A quartz fiber reinforced phenolic aerogel composite material with a densified surface layer and a preparation method thereof

Abstract

The present invention belongs to the technical field of heat-insulating materials, and discloses a quartz fiber reinforced phenolic aerogel composite material with a densified surface layer and a preparation method thereof. The composite material comprises a densified surface layer and a lightweight inner layer, wherein the densified surface layer is based on a polycarbosilane-modified bismaleimide resin and is reinforced by a quartz fiber woven fabric; the lightweight inner layer is based on a phenolic aerogel and is reinforced by a quartz fiber needle-punched felt. The preparation method comprises first connecting the surface woven fabric and the inner needle-punched felt by needle-punching them into a whole, and then filling the surface matrix and the inner matrix in sequence. The aerogel composite material of the present invention has the characteristics of ablation resistance, surface toughness, and heat insulation, and its comprehensive density and comprehensive mechanical properties are controllable, which can meet the comprehensive requirements of the large-area thermal protection structure on the windward side of hypersonic vehicles for heat insulation, low-speed impact resistance, lightness, and certain mechanical strength for the phenolic aerogel composite material.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat-insulating materials, and in particular relates to a quartz fiber reinforced phenolic aerogel composite material with a densified surface layer and a preparation method thereof. Background Art

[0002] In recent years, the trend toward high-speed cruising, wide-range flight, and horizontal takeoff and landing in hypersonic vehicles has posed comprehensive performance requirements for thermal protection materials and structures. For example, for large-area external thermal protection structures on the windward side, the thermal insulation materials used must not only be lightweight, ablation-resistant, and highly effective in insulating, but also possess resistance to sand impact and high comprehensive mechanical properties. Furthermore, the production cycle and cost of the thermal insulation materials must also be considered.

[0003] Phenolic resin aerogel has the advantages of short preparation cycle and mass production. With its advantages in process and cost, phenolic aerogel is widely used in the field of thermal protection of aerospace vehicles as an ablative thermal protection material. However, with the changes in the service environment and working conditions of hypersonic aircraft, new thermal, mechanical and weight requirements have been put forward for phenolic aerogel, a traditional thermal protection material. The use of flexible fiber felt or chopped fibers to reinforce phenolic aerogel can improve the strength and toughness of phenolic aerogel composites to a certain extent. However, this method does not target the characteristics of one-sided aerodynamic heating in the application environment. The prepared fiber-reinforced phenolic aerogel composite material has a homogeneous structure and is still insufficient in ablation resistance and impact resistance, and cannot meet the needs of high-speed aircraft for new thermal insulation materials.

[0004] In recent years, researchers have used inorganic particle-modified resins and quartz fibers as a dense surface layer to improve the ablation resistance of phenolic aerogel composites. However, this method significantly increases the weight of the dense surface layer, achieving ablation resistance at the expense of significant weight. Furthermore, the solid inorganic particles and liquid resins struggle to achieve molecular-level bonding, and surface defects caused by particle agglomeration or uneven dispersion severely compromise the composite's thermal insulation properties. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a quartz fiber reinforced phenolic aerogel composite material with a densified surface layer and a preparation method thereof in view of the shortcomings of the existing technology. First, in view of the characteristics of single-sided aerodynamic heating, the fiber preform is designed and prepared with the idea of ​​local reinforcement and overall connectivity. Secondly, for the fiber preforms in different areas, the dense surface matrix and the loose inner matrix are filled in sequence. The composite material finally prepared has good ablation resistance, thermal insulation performance and impact resistance, and the comprehensive density can be adjusted to meet the use requirements of hypersonic aircraft.

[0006] In order to solve the technical problem raised by the present invention, the present invention provides a quartz fiber reinforced phenolic aerogel composite material with a densified surface layer, comprising a densified surface layer and a lightweight inner layer; the densified surface layer is based on a polycarbosilane-modified bismaleimide resin and is reinforced by a quartz fiber woven fabric; the lightweight inner layer is based on a phenolic aerogel and is reinforced by a quartz fiber needle-punched felt.

[0007] In the above solution, the polycarbosilane-modified bismaleimide resin consists of bismaleimide resin, polycarbosilane and a silane coupling agent.

[0008] Furthermore, the polycarbosilane is liquid polycarbosilane, and its number average molecular weight is 1000-2000.

[0009] Furthermore, the solid content of the bismaleimide resin is 75-95%.

[0010] Furthermore, the silane coupling agent is γ-aminopropyltriethoxysilane (KH550).

[0011] Furthermore, in the polycarbosilane-modified bismaleimide resin, the mass ratio of the bismaleimide resin, the polycarbosilane, and the silane coupling agent is 100:(5-35):(0.3-5).

[0012] In the above solution, the quartz fiber woven fabric is a 2.5D woven fabric with a warp density of 11 to 13 yarns / cm, a weft density of 9 to 11 yarns / cm, and a thickness of 1 to 3 mm.

[0013] In the above solution, the density of the quartz fiber needle felt is 0.2-0.5 g / cm 3 , thickness is 9~29mm.

[0014] In the above solution, the volume density of the composite material is 0.3 to 0.7 g / cm 3 The room temperature thermal conductivity is 0.07~0.11W / m·K, the bending strength is 9~13MPa, and the hardness is 94~100HA.

[0015] The present invention also provides a method for preparing a quartz fiber reinforced phenolic aerogel composite material having a densified surface layer, comprising the following steps:

[0016] 1) connecting the quartz fiber woven fabric and the quartz fiber needle-punched felt by needle-punching to form a connected fiber preform;

[0017] 2) Mixing polycarbosilane with anhydrous ethanol and adding it to the bismaleimide resin, stirring and then ultrasonically dispersing it, followed by adding a silane coupling agent. Stirring and heating are continued to accelerate the volatilization of the anhydrous ethanol. A polycarbosilane-modified bismaleimide resin film is prepared by calendering.

[0018] 3) covering the surface of the quartz fiber woven fabric of the fiber preform with a polycarbosilane-modified bismaleimide resin film, then sealing it in a vacuum bag and evacuating it, heating it to melt-infiltrate the polycarbosilane-modified bismaleimide resin film into the quartz fiber woven fabric, then heating it to solidify it, removing it, heat-treating it in an inert atmosphere, and cooling it to room temperature to obtain a fiber preform with a densified surface layer;

[0019] 4) mixing phenolic resin and anhydrous ethanol, heating and dissolving them, and then adding hexamethylenetetramine to prepare a phenolic aerogel precursor solution;

[0020] 5) placing the fiber preform with a densified surface layer into a mold, and transferring the phenolic aerogel precursor solution from the surface of the quartz fiber needle felt of the fiber preform inward through a resin transfer molding process, so that the phenolic aerogel precursor solution infiltrates the quartz fiber needle felt. Then, applying pressure into the mold, heating and heat preservation are performed, demolding, taking out, and drying to obtain a quartz fiber reinforced phenolic aerogel composite material with a densified surface layer.

[0021] In the above solution, the needle density of the needle connection is 25 to 35 needles / cm 2 .

[0022] In the above scheme, in step 2), the mass ratio of bismaleimide resin to anhydrous ethanol is 100:(10-30).

[0023] In the above scheme, in step 2), the stirring rate is 500-1000 r / min, the stirring time before the addition of the silane coupling agent is 10-20 min, and the stirring time after the addition of the silane coupling agent is 0.5-2 h.

[0024] In the above scheme, in step 2), the ultrasonic dispersion time is 5 to 20 minutes.

[0025] In the above scheme, in step 2), the heating temperature is 80-90° C. and the heating time is 2-4 hours, until the residual mass of anhydrous ethanol does not exceed 15% of the sum of the mass of polycarbosilane and bismaleimide resin.

[0026] In the above solution, the thickness of the polycarbosilane-modified bismaleimide resin film is the same as the thickness of the quartz fiber woven fabric.

[0027] In the above solution, the vacuum degree of the vacuum bag after evacuation is 0.09-0.1 MPa.

[0028] In the above solution, the infiltration temperature of the polycarbosilane-modified bismaleimide resin film is 140-150° C., and the film is kept at this temperature for 2-6 hours.

[0029] In the above scheme, in step 3), the curing adopts a three-stage gradient temperature curing, the temperature of the first stage is 175-185°C, the temperature of the second stage is 205-215°C, and the temperature of the third stage is 225-235°C, and the insulation time of each stage is 1-3 hours.

[0030] In the above scheme, the ventilation rate of the inert atmosphere is 20 to 50 ml / min.

[0031] In the above scheme, the temperature of the heat treatment is 900-1000° C., the heating rate is 2-10° C. / min, and the treatment time is 10-30 min.

[0032] In the above solution, the phenolic resin is a linear phenolic resin with a number average molecular weight of 300 to 800.

[0033] In the above scheme, in step 4), the heating temperature is 60-80° C. and the heating time is 0.5-2 h.

[0034] In the above scheme, in step 4), the mass ratio of phenolic resin, anhydrous ethanol and hexamethylenetetramine is 100:(10-60):(10-20).

[0035] In the above solution, in step 5), an air compressor is used to inject a pressure of 0.3 to 0.5 MPa into the mold.

[0036] In the above scheme, in step 5), the heating temperature is 90-100° C. and the insulation time is 24-48 hours.

[0037] In the above scheme, in step 5), the drying is natural drying, and the drying time is 24 to 48 hours.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1) The composite material of the present invention adopts a localized reinforcement design to address the characteristics of single-sided start-up heating. First, the matrix adopts a localized reinforcement design, using liquid polycarbosilane and liquid bismaleimide resin for blending, which is fully combined at the molecular level and achieves densification with a low mass cost. The internal matrix adopts phenolic aerogel, and its porous and lightweight structure gives the material good thermal insulation properties. The surface and inner layers are connected by needle punching to form an integrated fiber preform. As a result, it has excellent comprehensive performance and meets the requirements of use in hypersonic vehicles.

[0040] 2) The composite material of the present invention uses polycarbosilane-modified bismaleimide resin as the matrix of the densified surface layer. First, compared with phenolic resin, bismaleimide resin does not produce small molecules during the curing process, making the surface denser and improving heat resistance. Second, the polycarbosilane-modified bismaleimide resin is used. The cracking products generated after heat treatment can form a protective layer, reducing the thermal decomposition and mass loss of the material. The thermal protective layer can block the transfer of heat to the interior of the material, improving the material's ablation resistance and thermal stability, so that the composite material can be used in a hot environment and has excellent ablation resistance and impact resistance. Third, the use of liquid and liquid blending avoids the sedimentation of solid particles, achieves molecular level bonding, ensures the uniformity of dispersion, and further adopts a stirring-ultrasound-stirring preparation process. The final composite material has more stable properties. Fourth, the infiltration is carried out in the temperature range where the resin viscosity is minimum, and the temperature is gradually increased during curing to avoid the sudden increase in curing temperature to generate thermal stress, making the infiltration more uniform and the curing degree higher, so that the mechanical properties of the material are better.

[0041] 3) The composite material of the present invention uses a fiber preform as a skeleton. The surface layer adopts high-toughness 2.5D quartz fiber woven cloth to further strengthen the toughness and surface hardness of the surface layer. The internal reinforcement adopts quartz fiber felt to ensure the thermal insulation performance while increasing the strength and toughness of the phenolic aerogel. The dense surface layer and the lightweight inner layer are connected by a needle-punched structure, so that the dense surface layer and the lightweight inner layer are not easy to fall off, thereby ensuring the integrity of the composite material. The overall molding process of the composite material is simple and the preparation cycle is short. It can meet the needs of large-area external heat protection structure on the windward side of ultra-high-speed aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a physical picture of the composite material obtained in Example 1.

[0043] Figure 2 This is a scanning electron microscope image of the composite material obtained in Example 1.

[0044] Figure 3 This is a background temperature curve of the composite material obtained in Example 1 subjected to a butane flame ablation test.

[0045] Figure 4 This is a diagram showing the state of the composite material obtained in Example 1 after being subjected to a low-speed impact test with an impact energy of 23J.

[0046] Figure 5 This is a state diagram of the composite material obtained in Comparative Example 1 after being subjected to a low-speed impact test with an impact energy of 18J.

[0047] Figure 6 This is a background temperature curve of the composite material obtained in Comparative Example 2 subjected to a butane flame ablation test. DETAILED DESCRIPTION

[0048] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0049] In the following examples, the polycarbosilane used was liquid polycarbosilane, which was sourced from Shandong Zibo Qiquan Industry and Trade Co., Ltd. and had a number average molecular weight M n 1000~1600; Bismaleimide resin is N,N'-m-phenylene bismaleimide, which comes from Tianjin Qingkuai Technology Co., Ltd., and its weight average molecular weight M w The silane coupling agent is γ-aminopropyltriethoxysilane (KH550); the phenolic resin is a solid linear phenolic resin from Henan Hengyuan New Materials Co., Ltd., with a number average molecular weight of M n It ranges from 300 to 800.

[0050] Example 1

[0051] A quartz fiber reinforced phenolic aerogel composite material with a densified surface layer comprises a densified surface layer and a lightweight inner layer; the densified surface layer uses polycarbosilane modified bismaleimide resin as a matrix and quartz fiber woven fabric as a reinforcement; the lightweight inner layer uses phenolic aerogel as a matrix and quartz fiber needle-punched felt as a reinforcement.

[0052] The polycarbosilane-modified bismaleimide resin is composed of bismaleimide resin, polycarbosilane, and silane coupling agent in a mass ratio of 100:30:5. The quartz fiber woven fabric is a 2.5D woven fabric with a warp density of 12±0.5 yarns / cm, a weft density of 10±0.4 yarns / cm, and a thickness of 2 mm. The density of the quartz fiber needle felt is 0.5 g / cm. 3 , thickness is 28mm.

[0053] The method for preparing the composite material comprises the following steps:

[0054] 1) Connect the quartz fiber woven fabric and the quartz fiber needle felt by needle punching, with a needle punching density of 30 needles / cm 2 , forming a connected fiber preform;

[0055] 2) polycarbosilane and anhydrous ethanol were mixed and added to bismaleimide resin, with the mass ratio of bismaleimide resin to anhydrous ethanol being 100:30. The mixture was stirred at a rate of 800 r / min for 10 minutes, and then ultrasonically dispersed for 15 minutes. A silane coupling agent was then added, and stirring was continued at a rate of 800 r / min for 0.5 hours. The mixture was then heated to 80° C. and kept warm for 2 hours to accelerate the volatilization of ethanol, so that the residual mass of anhydrous ethanol did not exceed 15% of the sum of the masses of polycarbosilane and bismaleimide resin. A polycarbosilane-modified bismaleimide resin film with a thickness of 2 mm was then prepared by calendering;

[0056] 3) Covering the surface of the quartz fiber woven fabric of the fiber preform with a polycarbosilane-modified bismaleimide resin film, then placing it in a vacuum bag and evacuating it. After the vacuum degree reaches 0.1 MPa, the vacuum valve is closed and sealed, and the preform is placed in an oven. The preform is heated to 140°C in the oven and kept warm for 2 hours to allow the polycarbosilane-modified bismaleimide resin film to melt into the quartz fiber woven fabric. The preform is then cured using a three-stage gradient temperature increase method. The three stages are 180°C, 210°C, and 230°C, respectively. The holding time for each stage is 2 hours. After the curing is completed, the preform is taken out and placed in a tubular atmosphere furnace. Nitrogen is introduced (the ventilation rate is 30 ml / min), and the temperature is increased to 1000°C at a rate of 5°C / min for heat treatment for 10 minutes to obtain a fiber preform with a densified surface layer.

[0057] 4) mixing phenolic resin with anhydrous ethanol, heating to 80° C. and dissolving for 0.5 h, and then adding hexamethylenetetramine to prepare a phenolic aerogel precursor solution; wherein the mass ratio of the linear phenolic resin, anhydrous ethanol, and hexamethylenetetramine is 100:25:10;

[0058] 5) placing the fiber preform with a densified surface layer into a mold, and transferring the phenolic aerogel precursor solution from the surface of the quartz fiber needle felt of the fiber preform inward through a resin transfer molding process, so that the phenolic aerogel precursor solution infiltrates the quartz fiber needle felt. Then, an air compressor is used to pressurize the mold with a pressure of 0.4 MPa. After the pressing is completed, the mold is heated to 90°C and kept warm for 24 hours. The mold is demolded, taken out and naturally dried for 24 hours to obtain a quartz fiber reinforced phenolic aerogel composite material with a densified surface layer.

[0059] The properties of the composite material prepared in this example were tested, including:

[0060] 1) Density determination: Bulk density was determined according to GB / T 2998-2015. The product dimensions were 100.1 mm × 100.3 mm × 29.8 mm. Before testing, the product was dried in an oven at 110°C ± 5°C, then cooled to room temperature in a desiccator. The test was repeated five times and the average value was calculated.

[0061] 2) Thermal conductivity: Determine the room temperature thermal conductivity according to standard YB / T 4130-2005. The product size is 100.1mm×100.3mm×29.8mm. Repeat the test five times and take the average value.

[0062] 3) Butane flame ablation test: The test sample is a cylindrical specimen with a size of φ40mm×30mm. The densified surface layer of the specimen is ablated for 500s. An infrared temperature gun and thermocouple are used to record the temperature of the front (densified surface layer) and back of the composite material during the ablation process. The thickness and mass before and after ablation are measured, and the ablation rate is calculated.

[0063] 4) Low-speed impact test: The test sample is a cubic specimen with a size of 100mm×100mm×10mm. A drop hammer tester is used. Hammers of various weights ranging from 100g to 2kg are selected. Free-fall tests are performed at different heights. The test is carried out in a manner that increases the drop hammer energy. The state of the specimen after the impact is observed.

[0064] 5) Bending test: According to GB / T1449, the test sample size is 80 mm × 15 mm × 4 mm cubic spline with dense surface layer, and the test is carried out using an electronic universal testing machine with a loading rate of 1 mm / min. The test is repeated four times and the average value is obtained;

[0065] 6) Hardness test: According to the standard ASTM D2240, the sample size is 100 mm × 100 mm × 30 mm. The hardness of five locations on the sample surface is tested using a Shore hardness tester and the average value is obtained.

[0066] Table 1 Performance test results of the composite material obtained in Example 1

[0067]

[0068] Combined with Table 1 and Figures 1 to 4 The properties of the composite material prepared in this example were analyzed:

[0069] Figure 1 The composite material obtained in this example is shown in the figure. As can be seen from the figure, the composite material has a complete appearance without defects, and the densified surface layer is tightly connected to the lightweight inner layer. After testing, its density is 0.624g / cm 3 , and the thermal conductivity is 0.1049W / m·K, indicating that it has light weight and heat insulation properties.

[0070] Figure 2 This is a scanning electron microscope image of the composite material obtained in this embodiment. It can be seen from the figure that the fibers and resin in the densified surface layer and the lightweight inner layer are well bonded, and the bonding interface of the two layers is in good contact and tightly linked, with good integrity and is not easy to fall off during use.

[0071] Figure 3 The back temperature curve of the composite material obtained in this example subjected to a butane flame ablation test is shown. As can be seen from the figure, after 500 seconds of butane flame heating, the surface temperature of the composite material is relatively high, but the back temperature remains at a relatively low level with a low rate of increase, demonstrating excellent thermal insulation performance. At the same time, the linear ablation rate and mass ablation rate in Table 1 are both at a relatively low level, indicating that the composite material has good ablation resistance.

[0072] Figure 4 This is a state diagram of the composite material obtained in this example after a low-speed impact test with an impact energy of 23J. As can be seen from the figure, after the impact, the composite material did not undergo obvious deformation and the surface remained intact, indicating that the composite material has strong impact resistance.

[0073] Table 1 also shows the flexural strength and hardness of the composite material, which has high strength and toughness, indicating that the overall mechanical properties of the composite material are good.

[0074] Comparative Example 1

[0075] The difference between Comparative Example 1 and Example 1 is that the densified surface layer is based on unmodified bismaleimide resin.

[0076] Table 2 Performance test results of the composite material obtained in Comparative Example 1

[0077]

[0078]

[0079] From the data in Table 2, it can be seen that the densified surface layer directly uses unmodified bismaleimide resin as the matrix. Compared with Example 1, the overall density and thermal conductivity of the composite material are slightly reduced, but its mechanical properties are significantly reduced, and the ablation rate also increases significantly, and the ablation resistance is significantly reduced.

[0080] The composite material obtained in this comparative example was subjected to a low-speed impact test, and the test was carried out in a manner of increasing the drop hammer energy. The results showed that Figure 5 As shown in the figure, when the impact energy is 18J, the composite material undergoes obvious deformation, impact marks appear on the surface, and the impact resistance is significantly reduced.

[0081] Comparative Example 2

[0082] The difference between Comparative Example 2 and Example 1 is that the densified surface layer is based on inorganic particle-modified bismaleimide resin, and the inorganic particle-modified bismaleimide resin is composed of bismaleimide resin, boron carbide and zirconium boride in a mass ratio of 80:30:10.

[0083] Table 3 Performance test results of the composite material obtained in Comparative Example 2

[0084]

[0085] It can be seen from the data in Table 2 that the densified surface layer is based on the inorganic particle-modified bismaleimide resin. Compared with Example 1, the overall density of the composite material has increased to a certain extent, and the thermal conductivity has also been significantly improved, indicating that the presence of inorganic particles makes the interior of the resin denser and has a stronger heat transfer capacity, reduces the thermal insulation performance, and significantly increases the ablation rate.

[0086] The composite material obtained in this comparative example was subjected to a butane flame ablation test. Figure 6 It can be seen that inorganic particles increase the thermal conductivity and heat transfer capacity of the dense surface layer, which ultimately leads to excessive heat transfer, a high increase in the back temperature, and a significant decrease in the thermal insulation performance of the composite material.

[0087] Example 2

[0088] A quartz fiber reinforced phenolic aerogel composite material with a densified surface layer comprises a densified surface layer and a lightweight inner layer; the densified surface layer uses polycarbosilane modified bismaleimide resin as a matrix and quartz fiber woven fabric as a reinforcement; the lightweight inner layer uses phenolic aerogel as a matrix and quartz fiber needle-punched felt as a reinforcement.

[0089] The polycarbosilane-modified bismaleimide resin is composed of bismaleimide resin, polycarbosilane, and silane coupling agent in a mass ratio of 100:25:3. The quartz fiber woven fabric is a 2.5D woven fabric with a warp density of 11 yarns / cm, a weft density of 11 yarns / cm, and a thickness of 1 mm. The density of the quartz fiber needle-punched felt is 0.3 g / cm. 3 , thickness is 29mm.

[0090] The method for preparing the composite material comprises the following steps:

[0091] 1) Connect the quartz fiber woven cloth and the quartz fiber needle felt by needle punching, with a needle punching density of 28 needles / cm 2 , forming a connected fiber preform;

[0092] 2) polycarbosilane and anhydrous ethanol were mixed and added to bismaleimide resin, with the mass ratio of bismaleimide resin to anhydrous ethanol being 100:25. The mixture was stirred at 700 r / min for 15 minutes, then ultrasonically dispersed for 20 minutes, and then a silane coupling agent was added. The mixture was stirred at 500 r / min for 1 hour, and then heated to 85° C. and kept warm for 2 hours to accelerate the volatilization of ethanol, so that the residual mass of anhydrous ethanol did not exceed 15% of the sum of the mass of polycarbosilane and bismaleimide resin. A polycarbosilane-modified bismaleimide resin film with a thickness of 1 mm was then prepared by calendering;

[0093] 3) Covering the surface of the quartz fiber woven fabric of the fiber preform with a polycarbosilane-modified bismaleimide resin film, then placing it in a vacuum bag and evacuating it. After the vacuum degree reaches 0.095 MPa, the vacuum valve is closed and sealed, and the preform is placed in an oven. The preform is heated to 150° C. in the oven and kept warm for 2 hours to allow the polycarbosilane-modified bismaleimide resin film to melt into the quartz fiber woven fabric. The preform is then cured using a three-stage gradient temperature increase method. The three temperatures are 175° C., 205° C., and 225° C., respectively, and the holding time for each stage is 3 hours. After the curing is completed, the preform is taken out and placed in a tubular atmosphere furnace. Nitrogen is introduced (the ventilation rate is 20 ml / min), and the temperature is increased to 900° C. at a rate of 6° C. / min and heat-treated for 20 minutes to obtain a fiber preform with a densified surface layer.

[0094] 4) mixing phenolic resin with anhydrous ethanol, heating to 60° C. and dissolving for 2 h, and then adding hexamethylenetetramine to prepare a phenolic aerogel precursor solution; wherein the mass ratio of the linear phenolic resin, anhydrous ethanol, and hexamethylenetetramine is 100:30:15;

[0095] 5) placing the fiber preform with a densified surface layer into a mold, and transferring the phenolic aerogel precursor solution from the surface of the quartz fiber needle felt of the fiber preform inward through a resin transfer molding process, so that the phenolic aerogel precursor solution infiltrates the quartz fiber needle felt. Then, an air compressor is used to pressurize the mold with a pressure of 0.3 MPa. After the pressing is completed, the mold is heated to 100° C. and kept warm for 36 hours. The mold is demolded, taken out and naturally dried for 36 hours to obtain a quartz fiber reinforced phenolic aerogel composite material with a densified surface layer.

[0096] Table 4 Performance test results of the composite material obtained in Example 2

[0097]

[0098] Example 3

[0099] A quartz fiber reinforced phenolic aerogel composite material with a densified surface layer comprises a densified surface layer and a lightweight inner layer; the densified surface layer uses polycarbosilane modified bismaleimide resin as a matrix and quartz fiber woven fabric as a reinforcement; the lightweight inner layer uses phenolic aerogel as a matrix and quartz fiber needle-punched felt as a reinforcement.

[0100] Among them: the polycarbosilane modified bismaleimide resin is composed of bismaleimide resin, polycarbosilane and silane coupling agent in a mass ratio of 100:35:5; the quartz fiber woven fabric is a 2.5D woven fabric with a warp density of 13 yarns / cm, a weft density of 11 yarns / cm, and a thickness of 3mm; the density of the quartz fiber needle felt is 0.4g / cm 3 , thickness is 27mm.

[0101] The method for preparing the composite material comprises the following steps:

[0102] 1) Connect the quartz fiber woven fabric and quartz fiber needle felt by needle punching, with a needle punching density of 35 needles / cm 2 , forming a connected fiber preform;

[0103] 2) polycarbosilane and anhydrous ethanol were mixed and added to bismaleimide resin, with the mass ratio of bismaleimide resin to anhydrous ethanol being 100:20. The mixture was stirred at 900 r / min for 10 minutes, then ultrasonically dispersed for 20 minutes, and then a silane coupling agent was added. The mixture was stirred at 900 r / min for 2 hours, and then heated to 90° C. and kept warm for 2.5 hours to accelerate the volatilization of ethanol, so that the residual mass of anhydrous ethanol did not exceed 15% of the sum of the mass of polycarbosilane and bismaleimide resin. A polycarbosilane-modified bismaleimide resin film with a thickness of 3 mm was then prepared by calendering;

[0104] 3) The polycarbosilane-modified bismaleimide resin film is covered on the surface of the quartz fiber woven fabric of the fiber preform, and then placed in a vacuum bag and evacuated. After the vacuum degree reaches 0.099 MPa, the vacuum valve is closed and sealed, and the preform is placed in an oven. The preform is heated to 150° C. in the oven and kept warm for 3 hours to allow the polycarbosilane-modified bismaleimide resin film to melt into the quartz fiber woven fabric. The preform is then cured in three stages using a gradient temperature increase method. The three stages are 185° C., 215° C., and 235° C., and the holding time for each stage is 1.5 hours. After the curing is completed, the preform is taken out and placed in a tubular atmosphere furnace. Nitrogen is introduced (the ventilation rate is 40 ml / min), and the temperature is increased to 1000° C. at a rate of 8° C. / min and heat-treated for 15 minutes to obtain a fiber preform with a densified surface layer.

[0105] 4) mixing phenolic resin with anhydrous ethanol, heating to 75° C. to dissolve for 1 hour, and then adding hexamethylenetetramine to prepare a phenolic aerogel precursor solution; wherein the mass ratio of the linear phenolic resin, anhydrous ethanol, and hexamethylenetetramine is 100:40:12;

[0106] 5) placing the fiber preform with a densified surface layer into a mold, and transferring the phenolic aerogel precursor solution from the surface of the quartz fiber needle felt of the fiber preform inward through a resin transfer molding process, so that the phenolic aerogel precursor solution infiltrates the quartz fiber needle felt. Then, an air compressor is used to pressurize the mold with a pressure of 0.45 MPa. After the pressing is completed, the mold is heated to 90°C and kept warm for 24 hours. The mold is demolded, taken out and naturally dried for 36 hours to obtain a quartz fiber reinforced phenolic aerogel composite material with a densified surface layer.

[0107] Table 5 Performance test results of the composite material obtained in Example 3

[0108]

[0109] The above embodiments are merely examples for clarification and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications may be made based on the above descriptions. It is not necessary and impossible to enumerate all implementation methods here, and any obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A quartz fiber reinforced phenolic aerogel composite material with a densified surface layer, characterized in that: The invention comprises a densified surface layer and a lightweight inner layer; the densified surface layer is based on a polycarbosilane-modified bismaleimide resin and reinforced with a quartz fiber woven fabric, wherein the polycarbosilane-modified bismaleimide resin is composed of a bismaleimide resin, polycarbosilane and a silane coupling agent; the lightweight inner layer is based on a phenolic aerogel and reinforced with a quartz fiber needle-punched felt. The method for preparing the quartz fiber reinforced phenolic aerogel composite material with a densified surface layer comprises the following steps: 1) connecting the quartz fiber woven fabric and the quartz fiber needle-punched felt by needle-punching to form a connected fiber preform; 2) The polycarbosilane and anhydrous ethanol are mixed and added to the bismaleimide resin, first stirred and then ultrasonically dispersed, followed by adding the silane coupling agent, and then continued stirring and heating to volatilize the anhydrous ethanol, and then calendering to obtain a polycarbosilane-modified bismaleimide resin film; 3) Covering the surface of the quartz fiber woven fabric of the fiber preform with a polycarbosilane-modified bismaleimide resin film, placing the preform in a vacuum bag, evacuating the bag, and sealing the bag. Heating the bag causes the polycarbosilane-modified bismaleimide resin film to melt-infiltrate the quartz fiber woven fabric. Then, performing a three-stage gradient temperature curing process, wherein the first stage is at a temperature of 175-185°C, the second stage is at a temperature of 205-215°C, and the third stage is at a temperature of 225-235°C. Each stage is kept at this temperature for 1-3 hours. The preform is then removed, heat-treated in an inert atmosphere, and cooled to obtain a fiber preform having a densified surface layer. 4) Mixing phenolic resin and anhydrous ethanol, heating and dissolving, and then adding hexamethylenetetramine to prepare a phenolic aerogel precursor solution; 5) placing the fiber preform with a densified surface layer into a mold, and transferring the phenolic aerogel precursor solution from the surface of the quartz fiber needle felt of the fiber preform inward through a resin transfer molding process, so that the phenolic aerogel precursor solution infiltrates the quartz fiber needle felt. Then, pressure is applied to the mold, followed by heating and insulation, demolding, taking out, and drying to obtain a quartz fiber reinforced phenolic aerogel composite material with a densified surface layer.

2. The quartz fiber reinforced phenolic aerogel composite material with a densified surface layer according to claim 1, characterized in that: In the polycarbosilane-modified bismaleimide resin, the mass ratio of bismaleimide resin, polycarbosilane, and silane coupling agent is 100:(5-35):(0.3-5).

3. The quartz fiber reinforced phenolic aerogel composite material with a densified surface layer according to claim 1, characterized in that: The polycarbosilane is liquid polycarbosilane with a number average molecular weight of 1000-2000; the solid content of the bismaleimide resin is 75-95%; and the silane coupling agent is γ-aminopropyltriethoxysilane.

4. The quartz fiber reinforced phenolic aerogel composite material with a densified surface layer according to claim 1, characterized in that: The quartz fiber woven fabric is a 2.5D woven fabric with a warp density of 11 to 13 yarns / cm, a weft density of 9 to 11 yarns / cm, and a thickness of 1 to 3 mm; the quartz fiber needle-punched felt has a density of 0.2 to 0.5 g / cm³ and a thickness of 9 to 29 mm.

5. The quartz fiber reinforced phenolic aerogel composite material with a densified surface layer according to claim 1, characterized in that: The volume density of the composite material is 0.3-0.7 g / cm 3 The room temperature thermal conductivity is 0.07~0.11 W / m∙K, the flexural strength is 9~13MPa, and the Shore hardness is 94~100HA.

6. A method for preparing the quartz fiber reinforced phenolic aerogel composite material having a densified surface layer according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) connecting the quartz fiber woven fabric and the quartz fiber needle-punched felt by needle-punching to form a connected fiber preform; 2) The polycarbosilane and anhydrous ethanol are mixed and added to the bismaleimide resin, first stirred and then ultrasonically dispersed, followed by adding the silane coupling agent, and then continued stirring and heating to volatilize the anhydrous ethanol, and then calendering to obtain a polycarbosilane-modified bismaleimide resin film; 3) Covering the surface of the quartz fiber woven fabric of the fiber preform with a polycarbosilane-modified bismaleimide resin film, placing the preform in a vacuum bag, evacuating the bag, and sealing the bag. Heating the bag causes the polycarbosilane-modified bismaleimide resin film to melt-infiltrate the quartz fiber woven fabric. Then, performing a three-stage gradient temperature curing process, wherein the first stage is at a temperature of 175-185°C, the second stage is at a temperature of 205-215°C, and the third stage is at a temperature of 225-235°C. Each stage is kept at this temperature for 1-3 hours. The preform is then removed, heat-treated in an inert atmosphere, and cooled to obtain a fiber preform having a densified surface layer. 4) Mixing phenolic resin and anhydrous ethanol, heating and dissolving, and then adding hexamethylenetetramine to prepare a phenolic aerogel precursor solution; 5) placing the fiber preform with a densified surface layer into a mold, and transferring the phenolic aerogel precursor solution from the surface of the quartz fiber needle felt of the fiber preform inward through a resin transfer molding process, so that the phenolic aerogel precursor solution infiltrates the quartz fiber needle felt. Then, pressure is applied to the mold, followed by heating and insulation, demolding, taking out, and drying to obtain a quartz fiber reinforced phenolic aerogel composite material with a densified surface layer.

7. The method for preparing the quartz fiber reinforced phenolic aerogel composite material with a densified surface layer according to claim 6, characterized in that: In step 2), the stirring rate is 500-1000 r / min, the stirring time before the addition of the silane coupling agent is 10-20 min, the ultrasonic dispersion time is 5-20 min, and the stirring time after the addition of the silane coupling agent is 0.5-2 h; the heating temperature is 80-90° C., and the heating time is 2-4 h, until the residual mass of anhydrous ethanol does not exceed 15% of the sum of the mass of the polycarbosilane and the bismaleimide resin; the thickness of the polycarbosilane-modified bismaleimide resin film is the same as the thickness of the quartz fiber woven fabric.

8. The method for preparing a quartz fiber reinforced phenolic aerogel composite material having a densified surface layer according to claim 6, characterized in that: In step 3), the vacuum degree of the vacuum bag after evacuation is 0.09-0.1 MPa; the infiltration temperature is 140-150° C., and the infiltration time is 2-6 hours; the heat treatment temperature is 900-1000° C., the heating rate is 2-10° C. / min, and the treatment time is 10-30 minutes.

9. The method for preparing a quartz fiber reinforced phenolic aerogel composite material having a densified surface layer according to claim 6, characterized in that: In step 4), the mass ratio of the phenolic resin, anhydrous ethanol, and hexamethylenetetramine is 100:(10-60):(10-20); the phenolic resin is a linear phenolic resin with a number average molecular weight of 300-800.

10. The method for preparing a quartz fiber reinforced phenolic aerogel composite material having a densified surface layer according to claim 6, characterized in that: In step 5), an air compressor is used to inject a pressure of 0.3-0.5 MPa into the mold, the heating temperature is 90-100°C, and the holding time is 24-48 hours.

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