Lightweight heat-insulating integrated protective cover plate and preparation method thereof

Abstract

The application provides a light heat-insulating integrated protective cover plate, and relates to the field of protective cover plates.The light heat-insulating integrated protective cover plate comprises a high-density bearing layer (1), a low-density heat-insulating layer (2) and a high-density anti-ablation layer (3), the high-density bearing layer (1) is located on the side close to the passenger cabin, modified carbon fiber cloth is used as the reinforcing fiber, and phenolic-polyimide dynamic crosslinking resin is used as the special resin for the bearing layer; the low-density heat-insulating layer (2) uses modified quartz fiber felt as the reinforcing fiber, and siloxane grafted phenolic resin is used as the special resin for the heat-insulating layer; the high-density anti-ablation layer (3) is located on the side close to the battery cell, modified high-silica fiber cloth is used as the reinforcing fiber, and boron-carbon synergistic phenolic resin is used as the special resin for the anti-ablation layer. The protective cover plate has excellent heat-insulating and anti-ablation performance, good protection reliability and high stability.

Description

Technical Field

[0001] This invention relates to the field of protective cover technology, specifically to a lightweight, heat-insulating integrated protective cover and its preparation method. Background Technology

[0002] The integrated battery-body technology for new energy vehicles combines the battery cover with the vehicle floor, requiring the power battery system to have both energy output and load-bearing capacity. This integrated body structure significantly improves the torsional stiffness, bending stiffness, and lightweighting of the vehicle body, while saving vertical space compared to traditional vehicle floor and battery pack structures, effectively increasing the volume utilization of the power battery system and the vertical space of the passenger compartment. However, this structural simplification places higher demands on the battery cover. To ensure the safety of the passenger compartment in new energy vehicles, the battery cover of the integrated battery-body structure must possess excellent mechanical, electrical insulation, flame retardant, heat insulation, and ablation resistance properties.

[0003] Currently, the battery protective cover (i.e., the top cover) of the integrated battery body structure is usually made of lightweight, high-strength, and corrosion-resistant 6000 series (6061, 6082) or 7000 series (7075) aluminum alloys, formed by stamping or die casting. However, aluminum alloys have extremely high thermal conductivity and limited ablation resistance, which is not conducive to thermal protection under thermal runaway conditions of the battery cell. They usually need to be bonded together with heat insulation materials such as mica sheets. However, mica sheets have high density, limited heat insulation performance, and poor resistance to particle erosion. This not only increases the weight of the protective cover and fails to meet the lightweight requirements of new energy vehicles, but also fails to achieve excellent protective effects. At the same time, this split-structure protective cover is prone to delamination and peeling under the erosion of high-temperature and high-speed flame jets, resulting in poor protective reliability. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a lightweight, heat-insulating, integrated protective cover. This protective cover is integrally molded through a multi-layer variable-density fiber-reinforced aerogel structure, which not only meets the lightweight requirements of new energy vehicles but also significantly improves heat insulation and ablation resistance performance, avoiding problems such as delamination and peeling under high-temperature and high-speed flame erosion. It offers high reliability and stability in protection.

[0005] Another object of the present invention is to provide a method for preparing a protective cover plate, for preparing the above-mentioned lightweight heat-insulating integrated protective cover plate.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A lightweight, heat-insulating integrated protective cover includes a high-density load-bearing layer, a low-density heat insulation layer, and a high-density ablation-resistant layer. The high-density load-bearing layer is located near the passenger compartment and uses modified carbon fiber cloth as reinforcing fiber and phenolic-polyimide dynamic cross-linked resin as the load-bearing layer resin. The low-density heat insulation layer uses modified quartz fiber felt as reinforcing fiber and siloxane-grafted phenolic resin as the heat insulation layer resin. The high-density ablation-resistant layer is located near the battery cell and uses modified high-silica fiber cloth as reinforcing fiber and boron-carbon synergistic phenolic resin as the ablation-resistant layer resin.

[0008] Based on further optimization of the above scheme, the thickness of the high-density load-bearing layer is 4-6 mm, the thickness of the low-density heat insulation layer is 2-4 mm, and the thickness of the high-density ablation-resistant layer is 0.25-0.75 mm.

[0009] A method for preparing a lightweight, heat-insulating, integrated protective cover plate includes: Step S1, Fiber material modification treatment: First, carbon fiber cloth, quartz fiber felt, and high silica fiber cloth are modified separately; then, the individually modified carbon fiber cloth, quartz fiber felt, and high silica fiber cloth are subjected to interface bridging modification. Step S2, Layered Resin Pre-impregnation: Modified carbon fiber cloth, quartz fiber felt, and high silica fiber cloth are respectively pre-impregnated in special resin to obtain the corresponding pre-impregnated fiber cloth. Step S3, Protective cover plate preforming: The pre-impregnated fiber cloth of the load-bearing layer, the pre-impregnated fiber cloth of the heat insulation layer, and the pre-impregnated fiber cloth of the ablation-resistant layer are laid in sequence. Interlayer bridging resin is evenly coated between each layer, and the stacked fiber preform is placed into a needle punching mold to obtain a preformed fiber preform. Then, the preformed fiber preform is taken out and reinforced by sewing with carbon fiber stitching to obtain an integrated fiber preform. Step S4, Mold Closure: Transfer the integrated fiber preform into the mold cavity and fix the mold by connecting with screws; Step S5, Vacuum-assisted resin transfer molding: Pre-vacuuming, negative pressure filling, and positive pressure compaction and degassing are performed sequentially; Step S6, Heating and Curing: Transfer the mold to an oven and cure it using a segmented heating and curing process; Step S7, Demolding and Drying: Remove the mold from the oven, cool it to room temperature, open the mold, and remove the wet gel; transfer the wet gel to a drying oven and heat it to dry, and you will get the product.

[0010] Based on further optimization of the above scheme, in step S1, the individual modification treatment of carbon fiber cloth, quartz fiber felt, and high silica fiber cloth is specifically as follows: Carbon fiber cloth modification treatment: Arrange carbon fibers in a tube furnace and introduce argon gas at a flow rate of 190-210 mL / min to ensure no oxygen residue in the tube furnace; keep the argon gas inlet and heat to 1150-1250℃ at a heating rate of 4.5-5.5℃ / min, then introduce a mixture of argon gas and silicon tetrachloride (SiCl4) vapor, with a volume ratio of argon gas to silicon tetrachloride (SiCl4) vapor of 8.1-9.9:0.9-1.1, and hold at this temperature for 1.8-2.2 h. SiC whiskers grow in situ on the surface of the carbon fiber cloth. After cooling to room temperature, remove and set aside for later use. Quartz fiber felt modification treatment: In a mixed solvent of anhydrous ethanol and deionized water, add CTAB (hexadecyltrimethylammonium bromide), with a volume-to-mass ratio of anhydrous ethanol:deionized water:0.1g of 10–12 mL:5–6 mL:0.1g. Stir magnetically at 230–270 rpm for 8–12 min. Then, add 14 mol / L ammonia water dropwise to stabilize the solution pH at 9–10. Next, add tetraethyl orthosilicate (TEOS) dropwise at a rate of 0.8–1.2 mL / min, with a volume ratio of TEOS to anhydrous ethanol of 1:10–12, and stir at 230–270 rpm for 8–12 min. The precursor sol was obtained by magnetic stirring at a speed of ~270 rpm for 1.8 to 2.2 hours. Then, the quartz fiber felt was fixed on the fixture of the pull-coating machine and immersed in the precursor sol at a speed of 5 mm / s. After complete immersion, it was kept immersed for 9 to 11 minutes, and then the fiber felt was pulled out of the sol at a speed of 5 mm / s. Finally, after drying at room temperature for 23 to 25 hours, the quartz fiber felt was transferred to a quartz crucible in a muffle furnace and heated to 780 to 820°C at a heating rate of 1.5 to 2.5°C / min. It was held at this temperature for 0.8 to 1.2 hours and then naturally cooled to room temperature before being taken out for use. Modification treatment of high-silica fiber cloth: Aluminum nitrate nonahydrate (Al(NO3)3·9H2O) was added to deionized water at a mass-to-volume ratio of 1g:3-3.2mL. The mixture was magnetically stirred at 280-320rpm for 28-32min. Then, fumed silica was added to the solution at a molar ratio of fumed silica to aluminum nitrate nonahydrate of 2:3. The mixture was stirred at 380-420rpm for 58-62min to obtain a mixed precursor solution. After that, the high-silica fiber cloth was laid flat. Place the mixed precursor liquid inside the polytetrafluoroethylene (PTFE) liner of the hydrothermal reactor, and slowly pour it into the PTFE liner, with the volume of the mixed precursor liquid accounting for 70% of the effective volume of the PTFE liner. Heat the mixture to 180–220°C at a heating rate of 2.5–3.5°C / min, hold it at this temperature for 11.5–12.5 h, and allow it to cool naturally to room temperature. Then remove the mixture and place it in the corundum crucible of the muffle furnace. Heat the mixture to 580–620°C at a heating rate of 1.5–2.5°C / min, hold it at this temperature for 1.8–2.2 h, and allow it to cool naturally to room temperature again before removing it for use.

[0011] Based on further optimization of the above scheme, the interface bridging modification in step S1 is specifically as follows: First, 4,4'-diaminodiphenylmethane (MDA) is added to anhydrous ethanol and stirred at 230-270 rpm for 38-42 min until the solution becomes transparent, thus preparing an MDA ethanol solution with a mass concentration of 1.8-2.2 wt%. Then, the modified carbon fiber cloth, modified quartz fiber felt, and modified high-silica fiber cloth are respectively immersed in the MDA ethanol solution and soaked at room temperature for 28-32 min. Finally, the soaked fiber cloth is removed and vacuum dried at a vacuum degree of -0.075--0.085 MPa and 98-102℃ for 0.8-1.2 h to obtain the final product.

[0012] Based on further optimization of the above scheme, step S2 specifically includes: Preparation of the carrier layer: The modified carbon fiber cloth from step S1 is impregnated with a special resin for the carrier layer, the content of which is 40%–45% (i.e., the special resin accounts for 40%–45% of the total mass of fiber and resin). After pre-impregnation at room temperature for 9–11 min, it is removed and dried at 58–62℃ for 28–32 min to obtain the carrier layer pre-impregnated fiber cloth. The specific preparation method of the special resin for the carrier layer is as follows: Linear phenolic resin, polyimide prepolymer (molecular weight 1000–1500), and hexamethylenetetramine are mixed and placed in a water bath at 48–52℃, and magnetically stirred at 280–320 rpm for 18–22 min. The mass ratio of linear phenolic resin, polyimide prepolymer, and hexamethylenetetramine is 40:10:1. Afterward, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085–-0.095 MPa for 28–32 min to obtain the carrier layer pre-impregnated fiber cloth. Preparation of the heat insulation layer: The modified quartz fiber felt from step S1 is impregnated with a special resin for the heat insulation layer. The content of the special resin for the heat insulation layer is 35% to 40% (i.e., the special resin for the heat insulation layer accounts for 30% to 40% of the total mass of fiber + resin). After pre-impregnation at room temperature for 14 to 16 minutes, it is taken out and dried at 58 to 62°C for 28 to 32 minutes to obtain the pre-impregnated fiber felt for the heat insulation layer. The specific preparation method of the special resin for the heat insulation layer is as follows: KH-550 is added dropwise to linear phenolic resin at a dropping rate of 2 drops / s. Then, the resin is magnetically stirred at a speed of 230 to 270 rpm for 1.8 to 2.2 hours in a water bath environment at 68 to 72°C. The mass ratio of KH-550 to linear phenolic resin is 1:9. Finally, the resin is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085 to -0.095 MPa for 28 to 32 minutes to obtain the heat insulation layer. Preparation of the ablation-resistant layer: The modified high-silica fiber cloth from step S1 is impregnated with a special resin for the ablation-resistant layer. The content of the special resin for the ablation-resistant layer is 45% to 50% (i.e., the special resin for the ablation-resistant layer accounts for 45% to 50% of the total mass of fiber + resin). After pre-impregnation at room temperature for 9 to 11 minutes, it is taken out and dried at 58 to 62°C for 28 to 32 minutes to obtain the pre-impregnated fiber cloth for the ablation-resistant layer. The specific preparation method of the special resin for the ablation-resistant layer is as follows: linear phenolic resin and boron phenolic resin are mixed at a mass ratio of 7:3 and preheated in a water bath at 58 to 62°C for 9 to 11 minutes. Then, p-toluenesulfonic acid is added to the mixed resin. The mass ratio of p-toluenesulfonic acid to linear phenolic resin is 1:70. The mixture is magnetically stirred at a speed of 230 to 270 rpm for 28 to 32 minutes. Finally, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085 to -0.095 MPa for 28 to 32 minutes to obtain the final product.

[0013] Based on further optimization of the above scheme, in step S3, the coating thickness of the interlayer bridging resin is 0.04-0.06 mm; the specific preparation method of the interlayer bridging resin is as follows: maleic anhydride is added to linear phenolic resin, and the mixture is magnetically stirred at a speed of 280-320 rpm for 0.8-1.2 h in a constant temperature water bath at 78-82℃. After the reaction is completed, the mixture is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085 to -0.095 MPa for 18-22 min to obtain the final product.

[0014] Based on further optimization of the above scheme, in step S3, the needle-punching mold is made of EVA foam material, and the needle-punching density is 5-15 needles / cm. 2 Repeated punctures with a needle depth of 6-20 mm are performed to initially bond the three layers of pre-impregnated fibers, resulting in a pre-formed fiber preform. Then, the needled fiber blank is removed, and 800-1500 tex carbon fiber sutures are used to sew and reinforce the fiber preform with a suture angle of 40°-60° and a stitch length of 10-20 mm, resulting in an integrated fiber preform.

[0015] Based on further optimization of the above scheme, in step S4, a VARTM mold is adopted. According to the structural characteristics of the protective cover of the power battery of new energy vehicles, it is designed as an integrated molding mold, including an upper mold, a sealing gasket, a glue injection port, a lower mold, and a glue outlet. At the same time, before the mold is closed in step S4, an airtightness test is required. That is, after the mold is assembled, it is immersed in water as a whole, keeping the glue outlet closed and the glue injection port open. Then, compressed air is introduced through the glue injection port, and it is observed whether there are bubbles emerging from the edge of the mold in the water tank. If there are no bubbles, it proves that the mold has good airtightness.

[0016] Based on further optimization of the above scheme, step S5 specifically includes: Pre-vacuuming: Close the ball valve at the bottom inlet of the mold, open the ball valve at the outlet, start the vacuum pump, adjust the pressure to -0.02 to -0.1 MPa, maintain the pressure until the pressure gauge reading stabilizes, and expel the air from the mold. Negative pressure filling: Inject interlayer bridging resin into the injection tank, adjust the negative pressure inside the mold to -0.03 to -0.05 MPa, close the ball valve at the mold outlet, open the ball valve at the injection tank and the bottom inlet of the mold, and slowly draw the resin in by relying on the negative pressure inside the mold. The filling time is 5 to 8 minutes until the pores of each layer are fully filled by the resin, and then close the ball valve at the inlet. Positive pressure compaction and venting: Open the ball valve at the outlet, adjust the pressure of the air compressor pressure reducing valve to 0.2-0.6 MPa, maintain the pressure for 1-5 minutes, and force the residual gas and excess resin in the mold to the outlet; repeat the "pressure holding-venting operation" until no air bubbles are discharged from the resin, and then close the ball valves at the outlet and injection port.

[0017] Based on further optimization of the above scheme, the segmented heating and curing process in step S6 is as follows: first, the temperature is raised to 78-82℃ at a heating rate of 0.8-1.2℃ / min and held for 0.8-1.2h; then, the temperature is raised to 118-122℃ at a heating rate of 0.8-1.2℃ / min and held for 1.8-2.2h; then, the temperature is raised to 158-162℃ at a heating rate of 1.3-1.7℃ / min and held for 2.8-3.2h; finally, the temperature is raised to 198-202℃ at a heating rate of 0.8-1.2℃ / min and held for 0.8-1.2h.

[0018] Based on further optimization of the above scheme, in step S7, the wet gel is kept in a drying oven at 58-62℃ for 47-49 hours.

[0019] The following are the effects of the technical solution of the present invention: This invention utilizes modified carbon fiber cloth as reinforcing fiber and phenolic-polyimide dynamically crosslinked resin as a special resin for the load-bearing layer to form a high-density load-bearing layer. This not only effectively improves the interfacial compatibility and high-temperature oxidation resistance of carbon fiber and phenolic resin, but also imparts toughness to the resin, preventing micro-cracks or cracking of the load-bearing layer during impact. A low-density insulation layer is formed using modified quartz fiber felt as reinforcing fiber and siloxane-grafted phenolic resin as a special resin for the insulation layer. This not only enhances the chemical bond between the fiber and resin, preventing debonding during thermal shock, but also improves the high-temperature resistance and structural integrity of the insulation layer, avoiding delamination and insulation performance degradation of the low-density insulation layer at high temperatures. A high-density ablation-resistant layer is formed using modified high-silica fiber cloth as reinforcing fiber and boron-carbon synergistic phenolic resin as a special resin for the ablation-resistant layer. This not only forms a dense anti-oxidation layer after carbonization, improving the erosion resistance of the protective cover, but also effectively enhances the interfacial bond between the fiber and the carbon layer, preventing interfacial peeling during ablation, thus ensuring continuous ablation resistance. In addition, by combining interface bridging modification with interlayer bridging resin, a continuous bridging interface is formed between layers, effectively eliminating the surface energy difference of different fiber materials, eliminating weak areas, improving interlayer shear strength, avoiding problems such as peeling and cracking between layers, and ensuring the integrity and performance stability of the cover plate.

[0020] This invention employs a structural design consisting of a high-density load-bearing layer, a low-density heat insulation layer, and a high-density ablation-resistant layer. The high-density ablation-resistant layer resists the high-temperature flame erosion caused by thermal runaway of the battery cell and prevents flame penetration. The low-density heat insulation layer effectively blocks heat conduction and prevents a sudden rise in temperature on the passenger compartment side. The high-density load-bearing layer achieves excellent impact resistance and temperature resistance, ensuring structural integrity. The three layers are highly integrated and have no risk of delamination, thus synergistically providing protection. While improving high-temperature resistance and ablation resistance, it also takes into account the need for lightweighting and avoids material redundancy, effectively aligning with the development trend of new energy vehicles. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the integrated protective cover plate in an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the structure of a vacuum-assisted resin transfer molding mold in an embodiment of the present invention.

[0023] Figure 3 This is a flowchart of the vacuum-assisted resin transfer molding process in an embodiment of the present invention.

[0024] The components include: 1. High-density load-bearing layer; 2. Low-density heat insulation layer; 3. High-density ablation-resistant layer; 4. Upper mold; 5. Sealing ring; 6. Injection port; 7. Lower mold; 8. Outlet port; 9. Integrated fiber preform; 10. Interlayer bridging resin; 11. Vacuum-assisted resin transfer molding mold; 12. Compressed air; 13. Injection tank; 14. Return tank; and 15. Vacuum pump. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0026] Example 1: A lightweight, heat-insulating, integrated protective cover, such as Figure 1 As shown, the structure includes a high-density load-bearing layer 1, a low-density heat insulation layer 2, and a high-density ablation-resistant layer 3. The high-density load-bearing layer 1 is located near the passenger compartment and uses modified carbon fiber cloth as the reinforcing fiber and phenolic-polyimide dynamic cross-linked resin as the special resin for the load-bearing layer. Its thickness is 4-6 mm (preferably 5 mm). The low-density heat insulation layer 2 uses modified quartz fiber felt as the reinforcing fiber and siloxane-grafted phenolic resin as the special resin for the heat insulation layer. Its thickness is 2-4 mm (preferably 3 mm). The high-density ablation-resistant layer 3 is located near the battery cell and uses modified high-silica fiber cloth as the reinforcing fiber and boron-carbon synergistic phenolic resin as the special resin for the ablation-resistant layer. Its thickness is 0.25-0.75 mm (preferably 0.5 mm).

[0027] Example 2: A method for preparing a lightweight, heat-insulating, integrated protective cover, used to prepare the integrated protective cover as described in Example 1, comprising: Step S1, Fiber Material Modification Treatment: First, carbon fiber cloth, quartz fiber felt, and high-silica fiber cloth are modified individually, specifically including: Carbon fiber cloth modification treatment: Carbon fibers are arranged in a tube furnace, and argon gas is introduced at a flow rate of 190 mL / min to ensure that there is no oxygen residue in the tube furnace; while maintaining the argon gas supply, the temperature is raised to 1150℃ at a heating rate of 4.5℃ / min, and then a mixture of argon gas and silicon tetrachloride (SiCl4) vapor is introduced, with a volume ratio of argon gas to silicon tetrachloride (SiCl4) vapor of 8.1:0.9. The temperature is maintained for 2.2 h, and SiC whiskers are grown in situ on the surface of the carbon fiber cloth. After cooling to room temperature, it is taken out for use. Quartz fiber felt modification treatment: CTAB (hexadecyltrimethylammonium bromide) was added to a mixed solvent of anhydrous ethanol and deionized water. The volume-to-mass ratio of anhydrous ethanol, deionized water, and CTAB was 10 mL:5 mL:0.1 g. The mixture was magnetically stirred at 230 rpm for 12 min. Then, 14 mol / L ammonia was added dropwise to stabilize the solution pH at 9. Afterward, tetraethyl orthosilicate (TEOS) was added dropwise at a rate of 0.8 mL / min. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol was 1:10. The precursor sol was obtained by magnetic stirring at 230 rpm for 2.2 h. Then, the quartz fiber felt was fixed on the fixture of the pull-coating machine and immersed in the precursor sol at a rate of 5 mm / s. After being completely immersed, it was kept immersed for 9 min and then pulled out of the sol at a rate of 5 mm / s. Finally, after drying at room temperature for 23 h, the quartz fiber felt was transferred to a quartz crucible in a muffle furnace and heated to 780 °C at a heating rate of 1.5 °C / min. It was held at this temperature for 1.2 h and then naturally cooled to room temperature before being taken out for use. Modification treatment of high-silica fiber cloth: Aluminum nitrate nonahydrate (Al(NO3)3·9H2O) was added to deionized water at a mass-to-volume ratio of 1 g:3 mL. The mixture was magnetically stirred at 280 rpm for 32 min. Then, fumed silica was added to the solution at a molar ratio of 2:3 to fumed silica nonahydrate. The mixture was stirred at 380 rpm for 62 min to obtain a mixed precursor solution. Afterwards, high-silica fiber cloth was... The PVC-U liner was laid flat on the bottom of the PVC-U liner of the hydrothermal reactor. The mixed precursor liquid was slowly poured into the PVC-U liner, and the volume of the mixed precursor liquid accounted for 70% of the effective volume of the PVC-U liner. The temperature was increased to 180°C at a heating rate of 2.5°C / min and held for 12.5 hours. After naturally cooling to room temperature, it was taken out and placed in the corundum crucible of the muffle furnace. The temperature was increased to 580°C at a heating rate of 1.5°C / min and held for 2.2 hours. After naturally cooling to room temperature again, it was taken out for use.

[0028] Then, the separately modified carbon fiber cloth, quartz fiber felt, and high-silica fiber cloth were subjected to interface bridging modification. Specifically, 4,4'-diaminodiphenylmethane (MDA) was first added to anhydrous ethanol and stirred at 230 rpm for 42 min until the solution became transparent, thus preparing a 1.8 wt% MDA ethanol solution. Then, the modified carbon fiber cloth, modified quartz fiber felt, and modified high-silica fiber cloth were immersed in the MDA ethanol solution and soaked at room temperature for 28 min. Finally, the soaked fiber cloths were removed and vacuum dried at -0.075 MPa and 98 °C for 1.2 h to obtain the final product.

[0029] Step S2, Layered Resin Pre-impregnation: The modified carbon fiber cloth, quartz fiber mat, and high-silica fiber cloth are respectively pre-impregnated in a special resin to obtain the corresponding pre-impregnated fiber cloth; specifically: Preparation of the carrier layer: The modified carbon fiber cloth from step S1 is impregnated with a special resin for the carrier layer. The content of the special resin for the carrier layer is 40% (i.e., the special resin for the carrier layer accounts for 40% of the total mass of fiber + resin). After pre-impregnation at room temperature for 11 min, it is taken out and dried at 58℃ for 32 min to obtain the carrier layer pre-impregnated fiber cloth. The specific preparation method of the special resin for the carrier layer is as follows: Linear phenolic resin (CAS: 65733-76-8, the same below), polyimide prepolymer (molecular weight 1000~1500) and hexamethylenetetramine are mixed and placed in a water bath at 48℃ and magnetically stirred at 280 rpm for 22 min. The mass ratio of linear phenolic resin, polyimide prepolymer and hexamethylenetetramine is 40:10:1. Then, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085MPa for 32 min to obtain the final product. Preparation of the heat insulation layer: The modified quartz fiber felt from step S1 is impregnated with a special resin for the heat insulation layer. The content of the special resin for the heat insulation layer is 35% (that is, the special resin for the heat insulation layer accounts for 30% of the total mass of fiber + resin). After pre-impregnation at room temperature for 16 minutes, it is taken out and dried at 58℃ for 32 minutes to obtain the pre-impregnated fiber felt for the heat insulation layer. The specific preparation method of the special resin for the heat insulation layer is as follows: KH-550 is added to the linear phenolic resin at a dropping rate of 2 drops / s. Then, the resin is magnetically stirred at 230 rpm for 2.2 hours in a water bath at 68℃. The mass ratio of KH-550 to the linear phenolic resin is 1:9. Finally, the resin is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085MPa for 32 minutes to obtain the final product. Preparation of the ablation-resistant layer: The modified high-silica fiber cloth from step S1 is impregnated with a special resin for the ablation-resistant layer. The content of the special resin for the ablation-resistant layer is 45% (i.e., the special resin for the ablation-resistant layer accounts for 45% of the total mass of fiber + resin). After pre-impregnation at room temperature for 11 minutes, it is taken out and dried at 58℃ for 32 minutes to obtain the pre-impregnated fiber cloth for the ablation-resistant layer. The specific preparation method of the special resin for the ablation-resistant layer is as follows: linear phenolic resin and boron phenolic resin (such as FB type resin) are mixed at a mass ratio of 7:3 and preheated in a water bath environment at 58℃ for 11 minutes. Then, p-toluenesulfonic acid is added to the mixed resin. The mass ratio of p-toluenesulfonic acid to linear phenolic resin is 1:70. The mixture is magnetically stirred at a speed of 230 rpm for 32 minutes. Finally, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085MPa for 32 minutes to obtain the final product.

[0030] Step S3, Protective Cover Pre-forming: The pre-impregnated fiber cloth is laid in the following order: load-bearing layer pre-impregnated fiber cloth - heat insulation layer pre-impregnated fiber cloth - ablation-resistant layer pre-impregnated fiber cloth. Interlayer bridging resin is evenly coated between each layer. The laminated fiber preform is then placed into a needle-punching mold made of EVA foam material, using a needle-punching density of 5 needles / cm. 2 Repeated punctures with a needle depth of 6 mm were performed to initially bond the three layers of prepreg fibers, resulting in a preformed fiber preform. The coating thickness of the interlayer bridging resin was 0.04 mm. The specific preparation method was as follows: maleic anhydride was added to linear phenolic resin, and the mixture was magnetically stirred at 280 rpm for 1.2 h in a constant temperature water bath at 78 °C. After the reaction was completed, the mixture was naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085 MPa for 22 min to obtain the final product.

[0031] Afterwards, the needle-punched fiber preform is removed, and 800tex carbon fiber thread is used to sew it with a 40° thread angle and a 10mm stitch length to obtain an integrated fiber preform.

[0032] Step S4, Mold Closure: Transfer the integrated fiber preform into the mold cavity and fix the mold by connecting with screws; use VARTM mold, designed as an integrated molding mold according to the structural characteristics of the protective cover of the power battery of new energy vehicles, including upper mold, sealing gasket, injection port, lower mold, and dispensing port; at the same time, before closing the mold in step S4, an airtightness test is required, that is, first immerse the mold in water after assembly, keep the dispensing port closed and the injection port open; then introduce compressed air through the injection port and observe whether there are bubbles emerging from the edge of the mold in the water tank. If there are no bubbles, it proves that the mold has good airtightness.

[0033] Step S5, Vacuum-assisted resin transfer molding: This involves sequentially performing pre-vacuuming, negative pressure filling, and positive pressure compaction and degassing; specifically: Pre-vacuuming: Close the ball valve at the bottom inlet of the mold, open the ball valve at the outlet, start the vacuum pump, adjust the pressure to -0.02MPa, maintain the pressure until the pressure gauge reading stabilizes, and expel the air from the mold. Negative pressure filling: Inject interlayer bridging resin into the injection tank, adjust the negative pressure inside the mold to -0.03MPa, close the ball valve at the mold outlet, open the ball valve at the injection tank and the bottom inlet of the mold, and slowly draw the resin in by relying on the negative pressure inside the mold. The filling time is 8 minutes until the pores of each layer are fully filled by the resin, and then close the ball valve at the inlet. Positive pressure compaction and venting: Open the ball valve at the outlet, adjust the pressure of the air compressor pressure reducing valve to 0.2MPa, maintain the pressure for 5 minutes, and force the residual gas and excess resin in the mold to the outlet; repeat the "pressure holding-venting operation" until no air bubbles are discharged from the resin, and then close the ball valves at the outlet and injection port.

[0034] Step S6, Heating and Curing: Transfer the mold to an oven and cure it using a segmented heating and curing process. The segmented heating and curing process is as follows: First, heat the mold to 78°C at a heating rate of 0.8°C / min and hold for 1.2 hours (to allow the filler resin and prepreg resin to initially impregnate and fuse, while further evaporating the solvent and avoiding residual bubbles). Then, heat the mold to 118°C at a heating rate of 0.8°C / min and hold for 2.2 hours (to form a preliminary gel network). Next, heat the mold to 158°C at a heating rate of 1.3°C / min and hold for 3.2 hours (to form a dense cross-linked network of phenolic resin; to complete the imidization of the PI prepolymer in the load-bearing layer; to fully cross-link the siloxane graft groups in the heat insulation layer; and to begin carbonization of the ablation-resistant layer). After that, heat the mold to 198°C at a heating rate of 0.8°C / min and hold for 1.2 hours (to eliminate residual small molecule byproducts, increase the cross-linking density; to make the carbon layer of the ablation-resistant layer denser; and to promote interlayer bonding).

[0035] Step S7, Demolding and Drying: Remove the mold from the oven, cool it to room temperature, open the mold, and remove the wet gel; transfer the wet gel to a drying oven and keep it at 58°C for 49 hours to obtain the final product.

[0036] Example 3: A method for preparing a lightweight, heat-insulating, integrated protective cover, used to prepare the integrated protective cover as described in Example 1, comprising: Step S1, Fiber Material Modification Treatment: First, carbon fiber cloth, quartz fiber felt, and high-silica fiber cloth are modified individually, specifically including: Carbon fiber cloth modification treatment: Carbon fiber is arranged in a tube furnace, and argon gas is introduced at a flow rate of 200 mL / min to ensure that there is no oxygen residue in the tube furnace; while keeping the argon gas introduced, the temperature is raised to 1200℃ at a heating rate of 5℃ / min, and then a mixture of argon gas and silicon tetrachloride (SiCl4) vapor is introduced with a volume ratio of argon gas to silicon tetrachloride (SiCl4) vapor of 9:1. The temperature is maintained for 2 hours, and SiC whiskers are grown in situ on the surface of the carbon fiber cloth. After cooling to room temperature, it is taken out for use. Quartz fiber felt modification treatment: CTAB (hexadecyltrimethylammonium bromide) was added to a mixed solvent of anhydrous ethanol and deionized water, with a volume-to-mass ratio of anhydrous ethanol:5.5 mL:0.1 g. The mixture was magnetically stirred at 250 rpm for 10 min. Then, 14 mol / L ammonia solution was added dropwise to stabilize the solution pH at 9.5. Afterward, tetraethyl orthosilicate (TEOS) was added dropwise at a rate of 1 mL / min, with a volume ratio of tetraethyl orthosilicate to anhydrous ethanol of 1:11. The precursor sol was obtained by magnetic stirring at 250 rpm for 2 hours. Then, the quartz fiber felt was fixed on the fixture of the pull-coating machine and immersed in the precursor sol at a rate of 5 mm / s. After being completely immersed, it was kept immersed for 10 minutes and then pulled out of the sol at a rate of 5 mm / s. Finally, after drying at room temperature for 24 hours, the quartz fiber felt was transferred to the quartz crucible of the muffle furnace and heated to 800℃ at a heating rate of 2℃ / min. It was held at this temperature for 1 hour and then naturally cooled to room temperature before being taken out for use. High-silica fiber cloth modification treatment: Aluminum nitrate nonahydrate (Al(NO3)3·9H2O) was added to deionized water at a mass-to-volume ratio of 1g:3.1mL. The mixture was magnetically stirred at 300rpm for 30min. Then, fumed silica was added to the solution at a molar ratio of 2:3 to fumed silica. The mixture was stirred at 400rpm for 60min to obtain a mixed precursor solution. The high-silica fiber cloth was then laid flat on the bottom of the polytetrafluoroethylene (PTFE) liner of the hydrothermal reactor. The mixed precursor solution was slowly poured into the PTFE liner, with the volume of the mixed precursor solution accounting for 70% of the effective volume of the PTFE liner. The temperature was increased to 200℃ at a heating rate of 3℃ / min and held for 12h. After naturally cooling to room temperature, the mixture was removed and placed in a corundum crucible in a muffle furnace. The temperature was increased to 600℃ at a heating rate of 2℃ / min and held for 2h. After naturally cooling to room temperature again, the mixture was removed for use.

[0037] Then, the individually modified carbon fiber cloth, quartz fiber felt, and high-silica fiber cloth were subjected to interface bridging modification. Specifically, 4,4'-diaminodiphenylmethane (MDA) was first added to anhydrous ethanol and stirred at 250 rpm for 40 min until the solution became transparent, thus preparing a 2 wt% MDA ethanol solution. Then, the modified carbon fiber cloth, modified quartz fiber felt, and modified high-silica fiber cloth were immersed in the MDA ethanol solution and soaked at room temperature for 30 min. Finally, the soaked fiber cloths were removed and vacuum dried at -0.08 MPa and 100℃ for 1 h to obtain the final product.

[0038] Step S2, Layered Resin Pre-impregnation: The modified carbon fiber cloth, quartz fiber mat, and high-silica fiber cloth are respectively pre-impregnated in a special resin to obtain the corresponding pre-impregnated fiber cloth; specifically: Preparation of the carrier layer: The modified carbon fiber cloth from step S1 is impregnated with a special resin for the carrier layer. The content of the special resin for the carrier layer is 42% (i.e., the special resin for the carrier layer accounts for 42% of the total mass of fiber + resin). After pre-impregnation at room temperature for 10 min, it is taken out and dried at 60℃ for 30 min to obtain the carrier layer pre-impregnated fiber cloth. The specific preparation method of the special resin for the carrier layer is as follows: First, linear phenolic resin (CAS: 65733-76-8, the same below), polyimide prepolymer (molecular weight 1000~1500) and hexamethylenetetramine are mixed and placed in a water bath at 50℃, and magnetically stirred at 300 rpm for 20 min. The mass ratio of linear phenolic resin, polyimide prepolymer and hexamethylenetetramine is 40:10:1. Then, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.09MPa for 30 min to obtain the final product. Preparation of the heat insulation layer: The modified quartz fiber felt from step S1 is impregnated with a special resin for the heat insulation layer. The content of the special resin for the heat insulation layer is 37% (i.e., the special resin for the heat insulation layer accounts for 37% of the total mass of fiber + resin). After pre-impregnation at room temperature for 15 minutes, it is taken out and dried at 60℃ for 30 minutes to obtain the pre-impregnated fiber felt for the heat insulation layer. The specific preparation method of the special resin for the heat insulation layer is as follows: KH-550 is added to the linear phenolic resin at a dropping rate of 2 drops / s. Then, the resin is magnetically stirred at 250 rpm for 2 hours in a water bath at 70℃. The mass ratio of KH-550 to the linear phenolic resin is 1:9. Finally, the resin is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.09MPa for 30 minutes to obtain the final product. Preparation of the ablation-resistant layer: The modified high-silica fiber cloth from step S1 is impregnated with a special resin for the ablation-resistant layer. The content of the special resin for the ablation-resistant layer is 47% (i.e., the special resin for the ablation-resistant layer accounts for 47% of the total mass of fiber + resin). After pre-impregnation at room temperature for 10 minutes, it is taken out and dried at 60℃ for 30 minutes to obtain the pre-impregnated fiber cloth for the ablation-resistant layer. The specific preparation method of the special resin for the ablation-resistant layer is as follows: linear phenolic resin and boron phenolic resin (such as FB type resin) are mixed at a mass ratio of 7:3 and preheated in a water bath environment at 60℃ for 10 minutes. Then, p-toluenesulfonic acid is added to the mixed resin. The mass ratio of p-toluenesulfonic acid to linear phenolic resin is 1:70. The mixture is magnetically stirred at a speed of 250 rpm for 30 minutes. Finally, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.09MPa for 30 minutes to obtain the final product.

[0039] Step S3, Pre-forming of the protective cover: The pre-impregnated fiber cloth is laid in the following order: pre-impregnated fiber cloth for the load-bearing layer, pre-impregnated fiber cloth for the heat insulation layer, and pre-impregnated fiber cloth for the ablation-resistant layer. Interlayer bridging resin is evenly coated between each layer. The laminated fiber preform is then placed into a needle-punching mold made of EVA foam material, with a needle-punching density of 10 needles / cm. 2Repeated punctures with a needle depth of 13 mm were performed to initially bond the three layers of prepreg fibers, resulting in a preformed fiber preform. The coating thickness of the interlayer bridging resin was 0.05 mm. The specific preparation method was as follows: maleic anhydride was added to linear phenolic resin, and the mixture was magnetically stirred at 300 rpm for 1 hour in a constant temperature water bath at 80°C. After the reaction was completed, the mixture was naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.09 MPa for 20 minutes to obtain the final product.

[0040] Afterwards, the needle-punched fiber preform is removed, and 1150tex carbon fiber thread is used to sew it with a 50° thread angle and a 15mm stitch length to obtain an integrated fiber preform.

[0041] Step S4, Mold Closure: Transfer the integrated fiber preform into the mold cavity and fix the mold by connecting with screws; use VARTM mold, designed as an integrated molding mold according to the structural characteristics of the protective cover of the power battery of new energy vehicles, including upper mold, sealing gasket, injection port, lower mold, and dispensing port; at the same time, before closing the mold in step S4, an airtightness test is required, that is, first immerse the mold in water after assembly, keep the dispensing port closed and the injection port open; then introduce compressed air through the injection port and observe whether there are bubbles emerging from the edge of the mold in the water tank. If there are no bubbles, it proves that the mold has good airtightness.

[0042] Step S5, Vacuum-assisted resin transfer molding: This involves sequentially performing pre-vacuuming, negative pressure filling, and positive pressure compaction and degassing; specifically: Pre-vacuuming: Close the ball valve at the bottom inlet of the mold, open the ball valve at the outlet, start the vacuum pump, adjust the pressure to -0.06MPa, maintain the pressure until the pressure gauge reading stabilizes, and expel the air from the mold. Negative pressure filling: Inject interlayer bridging resin into the injection tank, adjust the negative pressure inside the mold to -0.04MPa, close the ball valve at the mold outlet, open the ball valve at the injection tank and the bottom inlet of the mold, and slowly draw the resin in by relying on the negative pressure inside the mold. The filling time is 6.5 minutes, until the pores of each layer are fully filled by the resin, and then close the ball valve at the inlet. Positive pressure compaction and venting: Open the ball valve at the outlet, adjust the pressure of the air compressor pressure reducing valve to 0.4MPa, maintain the pressure for 3 minutes, and force the residual gas and excess resin in the mold to the outlet; repeat the "pressure holding-venting operation" until no air bubbles are discharged from the resin, and then close the ball valves at the outlet and injection port.

[0043] Step S6, Heating and Curing: Transfer the mold to an oven and cure it using a segmented heating and curing process. The segmented heating and curing process is as follows: First, heat the mold to 80°C at a heating rate of 1°C / min and hold for 1 hour (to allow the filler resin and prepreg resin to initially impregnate and fuse, while further evaporating the solvent and avoiding residual bubbles). Then, heat the mold to 120°C at a heating rate of 1°C / min and hold for 2 hours (to form a preliminary gel network). Next, heat the mold to 160°C at a heating rate of 1.5°C / min and hold for 3 hours (to form a dense cross-linked network of phenolic resin; to complete the imidization of the PI prepolymer in the load-bearing layer; to fully cross-link the siloxane graft groups in the insulation layer; and to begin carbonization of the ablation-resistant layer). Then, heat the mold to 200°C at a heating rate of 1°C / min and hold for 1 hour (to eliminate residual small molecule byproducts, increase the cross-linking density; to make the carbon layer of the ablation-resistant layer denser; and to promote interlayer bonding).

[0044] Step S7, Demolding and Drying: Remove the mold from the oven, cool it to room temperature, open the mold, and remove the wet gel; transfer the wet gel to a drying oven and keep it at 60°C for 48 hours to obtain the final product.

[0045] Example 4: A method for preparing a lightweight, heat-insulating, integrated protective cover, used to prepare the integrated protective cover as described in Example 1, comprising: Step S1, Fiber Material Modification Treatment: First, carbon fiber cloth, quartz fiber felt, and high-silica fiber cloth are modified individually, specifically including: Carbon fiber cloth modification treatment: Carbon fibers are arranged in a tube furnace, and argon gas is introduced at a flow rate of 210 mL / min to ensure that there is no oxygen residue in the tube furnace; while maintaining the argon gas supply, the temperature is raised to 1250℃ at a heating rate of 5.5℃ / min, and then a mixture of argon gas and silicon tetrachloride (SiCl4) vapor is introduced, with a volume ratio of argon gas to silicon tetrachloride (SiCl4) vapor of 9.9:1.1. The temperature is maintained for 1.8h, and SiC whiskers are grown in situ on the surface of the carbon fiber cloth. After cooling to room temperature, it is taken out for use. Quartz fiber felt modification treatment: CTAB (hexadecyltrimethylammonium bromide) was added to a mixed solvent of anhydrous ethanol and deionized water. The volume-to-mass ratio of anhydrous ethanol, deionized water, and CTAB was 12 mL:6 mL:0.1 g. The mixture was magnetically stirred at 270 rpm for 8 min. Then, 14 mol / L ammonia solution was added dropwise to stabilize the pH at 10. Next, tetraethyl orthosilicate (TEOS) was added dropwise at a rate of 1.2 mL / min. The volume ratio of tetraethyl orthosilicate to anhydrous ethanol was 1:12. The precursor sol was obtained by magnetic stirring at 70 rpm for 1.8 h. Then, the quartz fiber felt was fixed on the fixture of the pull-coating machine and immersed in the precursor sol at a rate of 5 mm / s. After being completely immersed, it was kept immersed for 11 min and then pulled out of the sol at a rate of 5 mm / s. Finally, after drying at room temperature for 25 h, the quartz fiber felt was transferred to a quartz crucible in a muffle furnace and heated to 820 °C at a heating rate of 2.5 °C / min. It was held at this temperature for 0.8 h and then naturally cooled to room temperature before being taken out for use. High-silica fiber cloth modification treatment: Aluminum nitrate nonahydrate (Al(NO3)3·9H2O) was added to deionized water at a mass-to-volume ratio of 1 g: 3.2 mL. The mixture was magnetically stirred at 320 rpm for 28 min. Then, fumed silica was added to the solution at a molar ratio of 2:3 to fumed silica nonahydrate. The mixture was stirred at 420 rpm for 58 min to obtain a mixed precursor solution. Afterwards, high-silica fiber cloth was... The fiber cloth is laid flat on the bottom of the polytetrafluoroethylene (PTFE) liner of the hydrothermal reactor, and the mixed precursor liquid is slowly poured into the PTFE liner, with the volume of the mixed precursor liquid accounting for 70% of the effective volume of the PTFE liner. The temperature is raised to 220℃ at a heating rate of 3.5℃ / min and held for 11.5h. After naturally cooling to room temperature, it is taken out and placed in the corundum crucible of the muffle furnace. The temperature is raised to 620℃ at a rate of 2.5℃ / min and held for 1.8h. After naturally cooling to room temperature again, it is taken out for use.

[0046] Then, the individually modified carbon fiber cloth, quartz fiber felt, and high-silica fiber cloth were subjected to interface bridging modification. Specifically, 4,4'-diaminodiphenylmethane (MDA) was first added to anhydrous ethanol and stirred at 270 rpm for 38 min until the solution became transparent, thus preparing a 2.2 wt% MDA ethanol solution. Then, the modified carbon fiber cloth, modified quartz fiber felt, and modified high-silica fiber cloth were immersed in the MDA ethanol solution and soaked at room temperature for 32 min. Finally, the soaked fiber cloths were removed and vacuum dried at -0.085 MPa and 102 °C for 0.8 h to obtain the final product.

[0047] Step S2, Layered Resin Pre-impregnation: The modified carbon fiber cloth, quartz fiber mat, and high-silica fiber cloth are respectively pre-impregnated in a special resin to obtain the corresponding pre-impregnated fiber cloth; specifically: Preparation of the carrier layer: The modified carbon fiber cloth from step S1 is impregnated with a special resin for the carrier layer. The content of the special resin for the carrier layer is 45% (i.e., the special resin for the carrier layer accounts for 45% of the total mass of fiber + resin). After pre-impregnation at room temperature for 9 minutes, it is taken out and dried at 62℃ for 28 minutes to obtain the carrier layer pre-impregnated fiber cloth. The specific preparation method of the special resin for the carrier layer is as follows: Linear phenolic resin (CAS: 65733-76-8, the same below), polyimide prepolymer (molecular weight 1000~1500) and hexamethylenetetramine are mixed and placed in a water bath at 52℃ and magnetically stirred at 320 rpm for 18 minutes. The mass ratio of linear phenolic resin, polyimide prepolymer and hexamethylenetetramine is 40:10:1. Then, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.095MPa for 28 minutes to obtain the carrier layer pre-impregnated fiber cloth. Preparation of the heat insulation layer: The modified quartz fiber felt from step S1 is impregnated with a special resin for the heat insulation layer. The content of the special resin for the heat insulation layer is 40% (i.e., the special resin for the heat insulation layer accounts for 40% of the total mass of fiber + resin). After pre-impregnation at room temperature for 14 minutes, it is taken out and dried at 62℃ for 28 minutes to obtain the pre-impregnated fiber felt for the heat insulation layer. The specific preparation method of the special resin for the heat insulation layer is as follows: KH-550 is added to the linear phenolic resin at a dropping rate of 2 drops / s. Then, the resin is magnetically stirred at 270 rpm for 1.8 hours in a water bath at 72℃. The mass ratio of KH-550 to the linear phenolic resin is 1:9. Finally, the resin is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.095MPa for 28 minutes to obtain the final product. Preparation of the ablation-resistant layer: The modified high-silica fiber cloth from step S1 is impregnated with a special resin for the ablation-resistant layer. The content of the special resin for the ablation-resistant layer is 50% (i.e., the special resin for the ablation-resistant layer accounts for 50% of the total mass of fiber + resin). After pre-impregnation at room temperature for 9 minutes, it is taken out and dried at 62℃ for 28 minutes to obtain the pre-impregnated fiber cloth for the ablation-resistant layer. The specific preparation method of the special resin for the ablation-resistant layer is as follows: linear phenolic resin and boron phenolic resin (such as FB type resin) are mixed at a mass ratio of 7:3 and preheated in a water bath environment at 62℃ for 9 minutes. Then, p-toluenesulfonic acid is added to the mixed resin. The mass ratio of p-toluenesulfonic acid to linear phenolic resin is 1:70. The mixture is magnetically stirred at a speed of 270 rpm for 28 minutes. Finally, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.095MPa for 28 minutes to obtain the final product.

[0048] Step S3, Protective Cover Pre-forming: The pre-impregnated fiber cloth is laid in the following order: load-bearing layer pre-impregnated fiber cloth - heat insulation layer pre-impregnated fiber cloth - ablation-resistant layer pre-impregnated fiber cloth. Interlayer bridging resin is evenly coated between each layer. The laminated fiber preform is then placed into a needle-punching mold made of EVA foam material, using a needle-punching density of 15 needles / cm. 2 Repeated punctures with a needle depth of 20 mm were performed to initially bond the three layers of prepreg fibers, resulting in a preformed fiber preform. The coating thickness of the interlayer bridging resin was 0.06 mm. The specific preparation method was as follows: maleic anhydride was added to linear phenolic resin, and the mixture was magnetically stirred at 320 rpm for 0.8 h in a constant temperature water bath at 82 °C. After the reaction was completed, the mixture was naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.095 MPa for 18 min to obtain the final product.

[0049] Afterwards, the needle-punched fiber preform is removed, and 1500tex carbon fiber suture is used to sew it with a 60° suture angle and a 20mm stitch length to obtain an integrated fiber preform.

[0050] Step S4, Mold Closure: Transfer the integrated fiber preform into the mold cavity and fix the mold by connecting with screws; use VARTM mold, designed as an integrated molding mold according to the structural characteristics of the protective cover of the power battery of new energy vehicles, including upper mold, sealing gasket, injection port, lower mold, and dispensing port; at the same time, before closing the mold in step S4, an airtightness test is required, that is, first immerse the mold in water after assembly, keep the dispensing port closed and the injection port open; then introduce compressed air through the injection port and observe whether there are bubbles emerging from the edge of the mold in the water tank. If there are no bubbles, it proves that the mold has good airtightness.

[0051] Step S5, Vacuum-assisted resin transfer molding: This involves sequentially performing pre-vacuuming, negative pressure filling, and positive pressure compaction and degassing; specifically: Pre-vacuuming: Close the ball valve at the bottom inlet of the mold, open the ball valve at the outlet, start the vacuum pump, adjust the pressure to -0.1MPa, maintain the pressure until the pressure gauge reading stabilizes, and expel the air from the mold. Negative pressure filling: Inject interlayer bridging resin into the injection tank, adjust the negative pressure inside the mold to -0.05MPa, close the ball valve at the mold outlet, open the ball valve at the injection tank and the bottom inlet of the mold, and slowly draw the resin in by relying on the negative pressure inside the mold. The filling time is 8 minutes until the pores of each layer are fully filled by the resin, and then close the ball valve at the inlet. Positive pressure compaction and venting: Open the ball valve at the outlet, adjust the pressure of the air compressor pressure reducing valve to 0.6MPa, maintain the pressure for 1 minute, and force the residual gas and excess resin in the mold to the outlet; repeat the "pressure holding-venting operation" until no air bubbles are discharged from the resin, and then close the ball valves at the outlet and injection port.

[0052] Step S6, Heating and Curing: Transfer the mold to an oven and cure it using a segmented heating and curing process. The segmented heating and curing process is as follows: First, heat the mold to 82℃ at a heating rate of 1.2℃ / min and hold for 0.8h (to allow the filler resin and prepreg resin to initially impregnate and fuse, while further evaporating the solvent and avoiding residual bubbles). Then, heat the mold to 122℃ at a heating rate of 1.2℃ / min and hold for 1.8h (to form a preliminary gel network). Next, heat the mold to 162℃ at a heating rate of 1.7℃ / min and hold for 2.8h (to form a dense cross-linked network of phenolic resin; to complete the imidization of the PI prepolymer in the load-bearing layer; to fully cross-link the siloxane graft groups in the heat insulation layer; and to begin carbonization of the ablation-resistant layer). After that, heat the mold to 202℃ at a heating rate of 1.2℃ / min and hold for 0.8h (to eliminate residual small molecule byproducts, increase the cross-linking density; to make the carbon layer of the ablation-resistant layer denser; and to promote interlayer bonding).

[0053] Step S7, Demolding and Drying: Remove the mold from the oven, cool it to room temperature, open the mold, and remove the wet gel; transfer the wet gel to a drying oven and keep it at 62°C for 47 hours to obtain the final product.

[0054] Comparative Example 1: A method for preparing a protective cover plate includes: Step S1, Fiber material modification treatment: First, the quartz fiber felt and high silica fiber cloth are modified separately. The modification treatment of the quartz fiber felt and high silica fiber cloth is the same as in Example 3, and unmodified carbon fiber cloth is used.

[0055] Then, the individually modified quartz fiber felt, high silica fiber cloth, and unmodified carbon fiber cloth were subjected to interface bridging modification; the specific interface bridging modification method was the same as in Example 3.

[0056] Step S2, layered resin pre-impregnation: consistent with step S2 in Example 3.

[0057] Step S3, Pre-forming of the protective cover plate: Same as step S3 in Example 3.

[0058] Step S4, mold closing: Same as step S4 in Example 3.

[0059] Step S5, Vacuum-assisted resin transfer molding: Same as step S5 in Example 3.

[0060] Step S6, Heating and Curing: Same as step S6 in Example 3.

[0061] Step S7, Demolding and Drying: Same as step S7 in Example 3.

[0062] Comparative Example 2: A method for preparing a protective cover plate includes: Step S1, Fiber material modification treatment: First, carbon fiber cloth and high silica fiber cloth are modified separately. The modification treatment of carbon fiber cloth and high silica fiber cloth is the same as in Example 3, and unmodified quartz fiber felt is used.

[0063] Then, the separately modified carbon fiber cloth, high silica fiber cloth, and unmodified quartz fiber felt were subjected to interface bridging modification; the specific interface bridging modification method was the same as in Example 3.

[0064] Step S2, layered resin pre-impregnation: consistent with step S2 in Example 3.

[0065] Step S3, Pre-forming of the protective cover plate: Same as step S3 in Example 3.

[0066] Step S4, mold closing: Same as step S4 in Example 3.

[0067] Step S5, Vacuum-assisted resin transfer molding: Same as step S5 in Example 3.

[0068] Step S6, Heating and Curing: Same as step S6 in Example 3.

[0069] Step S7, Demolding and Drying: Same as step S7 in Example 3.

[0070] Comparative Example 3: A method for preparing a protective cover plate includes: Step S1, Fiber material modification treatment: First, carbon fiber cloth and quartz fiber felt are modified separately. The modification treatment of carbon fiber cloth and quartz fiber felt is the same as in Example 3, and unmodified high silica fiber cloth is used.

[0071] Then, the separately modified carbon fiber cloth, quartz fiber felt, and unmodified high silica fiber cloth were subjected to interface bridging modification; the specific interface bridging modification method was the same as in Example 3.

[0072] Step S2, layered resin pre-impregnation: consistent with step S2 in Example 3.

[0073] Step S3, Pre-forming of the protective cover plate: Same as step S3 in Example 3.

[0074] Step S4, mold closing: Same as step S4 in Example 3.

[0075] Step S5, Vacuum-assisted resin transfer molding: Same as step S5 in Example 3.

[0076] Step S6, Heating and Curing: Same as step S6 in Example 3.

[0077] Step S7, Demolding and Drying: Same as step S7 in Example 3.

[0078] Comparative Example 4: A method for preparing a protective cover plate includes: Step S1, Fiber material modification treatment: Carbon fiber cloth, quartz fiber felt and high silica fiber cloth are modified separately. The individual modification treatment of carbon fiber cloth, quartz fiber felt and high silica fiber cloth is the same as in Example 3, without interface bridging modification.

[0079] Step S2, layered resin pre-impregnation: consistent with step S2 in Example 3.

[0080] Step S3, Pre-forming of the protective cover plate: Same as step S3 in Example 3.

[0081] Step S4, mold closing: Same as step S4 in Example 3.

[0082] Step S5, Vacuum-assisted resin transfer molding: Same as step S5 in Example 3.

[0083] Step S6, Heating and Curing: Same as step S6 in Example 3.

[0084] Step S7, Demolding and Drying: Same as step S7 in Example 3.

[0085] Comparative Example 5: A method for preparing a protective cover plate includes: Step S1, fiber material modification treatment: consistent with step S1 in Example 3.

[0086] Step S2, Layered Resin Pre-impregnation: The modified quartz fiber felt and high-silica fiber cloth are pre-impregnated in special resins respectively. The special resins corresponding to the quartz fiber felt and high-silica fiber cloth are the same as those in Example 3. The modified carbon fiber cloth is impregnated in phenolic resin to obtain the corresponding pre-impregnated fiber cloth.

[0087] Step S3, Pre-forming of the protective cover plate: Same as step S3 in Example 3.

[0088] Step S4, mold closing: Same as step S4 in Example 3.

[0089] Step S5, Vacuum-assisted resin transfer molding: Same as step S5 in Example 3.

[0090] Step S6, Heating and Curing: Same as step S6 in Example 3.

[0091] Step S7, Demolding and Drying: Same as step S7 in Example 3.

[0092] Comparative Example 6: A method for preparing a protective cover plate includes: Step S1, fiber material modification treatment: consistent with step S1 in Example 3.

[0093] Step S2, Layered Resin Pre-impregnation: The modified carbon fiber cloth and high-silica fiber cloth are pre-impregnated in special resins respectively. The special resins corresponding to the carbon fiber cloth and high-silica fiber cloth are the same as those in Example 3. The modified quartz fiber felt is impregnated in phenolic resin to obtain the corresponding pre-impregnated fiber cloth.

[0094] Step S3, Pre-forming of the protective cover plate: Same as step S3 in Example 3.

[0095] Step S4, mold closing: Same as step S4 in Example 3.

[0096] Step S5, Vacuum-assisted resin transfer molding: Same as step S5 in Example 3.

[0097] Step S6, Heating and Curing: Same as step S6 in Example 3.

[0098] Step S7, Demolding and Drying: Same as step S7 in Example 3.

[0099] Comparative Example 7: A method for preparing a protective cover plate includes: Step S1, fiber material modification treatment: consistent with step S1 in Example 3.

[0100] Step S2, Layered Resin Pre-impregnation: The modified carbon fiber cloth and quartz fiber felt are pre-impregnated in special resins respectively. The special resins corresponding to the carbon fiber cloth and quartz fiber felt are the same as those in Example 3. The modified high silica fiber cloth is impregnated in phenolic resin to obtain the corresponding pre-impregnated fiber cloth.

[0101] Preparation of the carrier layer: The modified carbon fiber cloth from step S1 is impregnated with a special resin for the carrier layer. The content of the special resin for the carrier layer is 42% (i.e., the special resin for the carrier layer accounts for 42% of the total mass of fiber + resin). After pre-impregnation at room temperature for 10 min, it is taken out and dried at 60℃ for 30 min to obtain the carrier layer pre-impregnated fiber cloth. The specific preparation method of the special resin for the carrier layer is as follows: First, linear phenolic resin (CAS: 65733-76-8, the same below), polyimide prepolymer (molecular weight 1000~1500) and hexamethylenetetramine are mixed and placed in a water bath at 50℃, and magnetically stirred at 300 rpm for 20 min. The mass ratio of linear phenolic resin, polyimide prepolymer and hexamethylenetetramine is 40:10:1. Then, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.09MPa for 30 min to obtain the final product. Preparation of the heat insulation layer: The modified quartz fiber felt from step S1 is impregnated with a special resin for the heat insulation layer. The content of the special resin for the heat insulation layer is 37% (i.e., the special resin for the heat insulation layer accounts for 37% of the total mass of fiber + resin). After pre-impregnation at room temperature for 15 minutes, it is taken out and dried at 60℃ for 30 minutes to obtain the pre-impregnated fiber felt for the heat insulation layer. The specific preparation method of the special resin for the heat insulation layer is as follows: KH-550 is added to the linear phenolic resin at a dropping rate of 2 drops / s. Then, the resin is magnetically stirred at 250 rpm for 2 hours in a water bath at 70℃. The mass ratio of KH-550 to the linear phenolic resin is 1:9. Finally, the resin is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.09MPa for 30 minutes to obtain the final product. Preparation of the ablation-resistant layer: The modified high-silica fiber cloth from step S1 is impregnated with a special resin for the ablation-resistant layer. The content of the special resin for the ablation-resistant layer is 47% (i.e., the special resin for the ablation-resistant layer accounts for 47% of the total mass of fiber + resin). After pre-impregnation at room temperature for 10 minutes, it is taken out and dried at 60℃ for 30 minutes to obtain the pre-impregnated fiber cloth for the ablation-resistant layer. The specific preparation method of the special resin for the ablation-resistant layer is as follows: linear phenolic resin and boron phenolic resin (such as FB type resin) are mixed at a mass ratio of 7:3 and preheated in a water bath environment at 60℃ for 10 minutes. Then, p-toluenesulfonic acid is added to the mixed resin. The mass ratio of p-toluenesulfonic acid to linear phenolic resin is 1:70. The mixture is magnetically stirred at a speed of 250 rpm for 30 minutes. Finally, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.09MPa for 30 minutes to obtain the final product.

[0102] Step S3, Pre-forming of the protective cover plate: Same as step S3 in Example 3.

[0103] Step S4, mold closing: Same as step S4 in Example 3.

[0104] Step S5, Vacuum-assisted resin transfer molding: Same as step S5 in Example 3.

[0105] Step S6, Heating and Curing: Same as step S6 in Example 3.

[0106] Step S7, Demolding and Drying: Same as step S7 in Example 3.

[0107] Experimental verification: The integrated protective cover plates prepared in Examples 2 to 4 and the protective cover plates prepared in Comparative Examples 1 to 7 were subjected to oxyacetylene ablation tests (i.e., oxyacetylene flame was used as a heat source to ablate the cover plates) according to the provisions of GJB 323B-2018 "Test Method for Ablation of Ablation Materials". The test environment and test conditions of Examples 2 to 4 and Comparative Examples 1 to 7 were kept consistent. The final linear ablation rates of the protective cover plates are shown in the table below (linear ablation rate is the rate at which the linear dimension of the material changes with time during the ablation process):

[0108] As can be clearly seen from the table above, the present invention employs a synergistic combination of a specific high-density load-bearing layer, a low-density heat insulation layer, and a high-density ablation-resistant layer to effectively reduce the linear ablation rate of the protective cover under flame ablation conditions, thereby avoiding problems such as delamination and peeling of the cover under high-temperature and high-speed flame flow, resulting in high reliability and stability of protection.

Claims

1. A lightweight, heat-insulating, integrated protective cover, characterized in that: It includes a high-density load-bearing layer, a low-density heat insulation layer, and a high-density ablation-resistant layer. The high-density load-bearing layer is located on the side closer to the passenger compartment, using modified carbon fiber cloth as the reinforcing fiber and phenolic-polyimide dynamic cross-linked resin as the special resin for the load-bearing layer. The low-density heat insulation layer uses modified quartz fiber felt as the reinforcing fiber and siloxane-grafted phenolic resin as the special resin for the heat insulation layer. The high-density ablation-resistant layer is located on the side closer to the battery cell, using modified high-silica fiber cloth as the reinforcing fiber and boron-carbon synergistic phenolic resin as the special resin for the ablation-resistant layer.

2. The lightweight, heat-insulating integrated protective cover according to claim 1, characterized in that: The thickness of the high-density load-bearing layer is 4-6 mm, the thickness of the low-density heat insulation layer is 2-4 mm, and the thickness of the high-density ablation-resistant layer is 0.25-0.75 mm.

3. A method for preparing a lightweight, heat-insulating, integrated protective cover according to claim 1 or 2, characterized in that: include: Step S1, Fiber material modification treatment: First, carbon fiber cloth, quartz fiber felt and high silica fiber cloth are modified separately. Then, the individually modified carbon fiber cloth, quartz fiber felt, and high silica fiber cloth were subjected to interface bridging modification. Step S2, Layered Resin Pre-impregnation: Modified carbon fiber cloth, quartz fiber felt, and high silica fiber cloth are respectively pre-impregnated in special resin to obtain the corresponding pre-impregnated fiber cloth. Step S3, Protective cover plate preforming: The pre-impregnated fiber cloth of the load-bearing layer, the pre-impregnated fiber cloth of the heat insulation layer, and the pre-impregnated fiber cloth of the ablation-resistant layer are laid in sequence. Interlayer bridging resin is evenly coated between each layer, and the stacked fiber preform is placed into a needle punching mold to obtain a preformed fiber preform. Then, the preformed fiber preform is taken out and reinforced by sewing with carbon fiber stitching to obtain an integrated fiber preform. Step S4, Mold Closure: Transfer the integrated fiber preform into the mold cavity and fix the mold by connecting with screws; Step S5, Vacuum-assisted resin transfer molding: Pre-vacuuming, negative pressure filling, and positive pressure compaction and degassing are performed sequentially; Step S6, Heating and Curing: Transfer the mold to an oven and cure it using a segmented heating and curing process; Step S7, Demolding and Drying: Remove the mold from the oven, cool it to room temperature, open the mold, and remove the wet gel; transfer the wet gel to a drying oven and heat it to dry, and you will get the product.

4. The method for preparing a lightweight, heat-insulating, integrated protective cover according to claim 3, characterized in that: In step S1, the individual modification treatments of carbon fiber cloth, quartz fiber felt, and high-silica fiber cloth are specifically as follows: Carbon fiber cloth modification treatment: Arrange carbon fibers in a tube furnace and introduce argon gas at a flow rate of 190-210 mL / min to ensure no oxygen residue in the tube furnace; keep the argon gas inlet and heat to 1150-1250℃ at a heating rate of 4.5-5.5℃ / min, then introduce a mixture of argon gas and silicon tetrachloride vapor with a volume ratio of 8.1-9.9:0.9-1.1, and hold at this temperature for 1.8-2.2 h. SiC whiskers grow in situ on the surface of the carbon fiber cloth. After cooling to room temperature, remove and set aside for later use. Quartz fiber felt modification treatment: In a mixed solvent of anhydrous ethanol and deionized water, CTAB is added at a volume-to-mass ratio of 10–12 mL: 5–6 mL: 0.1 g. The mixture is magnetically stirred at 230–270 rpm for 8–12 min. Then, 14 mol / L ammonia is added dropwise to stabilize the solution pH at 9–10. Next, tetraethyl orthosilicate is added dropwise at a rate of 0.8–1.2 mL / min at a volume ratio of 1:10–12 to anhydrous ethanol, while stirring at 230–270 rpm. The precursor sol was obtained by magnetic stirring for 1.8–2.2 h. Then, the quartz fiber felt was fixed on the clamp of the dip coater and immersed in the precursor sol at a rate of 5 mm / s. After complete immersion, it was kept immersed for 9–11 min and then pulled out of the sol at a rate of 5 mm / s. Finally, after drying at room temperature for 23–25 h, the quartz fiber felt was transferred to a quartz crucible in a muffle furnace and heated to 780–820 °C at a heating rate of 1.5–2.5 °C / min. It was held at this temperature for 0.8–1.2 h and then naturally cooled to room temperature before being taken out for use. High-silica fiber cloth modification treatment: Aluminum nitrate nonahydrate was added to deionized water at a mass-to-volume ratio of 1 g: 3–3.2 mL. The mixture was magnetically stirred at 280–320 rpm for 28–32 min. Then, fumed silica was added to the solution at a molar ratio of fumed silica to aluminum nitrate nonahydrate of 2:

3. The mixture was stirred at 380–420 rpm for 58–62 min to obtain a mixed precursor solution. Afterward, the high-silica fiber cloth was spread evenly on the surface of the mixture in a hydrothermal reactor. The inner lining of the polytetrafluoroethylene (PTFE) is prepared, and the mixed precursor liquid is slowly poured into the PTFE lining, with the volume of the mixed precursor liquid accounting for 70% of the effective volume of the PTFE lining. The temperature is increased to 180–220°C at a heating rate of 2.5–3.5°C / min, and held at this temperature for 11.5–12.5 hours. After naturally cooling to room temperature, the mixture is removed and placed in a corundum crucible in a muffle furnace. The temperature is increased to 580–620°C at a heating rate of 1.5–2.5°C / min, and held at this temperature for 1.8–2.2 hours. After naturally cooling to room temperature again, the mixture is removed for use. Based on further optimization of the above scheme, the interface bridging modification in step S1 is specifically as follows: First, 4,4'-diaminodiphenylmethane is added to anhydrous ethanol and stirred at 230-270 rpm for 38-42 min until the solution becomes transparent, thus preparing an MDA ethanol solution with a mass concentration of 1.8-2.2 wt%. Then, the modified carbon fiber cloth, modified quartz fiber felt, and modified high-silica fiber cloth are respectively immersed in the MDA ethanol solution and soaked at room temperature for 28-32 min. Finally, the soaked fiber cloth is removed and vacuum dried at a vacuum degree of -0.075--0.085 MPa and 98-102℃ for 0.8-1.2 h to obtain the final product.

5. A method for preparing a lightweight, heat-insulating, integrated protective cover according to claim 3 or 4, characterized in that: Step S2 specifically involves: Preparation of the carrier layer: The modified carbon fiber cloth from step S1 is impregnated with a special resin for the carrier layer, with a resin content of 40%–45%. After pre-impregnation at room temperature for 9–11 minutes, it is removed and dried at 58–62°C for 28–32 minutes to obtain a pre-impregnated fiber cloth for the carrier layer. The specific preparation method of the special resin for the carrier layer is as follows: Linear phenolic resin, polyimide prepolymer, and hexamethylenetetramine are mixed and placed in a water bath at 48–52°C, and magnetically stirred at 280–320 rpm for 18–22 minutes. The mass ratio of linear phenolic resin, polyimide prepolymer, and hexamethylenetetramine is 40:10:

1. After natural cooling to room temperature, it is degassed in a vacuum degassing tank with a vacuum degree of -0.085–-0.095 MPa for 28–32 minutes to obtain the final product. Preparation of the heat insulation layer: The modified quartz fiber felt from step S1 is impregnated with a special resin for the heat insulation layer, the content of the special resin for the heat insulation layer is 35% to 40%, pre-impregnated at room temperature for 14 to 16 minutes, then removed and dried at 58 to 62°C for 28 to 32 minutes to obtain a pre-impregnated fiber felt for the heat insulation layer; The specific preparation method of the special resin for the heat insulation layer is as follows: KH-550 is added dropwise to linear phenolic resin at a dropping rate of 2 drops / s, and then magnetically stirred at 230 to 270 rpm for 1.8 to 2.2 hours in a water bath at 68 to 72°C, the mixture is kept in a water bath at 230 to 270 rpm, the mass ratio of KH-550 to linear phenolic resin is 1:9, and finally cooled naturally to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085 to -0.095 MPa for 28 to 32 minutes to obtain the final product; Preparation of the ablation-resistant layer: The modified high-silica fiber cloth from step S1 is impregnated with a special resin for the ablation-resistant layer, with a resin content of 45%–50%. After pre-impregnation at room temperature for 9–11 minutes, it is removed and dried at 58–62°C for 28–32 minutes to obtain the pre-impregnated fiber cloth for the ablation-resistant layer. The specific preparation method of the special resin for the ablation-resistant layer is as follows: linear phenolic resin and boron phenolic resin are mixed at a mass ratio of 7:3 and preheated in a water bath at 58–62°C for 9–11 minutes. Then, p-toluenesulfonic acid is added to the mixed resin, with a mass ratio of p-toluenesulfonic acid to linear phenolic resin of 1:

70. The mixture is magnetically stirred at a speed of 230–270 rpm for 28–32 minutes. Finally, it is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085–-0.095 MPa for 28–32 minutes to obtain the final product.

6. A method for preparing a lightweight, heat-insulating, integrated protective cover according to claim 3 or 4, characterized in that: In step S3, the coating thickness of the interlayer bridging resin is 0.04–0.06 mm. The specific preparation method of the interlayer bridging resin is as follows: maleic anhydride is added to linear phenolic resin, and the mixture is magnetically stirred at a speed of 280–320 rpm for 0.8–1.2 h in a constant temperature water bath at 78–82 °C. After the reaction is completed, the mixture is naturally cooled to room temperature and degassed in a vacuum degassing tank with a vacuum degree of -0.085–-0.095 MPa for 18–22 min to obtain the final product.

7. The method for preparing a lightweight, heat-insulating, integrated protective cover according to claim 6, characterized in that: In step S3, the needle-punching mold is made of EVA foam material, and the needle-punching density is 5-15 needles / cm. 2 Repeated punctures with a needle depth of 6-20 mm are performed to initially bond the three layers of pre-impregnated fibers, resulting in a pre-formed fiber preform. Then, the needled fiber blank is removed, and 800-1500 tex carbon fiber sutures are used to sew and reinforce the fiber preform with a suture angle of 40°-60° and a stitch length of 10-20 mm, resulting in an integrated fiber preform.

8. The method for preparing a lightweight, heat-insulating, integrated protective cover according to claim 7, characterized in that: In step S4, a VARTM mold is used, which is designed as an integrated molding mold based on the structural characteristics of the protective cover of the power battery of new energy vehicles. The mold includes an upper mold, a sealing gasket, a glue injection port, a lower mold, and a glue outlet. At the same time, before the mold is assembled in step S4, an airtightness test is required. That is, the mold is first assembled and then immersed in water, keeping the glue outlet closed and the glue injection port open. Then, compressed air is introduced through the glue injection port, and it is observed whether there are bubbles emerging from the edge of the mold in the water tank. If there are no bubbles, it proves that the mold has good airtightness.

9. The method for preparing a lightweight, heat-insulating, integrated protective cover according to claim 8, characterized in that: In step S7, the wet gel is kept in a drying oven at 58-62°C for 47-49 hours.

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