Ablation-resistant heat-shielding integrated gradient structure composite material and a preparation method thereof

Abstract

The application discloses a kind of ablation-resistant heat-proof / heat-insulation integrated gradient structure composite material and preparation method thereof.The ablation-resistant heat-proof / heat-insulation integrated gradient structure composite material includes ablation-resistant layer and heat-insulation layer;The ablation-resistant layer is combined by carbon nanotube and MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix, and the heat-insulation layer is combined by hollow microsphere and MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix.The application combines high-thermal-conductivity ablation-resistant layer and low-thermal-conductivity heat-insulation layer to integrally form lightweight high-strength, heat-proof / heat-insulation composite material.The composite material of the application is of gradient structure, with advantages of lightweight high-strength, low thermal conductivity, ablation resistance and heat insulation in high heat flux density conditions, and can be used as thermal protection material in extreme thermal environment.The forming process of the application is simple, with short preparation period, high strength after high-temperature oxidation, and excellent ablation resistance and heat insulation performance.

Description

Technical Field

[0001] This invention relates to the field of ablation heat protection materials technology, and in particular to an ablation-resistant and heat-insulating integrated gradient structure composite material and its preparation method. Background Technology

[0002] Ablation thermal protection materials utilize surface sublimation, melting, and carbonization oxidation reactions, as well as the re-radiation of the amorphous carbon layer formed after ablation, under high aerodynamic heating conditions. This process dissipates heat at the expense of the materials themselves, ensuring the normal operation of internal instruments and achieving active protection against surface aerodynamic heating. Due to their advantages such as high heat dissipation efficiency, reliable operation, and strong adaptability to changes in flow fields, they are widely used in thermal protection structures.

[0003] Existing ablation-resistant heat-insulating materials use carbon fiber as reinforcement, leveraging its excellent high-temperature stability, high specific strength, and corrosion resistance to significantly improve the mechanical strength of the composite material after ablation. However, these materials suffer from high density, poor processability, and limited heat insulation performance. To adapt to the service environment of higher Mach number aircraft, many researchers have adopted methods such as adding hollow microspheres or using sol-gel methods to construct porous materials to improve the heat insulation performance of composite materials. Patent CN115181393A discloses a modified resin-based composite material for heat insulation and its preparation method. This method utilizes hollow microspheres combined with sol-gel reactions to construct a micro-nano porous structure, achieving lightweight and heat-insulating effects. However, the preparation process is complex, the reaction time is long, and the strength is relatively low.

[0004] Therefore, it is of great significance to provide an integrated ablation-resistant / heat-insulating composite material that has a simple process, a stable and controllable structure, and good ablation resistance and heat insulation properties. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the above-mentioned technologies and to propose an ablation-resistant heat insulation integrated gradient structure composite material and its preparation method, thereby solving the technical problems of complex preparation process and poor heat insulation effect of ablation-resistant heat insulation materials in the prior art.

[0006] In a first aspect, the present invention provides an integrated gradient structure composite material for ablation resistance and thermal insulation, comprising an ablation-resistant layer and a thermal insulation layer; the ablation-resistant layer is formed by combining carbon nanotubes (CNTs) with a MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix, and the thermal insulation layer is formed by combining hollow microspheres with a MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix.

[0007] Secondly, the present invention provides a method for preparing an integrated gradient structure composite material with ablation resistance and thermal insulation, comprising the following steps:

[0008] S1. Dissolve boron phenolic resin powder thoroughly in an organic solvent, then add modified filler and functional filler to obtain slurries with different functions; wherein, the modified filler is MoSi2 and mica, and the functional filler is carbon nanotubes and hollow microspheres.

[0009] S2. Apply slurries with different functions evenly to the reinforcing phase carbon fiber cloth, and obtain prepregs with different functions after drying;

[0010] S3. Prepregs with different functions are laid up in functional order, and then molded and cured to obtain an integrated gradient structure composite material with ablation resistance and heat insulation.

[0011] Compared with the prior art, the beneficial effects of the present invention include:

[0012] This invention integrates a high thermal conductivity, ablation-resistant layer and a low thermal conductivity, insulating layer to create a lightweight, high-strength, heat-resistant / insulating composite material. The composite material of this invention has a gradient structure, possessing advantages such as lightweight, high strength, low thermal conductivity, and ablation resistance and insulation under high heat flux conditions, making it suitable as a thermal protection material for extreme thermal environments. The molding process of this invention is simple, the preparation cycle is short, and the material exhibits high strength, excellent ablation resistance, and superior insulation performance after high-temperature oxidation. Attached Figure Description

[0013] Figure 1 A schematic diagram of one embodiment of the ablation-resistant / heat-insulating integrated gradient structure composite material provided by the present invention;

[0014] Figure 2 In the middle (a)-(c), the surface morphology of the ablation-resistant and heat-insulating integrated gradient structure composite material prepared in Examples 1-3 of the present invention after ablation is shown. Detailed Implementation

[0015] 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.

[0016] In a first aspect, the present invention provides an integrated gradient structure composite material for ablation resistance and thermal insulation, comprising an ablation-resistant layer and a thermal insulation layer; the ablation-resistant layer is formed by combining carbon nanotubes (CNTs) with a MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix, and the thermal insulation layer is formed by combining hollow microspheres with a MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix.

[0017] The structural design concept of this invention is as follows: using MoSi2 / mica (mica) modified carbon fiber reinforced boron phenolic resin as the matrix, carbon nanotubes and hollow microspheres are added to the modified filler (MoSi2 / mica) to regulate the thermal conductivity of the composite material. Based on improving the mechanical strength and ablation resistance of the composite material after high-temperature ablation by the modified filler, the thermal conductivity of the composite material at different thicknesses is further changed to achieve an integrated design of heat protection / insulation, ultimately improving both ablation resistance and heat protection / insulation capabilities.

[0018] In this invention, the ablation-resistant layer is disposed on the side close to the ablation surface, and the heat insulation layer is disposed on the side close to the ablation back surface.

[0019] In some preferred embodiments of the present invention, the proportion of hollow microspheres in the insulation layer gradually increases along the direction away from the ablation-resistant layer. The present invention achieves a density gradient design of the insulation layer through hollow microspheres of varying proportions, further reducing the density of the composite material while improving both insulation and ablation resistance.

[0020] In this embodiment, the mass ratio of boron phenolic resin to the total mass of MoSi2 and mica in the MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix is ​​(1-3):1, preferably 2:1. Under this mass ratio condition, it exhibits optimal high-temperature mechanical properties.

[0021] In this embodiment, the mass ratio of MoSi2 to mica in the MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix is ​​(4-19):1, and more specifically 9:1. Under this mass ratio condition, it exhibits optimal high-temperature mechanical properties and ablation resistance.

[0022] In this embodiment, carbon nanotubes account for 0.5-5% of the total mass of MoSi2 and mica, preferably 1%. If the proportion of carbon nanotubes is too high, the temperature on the back side of the composite material will increase significantly during the ablation test. At the same time, the inventors found in the experiment that when the proportion of carbon nanotubes in the total mass of MoSi2 and mica is 1 wt.%, the mass ablation rate is not much different from other proportions, but the linear ablation rate is lower and the mechanical properties are better.

[0023] In this embodiment, hollow microspheres account for 10-50% of the total volume of MoSi2 and mica, including but not limited to 10%, 20%, 30%, 40%, and 50%. The content of hollow microspheres is related to thermal conductivity; the higher the content, the lower the thermal conductivity and the better the thermal insulation performance. However, the content of hollow microspheres should not be too high, as this will lead to poor ablation resistance.

[0024] In this embodiment, the raw materials of the above-mentioned MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix, by weight, include: 30-50 parts of boron phenolic resin powder, 30-50 parts of organic solvent, 15-19 parts of MoSi2, 1-5 parts of mica, and 30-50 parts of carbon fiber cloth.

[0025] Furthermore, the organic solvent is anhydrous ethanol.

[0026] Furthermore, the mass ratio of boron phenolic resin powder to organic solvent is 1:(0.8-1.2), and more specifically 1:1.

[0027] In this embodiment, the areal density of the carbon fiber cloth is 100-500 gsm, including but not limited to 100 gsm, 200 gsm, 300 gsm, 400 gsm, 500 gsm, etc.

[0028] In some specific embodiments of the present invention, the areal density of the carbon fiber cloth is 400 gsm.

[0029] In this embodiment, the thickness ratio of the ablation-resistant layer to the heat insulation layer is 1:(0.1-10), including but not limited to 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0030] In some specific embodiments of the present invention, the thickness ratio of the ablation-resistant layer to the heat insulation layer is 1:(2-4).

[0031] In this embodiment, the thickness of the ablation-resistant / heat-insulating integrated gradient structure composite material is 5-15 mm, and the diameter is 20-40 mm.

[0032] Secondly, the present invention provides a method for preparing an integrated gradient structure composite material with ablation resistance and thermal insulation, comprising the following steps:

[0033] S1. Dissolve boron phenolic resin powder thoroughly in an organic solvent, then add modified filler and functional filler to obtain slurries with different functions; wherein, the modified filler is MoSi2 and mica, and the functional filler is carbon nanotubes and hollow microspheres.

[0034] S2. Apply slurries with different functions evenly to the reinforcing phase carbon fiber cloth, and obtain prepregs with different functions after drying;

[0035] S3. Prepregs with different functions are laid up in functional order, and then molded and cured to obtain an integrated gradient structure composite material with ablation resistance and heat insulation.

[0036] In this embodiment, in step S3, before laying the prepreg in functional order, the prepreg is cut to the required size.

[0037] In this embodiment, step S3, the process of laying layers in functional order includes: first laying hollow microsphere prepreg in order of decreasing hollow microsphere content, and then laying carbon nanotube prepreg.

[0038] In this embodiment, in step S3, the molding and curing conditions are as follows: first, preheat at 90-110℃ for 0.5-2 hours; then raise the temperature to 110-130℃, set the pressure to 3-5MPa and hold for 0.5-2 hours; then raise the temperature to 170-190℃ and hold for 1-3 hours, then raise the temperature to 190-210℃ and hold for 0.5-2 hours, after heating is finished, hold the pressure for 1-3 hours to form, and let it cool naturally before demolding.

[0039] In some specific embodiments of the present invention, the preparation method of the above-mentioned ablation-resistant / heat-insulating integrated gradient structure composite material includes the following steps:

[0040] (1) Prepare a mixed slurry containing modified filler and boron phenolic resin;

[0041] (2) According to the mass percentage, carbon nanotubes with different mass contents are added to the above mixed slurry, stirred and mixed evenly, and then coated on carbon fiber cloth and dried to prepare carbon nanotube prepreg.

[0042] (3) Hollow microspheres with different volume contents are added to the above mixture according to the volume percentage, stirred and mixed evenly, and then coated on carbon fiber cloth and dried to prepare hollow microsphere prepreg.

[0043] (4) Carbon nanotube prepreg and hollow microsphere prepreg are cut, molded, cured and demolded in sequence to obtain an ablation-resistant / heat-insulating integrated gradient structure composite material.

[0044] By employing the above steps, this invention fully utilizes the flexibility in preparing prepregs, making the molding process simpler.

[0045] Furthermore, in step (1) above, the step of preparing the mixed slurry containing modified filler and boron phenolic resin includes:

[0046] Boron phenolic resin powder is mixed with an organic solvent and mechanically stirred at 40-60℃ until the boron phenolic resin powder is completely dissolved to obtain a clear solution.

[0047] Add the modified filler to the clear solution and continue mechanical stirring at 40-60℃ for 0.5-2 hours until the modified filler is uniformly dispersed to obtain a mixed slurry.

[0048] Furthermore, in steps (2) and (3) above, the mixing method is: ultrasonic stirring at 40-60℃ for 0.5-2h.

[0049] Example 1

[0050] An ablation-resistant and heat-insulating integrated gradient structure composite material, wherein the ablation-resistant layer is a MoSi2 / mica modified carbon fiber reinforced boron phenolic resin composite material containing 1% by mass of CNTs, and the heat-insulating layer is a MoSi2 / mica modified carbon fiber reinforced boron phenolic resin composite material containing 30% by volume of hollow microspheres.

[0051] The preparation steps of the above-mentioned ablation-resistant / heat-insulating integrated gradient structure composite material include:

[0052] (1) Weigh out 40 parts of boron phenolic resin, 40 parts of anhydrous ethanol, 18 parts of MoSi2 powder, 2 parts of mica powder and 40 parts of carbon fiber cloth by weight.

[0053] (2) Dissolve 40 parts of boron phenolic resin in 40 parts of anhydrous ethanol at 50°C to prepare a resin solution. Then take 18 parts of MoSi2 and 2 parts of mica, add them to the resin solution and mix for 1.5 hours to prepare a slurry.

[0054] (3) Based on the total mass of modified fillers MoSi2 and mica being 100%, 1% of CNTs were added to the slurry. After ultrasonic stirring at 50°C for 1 hour, the slurry was manually and evenly coated onto the carbon fiber cloth. The carbon fiber cloth was fully impregnated and dried to prepare prepreg 1.

[0055] (4) Based on the total volume of modified fillers MoSi2 and mica being 100%, hollow microspheres accounting for 30% of the modified fillers were added to the slurry and ultrasonically stirred at 50°C for 1 hour. The slurry was then manually and evenly coated onto the carbon fiber cloth, fully impregnated with the carbon fiber cloth, and dried to prepare prepreg 2.

[0056] (5) Cut the different prepregs into several pieces. The discs are stacked in sequence. First, 15 samples cut from prepreg 2 are placed in the discs, followed by 6 samples cut from prepreg 1. The discs are placed in a five-hole mold and then on a flat vulcanizing machine. The temperature is first set to 100℃ for 1 hour. Then the temperature is raised to 120℃, the pressure is set to 3MPa and held for 1 hour. Then the temperature is raised to 180℃ and held for 2 hours. Then the temperature is raised to 200℃ and held for 1 hour. After the heating is turned off, the pressure is maintained for 2 hours to form the composite material. After cooling, the mold is removed to obtain the ablation-resistant and heat-insulating integrated gradient structure composite material.

[0057] Example 2

[0058] Example 2 was carried out in basically the same way as Example 1, except that CNTs were not added in step (3).

[0059] Example 3

[0060] Example 3 was carried out in the same manner as Example 1, except that in step (4), hollow microspheres with a volume fraction of 40% and 50% were added in sequence to prepare prepregs 3 and 4.

[0061] In step (5), five samples cut from prepreg 4 are placed in sequence, followed by five samples cut from prepreg 3, then five samples cut from prepreg 2, and finally six samples cut from prepreg 1. The ablation-resistant / heat-insulating integrated gradient structure composite material is then produced using the same molding and curing process. Please refer to the structural schematic diagram. Figure 1 .

[0062] Experimental group 1

[0063] The composite material samples prepared in Examples 1-3 were subjected to oxyacetylene ablation experiments. The oxygen flow rate was 1142 L / h and the acetylene flow rate was 838 L / h (flame temperature approximately 2200-2400℃). The highest temperature on the back side during ablation was measured to characterize their ablation resistance and thermal insulation performance. The test results are shown in Table 1. In the test results of mass ablation rate and linear ablation rate, the number before the ± sign is the average value, and the number after the ± sign is the standard deviation.

[0064] Table 1. Linear ablation rate, mass ablation rate, and back surface temperature of Examples 1-3

[0065]

[0066] The ablation resistance was characterized by mass ablation rate and linear ablation rate. The linear ablation rate is the depth of the lowest point of surface ablation. As shown in Table 1, by combining the ablation-resistant layer and the insulating layer, and by achieving density gradient changes through hollow microspheres, Example 3 exhibits a lower back surface temperature of 49.8°C during oxyacetylene ablation, while maintaining excellent ablation resistance. The mass ablation rate is 0.0401 ± 0.0025 g / s, and the linear ablation rate is 0.015 ± 0.002 mm / s.

[0067] Compared with Example 1, Example 2 did not add CNTs, and the mass ablation rate and linear ablation rate were lower than those of Example 1. This may be because the thermal conductivity gradient change in Example 2 is more gradual, and the heat radiated from the insulation layer to the ablation layer is less, which reduces the degree of ablation of the material. However, the temperature on the back side will show a slight increase, which is related to the thermal diffusion capacity of the ablation layer. The higher the thermal diffusion capacity of the ablation layer, the wider and more even the heat diffusion inside the ablation layer is under the same heat, so the thermal insulation capacity of the ablation back side is better, which is reflected in the fact that the back side temperature of Example 1 is slightly lower than that of Example 2.

[0068] Compared with Example 1, in Example 3, the volume content gradient change of hollow microspheres in the insulation layer further reduced the mass ablation rate, linear ablation rate, and back surface temperature. This indicates that the volume content gradient change of hollow microspheres in the insulation layer can more effectively reduce the back surface temperature and mitigate the change in the internal thermal conductivity of the material. It can be seen that the volume content gradient change of hollow microspheres in the insulation layer can play a synergistic role in the ablation resistance layer and the insulation layer, while improving the ablation resistance and insulation performance.

[0069] Please see Figure 2 , Figure 2 These are surface morphology images of the ablation-resistant / heat-insulating integrated gradient structure composite materials prepared in Examples 1-3 of this invention after ablation. Figure 2 It can be seen that the samples with higher ablation rates show more obvious ablation on their surfaces, and the severely ablated areas are larger.

[0070] Comparative Example 1

[0071] (1) Weigh out 40 parts of boron phenolic resin, 40 parts of anhydrous ethanol, 18 parts of MoSi2 powder, 2 parts of mica powder and 40 parts of carbon fiber cloth by weight.

[0072] (2) Dissolve 40 parts of boron phenolic resin in 40 parts of anhydrous ethanol at 50°C to prepare a resin solution. Then take 18 parts of MoSi2 and 2 parts of mica, add them to the resin solution and mix for 1.5 hours to prepare a slurry.

[0073] (3) The slurry is manually and evenly coated onto the carbon fiber cloth, and the carbon fiber cloth is fully impregnated and dried to prepare the prepreg.

[0074] (4) Cut the prepreg into several pieces For the circular sheet, 21 prepreg sheets are placed into a five-hole mold and placed on a flat vulcanizing machine. First, the temperature is set to 100℃ for preheating for 1 hour; then the temperature is raised to 120℃, the pressure is set to 3MPa and held for 1 hour; then the temperature is raised to 180℃ and held for 2 hours, then the temperature is raised to 200℃ and held for 1 hour. After the heating is turned off, the pressure is maintained for 2 hours to form the composite material. After cooling, the mold is removed to obtain an ablation-resistant / heat-insulating integrated homogeneous composite material.

[0075] Comparative Example 2

[0076] Weigh out 40 parts by weight of boron phenolic resin, 40 parts of anhydrous ethanol, 18 parts of MoSi2 powder, 2 parts of Mica powder, and 40 parts of carbon fiber cloth. Based on the total volume of the modified fillers MoSi2 and Mica being 100%, weigh out hollow microspheres accounting for 30% of the volume fraction of the modified fillers.

[0077] The preparation method of the homogeneous composite material is the same as that of Comparative Example 1.

[0078] Comparative Example 3

[0079] Weigh out 40 parts by weight of boron phenolic resin, 40 parts of anhydrous ethanol, 18 parts of MoSi2 powder, 2 parts of Mica powder, and 40 parts of carbon fiber cloth. Based on a total mass of 100% for the modified fillers MoSi2 and Mica, weigh out CNTs accounting for 1% of the modified filler mass.

[0080] The preparation method of the homogeneous composite material is the same as that of Comparative Example 1.

[0081] Experimental group 2

[0082] The composite material samples prepared in Comparative Examples 1-3 were subjected to oxyacetylene ablation tests. The oxygen flow rate was 1142 L / h and the acetylene flow rate was 838 L / h (flame temperature approximately 2200-2400℃). The highest temperature on the back side during ablation was measured to characterize their ablation resistance and thermal insulation performance. The test results are shown in Table 2. In the test results of mass ablation rate and linear ablation rate, the number before the ± sign is the average value, and the number after the ± sign is the standard deviation.

[0083] Table 2 shows the linear ablation rate, mass ablation rate, and back surface temperature for Comparative Examples 1-3.

[0084]

[0085]

[0086] As shown in Table 2, by comparing the composite material without functional fillers (Comparative Example 1) with the homogeneous composite material with carbon nanotubes (Comparative Example 3) and hollow microspheres (Comparative Example 2) respectively, it can be seen that the addition of hollow microspheres can significantly reduce the back surface temperature during oxyacetylene ablation. The addition of carbon nanotubes can make it easier for heat to diffuse evenly into the interior of the material, resulting in a slight increase in the mass ablation rate, but the change is not significant. In addition, the back surface temperature increases, but the linear ablation rate decreases significantly, indicating that the uniform diffusion of heat has a significant impact on the linear ablation rate.

[0087] Meanwhile, compared with Examples 1-3 and Comparative Examples 1-3, the mass ablation rate and linear ablation rate of the homogeneous material are generally lower than those of the gradient composite material of the present invention, indicating that the influence of the change in thermal conductivity in the gradient material on the ablation performance of the composite material is complex. The interface insulation layer with the change in thermal conductivity causes heat to radiate back to the ablation-resistant layer close to the oxyacetylene flame, thereby resulting in greater linear ablation and mass ablation of the gradient material.

[0088] Furthermore, a comparison between Example 2 and Comparative Example 2 shows that the combination of the surface ablation-resistant layer and the heat insulation layer can further reduce the back surface temperature, indicating that uniform heat transfer near the ablation surface is more conducive to demonstrating the heat insulation effect of the heat insulation layer.

[0089] As can be seen from Tables 1-2, this invention combines the advantages of two functional fillers and utilizes the layup sequence to co-cur and mold prepregs with different functional fillers, producing a lightweight, high-strength, ablation-resistant, heat-insulating integrated gradient structure composite material. This material leverages the synergistic effect of the ablation-resistant layer and the heat-insulating layer, exhibiting a lower back surface temperature during ablation and demonstrating superior ablation resistance. The molding process of this invention is simple and has a short cycle time.

[0090] In summary, this invention combines the excellent ablation resistance of high thermal conductivity composites with the excellent thermal insulation properties of low thermal conductivity composites. By adding carbon nanotubes to form a high thermal conductivity ablation-resistant layer, it provides excellent ablation resistance. Furthermore, by adding hollow microspheres and introducing a density gradient structure, it minimizes the thermal conductivity and density of the composite material, reducing the backside temperature during ablation and providing excellent thermal insulation. This invention utilizes a compression molding and co-curing process. Different functional fillers are added during prepreg preparation, and the layers are laid in sequence according to their respective functions before compression molding and curing. This process is simple and has a short preparation cycle. The composite material prepared by this invention exhibits low mass ablation rate and linear ablation rate after high-temperature oxyacetylene gas ablation, and also has a lower backside temperature.

[0091] 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 composite material with an integrated gradient structure for ablation resistance and thermal insulation, characterized in that, It includes an ablation-resistant layer and a heat-insulating layer; the ablation-resistant layer is composed of carbon nanotubes and a MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix, and the heat-insulating layer is composed of hollow microspheres and a MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix; wherein... In the MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix, the mass ratio of boron phenolic resin to the total mass of MoSi2 and mica is (1-3):1, and the mass ratio of MoSi2 to mica is (4-19):

1. The carbon nanotubes account for 1% of the total mass of the MoSi2 and mica, and the hollow microspheres account for 10-50% of the total volume of the MoSi2 and mica. In the heat insulation layer, the proportion of hollow microspheres increases gradually along the direction away from the ablation-resistant layer; The thickness ratio of the ablation-resistant layer to the heat insulation layer is 1:(2-4).

2. The ablation-resistant / heat-insulating integrated gradient structure composite material according to claim 1, characterized in that, By weight, the raw materials of the MoSi2 / mica modified carbon fiber reinforced boron phenolic resin matrix include: 30-50 parts boron phenolic resin powder, 30-50 parts organic solvent, 15-19 parts MoSi2, 1-5 parts mica, and 30-50 parts carbon fiber cloth; the organic solvent is anhydrous ethanol.

3. A method for preparing an integrated gradient structure composite material with ablation resistance and thermal insulation as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Dissolve boron phenolic resin powder fully in an organic solvent, then add modified filler and functional filler to obtain slurries with different functions; wherein, the modified filler is MoSi2 and mica, and the functional filler is carbon nanotubes and hollow microspheres. S2. The slurries with different functions are uniformly coated onto the reinforcing phase carbon fiber cloth, and after drying, prepregs with different functions are obtained. S3. The prepregs with different functions are laid up in functional order, and then molded and cured to obtain an ablation-resistant / heat-insulating integrated gradient structure composite material.

4. The method for preparing the ablation-resistant / heat-insulating integrated gradient structure composite material according to claim 3, characterized in that, In step S3, the process of laying layers in functional order includes: first laying hollow microsphere prepreg in order of decreasing hollow microsphere content, and then laying carbon nanotube prepreg.

5. The method for preparing the ablation-resistant / heat-insulating integrated gradient structure composite material according to claim 3, characterized in that, In step S3, the molding and curing conditions are as follows: first, preheat at 90-110 ℃ for 0.5-2 hours; then raise the temperature to 110-130 ℃, set the pressure to 3-5 MPa and hold for 0.5-2 hours; then raise the temperature to 170-190 ℃ and hold for 1-3 hours, then raise the temperature to 190-210 ℃ and hold for 0.5-2 hours, after heating is finished, hold the pressure for 1-3 hours to form, and let it cool naturally before demolding.

6. The method for preparing the ablation-resistant / heat-insulating integrated gradient structure composite material according to claim 3, characterized in that, Includes the following steps: (1) Prepare a slurry containing modified filler and boron phenolic resin; (2) According to the mass percentage, carbon nanotubes with different mass contents are added to the mixed slurry, stirred and mixed evenly, and then coated on carbon fiber cloth and dried to prepare carbon nanotube prepreg. (3) Hollow microspheres with different volume contents are added to the mixture slurry according to the volume percentage, stirred and mixed evenly, and then coated on carbon fiber cloth and dried to prepare hollow microsphere prepreg. (4) Carbon nanotube prepreg and hollow microsphere prepreg are cut, molded, cured and demolded in sequence to obtain an ablation-resistant / heat-insulating integrated gradient structure composite material.

Images