A forming method of high-temperature-resistant polyimide composite grid reinforced structure

Abstract

The application discloses a forming method of a high-temperature-resistant polyimide composite grid-reinforced structure. The forming method adopts a two-step forming process, a polyimide composite prefabricated body is laid on an optimized grid-reinforced structure mold, small molecular byproducts are effectively discharged in an imidization reaction process by using the vacuum advantage of a hot pressing tank process, the flow of resin is promoted in a cross-linking and curing reaction stage by using the high-temperature and high-pressure characteristics of a mold pressing process, and the high-temperature-resistant polyimide composite grid-reinforced structure workpiece is prepared by combining the two forming processes. The application can effectively solve the internal defect problem in the process of preparing the high-temperature-resistant polyimide composite grid-reinforced structure.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite material molding technology, and in particular, it is a molding method for a high-temperature resistant polyimide composite material mesh reinforcement structure. Background Technology

[0002] With the rapid development of aerospace technology, lightweight and multifunctional integration is the future trend of advanced aerospace equipment. Currently, structural components of in-service aircraft equipment mainly rely on metals and resin-based composites. Traditional metal materials are no longer sufficient to meet the diverse application requirements of aerospace components, and existing resin-based composite material systems (based on epoxy resin and bismaleimide resin) are also ill-suited to the high-temperature heat radiation, impact, and vibration environments. Currently, high-temperature load-bearing structures mostly employ a combination of titanium alloys and high-temperature alloys. While titanium alloys have mature application technology in aerospace devices, high-temperature alloys remain difficult to process, have complex molding processes, and are expensive to manufacture. Especially in aircraft operating in extreme environments, there are strict requirements on the overall structural weight, which greatly limits the application of metal materials. Therefore, high-temperature resistant resin-based composite materials have attracted significant attention.

[0003] Polyimide composites possess excellent high-temperature resistance, radiation resistance, fatigue resistance, high specific strength and specific modulus, and advantages such as lightweight and designable stiffness. They have been widely used in components such as engine nozzle trimmers, radomes, bypass casings, and ultra-high-speed fan blades, significantly reducing component weight. Furthermore, polyimide composites serve as ideal high-temperature resistant structural materials. However, the high rigidity of the high-temperature resistant polyimide resin molecular chain structure leads to the release of small-molecule byproducts during curing. Additionally, the resin melt has a relatively high minimum viscosity, resulting in a narrow processing window. This makes the composite material prone to internal porosity defects, making polyimide composites less suitable for molding complex structures.

[0004] In particular, in the aerospace field, composite shells for aircraft primarily utilize skin-reinforced mesh structures as crucial load-bearing components. Existing research on polyimide composite parts mainly focuses on molding processes for simple, thin-walled structures, employing single molding methods (such as autoclave molding, compression molding, or resin transfer molding) to fabricate components. No reports have been found on polyimide composite molding processes for complex parts with skin-reinforced mesh structures. Autoclave molding offers advantages such as uniform and stable molding pressure and temperature, and the constant vacuum pressure maintained by the vacuum bag effectively removes byproducts generated during the polyimide resin reaction. To date, the vast majority of high-load-bearing composite parts in the aerospace field utilize autoclave processes. However, conventional autoclaves struggle to provide the necessary high temperatures and pressures, and high-temperature, high-pressure vacuum autoclaves are costly to manufacture (temperature > 300°C, pressure > 2.0 MPa), require extremely expensive auxiliary materials, and consume significant energy. Summary of the Invention

[0005] The purpose of this invention is to provide a molding method for a high-temperature resistant polyimide composite mesh reinforced structure. This method improves the molding quality of complex high-temperature resistant polyimide composite structural parts by using a two-step process of autoclave heat treatment and molding curing, as well as optimizing the mold structure design.

[0006] The technical solution to achieve the purpose of this invention is as follows:

[0007] A molding method for a high-temperature resistant polyimide composite mesh-reinforced structure, employing a two-step molding process, includes the following steps:

[0008] Step 1: Use a modular mold structure. Before use, clean the mold, wipe off the sealant and release agent, and then assemble it for use.

[0009] Step 2: Lay polyimide prepreg. The laying process is to alternately lay ring and longitudinal ribs. The ring rib joint area is partially broken according to the proportion requirements, while the longitudinal ribs are continuous. A total of six sets are laid. After each set is completed, an ultrasonic welding gun is used to make the joints so that the fibers at the joints are dispersed to the R-corner area of ​​the mold mesh ribs. At the same time, the ribs are pre-compacted using the vacuum bag method.

[0010] Step 3: After the entire reinforcing strip is laid, perform two heat treatments using an autoclave:

[0011] First heat treatment: After the polyimide composite rib prefabricated parts are laid out, release cloth, release film and breathable felt are placed on the mold in sequence to wrap the entire mold, and pressure-sensitive tape is used to attach it. Finally, a vacuum bag is wrapped on it and sealed with sealing tape for vacuum treatment.

[0012] Second heat treatment: Before the second heat treatment, assemble the four-sided blocks on the mold base, then repair the ribs, lay the polyimide composite skin, and finally cover it with a cover plate; then carry out the second heat treatment, which is the same as the first heat treatment.

[0013] Step 4: After the second heat treatment is completed, remove the mold from the bag, clean up the overflowing resin, and then put the mold into the molding machine for post-processing and curing.

[0014] The significant advantages of this invention compared to existing technologies are:

[0015] This invention can significantly improve the molding quality of high-temperature resistant polyimide composite skin mesh reinforcement structures and reduce internal defects in the skin, ribs, and node areas. Compared to a single molding process, it can effectively complete the molding and manufacturing of complex structural parts and effectively reduce manufacturing costs. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the mold structure design.

[0017] Figure 2 It is a numerical model exploded view of the skin mesh reinforced structure mold device.

[0018] Figure 3 Example 1 describes the preparation of a high-temperature resistant polyimide composite skin mesh reinforced structure using a two-step method, including physical samples, non-destructive testing images, and microstructure diagrams.

[0019] Figure 4 Example 2 describes the preparation of a high-temperature resistant polyimide composite skin mesh reinforced structure using a two-step method, including physical samples, non-destructive testing images, and microstructure diagrams.

[0020] Figure 5 Example 3 describes the preparation of a high-temperature resistant polyimide composite skin mesh reinforced structure using a two-step method, including physical samples, non-destructive testing images, and microstructure diagrams.

[0021] Figure 6 Comparative Example 1 shows a high-temperature resistant polyimide composite material skin mesh reinforced structure prepared by molding process, including physical samples, non-destructive testing images, and microstructure diagrams. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments. Unless otherwise specified, the methods described are conventional methods. Unless otherwise specified, the materials described are all available from publicly available commercial sources. The high-temperature resistant polyimide composite skin mesh reinforced structure prepared by the two-step method has its molding quality tested by ultrasonic C-scan and its internal microstructure observed by metallographic examination. A comparative example is provided for the preparation of the high-temperature resistant polyimide composite skin mesh reinforced structure using a traditional compression molding process (high-temperature and high-pressure autoclaves are expensive, auxiliary materials are imported, and no comparative test is available) to illustrate that the preparation method of the present invention has a significant effect on improving the molding quality and reducing costs of the high-temperature resistant polyimide composite skin mesh reinforced structure.

[0023] Example 1

[0024] The high-temperature resistant polyimide is a thermosetting polyimide with a temperature resistance rating greater than 350℃. The system is a blend of phenylacetylene-terminated polyimide, norbornene-terminated polyimide, acetylene-terminated polyimide, or a blend of two or more terminated polyimides.

[0025] The steps for preparing the high-temperature resistant polyimide composite skin mesh reinforced structure in this embodiment are as follows:

[0026] Step 1: Clean each mold with acetone, wipe off the sealant and release agent, install the mesh reinforcement module on the base with pins and tighten with bolts, and set aside for use after assembly.

[0027] Combination Figure 1 and Figure 2 The mold adopts a modular assembly structure, consisting of a base 4, a mesh reinforcement module 2, stop blocks 1, and a top cover plate 3. Four stop blocks 1 are fixed to the upper end of the base 4, forming a rectangular cavity. The mesh reinforcement module 2 is placed inside the rectangular cavity, and the top cover plate 3 is fixed to the four stop blocks 1. Before use, the mold should be cleaned, and after wiping off the sealing agent and release agent, it should be assembled and ready for use. The modular assembly structure of the mold is suitable for both autoclave molding and compression molding processes. The mold is made of heat-resistant steel that has undergone high-temperature heat treatment.

[0028] The mold is suitable for both autoclave molding and compression molding processes, and is made of heat-resistant steel that has undergone high-temperature heat treatment. The radius (R-angle) at the grid ribs of the mold (2-1 and 2-2) is increased, with a design value of 2–4.

[0029] Step 2: The self-made phenylacetylene-terminated polyimide prepreg is laid according to the laying process requirements. The laying process is to lay the circumferential and longitudinal ribs alternately. The circumferential rib joint area is partially broken according to the required ratio, while the longitudinal ribs are continuous. A total of six groups are laid. The ratio of broken ribs is preferably 25%. After each group is completed, the joint is made by ultrasonic welding gun to disperse the fibers at the joint to the R-corner area. At the same time, the ribs are pre-compacted by vacuum bag method, with a vacuum degree of not less than 920 mbr and a time of not less than 30 minutes.

[0030] Step 3: After the entire rib is laid, it is heat-treated twice using an autoclave.

[0031] (1) For the first heat treatment, after the polyimide composite rib prefabrication parts are laid out, release cloth, release film and breathable felt are placed on the mold to wrap the entire mold, and pressure-sensitive tape is used to attach it. Finally, a vacuum bag is wrapped around it and sealed with sealing tape. The vacuum valve is opened and the vacuum system is connected with a quick connector to evacuate the vacuum. After completion, the mold is placed in an autoclave for heat treatment. The heat treatment process conditions are as follows: the autoclave heat treatment process is to heat the mold from room temperature to 80°C and hold it for 60 min; then heat it to 120°C and hold it for 60 min; then heat it to 180°C and hold it for 60 min; after holding, the mold is cooled to room temperature and the mold is removed from the autoclave; when heating, the pressure is increased. The pressure inside the autoclave is 0.3 MPa, the heating / cooling rate is 1.0°C / min, and the pressurization rate is 0.01 MPa / min.

[0032] (2) Before the second heat treatment, assemble the four-sided blocks on the mold base, then repair the ribs. The ribs should protrude from the mold surface at a height of 0.5 mm. Then, lay the polyimide composite skin according to the process design. The skin laying process is [0 / 90 / 45-45 / 0 / 90 / 45 / 0 / 45 / 90 / 0-45 / 45 / 90 / 0]. Finally, cover the mold with a cover plate. After completing the above work, perform the second heat treatment. The vacuum bag process and heat treatment process conditions are consistent with those in (1).

[0033] Step 4: After the second heat treatment, the mold is completely unpacked, and the resin that overflowed during the heat treatment is cleaned up. Then, the mold is placed in a high-temperature, high-pressure molding press for post-treatment curing. The high-temperature molding curing process parameters are as follows: heat from room temperature to 200℃ and hold for 60 minutes; then heat to 260℃ and hold for 80 minutes; then heat to 320℃ and hold for 30 minutes, and pressurize at 5 MPa after the holding period; then heat to 350℃ and hold for 120 minutes; after the holding period, slowly cool to room temperature and open the mold, with a heating / cooling rate of 1℃ / min.

[0034] During the high-temperature molding process, when the temperature reaches 320℃, an venting operation is required, during which venting is performed 5 times, with an interval of 1 minute between each venting operation.

[0035] This embodiment employs a two-step method to prepare a high-temperature resistant polyimide composite skin mesh reinforced structural component. For details on its molding quality, please refer to [link to relevant documentation]. Figure 3 The test results showed that the internal quality of the non-destructive test had no obvious delamination, and the local area was slightly loose. The metallographic test showed no obvious delamination or cracks in the microstructure.

[0036] Example 2

[0037] The steps for preparing the high-temperature resistant polyimide composite skin mesh reinforced structure in this embodiment are as follows:

[0038] Step 1: Clean each mold with acetone, wipe off the sealant and release agent, install the mesh reinforcement module on the base with pins and tighten with bolts, and set aside for use after assembly.

[0039] Step 2: The self-made phenylacetylene-terminated polyimide prepreg is laid according to the laying process requirements. The laying process is to lay the circumferential and longitudinal ribs alternately. The circumferential rib joint area is partially broken according to the required ratio, while the longitudinal ribs are continuous. A total of six groups are laid. The ratio of broken ribs is preferably 30%. After each group is completed, the joint is made by ultrasonic welding gun to disperse the fibers at the joint to the R-corner area. At the same time, the ribs are pre-compacted by vacuum bag method, with a vacuum degree of not less than 920 mbr and a time of not less than 30 min.

[0040] Step 3: After the entire rib is laid, it is heat-treated twice using an autoclave.

[0041] (1) For the first heat treatment, after the polyimide composite rib prefabrication piece is laid out, release cloth, release film and breathable felt are placed on it to wrap the entire mold, and pressure-sensitive tape is used to seal it. Finally, a vacuum bag is wrapped around it and sealed with sealing tape. The vacuum valve is opened and the vacuum system is connected with a quick connector to evacuate the vacuum. After completion, the mold is placed in an autoclave for heat treatment. The heat treatment process conditions are as follows: the autoclave heat treatment process is to heat the mold from room temperature to 90°C and hold it for 45 min; then heat it to 140°C and hold it for 45 min; then heat it to 190°C and hold it for 45 min; after holding, the mold is cooled to room temperature and the mold is removed from the autoclave; when heating, the pressure is increased, the pressure inside the autoclave is 0.7 MPa, the heating / cooling rate is 2.0°C / min, and the pressurization rate is 0.02 MPa / min.

[0042] (2) Before the second heat treatment, assemble the blocks around the mold, then repair the ribs. The ribs should protrude from the mold surface at a height of 1.0 mm. Then, lay the polyimide composite skin according to the process design. The skin laying process is [0 / 90 / 45-45 / 0 / 90 / 45 / 0 / 45 / 90 / 0-45 / 45 / 90 / 0]. Finally, cover the mold with a top plate. After completing the above work, perform the second heat treatment. The vacuum bag process and heat treatment process conditions are consistent with those in (1).

[0043] Step 4: After the second heat treatment, the mold is completely unpacked, and the resin that overflowed during the heat treatment is cleaned up. Then, the mold is placed in a high-temperature, high-pressure molding press for post-treatment curing. The high-temperature molding curing process parameters are as follows: heat from room temperature to 210°C and hold for 45 minutes; then heat to 280°C and hold for 55 minutes; then heat to 330°C and hold for 20 minutes, and pressurize at 7 MPa after the holding period; then heat to 360°C and hold for 75 minutes; after the holding period, slowly cool to room temperature and open the mold. The heating / cooling rate is 1.5°C / min.

[0044] During the high-temperature molding process, when the temperature reaches 330°C, an venting operation is required, which involves venting 5 times with a 2-minute interval between each venting operation.

[0045] This embodiment employs a two-step method to prepare a high-temperature resistant polyimide composite skin mesh reinforced structural component. For details on its molding quality, please refer to [link to relevant documentation]. Figure 4 The test results showed that the internal quality of the non-destructive test had no obvious delamination, and the local area was slightly loose. The metallographic test showed no obvious delamination or cracks in the microstructure.

[0046] Furthermore, the preferred ratio of broken reinforcing bars in the mesh reinforcement is 30%.

[0047] Furthermore, the height of the rib repair protruding from the mold surface is preferably 1.0 mm.

[0048] Example 3

[0049] The steps for preparing the high-temperature resistant polyimide composite skin mesh reinforced structure in this embodiment are as follows:

[0050] Step 1: Clean each mold with acetone, wipe off the sealant and release agent, install the mesh reinforcement module on the base with pins and tighten with bolts, and set aside for use after assembly.

[0051] Step 2: The self-made phenylacetylene-terminated polyimide prepreg is laid according to the laying process requirements. The laying process is to lay the circumferential and longitudinal ribs alternately. The circumferential rib joint area is partially broken according to the required ratio, while the longitudinal ribs are continuous. A total of six groups are laid. The ratio of broken ribs is preferably 40%. After each group is completed, the joint is made by ultrasonic welding gun to disperse the fibers at the joint to the R-corner area. At the same time, the ribs are pre-compacted by vacuum bag method, with a vacuum degree of not less than 920 mbr and a time of not less than 30 minutes.

[0052] Step 3: After the entire rib is laid, it is heat-treated twice using an autoclave.

[0053] (1) For the first heat treatment, after the polyimide composite rib prefabrication parts are laid out, release cloth, release film and breathable felt are placed on the mold to wrap the entire mold, and pressure-sensitive tape is used to attach it. Finally, a vacuum bag is wrapped around it and sealed with sealing tape. The vacuum valve is opened and the vacuum system is connected with a quick connector to evacuate the vacuum. After completion, the mold is placed in an autoclave for heat treatment. The heat treatment process conditions are as follows: the autoclave heat treatment process is to heat the mold from room temperature to 100°C and hold it for 30 min; then heat it to 160°C and hold it for 30 min; then heat it to 200°C and hold it for 30 min; after holding, the mold is cooled to room temperature and the mold is removed from the autoclave; when heating, the pressure is increased, the pressure inside the autoclave is 1.0 MPa, the heating / cooling rate is 3.0°C / min, and the pressurization rate is 0.03 MPa / min.

[0054] (2) Before the second heat treatment, assemble the blocks around the mold, then repair the ribs. The ribs should protrude from the mold surface at a height of 1.2 mm. Then, lay the polyimide composite skin according to the process design. The skin laying process is [0 / 90 / 45-45 / 0 / 90 / 45 / 0 / 45 / 90 / 0-45 / 45 / 90 / 0]. Finally, cover the mold with a top plate. After completing the above work, perform the second heat treatment. The vacuum bag process and heat treatment process conditions are consistent with those in (1).

[0055] Step 4: After the second heat treatment, the mold is completely unpacked, and the resin that overflowed during the heat treatment is cleaned up. Then, the mold is placed in a high-temperature, high-pressure molding press for post-treatment curing. The high-temperature molding curing process parameters are as follows: heat from room temperature to 220°C and hold for 30 minutes; then heat to 300°C and hold for 30 minutes; then heat to 340°C and hold for 10 minutes, after which pressurization begins at a pressure of 10 MPa; then heat to 380°C and hold for 30 minutes; after the holding period, slowly cool to room temperature and open the mold. The heating / cooling rate is 2°C / min.

[0056] During the high-temperature molding process, when the temperature reaches 340℃, an venting operation is required, which involves venting 5 times with a 3-minute interval between each venting operation.

[0057] This embodiment employs a two-step method to prepare a high-temperature resistant polyimide composite skin mesh reinforced structural component. For details on its molding quality, please refer to [link to relevant documentation]. Figure 5 The test results showed that: the internal quality of non-destructive testing showed no obvious delamination, with slight porosity in some local areas; metallographic examination of the microstructure showed no obvious delamination, only slight cracks.

[0058] Comparative Example 1

[0059] In this comparative example, the preparation method for the high-temperature resistant polyimide composite skin mesh reinforcement structure adopts a traditional compression molding process, and the specific steps are as follows:

[0060] Step 1: Clean each mold with acetone, wipe off the sealant and release agent, install the mesh reinforcement module on the base with pins and tighten with bolts, and set aside for use after assembly.

[0061] Step 2: The self-made phenylacetylene-terminated polyimide prepreg is laid according to the laying process requirements. The laying process involves alternating circumferential and longitudinal reinforcing strips, with partial breaks in the circumferential reinforcing strip joint areas according to the required proportions, while the longitudinal reinforcing strips remain continuous. A total of six sets are laid, with the preferred breakage ratio of the reinforcing strips being 30%. After each set is completed, an ultrasonic welding gun is used to create joints, dispersing the fibers at the joints to the R-corner area. Simultaneously, the reinforcing strips are pre-compacted using a vacuum bag method, with a vacuum degree of not less than 920 mbr and a time of not less than 30 minutes. After the reinforcing strips are laid, they are repaired, with the height protruding from the mold preferably being 1.0 mm.

[0062] Step 3: Lay the polyimide composite skin according to the process layering design. The skin laying process is [0 / 90 / 45-45 / 0 / 90 / 45 / 0 / 45 / 90 / 0-45 / 45 / 90 / 0]. Finally, cover the mold with a top plate and place the mold into a high-temperature and high-pressure molding machine for curing and molding. The curing and molding process conditions are as follows: heat from room temperature to 80°C and hold for 60 min; then heat to 100°C and hold for 30 min; then heat to 120°C and hold for 60 min; then heat to 160°C and hold for 30 min; then heat to 200°C and hold for 60 min; then heat to 220°C and hold for 30 min; then heat to 260°C and hold for 30 min; then heat to 320°C and hold for 30 min, and after the holding period, pressurize to 5 MPa, and vent the air 5 times during the pressurization period, with an interval of 1 min between each venting; then heat to 380°C and hold for 120 min; after the holding period, slowly cool to room temperature and open the mold, with a heating / cooling rate of 1°C / min.

[0063] This comparative example uses a one-step compression molding process to prepare a high-temperature resistant polyimide composite skin mesh reinforced structure. For details of the molding quality, please refer to [link to relevant documentation]. Figure 6 The test results show that, compared with the two-step method, the appearance quality of the ribs and node areas formed by the one-step molding process is significantly worse due to load-bearing pressure, resulting in uneven pressure on the skin. Non-destructive testing also shows that the skin's molding quality is significantly poor, with obvious internal porosity and delamination. Metallographic observation of the microstructure reveals pores and microcracks, indicating that the traditional one-step molding process is difficult to control the molding quality of polyimide composite mesh reinforced structures.

[0064] In summary, the molding quality of the sample parts in the examples is significantly better than that of the traditional one-step compression molding process.

[0065] This invention proposes a two-step molding process and optimized mold design. The two-step molding process consists of an autoclave heat treatment process and a compression molding process. The autoclave utilizes continuous vacuum negative pressure to promptly remove small molecule gases generated during the imidization reaction of the polyimide resin. The high temperature and high pressure of the compression molding machine effectively promotes melt flow of the resin during the cross-linking reaction stage, reducing delamination or looseness defects between the resin and fibers. Simultaneously, the designed mold is suitable not only for autoclave molding but also for compression molding. The increased radius of the mold's radius (R-angle) facilitates fiber dispersion at the rib joints, preventing fiber bridging, and also allows byproducts from the resin imidization reaction at the rib joints to overflow.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the essence of the present technical solution without departing from the scope of the present technical solution shall still fall within the protection scope of the present technical solution.

Claims

1. A method for molding a high-temperature resistant polyimide composite mesh-reinforced structure, characterized in that, The two-step molding process includes the following steps: Step 1: Use a modular mold structure. Before use, clean the mold, wipe off the sealant and release agent, and then assemble it for use. Step 2: Lay polyimide prepreg. The laying process involves alternating circumferential and longitudinal reinforcing bars. The circumferential reinforcing bar nodes are partially broken according to the required proportions, while the longitudinal reinforcing bars are continuous. A total of six sets are laid. After each set is completed, an ultrasonic welding gun is used to make the nodes so that the fibers at the nodes are dispersed to the R-angle area of ​​the grid reinforcing bar in the mold. The R-angle design value at the grid reinforcing bar nodes is 2~4. At the same time, the reinforcing bars are pre-compacted using the vacuum bag method. The pre-compacting vacuum degree is not less than 920mbr, and the time is not less than 30min. Step 3: After the entire reinforcing strip is laid, perform two heat treatments using an autoclave: First heat treatment: After the polyimide composite rib prefabricated parts are laid out, release cloth, release film and breathable felt are placed on the mold in sequence to wrap the entire mold, and pressure-sensitive tape is used to attach it. Finally, a vacuum bag is wrapped on it and sealed with sealing tape for vacuum treatment. Second heat treatment: Before the second heat treatment, assemble the four-sided blocks on the mold base, then repair the ribs so that they protrude from the mold surface by 0.5~1.2mm, lay the polyimide composite skin, and finally put on the cover plate; carry out the second heat treatment, which is the same as the first heat treatment. Step 4: After the second heat treatment, remove the entire mold from the bag, clean up any overflowing resin, and then place the mold into a molding machine for post-treatment curing. The molding process parameters are as follows: heat from room temperature to 200~220℃ and hold for 30~60 min; then heat to 260~300℃ and hold for 30~80 min; then heat to 320~340℃ and hold for 10~30 min, and after the holding period, start pressurizing at a pressure of 5~10 MPa; then heat to 350~380℃ and hold for 30~120 min; after the holding period, cool to room temperature and open the mold. The heating and cooling rates are both 1~2℃ / min. When the temperature reaches 320~340℃, perform venting, venting 5 times during the process, with an interval of 1~3 min between each venting.

2. The molding method of the high-temperature resistant polyimide composite mesh reinforced structure according to claim 1, characterized in that, The polyimide is a thermosetting polyimide with a temperature resistance rating greater than 350°C. The system is a phenylacetylene-terminated polyimide, norbornene-terminated polyimide, acetylene-terminated polyimide, or a blend of two or more terminated polyimides.

3. The molding method of the high-temperature resistant polyimide composite mesh reinforced structure according to claim 1, characterized in that, The broken rebar ratio in the rebar laying process described in step 2 is 25%~40%.

4. The molding method of the high-temperature resistant polyimide composite mesh reinforced structure according to claim 1, characterized in that, The first heat treatment process conditions described in step 3 are as follows: heat up from room temperature to 80~100℃ and hold for 30~60 min; then heat up to 120~160℃ and hold for 30~60 min; then heat up to 180~200℃ and hold for 30~60 min. After holding, cool down to room temperature and remove the mold from the tank. When heating, pressurize the tank. The internal pressure is 0.3~1.0 MPa, the heating / cooling rate is 1.0~3.0℃ / min, and the pressurization rate is 0.01~0.03 MPa / min. The second heat treatment process conditions are the same as the first heat treatment process conditions.

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