Vacuum infusion forming method for light-weight carbon fiber plate

Abstract

The invention relates to the technical field of composite material manufacturing, and discloses a light-weight carbon fiber plate vacuum infusion forming method which comprises matrix resin, a curing agent, a controllable phase change self-expanding pressing agent and a pressure response type gel triggering agent. The intelligent resin system is pre-arranged on a fiber pre-forming body and is sealed and vacuumized to form a sealed cavity, and then the controllable phase change self-expanding pressing agent is subjected to phase change gas production at a preset triggering temperature through programmed temperature rise, so that internal micro-positive pressure is formed in the cavity. The internal micro-positive pressure drives the resin to infiltrate the fibers, and activates the pressure response type gel triggering agent to initiate gel curing, and then high-temperature curing is completed. According to the method, through internal micro-positive pressure generated in situ, self-expanding, complete and uniform infiltration of the resin on fibers is achieved, the compaction effect can be continuously applied in the curing stage, the internal porosity and dry spot defects of a workpiece are remarkably reduced, and the mechanical property and the internal quality of a composite material plate are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite material manufacturing, in particular to a vacuum infusion forming method for lightweight carbon fiber plate. BACKGROUND

[0002] Carbon fiber reinforced resin matrix composite materials have been widely used in aerospace, rail transportation, new energy and other fields due to their light weight, high strength, high modulus and corrosion resistance. Vacuum infusion forming process is a mainstream low-cost manufacturing technology for preparing such composite materials, especially for preparing large-size and complex-structure parts. The basic process of the process includes: laying dry fiber preform in the mold, then sealing the whole system with a vacuum bag and vacuumizing, using the pressure difference between the inside and outside of the system to guide the liquid resin into and infiltrate the fiber preform, and finally heating and curing.

[0003] In the existing vacuum infusion forming process, the driving force of resin flow completely depends on the pressure difference between the external atmospheric pressure and the internal vacuum environment of the mold, and its theoretical upper limit is one standard atmospheric pressure. When applied to the manufacture of large-size or thick-section components, the resin needs to flow a long distance in a dense fiber network. At this time, the limited pressure difference is often not enough to completely overcome the flow resistance, especially when the resin viscosity gradually increases over time, which easily leads to the resin failing to completely penetrate all areas of the preform before gelation, thereby forming dry spot defects inside the parts.

[0004] In addition, during the curing stage when the resin changes from liquid to solid, chemical shrinkage occurs. At the same time, residual gas or resin curing by-products in the system that are not completely discharged may also form micro-bubbles. Under the action of only external atmospheric pressure, it is difficult to effectively suppress the internal stress caused by resin shrinkage and to completely discharge or crush these micro-bubbles. These factors together result in high porosity inside the final molded composite parts. Dry spots and high porosity, as typical manufacturing defects, can severely weaken the mechanical properties of the composite material, especially the interlaminar properties and fatigue life, limiting its application in high-performance structural parts. SUMMARY

[0005] In view of the shortcomings of the prior art, the present application provides a vacuum infusion forming method for lightweight carbon fiber plate, which solves the problem that the existing vacuum infusion process is difficult to achieve complete infiltration of the fiber preform and effectively suppress the curing shrinkage due to the limited driving pressure, thereby causing dry spots and high porosity inside the parts.

[0006] To achieve the above purpose, the present application is realized by the following technical scheme: the first aspect of the present application provides a vacuum infusion forming method for lightweight carbon fiber plate, which comprises the following steps: S1: preparing an intelligent resin system, which comprises a main resin, a curing agent, a controllable phase change-self-expanding pressure agent, and a pressure-responsive gel trigger; S2: laying a dry carbon fiber preform in a mold and prepositioning the intelligent resin system on the carbon fiber preform; S3: sealing the mold and the carbon fiber preform and vacuumizing, then isolating the system from the vacuum source to form a closed cavity; S4: programming the closed cavity to be heated to a preset trigger temperature, causing the controllable phase change-self-expanding pressure agent to undergo phase change and produce gas, forming an internal micro-positive pressure in the closed cavity; the internal micro-positive pressure drives the intelligent resin system to infiltrate the carbon fiber preform and causes the internal micro-positive pressure to reach the pressure activation threshold of the pressure-responsive gel trigger, thereby activating the pressure-responsive gel trigger to initiate the gelation of the intelligent resin system; then continue to heat to a preset curing temperature and keep the temperature to completely cure the intelligent resin system; S5: cooling and demolding to obtain a lightweight carbon fiber plate.

[0007] In some embodiments, the intelligent resin system comprises, by mass fraction: 100 parts of the main resin, 2.0-5.0 parts of the controllable phase change-self-expanding pressure agent, 0.5-2.0 parts of the pressure-responsive gel trigger, and 80-95 parts of the curing agent.

[0008] In some embodiments, the preset trigger temperature is 90-100℃, and the preset curing temperature is 145-155℃; the heating rate to the preset trigger temperature and the preset curing temperature is 1.0-3.0℃ / min.

[0009] In some embodiments, the temperature is kept at the preset curing temperature for 120-180 minutes.

[0010] In some embodiments, the controllable phase change-self-expanding pressure agent is a solid microparticle after surface coating treatment, the core substance of which is an azo compound, and the surface coating layer is a temperature-sensitive ethyl cellulose inhibition layer; the phase change trigger temperature range of the controllable phase change-self-expanding pressure agent is 85-95℃.

[0011] In some embodiments, the pressure-responsive gel trigger is a complex formed by a latent catalyst based on imidazole derivatives and a Lewis acid; the pressure activation threshold of the pressure-responsive gel trigger is 1.4-1.8 bar.

[0012] In some embodiments, the temperature is kept constant at the preset trigger temperature of 90-100℃ for 15-30 minutes.

[0013] In some embodiments, the main resin is a bisphenol A type epoxy resin, and the curing agent is methylhexahydrophthalic anhydride.

[0014] In some embodiments, the target vacuum degree in the vacuumizing in S3 is -0.09 MPa to -0.098 MPa.

[0015] In some embodiments, the way of pre-setting the intelligent resin system in S2 is to uniformly distribute the intelligent resin system on the surface of the carbon fiber preform through a multi-point array or a serpentine pipeline.

[0016] The present application provides a lightweight carbon fiber plate vacuum infusion molding method. It has the following beneficial effects: 1. The present application sets a controllable phase change self-expanding pressure agent in the intelligent resin system, which generates gas at the preset trigger temperature in situ, forming a uniform distribution of internal micro-positive pressure. This internal micro-positive pressure drives the resin to infiltrate the fiber from the microscale, effectively overcoming the resistance of traditional long-distance flow, achieving complete and uniform infiltration of the carbon fiber preform, and avoiding the generation of dry spot defects.

[0017] 2. The present application introduces a pressure-responsive gel trigger agent, establishing a direct linkage mechanism between the internal micro-positive pressure signal and the resin gel behavior. After the fiber is infiltrated by the internal micro-positive pressure, the pressure signal activates the gel trigger agent, ensuring that the resin system can immediately begin to gel after achieving the infiltration state, locking the infiltration structure and improving the stability and repeatability of the process.

[0018] 3. The internal micro-positive pressure generated by the controllable phase change-self-expanding pressure agent persists during the subsequent curing and holding stage, exerting a uniform compaction effect on the entire part. This persistent compaction effect effectively suppresses the microvoids caused by resin shrinkage during curing and helps to expel residual gas, thereby reducing the internal porosity of the final part and obtaining a dense composite structure. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0020] Embodiment: Embodiment 1 The present embodiment provides a preparation method of a lightweight carbon fiber plate, the specific steps are as follows: Preparation of intelligent resin system: Weigh out 100 parts by weight of bisphenol A type epoxy resin, 3.5 parts of controllable phase change self-expanding pressure agent, 1.3 parts of pressure-responsive gel triggering agent, and 88 parts of methylhexahydrophthalic anhydride curing agent. At 25°C, add the controllable phase change self-expanding pressure agent and the pressure-responsive gel triggering agent to the epoxy resin and mechanically stir for 25 minutes to disperse it evenly. Cool the mixture to below 20°C, add the methylhexahydrophthalic anhydride curing agent, and continue stirring for 12 minutes to obtain the smart resin system.

[0021] Lamination and sealing: Ten layers of T700 grade carbon fiber plain weave fabric are laid on a mold coated with a release agent to form a carbon fiber preform. The prepared smart resin system is pre-placed on the surface of the carbon fiber preform through a multi-point array. Then, the preform is sealed in a vacuum bag and evacuated to -0.095MPa before being isolated from the vacuum source.

[0022] Curing and molding: Place the sealed mold system in an oven and heat it according to the following procedure: The temperature was increased from room temperature to 95°C at a rate of 2.0°C / min and held at this temperature for 20 minutes.

[0023] Subsequently, the temperature was increased to 150°C at a rate of 2.0°C / min and held at this temperature for 150 minutes.

[0024] After curing, the temperature is reduced to below 60°C at a rate of 3.0°C / min.

[0025] Demolding: After the mold cools to room temperature, remove the vacuum bag and other auxiliary materials, and take out the formed lightweight carbon fiber sheet.

[0026] Example 2 This embodiment provides a method for preparing lightweight carbon fiber sheets, the specific steps of which are as follows: Preparation of intelligent resin system: Weigh out 100 parts by weight of bisphenol A type epoxy resin, 2.0 parts by weight of controllable phase change self-expanding pressure agent, 0.5 parts by weight of pressure-responsive gel trigger, and 80 parts by weight of methylhexahydrophthalic anhydride curing agent. At 20°C, add the controllable phase change self-expanding pressure agent and the pressure-responsive gel trigger to the epoxy resin and mechanically stir for 30 minutes to disperse it evenly. Cool the mixture to below 20°C, add the methylhexahydrophthalic anhydride curing agent, and continue stirring for 15 minutes to obtain the smart resin system.

[0027] Lamination and sealing: Eight layers of T700 grade carbon fiber plain weave fabric are laid on a mold coated with a release agent to form a carbon fiber preform. The smart resin system prepared in step 1 is pre-placed on the surface of the carbon fiber preform through a serpentine pipeline, then sealed in a vacuum bag, and evacuated to -0.09 MPa before isolating the system from the vacuum source.

[0028] Curing and molding: Place the sealed mold system in an oven and heat it according to the following procedure: The temperature was increased from room temperature to 90°C at a rate of 1.0°C / min and held at this temperature for 15 minutes.

[0029] Subsequently, the temperature was increased to 145°C at a rate of 1.0°C / min and held at this temperature for 120 minutes.

[0030] After curing, the temperature is reduced to below 60°C at a rate of 2.0°C / min.

[0031] Demolding: After the mold cools to room temperature, remove the vacuum bag and other auxiliary materials, and take out the formed lightweight carbon fiber sheet.

[0032] Example 3 This embodiment provides a method for preparing lightweight carbon fiber sheets, the specific steps of which are as follows: Preparation of intelligent resin system: Weigh out 100 parts by weight of bisphenol A type epoxy resin, 5.0 parts by weight of controllable phase change self-expanding pressure agent, 2.0 parts by weight of pressure-responsive gel triggering agent, and 95 parts by weight of methylhexahydrophthalic anhydride curing agent. At 20°C, add the controllable phase change self-expanding pressure agent and the pressure-responsive gel triggering agent to the epoxy resin and mechanically stir for 20 minutes to disperse it evenly. Cool the mixture to below 20°C, add the methylhexahydrophthalic anhydride curing agent, and continue stirring for 10 minutes to obtain the smart resin system.

[0033] Lamination and sealing: Twelve layers of T700 grade carbon fiber plain weave fabric are laid on a mold coated with a release agent to form a carbon fiber preform. The smart resin system prepared in step 1 is pre-placed on the surface of the carbon fiber preform using a multi-point array. The preform is then sealed in a vacuum bag and evacuated to -0.098 MPa before being isolated from the vacuum source.

[0034] Curing and molding: Place the sealed mold system in an oven and heat it according to the following procedure: The temperature was increased from room temperature to 100°C at a rate of 3.0°C / min and held at this temperature for 30 minutes.

[0035] Subsequently, the temperature was increased to 155°C at a rate of 3.0°C / min and held at this temperature for 180 minutes.

[0036] After curing, the temperature is reduced to below 60°C at a rate of 4.0°C / min.

[0037] Demolding: After the mold cools to room temperature, remove the vacuum bag and other auxiliary materials, and take out the formed lightweight carbon fiber sheet.

[0038] Comparative Example Comparative Example 1: Compared with Example 1, the difference is that no controllable phase change-self-expanding pressure agent is added when preparing the smart resin system, while the remaining component ratios, preparation methods and subsequent molding process steps are the same as in Example 1.

[0039] Comparative Example 2: Compared with Example 1, the difference is that no pressure-responsive gel triggering agent is added when preparing the smart resin system, while the remaining component ratios, preparation methods and subsequent molding process steps are the same as in Example 1.

[0040] Comparative Example 3: Compared with Example 1, the difference is that no controllable phase change-self-expanding pressure agent or pressure-responsive gel trigger is added when preparing the resin system. Instead, 100 parts of bisphenol A epoxy resin and 88 parts of methylhexahydrophthalic anhydride curing agent are mixed to prepare the resin system. The rest of the preparation methods and subsequent molding process steps are the same as in Example 1.

[0041] Comparative Example 4: Compared with Example 1, the difference is that the curing process parameters in step 3 are changed: the sealed mold system is directly heated from room temperature to 150°C at a rate of 2.0°C / min and held at this temperature for 150 minutes, eliminating the isothermal holding stage at 95°C. The remaining steps are the same as in Example 1.

[0042] Test Example 1: Comparative Test of Internal Quality and Microstructure of Board Material Experimental steps Appearance and internal defect inspection The carbon fiber sheet samples prepared in Examples 1-3 and Comparative Examples 1-4 were placed one by one on a high-strength, uniform backlight plate. In a darkroom environment, visual observation was performed from a direction perpendicular to the sheet surface, recording the presence of areas with uneven light transmission within the sheet. These areas were identified as internal defects such as dry spots, low-resin or high-resin areas. A qualitative description of the defects in each sample was provided.

[0043] Porosity test This test was performed in accordance with ASTM D3171 standard.

[0044] Sampling and weighing: Cut a 25mm×25mm sample from the center of each plate sample, and take 3 parallel samples. Weigh the initial mass of each sample using an electronic balance with an accuracy of 0.1mg.

[0045] Resin matrix digestion: The sample is placed in concentrated sulfuric acid and heated at 150°C until the resin matrix is ​​completely digested.

[0046] Fiber cleaning and weighing: Remove the remaining carbon fibers and clean them with hydrogen peroxide solution to remove residual resin, then rinse with deionized water until neutral. Dry the cleaned fibers in an oven at 110°C for 4 hours until constant weight, and then weigh them.

[0047] Calculation: Based on the known carbon fiber density and resin matrix density, as well as the measured initial mass of the sample and fiber mass, the porosity of the composite material is calculated using the following formula.

[0048] Micromorphological observation Sample preparation: Cut a 10mm × 10mm specimen from the center of each plate sample. Cold mount the specimen, and after the resin has cured, grind the specimen cross-section with sandpaper of different grits in sequence. Finally, mechanically polish until the cross-section is mirror-finished.

[0049] Observation: The polished sample was sputter-coated with gold and then placed in the sample chamber of a scanning electron microscope. Under the condition of accelerating voltage of 15kV, the micromorphology of the sample cross section was observed at magnification of 500x and 2000x, respectively. The wetting state of the fiber bundle, the interfacial bonding between the fiber and the matrix resin, and the presence of micropores were recorded.

[0050] The experimental data are shown in Table 1. Table 1. Internal quality test results of the sheet metal in each embodiment and comparative example. According to the test results in Table 1, no macroscopic internal defects were observed in the boards prepared in Examples 1, 2, and 3, and their porosity values ​​were all below 1.0%. In contrast, the boards prepared in Comparative Examples 1, 3, and 4 all exhibited obvious dry spots, with porosity values ​​exceeding 4.5%; the board prepared in Comparative Example 2 showed localized areas of low resin content, with a porosity value of 2.53%. These results indicate that the composite material boards prepared by the technical solution provided by this invention possess characteristics of low porosity and a dense internal structure.

[0051] In this technical solution, the controllable phase change-self-expanding pressure agent undergoes a phase change and generates gas when it reaches a preset trigger temperature, establishing a uniform internal micro-positive pressure throughout the sealed cavity. This internal micro-positive pressure provides an active, internally derived driving force for the resin-impregnated fiber preform. This driving force has a short operating distance, enabling the resin to fill the tiny gaps between fiber bundles at the microscale. Comparative Examples 1 and 3, lacking this pressure agent, rely solely on the limited pressure difference of the external vacuum, which cannot overcome the flow resistance of the resin in the fiber network, resulting in incomplete resin impregnation and ultimately the formation of dry spots and high porosity.

[0052] Furthermore, the pressure-responsive gel trigger in this technical solution is activated and initiates the gel reaction of the resin system after the internal micro-positive pressure reaches its pressure activation threshold. This mechanism ensures that the ideal wetting state is locked in place immediately after the resin has fully impregnated the fiber, preventing resin backflow or redistribution that may occur due to changes in resin viscosity during subsequent heating. Comparative Example 2, lacking this trigger, despite internal pressure-assisted wetting, could not achieve immediate fixation of the wetting state, resulting in the formation of local defects and micropores during curing, thus its porosity was higher than that of the example. The process conditions of Comparative Example 4 failed to provide the necessary isothermal platform for the controllable phase change-self-expanding pressure agent to complete the phase change, resulting in the inability to effectively establish internal micro-positive pressure, and its final result was similar to that of the case lacking this component.

[0053] Test Example 2: Comparison Test of Mechanical Properties Experimental steps (1) Tensile property test This test is performed in accordance with ASTM D3039 standard.

[0054] Specimen preparation: Tensile specimens were cut along the 0° direction of the carbon fibers from the plates prepared in Examples 1-3 and Comparative Examples 1-4. Five parallel specimens were prepared for each sample. The specimen size was 250 mm × 25 mm, and glass fiber reinforced plastic reinforcing sheets with a length of 50 mm were attached to both ends.

[0055] Testing: Tensile tests were performed using a universal testing machine. The loading speed was set to 2 mm / min. The maximum load and deformation of each specimen were recorded.

[0056] Calculation: Calculate the tensile strength and tensile modulus based on the test results.

[0057] Bending performance test: This test is performed in accordance with ASTM D790 standard.

[0058] Specimen preparation: Bending specimens were cut from the plates prepared in Examples 1-3 and Comparative Examples 1-4. Five parallel specimens were prepared for each sample. The specimen size was 100 mm × 15 mm.

[0059] Test: Three-point bending tests were performed using a universal testing machine. The span was set to 16 times the specimen thickness. The loading speed was set to 2 mm / min. The maximum load and mid-span deflection were recorded for each specimen.

[0060] Calculation: Calculate the bending strength and bending modulus based on the test results.

[0061] Interlaminar shear strength test: This test is performed in accordance with ASTM D2344 standard.

[0062] Specimen preparation: Short beam shear specimens were cut from the plates prepared in Examples 1-3 and Comparative Examples 1-4. Five parallel specimens were prepared for each sample. The specimen size was 20 mm × 10 mm.

[0063] Test: Short beam shear tests were performed using a universal testing machine. The support span was set to 4 times the specimen thickness. The loading rate was set to 1 mm / min. The maximum load on each specimen was recorded.

[0064] Calculation: Calculate the interlaminar shear strength based on the test results.

[0065] 2. Experimental data are shown in Table 2. Table 2. Test results of mechanical properties of the sheet metal in each embodiment and comparative example. According to the test results in Table 2, the carbon fiber sheets prepared in Examples 1, 2, and 3 have significantly higher mechanical properties than those prepared in Comparative Examples 1-4 in terms of tensile strength, tensile modulus, flexural strength, flexural modulus, and interlaminar shear strength.

[0066] In this technical solution, during the programmed heating process, the controllable phase change-self-expanding compressive agent decomposes and releases gas at a specific temperature, generating a uniform internal micro-positive pressure within the composite material system. This internal micro-positive pressure not only drives the resin to fully impregnate the fibers, eliminating dry spots, but also continuously applies compaction during resin curing, effectively reducing the porosity of the part. Pores are structural defects within composite materials, which can become stress concentration points, leading to crack initiation and propagation under load, thereby significantly reducing the material's mechanical properties. Therefore, the low porosity and structural density achieved through this internal micro-positive pressure mechanism are the foundation for the excellent mechanical properties of the sheet material in this embodiment.

[0067] Furthermore, the pressure-responsive gel initiator introduced in this technical solution immediately triggers resin gelation when the internal micro-positive pressure reaches the activation threshold. This timely initiation of the gelation process ensures that the resin begins to cure under optimal wetting conditions, avoiding uneven resin flow, fiber displacement, or pore reformation caused by delayed curing. Comparative Example 2, lacking this initiator, failed to quickly lock in the wetting state despite some internal pressure, resulting in mechanical properties lower than the examples. Comparative Examples 1, 3, and 4, failing to effectively establish internal micro-positive pressure or effectively utilize the pressure signal, exhibited severe internal defects (such as high porosity and dry spots), directly leading to a significant decrease in various mechanical performance indicators.

[0068] Test Example 3: Comparative Test of Dynamic Thermomechanical Properties Experimental steps This test aims to evaluate the glass transition temperature of composite sheet materials through dynamic thermomechanical analysis.

[0069] Sample preparation: Rectangular samples with dimensions of 60 mm × 12 mm × 2 mm were cut from the plates prepared in Examples 1-3 and Comparative Examples 1-4. Three parallel samples were prepared for each sample.

[0070] Testing: The test was conducted using a dynamic thermomechanical analyzer in three-point bending mode. The test parameters were set as follows: frequency 1 Hz, strain 0.1%, heating rate 3℃ / min, and test temperature range 30℃ to 200℃.

[0071] Data Analysis: Record the changes in the material's storage modulus (E'), loss modulus (E''), and loss factor with temperature during the testing process. The temperature corresponding to the peak value of the loss factor curve is taken as the glass transition temperature of the material.

[0072] The experimental data are shown in Table 3. Table 3. Test results of dynamic thermomechanical properties of the sheet metal in each embodiment and comparative example. According to the test results in Table 3, the glass transition temperature (Tg) of the plates prepared in Examples 1, 2, and 3 is above 151°C. In contrast, the glass transition temperature of the plates prepared in Comparative Examples 1-4 is below 149°C. Glass transition temperature is a key physical parameter characterizing the degree of cross-linking and curing of the resin matrix; a higher Tg value usually corresponds to a more complete curing reaction and a denser cross-linked network structure.

[0073] In this technical solution, the internal micro-positive pressure generated by the controllable phase change-self-expanding compressive agent persists throughout the curing process. This pressure not only compacts the fibers and resin but also eliminates the micropores that act as thermal barriers, thereby improving the heat conduction efficiency within the system during the curing stage, resulting in a more uniform and complete curing reaction of the resin matrix. Comparative Examples 1, 3, and 4, lacking effective internal pressure, suffer from numerous micropores that hinder uniform heat transfer, potentially leading to incomplete curing in localized areas. This results in a polymer network with lower crosslinking density, manifested as a lower glass transition temperature.

[0074] Furthermore, the pressure-responsive gel initiator in this technical solution is activated after the establishment of internal micro-positive pressure, enabling the resin system to rapidly and synchronously initiate gelation and crosslinking reactions after sufficient wetting. This efficient and uniform reaction initiation mechanism helps to form a polymer network with a complete structure and fewer defects. Although Comparative Example 2 has internal pressure, it lacks this initiator, and its curing reaction relies on a traditional, relatively slow thermal initiation process. The uniformity and efficiency of the reaction are not as good as those of the Example, so the integrity of the crosslinked network formed is slightly worse, and the glass transition temperature is correspondingly lower than that of the Example.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for vacuum casting of lightweight carbon fiber sheets, characterized in that, Includes the following steps: S1: Prepare a smart resin system, the smart resin system comprising a main resin, a curing agent, a controllable phase change self-expanding pressure-inducing agent, and a pressure-responsive gel triggering agent; S2: Lay the dried carbon fiber preform in the mold and pre-place the smart resin system on the carbon fiber preform; S3: Seal and evacuate the mold and the carbon fiber preform, and then isolate the system from the vacuum source to form a sealed cavity; S4: The sealed cavity is programmed to be heated to a preset trigger temperature, causing the controllable phase change-self-expanding pressure agent to undergo phase change and generate gas, forming an internal micro-positive pressure in the sealed cavity. The internal micro-positive pressure drives the smart resin system to wet the carbon fiber preform, and makes the internal micro-positive pressure reach the pressure activation threshold of the pressure-responsive gel trigger, thereby activating the pressure-responsive gel trigger to initiate the gelation of the smart resin system. Then continue heating to the preset curing temperature and hold at that temperature to allow the smart resin system to fully cure. S5: Cool down and demold to obtain lightweight carbon fiber sheet.

2. The method according to claim 1, characterized in that, The intelligent resin system comprises, by weight, 100 parts of the main resin, 2.0-5.0 parts of the controllable phase change-self-expanding pressure agent, 0.5-2.0 parts of the pressure-responsive gel trigger, and 80-95 parts of the curing agent.

3. The method according to claim 1, characterized in that, The preset trigger temperature is 90-100℃, and the preset curing temperature is 145-155℃; The heating rate to the preset trigger temperature and the heating rate to the preset curing temperature are both 1.0-3.0℃ / min.

4. The method according to claim 1, characterized in that, Hold at the preset curing temperature for 120-180 minutes.

5. The method according to claim 1, characterized in that, The controllable phase change self-expanding pressure agent is a solid microparticle with surface coating treatment. Its core substance is an azo compound, and its surface coating layer is a thermosensitive ethyl cellulose inhibition layer. The phase change triggering temperature range of the controllable phase change self-expanding pressure agent is 85-95℃.

6. The method according to claim 1, characterized in that, The pressure-responsive gel trigger is a complex formed by a latent catalyst based on an imidazole derivative and a Lewis acid, and the pressure activation threshold of the pressure-responsive gel trigger is 1.4-1.8 bar.

7. The method according to claim 3, characterized in that, The temperature is kept constant at the preset trigger temperature of 90-100℃ for 15-30 minutes.

8. The method according to claim 1, characterized in that, The main resin is bisphenol A type epoxy resin, and the curing agent is methylhexahydrophthalic anhydride.

9. The method according to claim 1, characterized in that, The target vacuum level for vacuuming in S3 is -0.09MPa to -0.098MPa.

10. The method according to claim 1, characterized in that, The method of pre-setting the smart resin system in S2 is as follows: the smart resin system is evenly distributed on the surface of the carbon fiber preform by means of a multi-point array or a serpentine pipeline.

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