High silica fiber-carbon fiber composite reinforced phenolic resin and preparation method thereof

Abstract

The invention discloses a high silica fiber-carbon fiber composite reinforced phenolic resin and a preparation method thereof. The preparation method comprises the following steps: providing a premix, and pretreating the premix; adding the pre-treated premix into a first mold cavity for pre-pressing, and then performing first cooling and mold stripping to obtain a pre-pressed material; and adding the pre-pressed material into a second mold cavity for pressurization, and then carrying out curing, secondary cooling demolding and post-curing to obtain the high silica fiber-carbon fiber composite reinforced phenolic resin. Wherein the pre-pressed material comprises a high silica fiber-phenolic resin pre-pressed material and a carbon fiber-phenolic resin pre-pressed material; according to the method, the high-silica fiber reinforced phenolic resin and the carbon fiber reinforced phenolic resin are compounded in the mode of independent pre-pressing, overall mold pressing and curing, an existing bonding procedure is omitted, the process is simple, the production efficiency is high, the high-silica fiber part and the carbon fiber part are distributed well, the defects of cracks, looseness and the like do not exist, and the risk of debonding does not exist.

Description

Technical Field

[0001] This invention relates to the field of composite material molding technology, and in particular to a high-silica fiber-carbon fiber composite reinforced phenolic resin and its preparation method. Background Technology

[0002] Compression molding is one of the important methods for molding composite materials. It has a long history, good process repeatability, and low manufacturing cost. Depending on the selection and ratio of resin and fiber, products with advantages such as light weight, high specific strength, good electrical insulation, high temperature resistance, and strong wave transmission can be prepared. It is an ideal thermal protection and ablation resistant material and is often used in the aerospace product field.

[0003] With the development of the aerospace industry, composite molded products are no longer limited to external heat insulation and protection; their use in various nozzles is gradually increasing. The inner non-metallic layer primarily uses carbon fiber reinforced phenolic resin, which has good ablation resistance; the outer non-metallic layer uses high-silica fiber reinforced phenolic resin, which has good heat insulation properties. Current technology often involves separately molding the high-silica and carbon fiber layers, machining the surfaces, and finally bonding them with adhesives to achieve good ablation resistance and heat insulation. However, the bonding is affected by the adhesive, the curing process, and the ambient temperature, resulting in low production efficiency and a risk of debonding.

[0004] Therefore, there is an urgent need to provide a new high-silica fiber-carbon fiber composite reinforced phenolic resin and its preparation method to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a high-silica fiber-carbon fiber composite reinforced phenolic resin and its preparation method, thereby solving the technical problems of cumbersome bonding process, low production efficiency and risk of debonding in the existing composite molding high-silica fiber products and carbon fiber products.

[0006] In a first aspect, the present invention provides a method for preparing a high-silica fiber-carbon fiber composite reinforced phenolic resin, comprising the following steps: Provide premixed materials and pretreat the premixed materials; The pre-treated premixed material is added to the cavity of the first mold for pre-compression, and then demolded after the first cooling process to obtain the pre-compressed material; The pre-compressed material is added to the cavity of the second mold and pressurized, followed by curing, second cooling and demolding, and post-curing to obtain a high-silica fiber-carbon fiber composite reinforced phenolic resin; wherein... Premixes include high silica fiber-phenolic resin premixes and carbon fiber-phenolic resin premixes; Precompression materials include high silica fiber-phenolic resin precompression materials and carbon fiber-phenolic resin precompression materials; In a second aspect, the present invention provides a high-silica fiber-carbon fiber composite reinforced phenolic resin, which is obtained by the preparation method of the high-silica fiber-carbon fiber composite reinforced phenolic resin provided in the first aspect of the present invention.

[0007] Compared with the prior art, the beneficial effects of the present invention include: This invention achieves the composite of high silica fiber reinforced phenolic resin and carbon fiber reinforced phenolic resin through separate pre-compression + overall molding + curing, omitting the existing bonding process. The process is simple, the production efficiency is high, and the high silica fiber part and carbon fiber part are well distributed without defects such as cracks and looseness, and there is no risk of debonding. Attached Figure Description

[0008] Figure 1 This is an optical photograph of the high-silica fiber-carbon fiber composite reinforced phenolic resin prepared in Example 1 of this invention. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0010] In a first aspect, the present invention provides a method for preparing a high-silica fiber-carbon fiber composite reinforced phenolic resin, comprising the following steps: S1. Provide premixed materials and pretreat the premixed materials; wherein, the premixed materials include high silica fiber-phenolic resin premixed materials and carbon fiber-phenolic resin premixed materials. S2. The pre-treated premixed material is added to the cavity of the first mold for pre-compression, and then demolded after the first cooling to obtain the pre-compressed material; wherein, the pre-compressed material includes high silica fiber-phenolic resin pre-compressed material and carbon fiber-phenolic resin pre-compressed material; S3. The pre-pressed material is added to the cavity of the second mold and pressurized, followed by curing, second cooling and demolding, and post-curing to obtain high silica-oxygen fiber-carbon fiber composite reinforced phenolic resin.

[0011] This invention optimizes the existing single-press curing process into a process of separate pre-pressing + overall molding + curing, which solves the problem in conventional curing methods where, after mixing and adding materials, the premixed material has fluidity and causes different fibers to mix and flow during the pressurization process, resulting in different fibers mixing together after curing and the molded products being unqualified.

[0012] This invention achieves the composite of high-silica fiber-reinforced phenolic resin and carbon fiber-reinforced phenolic resin through separate pre-compression and overall molding. On the one hand, it can eliminate the machining and bonding processes in the existing separate molding + machine pressing + adhesive bonding process, thereby improving production efficiency. On the other hand, it can reduce the feeding time in the overall molding stage (the feeding time in the overall molding stage has been shortened from more than half an hour per piece to just a few minutes). Furthermore, it can utilize the gaps in personnel during the curing stage to feed materials in the separate pre-compression stage, thereby improving the rolling production efficiency in the batch production process.

[0013] In this embodiment, step S1 includes the following process for preparing the premix: using fiber and phenolic resin as raw materials, the premix is ​​obtained through impregnation, first loosening, air drying, second loosening, and first drying.

[0014] The fibers include high-silica fibers and carbon fibers.

[0015] The phenolic resin is at least one of acetaminophen, magnesium phenolic resin, boron phenolic resin, and barium phenolic resin.

[0016] The mass ratio of fiber to phenolic resin is 1:(0.8~1).

[0017] The solid content of phenolic resin is 50% to 60%.

[0018] The raw materials for the premix also include solvents.

[0019] Specifically, the solvent is ethanol.

[0020] Specifically, the mass ratio of fiber to solvent is 1:(0.5~0.6).

[0021] Specifically, the volume fraction of the solvent is 90-99.5%.

[0022] The fiber length is 30mm to 50mm. By controlling the fiber length within this range, this invention can effectively improve the flowability of the premix during the molding process while ensuring the mechanical properties of the product, such as tensile, bending, impact, and compression. This avoids defects such as cracks and looseness caused by poor fiber flowability during the curing process. At the same time, reducing the fiber length can shorten the time required for the first loosening, drying, second loosening, and first drying processes in the premix preparation process, thereby improving production efficiency and product quality.

[0023] In the first drying process, the drying temperature is 60℃~70℃ and the drying time is 10min~30min.

[0024] In this embodiment, in step S1, the volatile content of the premix is ​​2% to 7%, including but not limited to 2%, 3%, 4%, 5%, 6%, 7%, etc.

[0025] In this embodiment, in step S1, the fiber mass percentage in the premix is ​​65%~75%. It should be noted that during the preparation of the premix, due to reasons such as resin raw material dripping and solids (including solvents in the resin and solvents added during the mixing process) evaporation, the actual fiber mass percentage in the premix differs from the fiber mass percentage in the raw materials of the premix.

[0026] In this embodiment, step S1, the process of pre-treating the premix includes: third loosening, pre-forming, and second drying of the premix.

[0027] During the preparation of premixed materials, due to large-scale production, a small amount of fibers may not be uniformly mixed with the resin during the impregnation process. After the second loosening process, a small amount of premixed material may not be completely loosened, easily leading to poor-quality premixed material such as polymer buildup and clumping after the first drying process. When these premixed materials are mixed with normal premixed materials for molding, they can easily cause defects such as poor fiber bonding and loose cracks during the molding and curing process. This invention, by adding the above-mentioned pretreatment process and establishing premixed material standards, can effectively improve the uniformity of molding quality, thereby reducing defects such as cracks. Simultaneously, by using pre-forming followed by material feeding according to different blank structures, defects such as loose cracks caused by uneven manual material feeding, resulting in uneven fiber filling of the mold cavity during molding, can be avoided to a certain extent.

[0028] In the third loosening process, the premixed material used for feeding is required to be free of clumps, polymers, and other excess substances, and the fiber bundles must contain 1 to 5 fibers.

[0029] In the preforming process, the premixed material after the third loosening treatment is divided into several parts for preforming. Each part shall not weigh more than 1kg. The preforming process yields blank blocks with a thickness of 5mm to 15mm.

[0030] In the second drying process, the drying temperature is 50℃~60℃, the drying time is 15min~60min, and the material is kept warm until it is fed.

[0031] In this embodiment, the process of adding the pretreated premixed material into the first mold cavity includes: preheating the first mold to 60℃~90℃ and holding it at that temperature for 30min~60min; then adding the pretreated premixed material into the first mold cavity in batches, with pressure applied and compacted after each addition; and closing the mold without pressure after the material addition is complete. This invention does not limit the pressure during the compaction process; those skilled in the art can select the appropriate pressure based on actual conditions, such as the self-weight pressure of a hydraulic press.

[0032] Specifically, during the process of adding the pre-treated premixed material evenly to the cavity of the first mold in multiple stages, pressure must be applied and compacted after each addition to ensure that the fiber clusters in the premixed material are tightly bonded together. This invention does not limit the number of additions; those skilled in the art can select the appropriate number based on the actual situation. For example, if the blank structure is relatively simple (e.g., a straight cylinder), the number of additions can be controlled to 1-3 times; if the blank structure is more complex, such as having steps, thin walls, or multiple curved surfaces, the number of additions can be controlled to 3-6 times. Compaction after addition ensures that the gap between the punch and die is less than 20mm and the equipment pressure is less than 1 / 10 of the molding pressure.

[0033] Specifically, the feeding temperature should be adjusted according to the volatile content of the premix. When the volatile content of the premix is ​​high, the mold temperature should be appropriately reduced during feeding. High volatile content results in good fluidity, and low-temperature feeding can promote uniform filling of the mold cavity by the premix, and also prevent excessive temperature fluidity from causing fibers and resin to overflow from the cavity. Specifically, the volatile content of the premix is ​​generally 2%~7%, and the feeding temperature (i.e., the insulation temperature of the first mold) is generally 60℃~90℃. If the volatile content is higher than the upper limit, the feeding temperature should be lower than the lower limit, and vice versa. The median volatile content is 70℃~80℃.

[0034] In this embodiment, step S2, the pre-pressing process includes: after adding material, heating the first mold to 85℃~90℃ and holding it at that temperature for 30min~90min; when the temperature of the first mold reaches 85℃±1℃, applying pressure to the pre-pressing pressure in one go; wherein, the calculation formula for the pre-pressing pressure is as follows: F1=1000×P×S×1 / 3, where F1 refers to the pre-pressing pressure, the unit is KN, P refers to the pressure per unit area on the surface of the blank during the pressurization process, the range of P is 24MPa~50MPa, and S refers to the projected area of ​​the product, the unit is m. 2 .

[0035] Pre-compression is a process where, during the resin's viscous flow but before curing, appropriate pressure is applied to force the resin and fibers to bond tightly together, allowing the material to flow and distribute evenly within the mold cavity. The premix is ​​pressurized and kept warm at a relatively low temperature to overcome internal friction within the premix and external friction between the material and the mold cavity, ensuring the material fully fills the mold cavity. During pre-compression, the temperature should not be too high. If the temperature exceeds 90℃, the resin will undergo a slow curing reaction, forming a mirror layer on the product surface. This hinders the cross-linking reaction at the bonding surfaces of the two parts during subsequent overall composite molding, easily causing delamination and cracking defects at the interface. After feeding, applying 1 / 3 of the molding pressure allows the resin to react initially during the mold closing and heating process. With its low viscosity and good flowability, the resin can be evenly distributed under pressure, which can compensate to some extent for the small amount of fiber-poor resin caused by incomplete kneading during premix preparation.

[0036] In this embodiment, step S2, the first cooling and demolding process includes: after pre-pressing, allowing the billet to cool naturally to below 60°C before demolding.

[0037] In this embodiment, step S3, the process of adding the pre-compression material into the second mold cavity includes: heating the second mold to 60℃~90℃ (preferably 75℃~85℃), and then adding the high silica fiber-phenolic resin pre-compression material and the carbon fiber-phenolic resin pre-compression material into the second mold cavity respectively. After the material is added, the mold is closed without pressure.

[0038] In this embodiment, step S3, the pressurization process includes: after feeding the material, heating the second mold to 103℃~107℃, and then pressurizing it to the molding pressure; wherein, the formula for calculating the molding pressure is as follows: F2=1000×P×S, where F2 refers to the molding pressure, the unit is kN, P refers to the pressure per unit area of ​​the blank surface during the pressurization molding process, the range of P is 24MPa~50MPa, and S refers to the projected area of ​​the product, the unit is m. 2 The second mold is heated from 60℃~90℃ to 103℃~107℃ over a period of 80min~200min. By controlling the heating time within this range, it is ensured that the premixed material is fully melted under pressure and has good fluidity.

[0039] Pressurization is applied during the viscous flow stage of the premix to overcome the internal friction of the premix and the external friction between the material and the mold cavity, ensuring that the material fully fills the mold cavity. Pressurization during the viscous flow stage of the premix requires applying pressure when the resin has good melt flowability.

[0040] In this embodiment, in step S3, the pressurization method can be either a single full press or multiple pressurizations. This invention does not limit this, and those skilled in the art can choose according to the actual situation. For example, for blanks with a short height and simple structure, a single pressurization is generally used; for others, pressurization is performed in 3 to 6 stages, with an interval of 5 to 10 minutes between each pressurization. For products with complex structures, using a gradient pressurization method is beneficial for improving the resin curing rate and enhancing the quality stability of the molded products.

[0041] In this embodiment, the curing process in step S3 includes: first heating the second mold to the peak temperature, then holding it at that temperature for 30 min to 90 min; then heating it to the end temperature. The holding time is determined based on the maximum thickness of the final blank. For every 1 mm increase in the maximum thickness of the blank, the holding time increases by 2 min to 5 min.

[0042] The heating rate is 0.1℃ / min to 0.5℃ / min.

[0043] The peak temperature is 130℃~140℃.

[0044] The final temperature is 160℃~180℃.

[0045] During the curing process, for cylindrical blanks, starting from the peak temperature, the temperature of the punch (i.e., the core mold) should be controlled to be 8℃~12℃ lower than that of the die (preferably 10℃). That is, when the die temperature rises to 175℃, the punch temperature should be 163℃~167℃ (preferably 165℃) to ensure the uniformity of the mold temperature.

[0046] During the curing process, the temperature is first raised to the temperature range where the resin polycondensation reaction is most intense (peak temperature), and the temperature and pressure are maintained for a period of time to allow most of the resin to cure. Then the temperature is raised to the end temperature to allow the unreacted resin to cure further.

[0047] In this embodiment, during step S3, the second cooling and demolding process involves cooling from the end temperature to 120°C at a cooling rate of 0.5°C / min to 2°C / min, followed by rapid cooling and demolding; after cooling to the peak temperature, the pressure is naturally released. By controlling the cooling rate and pressure from the end temperature to 120°C, the core-shell effect during cooling can be avoided, which can lead to stress concentration and cracking, as well as defects such as deformation caused by thermal changes in the billet.

[0048] In this embodiment, step S3, the post-curing process includes: holding the blank at 120°C~150°C for 60min~300min. By post-curing the blank, residual stress and volatiles are eliminated, and unreacted groups continue to crosslink, increasing density.

[0049] In this embodiment, the draft angle of the mold is 2°~2°30'. The present invention uses at least two sets of molds, which, through combination, can respectively satisfy the pre-compression of the high-silica fiber reinforced phenolic resin portion, the pre-compression of the carbon fiber reinforced phenolic resin portion, and the overall composite molding.

[0050] In a second aspect, the present invention provides a high-silica fiber-carbon fiber composite reinforced phenolic resin, which is obtained by the preparation method of the high-silica fiber-carbon fiber composite reinforced phenolic resin provided in the first aspect of the present invention.

[0051] To avoid redundancy, the molds in the following embodiments of the present invention are summarized as follows: The draft angle of the mold is 2°~2°30', adjusted according to the length-to-diameter ratio; the mold design requires a reasonable structure, high strength mold material, high surface finish of the mold cavity, and high temperature resistance; during the mold design process, the wall thickness should be as uniform as possible, the thickness should transition gradually, and sharp corners should be avoided. There are two sets of molds, which can be combined to respectively meet the pre-compression of the high silica fiber reinforced acetophenolic resin part, the pre-compression of the carbon fiber reinforced acetophenolic resin part, and the overall composite molding.

[0052] Example 1 1. Preparation of premix The premix preparation process is as follows: material receiving → shaving → resin mixing → impregnation → first loosening → air drying → second loosening → first drying → physicochemical testing → packaging and storage. In the shaving process, the fiber length is 30mm~50mm. In the resin mixing process, raw materials are weighed according to the following ratio for approximately 1kg of premix: 0.7kg fiber (high silica glass fiber yarn, standard GJB1679A-2008; carbon fiber short filament, standard Q / 0285YFC003-2014), 0.6kg resin (616 acetophenolic resin, solid content 55%, standard GJB1331-91), and 0.4kg ethanol (volume fraction 95%). In the first drying process, the temperature is 60℃ and the time is 20 minutes. The volatile matter content of the premix is ​​2.5%~3%.

[0053] 2. Premix pretreatment (a) Third looseness: The premixed material used for feeding should be free of clumps, polymers and other excess substances, and the fiber bundle should contain 1 to 5 fibers; (b) Pre-forming: Divide the premixed material into 6 equal parts for pre-forming. Each part shall not weigh more than 1kg. Pre-press it into a blank block with a thickness of 10mm. The length and width can be adjusted according to the actual product. (c) Second drying: After preforming, place it in an oven and keep it at 55°C until the material is added. The holding time is 25 minutes.

[0054] 3. Add ingredients (a) Preheating: Heat the mold to 75°C and keep it at that temperature for 40 minutes to preheat it; (b) Adding materials: Add the premixed material into the mold cavity in 6 portions, and pressurize it after each addition; 4. Preloading (a) Heating: After adding the material, heat the mold to 85°C and keep it at that temperature for 60 minutes; (b) Pressurization: When the mold temperature rises to 85°C, pressurize once with a pressure of 4000KN, and then release the pressure naturally after the pressurization.

[0055] 5. Cool down and demold After pre-compression, allow the mold to cool naturally to below 60°C before demolding.

[0056] 6. Add ingredients After heating the mold to 80°C, the pre-compressed high-silica fiber part and carbon fiber part are placed into the mold cavity according to the blank structure.

[0057] 7. Pressurize The mold temperature was raised to 105℃ for 125 minutes, and the pressure was increased in 4 stages with an interval of 10 minutes between each stage, resulting in a final pressure of 12000KN.

[0058] 8. Curing (a) Heating: Control the heating rate to 0.2℃ / min to raise the temperature to 135℃; (b) Heat preservation: Keep warm for 60 minutes; (c) Heating: Control the heating rate to 0.2℃ / min to heat up to 175℃ (die temperature). During the heating stage, the punch temperature needs to be 10℃ lower than the die temperature. That is, when the die temperature is heated to 175℃, the punch temperature is about 165℃. (d) Insulation: Insulate for 240 minutes.

[0059] 9. Cool down and demold Control the mold cooling rate to 1℃ / min to cool down to 120℃, then quickly cool down and demold; maintain the pressure until 135℃ and then release the pressure naturally.

[0060] 10. Post-curing After demolding, keep in an oven at 130°C for 120 minutes to eliminate residual internal stress and volatiles, and allow unreacted groups to continue crosslinking and increase density.

[0061] Following the method described in Example 1, 50 blanks (outer diameter 400mm, inner diameter 216mm, maximum thickness on one side 80mm (rotary body, thickness varies), height 145mm) have been continuously produced and are qualified. No internal cracks or other defects are found, and the high-silica fiber and carbon fiber portions are well-distributed. One of these products is as follows: Figure 1 As shown.

[0062] Please see Figure 1 ,pass Figure 1 It can be seen that the high-silica fiber-carbon fiber composite reinforced phenolic resin prepared by the method of the present invention has no internal defects such as cracks, the high-silica fiber part and the carbon fiber part are well distributed and tightly bonded, and there is no debonding phenomenon.

[0063] In summary, this invention achieves high-silica-carbon fiber composite reinforced acetaminophen resin product compression molding by improving the preparation of premix, feeding method, pressurization method, curing process, post-curing, and increasing the pre-treatment requirements of premix. The product has the ablation resistance of carbon fiber products and the thermal insulation properties of high-silica products, while greatly avoiding defects such as cracks and porosity of acetaminophen resin compression molding composites.

[0064] All other unspecified parts are existing technologies.

[0065] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a high-silica fiber-carbon fiber composite reinforced phenolic resin, characterized in that, Includes the following steps: Provide a premix and pretreat the premix; The premixed material after the pretreatment is added to the cavity of the first mold for pre-compression, and then demolded after the first cooling process to obtain the pre-compressed material; The pre-compressed material is added to the cavity of the second mold and pressurized, followed by curing, second cooling demolding, and post-curing to obtain a high-silica fiber-carbon fiber composite reinforced phenolic resin; wherein... The premix includes high silica fiber-phenolic resin premix and carbon fiber-phenolic resin premix; The precompression material includes high silica fiber-phenolic resin precompression material and carbon fiber-phenolic resin precompression material.

2. The method for preparing the high-silica fiber-carbon fiber composite reinforced phenolic resin according to claim 1, characterized in that, The preparation process of the premix includes: using fiber and phenolic resin as raw materials, and subjecting them to impregnation, first loosening, drying, second loosening, and first drying to obtain the premix; wherein, The fibers include high-silica fibers and carbon fibers; and / or, The phenolic resin is at least one selected from aminophenolic resin, magnesium phenolic resin, boron phenolic resin, and barium phenolic resin; and / or, The volatile matter content of the premix is ​​2% to 7%; and / or, In the premix, the fiber content is 65% to 75% by mass.

3. The method for preparing the high-silica fiber-carbon fiber composite reinforced phenolic resin according to claim 1, characterized in that, The pretreatment process for the premix includes: a third loosening, preforming, and a second drying of the premix; wherein, In the third loosening process, it is required that the premixed material used for feeding is free of clumps and excess polymer, and that the fiber bundle contains 1 to 5 fibers; and / or, In the preforming process, the premixed material after the third loosening treatment is divided into several portions for preforming, each portion weighing no more than 1 kg, to obtain blank blocks with a thickness of 5 mm to 15 mm; and / or, In the second drying process, the drying temperature is 50℃~60℃, the drying time is 15min~60min, and the material is kept warm until the material is added.

4. The method for preparing the high-silica fiber-carbon fiber composite reinforced phenolic resin according to claim 1, characterized in that, The process of adding the pre-treated premixed material into the first mold cavity includes: heating the first mold to 60℃~90℃ and holding it at that temperature for 30min~60min for preheating; then adding the pre-treated premixed material into the first mold cavity in batches, and pressing and compacting it after each addition.

5. The method for preparing the high-silica fiber-carbon fiber composite reinforced phenolic resin according to claim 1, characterized in that, The pre-compression process includes: after feeding the material, heating the first mold to 85℃~90℃ and holding it at that temperature for 30min~90min; when the temperature of the first mold reaches 85℃±1℃, applying pressure to the pre-compression pressure in one go; the calculation formula for the pre-compression pressure is as follows: F1=1000×P×S×1 / 3, where F1 refers to the pre-compression pressure, in kN, P refers to the pressure per unit area on the surface of the blank during the pressure molding process, P ranges from 24MPa to 50MPa, and S refers to the projected area of ​​the product, in m². 2 ; The first cooling and demolding process includes: after pre-pressing, allowing the billet to cool naturally to below 60°C before demolding.

6. The method for preparing the high-silica fiber-carbon fiber composite reinforced phenolic resin according to claim 1, characterized in that, The process of adding the pre-compression material into the second mold cavity includes: heating the second mold to 60℃~90℃, and then adding the high silica fiber-phenolic resin pre-compression material and the carbon fiber-phenolic resin pre-compression material into the second mold cavity respectively.

7. The method for preparing the high-silica fiber-carbon fiber composite reinforced phenolic resin according to claim 1, characterized in that, The pressurization process includes: after feeding the material, heating the second mold to 103℃~107℃, and then applying pressure to the molding pressure; wherein, The formula for calculating the molding pressure is as follows: F2 = 1000 × P × S, where F2 refers to the molding pressure in kN, P refers to the pressure per unit area on the surface of the blank during the molding process (ranging from 24 MPa to 50 MPa), and S refers to the projected area of ​​the product in m². 2 ; The heating time for the second mold from 60℃~90℃ to 103℃~107℃ is 80min~200min.

8. The method for preparing the high-silica fiber-carbon fiber composite reinforced phenolic resin according to claim 1, characterized in that, The curing process includes: first heating the second mold to its peak temperature, then holding it at that temperature for 30-90 minutes; then heating it to the final temperature, with the holding time increasing by 2-5 minutes for every 1mm increase in the maximum thickness of the blank; wherein... The heating rate is 0.1℃ / min to 0.5℃ / min; and / or, The peak temperature is 130℃~140℃; and / or, The termination temperature is 160℃~180℃; and / or, During the curing process, the blank is a cylindrical blank, and starting from the peak temperature, the temperature of the punch is controlled to be 8℃~12℃ lower than that of the die.

9. The method for preparing the high-silica fiber-carbon fiber composite reinforced phenolic resin according to claim 1, characterized in that, During the second cooling and demolding process, the temperature is reduced from the end temperature to 120°C at a cooling rate of 0.5°C / min to 2°C / min, followed by rapid cooling and demolding; after cooling to the peak temperature, the pressure is naturally released. And / or, The post-curing process includes: holding the blank at 120℃~150℃ for 60min~300min.

10. A high-silica fiber-carbon fiber composite reinforced phenolic resin, characterized in that, The high-silica fiber-carbon fiber composite reinforced phenolic resin is obtained by the preparation method of the high-silica fiber-carbon fiber composite reinforced phenolic resin according to any one of claims 1 to 9.

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