A high-silica / phenolic resin composite material and a method for preparing the same

Abstract

The application provides a high-silica / phenolic resin composite material and a preparation method thereof, and belongs to the technical field of composite materials. The preparation method of the high-silica / phenolic resin composite material comprises the following steps: performing desolventizing treatment on high-silica fiber / phenolic resin premix to obtain high-silica fiber / phenolic resin dry mix; performing pre-pressing treatment on the high-silica fiber / phenolic resin dry mix to obtain high-silica fiber / phenolic resin pre-pressing material; and laying a silicone rubber plate on the high-silica fiber / phenolic resin pre-pressing material, and then performing mold closing treatment, pre-curing treatment and curing treatment to obtain the high-silica / phenolic resin composite material. The preparation method provided by the application can realize the preparation of large-size composite materials without using a large-tonnage press during the mold pressing process, solves the problem that a large-tonnage press needs to be used for pressing during the preparation process of the existing large-size composite materials, and the prepared composite material has good internal quality stability, a small defect area and good popularization and application value.

Description

Technical Field

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

[0002] During flight, high-speed aircraft experience high surface temperatures, requiring materials with excellent ablation resistance for protection. High-silica fibers offer superior performance and low cost, while phenolic resins are characterized by high temperature resistance, low smoke emission, and low cost. A premix prepared by blending high-silica fibers and phenolic resins is pressed into a composite material. This composite material possesses the characteristics of both, along with low density, good thermal insulation, and ablation resistance, all at a low cost. Therefore, it is widely used in the ablation thermal protection structures of long-duration aircraft.

[0003] However, high-silica fiber / phenolic premixes have a randomly oriented structure, and the premixes cannot be placed relatively evenly in the mold cavity, which will cause uneven distribution of material in some areas. Therefore, a large pressure is required during molding, and the required molding pressure increases significantly with the increase in size. Due to the limitations of the existing press tonnage, it is not conducive to the preparation of large-size high-silica fiber / phenolic resin composite materials.

[0004] Therefore, there is an urgent need to provide a method for preparing large-size composite materials without using a large-tonnage press. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, this invention provides a high-silica / phenolic resin composite material and its preparation method. The preparation method provided by this invention can achieve the preparation of large-size composite materials without the need for a large-tonnage press during the molding process, thus solving the problem that the existing large-size composite material preparation process requires the use of a large-tonnage press for pressing. The resulting composite material has good internal quality stability and small defect area, and has good application value.

[0006] The present invention provides a method for preparing a high-silica / phenolic resin composite material in a first aspect, the method comprising the following steps:

[0007] Solvent removal treatment was performed on the high-silica fiber / phenolic resin premix to obtain a high-silica fiber / phenolic resin dry mix.

[0008] The high-silica fiber / phenolic resin dry mix is ​​pre-compressed to obtain a high-silica fiber / phenolic resin pre-compressed material.

[0009] The silicone rubber sheet is laid on the high-silica fiber / phenolic resin pre-compressed material, and after molding treatment, pre-curing treatment and curing treatment, the high-silica / phenolic resin composite material is obtained.

[0010] Preferably, the high-silica fiber / phenolic resin premix comprises high-silica fiber, phenolic resin, and solvent;

[0011] Preferably, the content of phenolic resin in the high silica fiber / phenolic resin premix is ​​40-52 wt%.

[0012] Preferably, the solvent content in the high-silica fiber / phenolic resin premix does not exceed 5 wt%.

[0013] Preferably, the solvent removal treatment is performed at a temperature of 70–100°C; and / or

[0014] The pre-compression process involves laying the high-silica fiber / phenolic resin dry mix in n layers and pre-compressing each layer.

[0015] Preferably, the mass of the high-silica fiber / phenolic resin dry mix added during the nth layup process is no greater than the mass of the high-silica fiber / phenolic resin dry mix added during the (n-1)th layup process; and / or

[0016] The pressure of the nth stratification preloading is not less than the pressure of the (n-1)th stratification preloading.

[0017] Preferably, the mass of the high-silica fiber / phenolic resin dry mix added during the layup process is 1 / 16 to 1 / 2 of the total mass of the high-silica fiber / phenolic resin dry mix; and / or

[0018] The pressure of the layered preloading is 3 to 10 MPa.

[0019] Preferably, the Shore hardness of the silicone rubber sheet is 50-80, more preferably 60-70;

[0020] The thickness of the silicone rubber sheet is 0.1 to 1 times the thickness of the composite material; and / or

[0021] The length of the silicone rubber sheet satisfies the following relationship: ad / 3 to ad / 5, where a is the length of the composite material and d is the thickness of the composite material; and / or

[0022] The width of the silicone rubber sheet satisfies the following relationship: bd / 3 to bd / 5, where b is the width of the composite material and d is the thickness of the composite material.

[0023] Preferably, the pressure of the mold closing process is 3–10 MPa; and / or

[0024] The pre-curing process involves raising the temperature to a preset temperature and performing multiple pressure releases and applications; and / or

[0025] The curing temperature is 150-170℃, and the curing time is not less than 4 hours.

[0026] Preferably, the pre-curing process includes heating to a first preset temperature at a heating rate of 5–30 °C / h, applying and releasing a first pressure multiple times, then heating to a second preset temperature, applying and releasing a second pressure multiple times; the second pressure is greater than the first pressure.

[0027] Preferably, the first preset temperature is 70-80°C;

[0028] Preferably, the second preset temperature is 90–120°C.

[0029] Preferably, the first pressure is 5 to 15 MPa; more preferably, the second pressure is 15 to 25 MPa.

[0030] In a second aspect, the present invention provides a high-silica / phenolic resin composite material, which is prepared using the preparation method described in the first aspect.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] This invention innovatively uses a flexible silicone rubber sheet during the molding process. Utilizing the flexible expansion characteristic of silicone rubber under heat, it can generate expansion force according to the shape, enabling conformal pressure to be applied to the high-silica fiber / phenolic resin dry mix. It can adapt to the different pressure requirements of different areas of the high-silica fiber / phenolic resin dry mix during the molding process, producing a composite material with higher compaction density and stable internal quality. This solves the problem of existing composite material molding processes where the premix is ​​difficult to fill evenly, requiring large-tonnage pressure for forced pressing, which leads to stress concentration and deformation within the composite material.

[0033] The addition of flexible silicone rubber sheet in this invention enables the preparation of large-size composite materials without the need for a large-tonnage press during the molding process. It is suitable for the preparation of large-size composite materials and solves the problem that existing large-size composite material preparation processes require the use of large-tonnage presses for pressing.

[0034] The method for preparing composite materials provided by this invention has good processability and operability, and is especially suitable for large-size (large-area) composite materials. It can greatly improve the internal quality of composite materials, reduce defects in composite materials, and the resulting composite materials have good internal quality stability and small defect area (not exceeding 0.3%), and have good value for promotion and application. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a flowchart of a method for preparing a high-silica / phenolic resin composite material provided by the present invention;

[0037] Figure 2 This is a schematic diagram of the upper and lower molds provided by the present invention;

[0038] Figure 3 This is a schematic diagram showing the positions of the silicone rubber sheet and the high-silica fiber / phenolic resin pre-compression material during the mold closing process in Embodiment 2 of the present invention.

[0039] Figure 4 This is a schematic diagram showing the positions of the silicone rubber sheet and the high-silica fiber / phenolic resin pre-compression material during the mold closing process in Embodiment 3 of the present invention.

[0040] Figure 5 This is a schematic diagram of the silicone rubber sheet laying in Embodiment 3 of the present invention. Detailed Implementation

[0041] 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 and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0042] The present invention provides a method for preparing a high-silica / phenolic resin composite material in a first aspect, the method comprising the following steps:

[0043] Solvent removal treatment was performed on the high-silica fiber / phenolic resin premix to obtain a high-silica fiber / phenolic resin dry mix.

[0044] The high-silica fiber / phenolic resin dry mix is ​​pre-compressed to obtain a high-silica fiber / phenolic resin pre-compressed material.

[0045] The silicone rubber sheet is laid on the high-silica fiber / phenolic resin pre-compressed material, and after molding treatment, pre-curing treatment and curing treatment, the high-silica / phenolic resin composite material is obtained.

[0046] Because the high-silica fiber / phenolic resin dry blend after solvent removal has a randomly oriented structure, the premix cannot be evenly placed in the mold cavity during molding, resulting in uneven local dispersion of the premix. Different areas of the fiber require different molding pressures, leading to higher molding pressures. Furthermore, the required molding pressure increases significantly with size, which is limited by the tonnage of existing presses, hindering the fabrication of large-size composite materials. To address these structural characteristics of the high-silica fiber / phenolic resin dry blend, this invention innovatively uses a flexible silicone rubber sheet during molding. Utilizing the flexible expansion characteristic of silicone rubber under heat, it can generate expansion force according to the shape, enabling conformal pressure application to the high-silica fiber / phenolic resin dry blend. This adapts to the different pressure requirements of different areas during molding, producing a composite material with higher compaction density and stable internal quality. This solves the problem of existing composite material molding processes where uneven premix placement necessitates high-tonnage pressure, leading to stress concentration and deformation within the composite material.

[0047] The addition of flexible silicone rubber sheet in this invention enables the preparation of large-size composite materials without the need for a large-tonnage press during the molding process. It is suitable for the preparation of large-size composite materials and solves the problem that existing large-size composite material preparation processes require the use of large-tonnage presses for pressing.

[0048] The method for preparing composite materials provided by this invention has good processability and operability, and is especially suitable for large-size (large-area) composite materials. It can greatly improve the internal quality of composite materials, reduce defects in composite materials, and the resulting composite materials have good internal quality stability and small defect area (not exceeding 0.3%), and have good value for promotion and application.

[0049] The high-silica / phenolic resin composite material prepared by this invention has a high compaction density (1.5~1.75 g / cm³). 3 The defect area is small (not exceeding 0.3%), which is much smaller than the defect area of ​​the composite material obtained by molding without silicone rubber sheet (exceeding 3%).

[0050] It should be noted that the process of applying a release agent to the mold surface is also included before the high-silica fiber / phenolic resin dry mix is ​​placed into the mold.

[0051] According to some preferred embodiments, the high-silica fiber / phenolic resin premix comprises high-silica fiber, phenolic resin and solvent;

[0052] Preferably, the content of phenolic resin in the high silica fiber / phenolic resin premix is ​​40-52 wt% (for example, it can be 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt% or 50 wt%).

[0053] Preferably, the solvent content in the high-silica fiber / phenolic resin premix does not exceed 5 wt%.

[0054] It should be noted that the present invention does not have special requirements for the types of high-silica fibers, phenolic resins and solvents, and those skilled in the art can select suitable phenolic resins according to actual needs; in some preferred embodiments of the present invention, the solvent is an alcohol.

[0055] According to some preferred embodiments, the solvent removal treatment is performed at a temperature of 70–100°C (e.g., 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or 100°C); and / or

[0056] The pre-compression process involves laying the high-silica fiber / phenolic resin dry mix in n layers and pre-compressing each layer.

[0057] In some preferred embodiments of the present invention, a forced-air drying oven is used for forced-air solvent removal.

[0058] According to some preferred embodiments, the mass of high-silica fiber / phenolic resin dry mix added during the nth layup is no greater than the mass of high-silica fiber / phenolic resin dry mix added during the (n-1)th layup; and / or

[0059] The pressure of the nth stratification preloading is not less than the pressure of the (n-1)th stratification preloading.

[0060] The high-silica fiber / phenolic resin dry mix of the present invention has a large thickness before compaction. Due to the limitation of mold size, it is not possible to prepare large-size composite materials by one-time lay-up and pre-compression. It should be noted that n is not less than 2. Furthermore, due to the loss of dry mix during the composite material molding process and the generation of volatile substances during the curing process, the total amount of high-silica fiber / phenolic resin dry mix used in the layup process should be greater than the mass of the composite material. Preferably, the high-silica fiber / phenolic resin dry mix is ​​1.05 to 1.2 times the mass of the composite material. Therefore, this invention employs a layered pre-compression method to pre-compress the high-silica fiber / phenolic resin dry mix. The high-silica fiber / phenolic resin dry mix is ​​laid up and pre-compressed in n layers. The mass of high-silica fiber / phenolic resin dry mix added in the nth layup is not greater than the mass added in the (n-1)th layup, and the pressure of the nth layered pre-compression is not less than the pressure of the (n-1)th layered pre-compression. This ensures that a large-size composite material with higher compaction density and better internal quality stability is obtained.

[0061] According to some preferred embodiments, the mass of the high-silica fiber / phenolic resin dry mix added during the layup process is 1 / 16 to 1 / 2 of the total mass of the high-silica fiber / phenolic resin dry mix (for example, it can be 1 / 16, 1 / 15, 1 / 14, 1 / 13, 1 / 12, 1 / 11, 1 / 12, 1 / 11, 1 / 10, 1 / 9, 1 / 8, 1 / 6, 1 / 5, 1 / 4, 1 / 3 or 1 / 2); and / or

[0062] The pressure of the layered preloading is 3 to 10 MPa (for example, it can be 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa or 10 MPa).

[0063] According to some preferred embodiments, the Shore hardness of the silicone rubber sheet is 50 to 80 (for example, it can be 50, 52, 55, 56, 58, 60, 62, 65, 66, 68, 70, 72, 75, 76, 78 or 80), preferably 60 to 70 (for example, it can be 60, 61, 62, 63, 64, 65, 66, 67, 68, 69 or 70).

[0064] The present invention uses silicone rubber sheets within the above-mentioned hardness range, which can ensure that the silicone rubber sheets have excellent conformability; if the hardness is too high, the conformability of the silicone rubber sheets is poor; if the hardness is too low, it is not conducive to the molding of composite materials.

[0065] According to some preferred embodiments, the thickness of the silicone rubber sheet is 0.1 to 1 times the thickness of the composite material (for example, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 times).

[0066] According to some preferred embodiments, the length of the silicone rubber sheet satisfies the following relationship: ad / 3 to ad / 5, where a is the length of the composite material and d is the thickness of the composite material; and / or

[0067] According to some preferred embodiments, the width of the silicone rubber sheet satisfies the following relationship: bd / 3 to bd / 5, where b is the width of the composite material and d is the thickness of the composite material.

[0068] The dimensions (length and width) of the silicone rubber sheet of this invention are smaller than the dimensions (length and width) of the composite material. The silicone rubber sheet is laid on the high-silica fiber / phenolic resin pre-compression material, with a gap left around the mold, which is conducive to the discharge of volatile substances in the premix during the molding process.

[0069] According to some preferred embodiments, the pressure of the mold closing process is 3 to 10 MPa (for example, it can be 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa, 9 MPa, 6 MPa, 9 MPa or 10 MPa).

[0070] According to some preferred embodiments, the pre-curing process involves raising the temperature to a preset temperature and then repeatedly depressurizing and pressurizing. It should be noted that the purpose of repeatedly applying and depressurizing pressure in the pre-curing process of the present invention is to remove volatile substances, air, and volatile substances generated during the pre-curing process from the premix.

[0071] According to some preferred embodiments, the curing temperature is 150–170°C (e.g., 150°C, 152°C, 155°C, 156°C, 158°C, 160°C, 162°C, 165°C, 166°C, 168°C, or 170°C), and the curing time is not less than 4 hours. Controlling the curing temperature within the above range ensures not only the curing of the phenolic resin but also does not affect the conformability of the silicone rubber sheet.

[0072] According to some preferred embodiments, the pre-curing process includes heating to a first preset temperature at a rate of 5–30°C / h (e.g., 5°C / h, 6°C / h, 8°C / h, 10°C / h, 12°C / h, 15°C / h, 16°C / h, 18°C / h, 20°C / h, 22°C / h, 25°C / h, 26°C / h, 28°C / h, or 30°C / h), and repeatedly applying and releasing a first pressure, then heating to a second preset temperature, and repeatedly applying and releasing a second pressure; the second pressure is greater than the first pressure.

[0073] It should be noted that in some preferred embodiments of the present invention, the pre-curing treatment includes two stages. The first stage involves raising the temperature to a first preset temperature while maintaining the pressure applied during the mold-closing process, and repeatedly applying and releasing the first pressure. The purpose of this repeated pressure application and release is to remove volatile substances from the premix. The second stage involves raising the temperature to a second preset temperature and repeatedly applying and releasing the second pressure. The purpose of this repeated pressure application and release is to remove moisture and volatile substances from the pre-curing process. Setting the second pressure to be greater than the first pressure in the present invention is advantageous for preparing composite materials with higher compaction density and more stable internal quality.

[0074] Preferably, the first preset temperature is 70-80°C (for example, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C or 80°C).

[0075] Preferably, the second preset temperature is 90 to 120°C (for example, it can be 90°C, 92°C, 95°C, 96°C, 98°C, 100°C, 102°C, 105°C, 106°C, 108°C, 110°C, 112°C, 115°C, 116°C, 118°C or 120°C).

[0076] According to some preferred embodiments, the first pressure is 5 to 15 MPa (e.g., it can be 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa or 15 MPa); and / or

[0077] The second pressure is 15 to 25 MPa (for example, it can be 15 MPa, 16 MPa, 17 MPa, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, 23 MPa, 24 MPa or 25 MPa).

[0078] It should be noted that, in some preferred embodiments of the present invention, the pre-curing process includes two stages. The first stage involves raising the temperature to a first preset temperature (70-80°C) while maintaining the pressure applied during the mold closing process, and performing multiple applications of the first pressure (5-15 MPa) and depressurization, preferably 3-5 times. The second stage involves raising the temperature to a second preset temperature (90-120°C), and performing multiple applications of the second pressure (15-25 MPa) and depressurization, preferably 3-5 times.

[0079] In a second aspect, the present invention provides a high-silica / phenolic resin composite material, which is prepared using the preparation method described in the first aspect.

[0080] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below in conjunction with embodiments.

[0081] The present invention does not specifically limit the source of the reagents used in the examples and comparative examples; they can be purchased directly or synthesized by oneself.

[0082] Example 1

[0083] Preparation of high-silica / phenolic resin composite materials with dimensions of 150mm x 150mm x 10mm:

[0084] (1) Prepared with a density of 1.7 g / cm³ 3 The theoretical weight of the plate is 382.5g. Weigh it according to 1.15 times. Weigh 439.9g of high silica fiber / phenolic resin premix with a solvent content of 3.9% and put it into the oven. Set the oven temperature to 90℃ to evaporate the solvent. The drying time is 30min to obtain high silica fiber / phenolic resin dry mix.

[0085] (2) Prepare the mold and apply phenolic release agent to the mold surface. The high silica fiber / phenolic resin dry mixture is placed into the mold cavity in two pre-compaction steps. First, weigh 220g of high silica fiber / phenolic resin dry mixture and place it into the mold cavity. Close the upper mold and pre-compact it with a pressure of 3MPa. After pre-compaction, open the upper mold and place the remaining high silica fiber / phenolic resin dry mixture into the mold cavity. Close the upper mold and apply a pressure of 5MPa to obtain the high silica fiber / phenolic resin pre-compressed material.

[0086] (3) Prepare a silicone rubber sheet with a length × width × thickness of 149 × 149 × 5 mm and a Shore hardness of 80. Remove the upper mold and place the silicone rubber sheet on the high silica fiber / phenolic resin pre-pressing material. Close the upper mold and place it on the press. Use the press to close the mold with a closing pressure of 3 MPa. After closing the mold, raise the temperature to 80°C at a heating rate of 25-30°C / h. Release the pressure, apply pressure (5 MPa), release the pressure, apply pressure (5 MPa), release the pressure, apply pressure (5 MPa), release the pressure, continue to raise the temperature to 110°C, apply pressure (15 MPa), release the pressure, apply pressure (15 MPa), release the pressure, apply pressure (15 MPa), release the pressure. Repeatedly apply pressure during the heating process to ensure that the mold is tightly closed. Continue to raise the temperature to 160°C and cure it for 4 hours under a pressure of 15 MPa. Then cool down to 80°C, remove the mold, and you will get the high silica / phenolic resin composite material.

[0087] The high-silica / phenolic resin composite material prepared in this embodiment was tested using industrial CT according to the GJB5312-2004 standard. The test slice distance was 2mm, and a defect of 0.5cm×0.6cm was measured, with a defect area of ​​only 0.13%.

[0088] Example 2

[0089] Preparation of a high-silica / phenolic resin composite material with a length × width × thickness of 500mm × 500mm × 50mm:

[0090] (1) Prepared with a density of 1.65 g / cm³ 3 The plate, with a theoretical weight of 20.63 kg, was weighed at 1.1 times the weight. The weight of the high silica fiber / phenolic resin premix with a solvent content of 4.3% was 22.69 kg. The plate was placed in an oven and the oven temperature was set to 90℃ to evaporate the solvent. The drying time was 30 min to obtain the high silica fiber / phenolic resin dry mix.

[0091] (2) Prepare the mold and apply phenolic release agent to the mold surface. The premixed material is placed into the mold cavity in four pre-compaction steps. First, weigh 11.35 kg of high silica fiber / phenolic resin dry mix, place it into the mold cavity, close the upper mold, and pre-compact it with a pressure of 3 MPa. After pre-compaction, open the upper mold. Second, weigh 5.68 kg of high silica fiber / phenolic resin dry mix, place it into the mold cavity, close the upper mold, and pre-compact it with a pressure of 5 MPa. After pre-compacting, open the upper mold. Third, weigh 2.84 kg of high silica fiber / phenolic resin dry mix, place it into the mold cavity, close the upper mold, and pre-compact it with a pressure of 8 MPa. After pre-compacting, open the upper mold. Fourth, place the remaining high silica fiber / phenolic resin dry mix into the mold cavity, close the upper mold, and apply a pressure of 8 MPa to obtain the high silica fiber / phenolic resin pre-compressed material.

[0092] (3) Prepare two silicone rubber sheets with a length × width × thickness of 498mm × 498mm × 5mm and a hardness of 70. Remove the upper mold and press... Figure 3 As shown, two silicone rubber sheets are stacked on top of the pre-compacted premixed material, the upper mold is closed, and the mold is placed on a press. The mold is closed using the press with a closing pressure of 8 MPa. After closing the mold, the temperature is increased to 80°C at a rate of 20-25°C / h. The pressure is then released, pressure is applied (5 MPa), released, pressure is applied (5 MPa), released, pressure is applied (5 MPa), and pressure is released. The temperature is then increased to 100°C, pressure is applied (15 MPa), released, pressure is applied (15 MPa), pressure is applied (15 MPa), released, pressure is applied (15 MPa), and pressure is released. Pressure is repeatedly applied during the heating process to ensure that the mold is tightly closed. Finally, the temperature is increased to 160°C and cured for 4 hours under a pressure of 15 MPa. After that, the temperature is reduced to 80°C, the mold is removed, and the high-silica / phenolic resin composite material is obtained.

[0093] The high-silica / phenolic resin composite material prepared in this embodiment was subjected to non-destructive testing using industrial CT with a cross-sectional distance of 5 mm, in accordance with the GJB5312-2004 standard. Four defects were detected, with dimensions of 0.5cm×1cm, 0.8cm×1.2cm, 1.1cm×1.3cm, and 1.2cm×1.9cm, respectively. The defect area was only 0.2%.

[0094] Example 3

[0095] Preparation of a high-silica / phenolic resin composite material with dimensions of 1000mm × 750mm × 100mm (length × width × thickness):

[0096] (1) Prepared according to a density of 1.6 g / cm³ 3 The plate, with a theoretical weight of 120 kg, was weighed at 1.05 times the weight. 126 kg of high-silica fiber / phenolic resin premix with a solvent content of 4.5% was weighed and placed in an oven at a temperature of 90°C to evaporate the solvent. The drying time was 30 min to obtain the high-silica fiber / phenolic resin dry mix.

[0097] (2) Prepare the mold and apply phenolic release agent to the mold surface. The premixed material is placed into the mold cavity using a four-stage pre-compaction method. First, weigh 31.5 kg of high-silica fiber / phenolic resin dry mix, place it into the mold cavity, close the upper mold, and pre-compact it with a pressure of 5 MPa. After pre-compaction, remove the upper mold. Second, weigh 31.5 kg of high-silica fiber / phenolic resin dry mix, place it into the mold cavity, close the upper mold, and pre-compact it with a pressure of 8 MPa. After pre-compacting, remove the upper mold. Third, weigh 15.75 kg of high-silica fiber / phenolic resin dry mix, place it into the mold cavity, close the upper mold, and pre-compact it with a pressure of 8 MPa. After pre-compacting, remove the upper mold. Fourth, weigh 15.75 kg of the same material, place it into the mold cavity, close the upper mold, and pre-compact it with a pressure of 8 MPa. After pre-compacting... Disassemble the upper mold; weigh 7.88 kg for the fifth time, place it into the mold cavity, close the upper mold, and pre-compact it with 8 MPa pressure. After pre-compaction, disassemble the upper mold; weigh 7.88 kg of high-silica fiber / phenolic resin dry mix for the sixth time, place it into the mold cavity, close the upper mold, and pre-compact it with 8 MPa pressure. After pre-compacting, disassemble the upper mold; weigh 3.94 kg of high-silica fiber / phenolic resin dry mix for the seventh time, place it into the mold cavity, close the upper mold, and pre-compact it with 10 MPa pressure. After pre-compacting, disassemble the upper mold; weigh 3.94 kg of high-silica fiber / phenolic resin dry mix for the eighth time, place it into the mold cavity, close the upper mold, and pre-compact it with 10 MPa pressure; for the ninth time, place the remaining material into the cavity, close the upper mold, and apply 10 MPa pressure to obtain the high-silica fiber / phenolic resin pre-compressed material.

[0098] (3) Prepare a silicone rubber sheet with dimensions of 994×744×20mm (length×width×thickness) and a hardness of 60. Cut it into four pieces with dimensions of 497×372×20mm (length×width×thickness). Remove the upper mold and press... Figure 4 and Figure 5 As shown, the high-silica fiber / phenolic resin pre-compressed material is placed with a spacing of 2mm. The upper mold is closed and placed on a press. The mold is closed using the press with a closing pressure of 8MPa. After closing the mold, the temperature is increased to 75℃ at a rate of 15-20℃ / h. The pressure is then released, pressure is applied (10MPa), released, pressure is applied (10MPa), released, pressure is applied (10MPa), and then the temperature is increased to 90℃. Pressure is applied (20MPa), released, pressure is applied (20MPa), released, pressure is applied (20MPa), released, pressure is applied (20MPa), and pressure is released. Pressure is repeatedly applied during the heating process to ensure that the mold is tightly closed. Finally, the temperature is increased to 160℃ and cured for 4 hours under a pressure of 20MPa. After that, the temperature is reduced to 80℃, the mold is opened, and the high-silica / phenolic resin composite material is obtained.

[0099] The high-silica / phenolic resin composite material prepared in this embodiment was subjected to non-destructive testing using industrial CT with a test slice distance of 5 mm, in accordance with the GJB5312-2004 standard. Four defects were detected, measuring 0.8 cm × 1.3 cm, 1.2 cm × 1.9 cm, 1.5 cm × 2 cm, and 2.2 cm × 3.2 cm, with a defect area of ​​only 0.18%.

[0100] Comparative Example 1

[0101] It is basically the same as Example 2, except that a silicone rubber sheet was not used in step (3);

[0102] The high-silica / phenolic resin composite material prepared in this comparative example was subjected to non-destructive testing using industrial CT according to the GJB5312-2004 standard. The test slice distance was 5 mm, and multiple defects were found, with the defect area being greater than 3%.

[0103] In summary, this invention, by innovatively using a flexible silicone rubber sheet during the molding process, enables conformal pressure application to the high-silica fiber / phenolic resin dry mix. It can adapt to the different pressure requirements of different areas of the high-silica fiber / phenolic resin dry mix during the molding process, thus producing large-size composite materials with higher compaction density, stable internal quality, and small defect area, and has good potential for widespread application.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-silica / phenolic resin composite material, characterized in that, The preparation method includes the following steps: Solvent removal treatment was performed on the high-silica fiber / phenolic resin premix to obtain a high-silica fiber / phenolic resin dry mix. The high-silica fiber / phenolic resin dry blend is pre-compressed to obtain a high-silica fiber / phenolic resin pre-compressed material. The pre-compressing process involves laying the high-silica fiber / phenolic resin dry blend in n layers and pre-compressing each layer. The mass of the high-silica fiber / phenolic resin dry blend added during the nth layering process is no greater than the mass of the high-silica fiber / phenolic resin dry blend added during the (n-1)th layering process. The pressure of the nth layer pre-compressing process is no less than the pressure of the (n-1)th layer pre-compressing process. A silicone rubber sheet is laid on the high-silica fiber / phenolic resin pre-compression material, and after molding, pre-curing, and curing, the high-silica / phenolic resin composite material is obtained. The length of the silicone rubber sheet satisfies the following relationship: ad / 3~ad / 5, where a is the length of the composite material and d is the thickness of the composite material. The width of the silicone rubber sheet satisfies the following relationship: bd / 3~bd / 5, where b is the width of the composite material and d is the thickness of the composite material. The thickness of the silicone rubber sheet is 0.1~1 times the thickness of the composite material. The pressure of the molding process is 3~10MPa. The pre-curing process includes heating to a first preset temperature at a heating rate of 5~30℃ / h, and repeatedly applying and releasing the first pressure, then heating to a second preset temperature, and repeatedly applying and releasing the second pressure. The second pressure is greater than the first pressure.

2. The preparation method according to claim 1, characterized in that, The high-silica fiber / phenolic resin premix comprises high-silica fiber, phenolic resin and solvent; the content of phenolic resin in the high-silica fiber / phenolic resin premix is ​​40~52wt%; the content of solvent in the high-silica fiber / phenolic resin premix does not exceed 5wt%.

3. The preparation method according to claim 1, characterized in that, The temperature for the solvent removal process is 70~100℃.

4. The preparation method according to claim 1, characterized in that, The mass of the high-silica fiber / phenolic resin dry mix added during the layup process is 1 / 16 to 1 / 2 of the total mass of the high-silica fiber / phenolic resin dry mix; and / or The pressure of the layered preloading is 3~10MPa.

5. The preparation method according to claim 1, characterized in that, The Shore hardness of the silicone rubber sheet is 50-80.

6. The preparation method according to claim 5, characterized in that, The silicone rubber sheet has a Shore hardness of 60-70.

7. The preparation method according to claim 1, characterized in that, The curing temperature is 150~170℃, and the curing time is not less than 4 hours.

8. The preparation method according to claim 1, characterized in that, The first preset temperature is 70~80℃; The second preset temperature is 90~120℃.

9. The preparation method according to claim 1, characterized in that, The first pressure is 5~15MPa; and / or The second pressure is 15~25MPa.

10. A high-silica / phenolic resin composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

Images