end faces of the main rod are respectively opened with mounting holes. The main rod body is opened with a cross-shaped mounting groove corresponding to the position of the branch rod. A screw hole is opened in the center of the bottom of the cross-shaped mounting groove. One end of the branch rod is milled to form an arc-shaped mating groove and a cross-shaped mounting piece is welded to the mating groove. Then, a through hole is opened in the axis of the branch rod, and the through hole passes through the cross-shaped mounting piece. The cross-shaped mounting piece on the branch rod is inserted into the cross-shaped mounting groove on the main rod, and the mating groove fits against the surface of the main rod body. Then, a long internal hexagon bolt is passed through the through hole of the branch rod and screwed into the screw hole of the main rod, thereby assembling and fixing the main rod and the branch rod to form the mandrel.

[0014] Positioning pins matching the mounting holes at both ends of the main rod are fixed on the base and cover plate respectively. The internal cavity of the metal forming female mold is used to accommodate the main rod of the core mold rod. The two ends of the main cavity channel of the core mold rod pass through the metal forming female mold respectively. The through-hole at one end is for the positioning pin to pass through, and the through-hole at the other end serves as the injection port. An injection gap is formed between the injection port and the corresponding end of the main rod fixed in the internal cavity channel. First, the mounting hole at one end of the core mold rod is nested with the guide pin welded on the base. Then, the metal forming female mold is assembled so that the core mold rod is fixed in the internal cavity of the metal forming female mold. Rubber is then injected from the injection gap. The cover plate is then placed on top to seal the injection port and completely seal the internal cavity. The core mold is then tightened with bolts. After standing for 24 hours, the core mold is demolded to obtain the corresponding molded core mold.

[0015] The radius of the arc of the branch rod's mating groove is equal to the radius of the main rod, and the surface of the mating groove is in close contact with the surface of the main rod.

[0016] The vulcanization temperature of the rubber used is 150-200℃, the pressure is 0.3-0.6MPa, the vulcanization time is 1-3h, and the wall thickness of the rubber layer is 1-5mm.

[0017] Step two requires that both the inner and outer layers of the support be made of fabric. The fabric used must be at least one of carbon fiber, glass fiber, or aramid, and the fiber mat must be at least one of chopped glass fiber mat or carbon fiber mat.

[0018] In step two, the first layer of dressing laid on the molding core is impregnated carbon fiber woven fabric, and the second layer is fiber felt. After each combination of these two layers is laid, it is wrapped with a release film, placed in a vacuum bag, and pre-compacted for 3 minutes. After the above four cycles are performed, the last layer of dressing is impregnated carbon fiber woven fabric, and then pre-compacted again to form a preform with a support skin laid on the molding core.

[0019] The mold used to make the core mold in step one is the same mold used in step three.

[0020] The molding process of this invention is simple to operate and has good repeatability, realizing integrated molding from design to manufacturing of composite hollow supports, thus improving production efficiency. The molding core mold surface is made of rubber, which makes full use of the elasticity of this flexible material, so that the molding pressure is evenly transmitted to the support skin, which can significantly reduce the probability of air leakage during production and facilitate demolding. The shape of the core mold is consistent with the product configuration, avoiding the occurrence of yarn trapping, making the inner surface of the support smooth and wrinkle-free, the support thickness uniform, and improving the molding performance of the product. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0022] Figure 1 This is an exploded view of the molding tooling in Example 1;

[0023] Figure 2 This is a schematic diagram of the mold closing process in Example 1;

[0024] Figure 3 This is a schematic diagram of the molding core mold in Example 1;

[0025] Figure 4 This is an exploded view of the molding tooling in Example 2;

[0026] Figure 5 An exploded view of the connection structure between the main rod and the branch rod;

[0027] Figure 6 This is an exploded view of the molding tooling in Example 3;

[0028] Figure 7 This is a schematic diagram of the molding core mold in Example 3;

[0029] Figure 8 This is a schematic diagram of the variable cross-section four-way composite hollow support in Example 3. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] The molding tooling used in this invention includes a mold and a core mold rod;

[0033] The molding core mold is made by using molding tooling. Specifically, the mold has an internal cavity that matches the shape of the hollow support of the composite material to be manufactured. The core mold rod is fixed in the internal cavity, and rubber is poured into the gap between the core mold rod and the internal cavity, thus forming a molding core mold with the core mold rod as the backbone and a rubber layer covering the outer wall of the core mold rod.

[0034] The mold of the present invention consists of a metal forming female mold, a base and a cover plate, and the internal cavity is mainly enclosed by the metal forming female mold.

[0035] The following are examples of the fabrication of molding cores for three different configurations of composite hollow supports:

[0036] Example 1: A molding mandrel for a composite hollow support with a variable cross-section straight segment.

[0037] like Figure 1 As shown, the metal forming female mold consists of two modules 11 and 12. The shape of the internal cavity 6 formed by the splicing of modules 11 and 12 is consistent with the outer shape of the hollow support of the composite material to be prepared.

[0038] The mandrel is determined according to the configuration of the hollow composite material support to be prepared, that is, the mandrel matches the internal channel structure of the hollow composite material support. In this embodiment, the hollow composite material support is a variable cross-section straight segment type, and its internal channel is a single channel that can be passed through by a straight rod. Therefore, a single straight metal rod 2 of equal diameter is selected as the mandrel. An insert hole 20 is opened on one end face of the metal rod 2. A positioning post 5 matching the insert hole 20 is fixed on the base 3. The two modules of the metal forming female mold have a through hole 62 at one end for the positioning post 5 to pass into the internal cavity 6. The two modules of the metal forming female mold have an inlet 61 at the other end face. Figure 2 As shown in (A), an injection gap is formed between the injection inlet 61 and the corresponding end of the metal rod 2 fixed inside the internal cavity 6, so that rubber can be injected into the gap between the internal cavity and the metal rod 2 through this injection gap. During assembly, [the following is done]... Figure 1 and Figure 2 As shown, first, the mounting hole 20 at one end of the metal rod 2 is nested with the guide post 5 welded to the base 3. Then, modules 11 and 12 are assembled, so that the metal rod 2 is fixed in the internal cavity 6 of the metal forming die. Modules 11 and 12 are fixed together using hexagonal socket head cap screws. Then, rubber is injected through the injection gap between the injection inlet 61 and the metal rod 2. Finally, the cover plate 4 is placed on to completely seal the internal cavity 6 and tightened with bolts. Figure 3 As shown in (B); the molding core obtained after demolding after standing for 24 hours is as follows. Figure 3 As shown, the core mold rod (metal rod 2) serves as the backbone, and the rubber layer 7 acts as the outer skin covering the outer periphery of the core mold rod. At this time, the shape of the rubber layer of the molded core mold is consistent with the shape of the variable cross-section straight segment composite hollow support to be prepared.

[0039] Example 2: Molding mandrel for a composite hollow support with a fixed cross-section tee:

[0040] like Figure 4 As shown, the metal forming female mold consists of two modules 11a and 12a. The shape of the internal cavity 6a formed by the splicing of modules 11a and 12a is consistent with the external shape of the hollow support of the composite material to be prepared.

[0041] Based on the shape of the hollow support of this type of composite material, the core mold rod is composed of two straight metal rods of equal diameter, 2a and 2b, which are fixedly connected together.

[0042] For details, see Figure 5 As shown, one metal rod 2a is the main rod, and the other metal rod 2b is the branch rod. Mounting holes 20a are respectively opened at both ends of the main rod 2a. A cross-shaped mounting groove 22 is opened in the middle of the main rod 2a, and a threaded hole 220 is opened at the center of the bottom of the mounting groove 22. One end of the branch rod 2b is milled to form an arc-shaped mating groove 23, and a cross-shaped mounting piece 24 is welded to the mating groove 23. A mounting through hole 240 for a long internal hexagon bolt 25 is opened at the axis of the branch rod 2b, and the mounting through hole 240 passes through the cross-shaped mounting piece 24. The cross-shaped mounting piece 24 on the branch rod 2b is inserted into the mounting groove 22 on the main rod 2a, and the mating groove 23 fits against the surface of the main rod 24. Then, the long internal hexagon bolt 25 passes through the mounting through hole 240 of the branch rod 2b and is threaded into the threaded hole 220 of the main rod 24, thereby assembling and fixing the main rod and the branch rod into a fixed assembly. Figure 4 The mandrel shown is a core mold rod. This structure is convenient for assembly and disassembly, and allows for easy removal of the branch rods and main rods from the rubber layer.

[0043] Preferably, the radius of the arc-shaped mating groove 23 is equal to the radius of the main rod 2a, so that the surface of the mating groove can fit tightly with the surface of the main rod 24, and fit as seamlessly as possible, so as to prevent rubber from seeping into the fitting gap.

[0044] like Figure 4As shown, a positioning post 5a matching the mounting hole 20a at one end of the main rod is fixed on the base 3a, and a positioning post 5b matching the mounting hole at the other end of the main rod can also be fixed on the cover plate 4a to enhance the overall stability of the core mold rod. The internal cavity 6a of the metal forming female mold is used to accommodate the main cavity channel of the core mold rod 2a. Both ends of the main cavity channel penetrate the metal forming female mold. The through-hole at one end serves as a through hole 62a for the positioning post 5a to enter the internal cavity 6, and the through-hole at the other end serves as a filling inlet 61a. A filling gap is formed between the filling inlet 61a and the corresponding end of the main rod 2a fixed in the main cavity channel of the internal cavity 6a, so that rubber can be filled into the gap between the internal cavity and the core mold rod through this filling gap. During assembly, the insert hole 20 at one end of the main rod 2a of the core mold rod is first nested with the guide post 5a welded on the base 3a. Then, modules 11a and 12a are assembled to fix the core mold rod in the internal cavity 6a of the metal forming female mold. Modules 11a and 12a are fixed together with hexagonal socket head cap screws. Rubber is then injected through the injection gap between the injection inlet 61a and the main rod 2a. The cover plate 4a is then placed on top to completely seal the internal cavity 6a and is tightened with bolts. After standing for 24 hours, the core mold is demolded to obtain the corresponding required forming core mold (not shown in the figure). That is, the core mold rod, which is composed of the main rod and the branch rod, is the backbone, and the rubber layer is used as the skin to cover the outer wall of the core mold rod.

[0045] Example 3: A molding mandrel for a composite hollow support with a variable cross-section four-way type:

[0046] like Figure 6 As shown, the metal forming female mold consists of three modules 11b, 12b, and 13b. The internal cavity shape formed by assembling modules 11b, 12b, and 13b is similar to the shape of the metal to be formed. Figure 8 The hollow support structure of the composite material shown has the same external shape.

[0047] Based on the shape of the hollow support of this type of composite material, the core mold rod is composed of three straight metal rods of equal diameter, 2a', 2b' and 2c', which are fixed together. It should be noted that "equal diameter" here means that the same metal rod has the same diameter along its axial direction, not that the three metal rods have the same diameter. The diameter of each metal rod is selected according to the channel size corresponding to the branch it supports. Of course, it is not impossible for the three metal rods to have the same diameter.

[0048] Specifically, one metal rod 2a' is the main rod, and the other two metal rods 2b' and 2c' are branch rods; mounting holes 20b are respectively opened on the end faces of the main rod 2a', and the main rod and the two branch rods are assembled and fixed together. Figure 6 The assembly structure of the core mold rod, main rod, and branch rod shown is the same as in Embodiment 2, and will not be described again here.

[0049] A positioning post 5a' matching the fitting hole 20b at one end of the main rod is fixed on the base 3b. A positioning post 5b' matching the fitting hole at the other end of the main rod can also be fixed on the cover plate 4b to enhance the overall stability of the core mold rod. The two ends of the main cavity channel of the metal forming female mold, which is used to accommodate the main rod 2a' of the core mold rod, respectively penetrate the metal forming female mold. The through-hole at one end serves as a through hole for the positioning post 5a' to enter the internal cavity 6, and the through-hole at the other end serves as a filling port. A filling gap is formed between the filling port and the corresponding end of the main rod 2a' fixed in the main cavity channel of the internal cavity, so that rubber can be filled into the gap between the internal cavity and the core mold rod through the filling gap. During assembly, first nest the insert hole 20b at one end of the main rod 2a' of the core mold rod with the guide post welded to the base 3b. Then assemble the three modules 11b, 12b, and 13b to fix the core mold rod inside the internal cavity of the metal forming female mold. Use hexagonal socket head cap screws to fix the three modules. Then inject rubber through the injection gap between the injection inlet and the main rod. Finally, cover the cover plate 4b to completely seal the internal cavity and tighten it with bolts. After standing for 24 hours, demold to obtain the corresponding required forming core mold (e.g., Figure 7 As shown in the figure, the core mold rod, which is composed of the main rod and the branch rod, serves as the backbone, and the rubber layer 7 acts as the outer skin covering the outer wall of the core mold rod.

[0050] The following describes the preparation of such... Figure 8 Taking the variable cross-section four-way composite hollow support shown as an example, the specific preparation method is as follows:

[0051] according to Figure 8 The bracket shown is manufactured using machining processes such as... Figure 6 The forming fixture shown; manufactured according to the method described in Embodiment 3 above. Figure 7 The molding core mold is shown. The manufacturing process parameters for the rubber layer are: vulcanization temperature 150-200℃, pressure 0.3-0.6MPa, and vulcanization time 1-3h.

[0052] Prepare the main and auxiliary materials required for bracket manufacturing; clean all molds and apply release agent; then impregnate carbon fiber woven fabric and carbon fiber felt with thermosetting resin. The first layer of dressing laid on the molding core mold 8 is the impregnated carbon fiber woven fabric, and the second layer is fiber felt. After every two layers, wrap with release film and place in a vacuum bag for pre-compactment for 3 minutes. After performing the above four cycles, the last layer of dressing is the impregnated carbon fiber woven fabric, and then pre-compactment is performed again.

[0053] After the layup is complete, the laid-up molding core 8 is inserted into the internal cavity jointly enclosed by the metal molding female mold, the base, and the cover plate. This entire assembly is then placed in the molding equipment. After molding, the cover plate, base, and metal molding female mold are disassembled in sequence. Then, the two branch rods are disconnected from the main rod, and the main rod and branch rods are pulled out from the rubber layer of the molding core 8. Finally, the rubber layer in the support channel is removed (the rubber layer needs to be broken into pieces so that it can be removed from the support channel openings a, b, and c), resulting in the following... Figure 8 The image shows a one-piece molded composite hollow support.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a hollow composite material scaffold by integral molding, characterized in that, include: Step 1: Making the molding core mold: The molding core mold is composed of a core mold rod as the backbone, which is assembled and connected from at least one straight metal rod of equal diameter. A rubber layer is used to cover the outer periphery of the metal rod of the core mold rod. The overall shape of the molding core mold is consistent with the shape of the hollow support of the composite material to be prepared. Step 2: Fabrication of the preform: A support skin is laid on the surface of the molding core mold to form the preform; Step 3: Mold closing: Place the preform into the internal cavity enclosed by the mold. The shape of the internal cavity is consistent with the shape of the internal cavity of the mold used to make the core mold in Step 1. After closing and securing the mold, send it into the molding equipment to solidify and form. Step 4: After curing and molding, first remove the mold, then disassemble the metal rods that make up the core mold rod and pull them out of the rubber layer, and finally remove the rubber layer in the channel to obtain the hollow composite material bracket. In step one, the mold for making the core mold consists of a metal forming female mold, a base and a cover plate. The metal forming female mold encloses an internal cavity that matches the shape of the hollow support of the composite material to be manufactured. The core mold rod is fixed in the internal cavity. Rubber is poured into the gap between the core mold rod and the internal cavity, thereby forming a core mold with the core mold rod as the backbone and a rubber layer covering the outer wall of the core mold rod. The mandrel consists of a main rod and at least one branch rod that are intersected and fixed together. The main rod and the branch rod are straight metal rods of equal diameter. The end faces of the main rod are respectively opened with mounting holes. The main rod body is opened with a cross-shaped mounting groove corresponding to the position of the branch rod. A screw hole is opened in the center of the bottom of the cross-shaped mounting groove. One end of the branch rod is milled to form an arc-shaped mating groove and a cross-shaped mounting piece is welded to the mating groove. Then, a through hole is opened in the axis of the branch rod, and the through hole passes through the cross-shaped mounting piece. The cross-shaped mounting piece on the branch rod is inserted into the cross-shaped mounting groove on the main rod, and the mating groove fits against the surface of the main rod body. Then, a long internal hexagon bolt is passed through the through hole of the branch rod and screwed into the screw hole of the main rod, thereby assembling and fixing the main rod and the branch rod to form the mandrel. Positioning pins matching the mounting holes at both ends of the main rod are fixed on the base and cover plate respectively. The internal cavity of the metal forming female mold is used to accommodate the main rod of the core mold rod. The two ends of the main cavity channel of the core mold rod pass through the metal forming female mold respectively. The through-hole at one end is for the positioning pin to pass through, and the through-hole at the other end serves as the injection port. An injection gap is formed between the injection port and the corresponding end of the main rod fixed in the internal cavity channel. First, the mounting hole at one end of the core mold rod is nested with the guide pin welded on the base. Then, the metal forming female mold is assembled so that the core mold rod is fixed in the internal cavity of the metal forming female mold. Rubber is then injected from the injection gap. The cover plate is then placed on top to seal the injection port and completely seal the internal cavity. The core mold is then tightened with bolts. After standing for 24 hours, the core mold is demolded to obtain the corresponding molded core mold.

2. The method for preparing a hollow composite material scaffold integrally molded according to claim 1, characterized in that, The radius of the arc of the branch rod's mating groove is equal to the radius of the main rod, and the surface of the mating groove is in close contact with the surface of the main rod.

3. The method for preparing a hollow composite material scaffold integrally molded according to claim 1, characterized in that, The vulcanization temperature of the rubber used is 150-200℃, the pressure is 0.3-0.6MPa, the vulcanization time is 1-3h, and the wall thickness of the rubber layer is 1-5mm.

4. The method for preparing a hollow composite material scaffold integrally molded according to claim 1, characterized in that, Step two requires that both the inner and outer layers of the support be made of fabric. The fabric used must be at least one of carbon fiber, glass fiber, or aramid, and the fiber mat must be at least one of chopped glass fiber mat or carbon fiber mat.

5. The method for preparing a hollow composite material scaffold integrally molded according to claim 1, characterized in that, In step two, the first layer of dressing laid on the molding core is impregnated carbon fiber woven fabric, and the second layer is fiber felt. After each combination of these two layers is laid, it is wrapped with a release film and placed in a vacuum bag for pre-compacting for 3 minutes. After the above four cycles are performed, the last layer of dressing is impregnated carbon fiber woven fabric, and then pre-compacting is performed again to form a preform.

6. The method for preparing a hollow composite material scaffold integrally molded according to claim 1, characterized in that, The mold used to make the core mold in step one is the same mold used in step three.

Images