Low-density heat-proof structure composite material and forming method thereof

Abstract

The invention discloses a low-density heat-proof structure composite material and a forming method thereof.The low-density heat-proof structure composite material comprises an ablation layer and a heat insulation layer, the thickness and density are designed, and a 2.5 D ablation layer and heat insulation layer integrated structure is obtained in a mode of combining needling and sewing; a prefabricated heat-proof structure fiber fabric is evenly filled with specially-made phenolic resin through an RTM forming technology, and the low-density functional structure material with the heat-proof function is obtained after curing.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat-proof composite materials, and in particular relates to a low-density heat-proof structural composite material and a molding method thereof. Background Art

[0002] With the continuous development of society, the requirements for materials in various industries are constantly increasing. Composite materials have entered the public eye due to their light weight, high strength, low thermal conductivity, designability, excellent corrosion resistance, high specific strength and specific stiffness, and other advantages. Due to these advantages, composite materials are widely used in aircraft, spacecraft, weapons, construction, high-pressure vessels, wind power, high-speed rail, automobiles (car bodies, wheels, battery boxes, motor rotors, etc.), electronic products (copper clad laminates, antennas, display frames, etc.), sporting goods (tennis rackets, skis, golf clubs, bicycles, etc.), and other fields.

[0003] Resin-based composites are the most widely used composite materials. Resin-based composite molding processes include hand lay-up, vacuum infusion molding, RTM molding, compression molding, filament winding, and autoclave molding. RTM molding is a typical wet molding method. The RTM molding process involves laying dry fiber reinforcements onto a mold. Liquid resin is pushed into the mold by vacuum and external pressure, fully impregnating the dry fiber reinforcements, filling pores, and removing air bubbles. Finally, the resin is cured at room temperature or by heating, and then demolded to produce the desired product.

[0004] Currently, composite materials are primarily constructed by stacking layers of fiber cloth, which can lead to delamination between layers. To achieve superior interlayer performance, fabrics such as needle-punched fabrics, 2.5D fabrics, and 3D fabrics have emerged. Preforms for resin-based heat-resistant materials are typically constructed using needle-punched, stitched, or 3D weaving techniques.

[0005] Resin-based composite materials offer flexible design capabilities, allowing for tailored product functionality. By varying the ratio of reinforcement or matrix materials, actual production needs can be met. Therefore, based on the product's strength, stiffness, actual thickness, quality, and functional requirements, the desired preform fabric can be created through a hybrid weaving process by designing the product's thickness and density.

[0006] The traditional molding method for preparing resin-based heat-resistant materials is compression molding, and the raw materials are chopped quartz fibers and phenolic resin.

[0007] The molding steps are: mold cleaning → applying mold release agent → closing the male mold and the female mold → testing air tightness → mixing the chopped fibers into the phenolic resin → injecting the mixed fibers and resin into the closed mold → molding → demolding to obtain the desired product.

[0008] The chopped fiber products produced by traditional compression molding have a high resin content, making it difficult to ensure both the density and strength of the product. The heat-resistant product has a single structure, and once the exterior of the heat-resistant product is damaged, the internal structure can be easily destroyed.

[0009] The general density of quartz fiber is 2.2g / cm 3 High density translates to high weight. To achieve a lighter product, the material needs to be lowered from high-density to low-density. However, simply reducing the material's density will also affect its functionality. Therefore, the quartz fiber fabric's structure has been modified to meet the lightweight requirements while maintaining its heat-resistant properties. Summary of the Invention

[0010] In response to the problems of low heat protection efficiency, poor mechanical properties, and great difficulty in molding in current heat-proof composite materials and production processes, the present invention provides a low-density heat-proof structural composite material and a molding method thereof. The low-density heat-proof structural composite material includes an ablation layer and a heat insulation layer. By designing the thickness and density, a combination of needling and stitching is adopted to achieve a mixed weaving method to obtain a 2.5D integrated structure of the ablation layer and the heat insulation layer; the RTM molding process is adopted to evenly fill the prefabricated heat-proof structural fiber fabric with a special phenolic resin, and after curing, a low-density functional structural material with heat protection function is obtained.

[0011] The purpose of the present invention is achieved through the following technical solutions:

[0012] A method for forming a low-density heat-resistant structural composite material comprises the following steps:

[0013] 1) Clean the mold surface with acetone, alcohol or other cleaning agents to remove dirt and dust. After drying at room temperature, apply mold release agent 5 times on the mold.

[0014] 2) Place a layer of PTFE release cloth on the contact surface of the female mold and the male mold with the product, and then apply 5 coats of release agent on the surface of the release cloth;

[0015] 3) obtaining a quartz fiber preform fabric by a combination of needling and stitching to obtain an ablative structural layer and a thermal insulation structural layer, wherein the thickness of the ablative layer is controlled to be 1 / 3 of the total thickness of the preform, and the thickness of the thermal insulation structural layer is controlled to be 2 / 3 of the total thickness of the preform, and the ablative structural layer and the thermal insulation structural layer are an integrated structure; after obtaining the fabric material, the quartz fiber preform fabric is placed on a male mold, the fabric is placed in the desired position, and the fabric surface is leveled;

[0016] 4) Install the silicone rubber sealing strips and silicone rubber sealing blocks into the sealing grooves of the base plate, male mold, and female mold, and fill the gaps with vulcanized silicone; hoist and install the female mold, and fix and tighten the female molds and the female molds with pins and bolts;

[0017] 5) preparing phenolic resin, resin curing agent and hydrochloric acid catalyst in a mass ratio of 1000:(30-50):(5-10) and stirring evenly;

[0018] 6) Install the mold and pressure tank vacuum valve, and connect the pressure tank and mold vacuum tube;

[0019] 7) Check the air tightness of the pressure tank, pipeline and mold. If the air tightness is good, close all connecting valves;

[0020] 8) Slowly inject the resin prepared in step 5) into the pressure tank, connect the vacuum pump and the pressure tank pipeline, and vacuum the prepared resin to remove bubbles; after the completion, turn off the vacuum pump, release the pressure, unplug the vacuum air pipe, connect the vacuum pipe to the nitrogen bottle air pipe, open the pressure tank injection valve and the mold glue inlet, so that the resin flows smoothly into the mold, maintain the filling pressure, and close the glue outlet valve when resin flows out of the glue outlet; after all the glue outlet valves of the mold are closed, start to remove bubbles from the resin in the mold cavity. When removing bubbles, open the mold glue outlet valves in sequence, and stop when no excess bubbles are discharged from all the glue outlets;

[0021] 9) Close the pressure tank valve, close the pressure tank outlet valve, open the pressure tank feed port, pour the discharged resin into the pressure tank, close the pressure tank feed port, connect the vacuum pipeline, and vacuum the resin in the pressure tank to remove bubbles; after the resin in the pressure tank is de-bubbled, release the vacuum pressure, connect the nitrogen bottle, open the nitrogen bottle valve, the pressure tank outlet and the mold inlet, and remove bubbles again. Stop the operation when no obvious large bubbles or dense small bubbles are seen at the outlet.

[0022] 10) Close all valves, remove the vacuum pipe, push the mold into the curing oven, and heat and cure the product according to the resin curing system;

[0023] 11) After the heat curing is completed, wait until the mold temperature drops to room temperature, remove the mold outer mold, place it in a cool place for 24 hours, and then perform post-curing heating;

[0024] 12) After post-curing is completed, demould the product, take it out and place it on the work surface, use an air grinder to remove the burrs of the product and polish the end surface of the product;

[0025] 13) Use CNC machine tools to drill holes in the product as needed, use an air blow gun to clean the surface of the product after drilling, and then spray paint the surface of the product after cleaning;

[0026] The obtained low-density heat-proof structural composite material has a surface layer of a 2.5D quartz fiber preform. The quartz fiber in the fabric serves as an ablation layer, and its thickness is controlled to be 1 / 3 of the total thickness of the preform. The inner thermal insulation structure layer is a needle-punched quartz fiber mesh with a thickness of 2 / 3 of the total thickness. The density of the mixed woven quartz fabric is 1.0-1.1; under the conditions of a combustion chamber of 1.2±0.05MPa, a residual oxygen coefficient of 0.6±0.05, and a test time of 60s, the average ablation rate is 0.019mm / s.

[0027] In the present invention:

[0028] The mold described in step 1) has the same function as the mold used in this industry. The main materials include steel, aluminum, fiberglass molds commonly used in resin-based composite materials, and carbon fiber molds. The mold is divided into a female mold and a male mold. Depending on the product characteristics and requirements, the use of a female mold, a male mold, or a closed mold with both female and male molds will be considered during the product design stage.

[0029] The release agent described in step 1) and step 2) refers to a liquid used to smoothly separate the cured product from the mold without damaging the product.

[0030] Laying a layer of polytetrafluoroethylene release cloth on the contact surface between the mold and the product in step 2) plays the same role as a release agent, allowing the product to be smoothly demolded from the mold; in addition, laying a layer of polytetrafluoroethylene release cloth here can play a breathable role, allowing the air remaining between the fabric and the mold to be removed, thereby improving product quality and reducing defects.

[0031] The quartz fiber preform described in step 3) refers to a preform with a needle-punched inner layer and a stitched woven outer layer. This is one of the core elements of the present invention. The proportion of the needle-punched and woven structures is directly related to the final density of the finished product and is also related to the final temperature resistance.

[0032] In the mixed braid described in step 3), the quartz fiber used as the surface ablation layer is selected from one of 2.5D type A quartz fiber, 2.5D type B quartz fiber, or 2.5D type C quartz fiber; further, 2.5D type B quartz fiber has the best comprehensive performance.

[0033] After the fabric is sheathed in the theoretical position in step 3), the theoretical position refers to the sheathing position where the inner and outer diameters of the front and rear end frames of the finished product after curing and post-processing meet the design requirements.

[0034] The quartz fiber preform fabric is obtained by mixed weaving of needle punching and stitching as described in step 3). The interior of the heat-resistant quartz fiber preform fabric obtained by mixed weaving is different due to the product performance requirements. The ablation layer and the thermal insulation structure layer are adjusted according to the specific temperature resistance requirements. When the total thickness of the product remains unchanged, the thickness ratio of the ablation layer and the thermal insulation structure layer is adjusted to ensure that the mechanical properties and heat insulation performance of the product are optimized. The thickness of the ablation layer is controlled in the range of 1 / 3 to 1 / 2, and the thickness of the thermal insulation structure layer is controlled in the range of 1 / 2 to 2 / 3. If the heat insulation performance requirements of the product are high, the thickness ratio of the ablation layer can be appropriately increased. If the heat insulation performance requirements are not high and there are certain requirements for mechanical properties, the thickness of the ablation layer can be appropriately reduced. In addition, the ablation layer and the thermal insulation layer are reinforced with chopped fibers and quartz fiber mesh, and then Z-PIN technology is used for z-direction puncture and stitching to enhance the interlayer strength of the product.

[0035] The auxiliary materials such as the silicone rubber sealing strips and silicone rubber sealing tapes described in step 4) are sealing materials frequently used in the RTM process. The sealing strips and tapes will not change at the operating temperature and can ensure the sealing of the mold during use.

[0036] The phenolic resin, resin curing agent and hydrochloric acid catalyst described in step 5) are preferably a hybrid IPC resin with the brand name AGPF-50. The following considerations are considered when selecting this type of resin:

[0037] a. The resin has low viscosity, good fluidity and high operability at room temperature;

[0038] b. The resin curing system is simple;

[0039] c. The heat resistance of the resin after curing meets the requirements. The ratio of resin to curing agent is based on the time used for subsequent infusion, debonding and other operations, combined with the curing system and taking into account the viscosity-temperature curve of the resin.

[0040] The hydrochloric acid catalyst is selected from hydrochloric acid with a mass fraction of 36-38%.

[0041] In step 6), the gas pipeline and the material pipeline are named according to the substances in the pipeline.

[0042] The air tightness test described in step 7) is carried out through an air tightness test. First, a relatively closed single component is tested for air tightness. After no problem is found, all management (except the glue outlet) is opened and an overall air tightness test is carried out. The air pressure used for the air tightness test should be higher than the highest air pressure used in the perfusion process. That is, to ensure the safety of the perfusion process, the perfusion pressure cannot exceed the test pressure.

[0043] The resin degassing described in step 8) refers to the use of vacuum equipment to remove bubbles after the glue liquid is mixed and prepared, so as to expel the air inside the glue liquid as much as possible. This prevents small bubbles generated by the flow of liquid resin during the RTM process of glue injection. Single bubbles that are too large or small bubbles that aggregate will affect product quality. Therefore, it is necessary to remove as many bubbles as possible before glue injection. This is a very important part of the RTM process.

[0044] The resin degassing described in step 9) refers to the phenomenon that during the glue injection process, the gas inside the mold cavity may not be removed cleanly enough, which may cause bubbles in the glue. Therefore, after the glue injection is completed, the product needs to be degased for the second time. Since the viscosity of the resin is low and the infusion speed is fast, in order to save costs, the discharged resin is collected and reloaded into the resin pressure tank. The resin in the pressure tank is vacuumed and degassing is performed for the second time. The specific operation is basically the same as step 8); the secondary degassing is a specific step for the low-viscosity resin used in the product in the present invention, and it is also one of the innovations of the present invention.

[0045] The product curing schedule described in step 10) refers to the external equipment parameters for the polymerization process from low-molecular-weight molecules to high-molecular-weight molecules in the mold after injection molding. This schedule is based on the resin-to-curing agent ratio, determined through testing: the mold is heated to 80°C, held for 32 hours, cooled to room temperature, left for 24 hours, then heated again for (40±5)°C for 4-4.5 hours, (60±5)°C for 4-4.5 hours, (80±5)°C for 4-4.5 hours, and (100±5)°C for 6-6.5 hours before finally being cooled to room temperature. The resin-to-curing agent ratio is designed to ensure the product remains usable after being stored at room temperature for at least 72 hours. To shorten the pot life, the curing agent ratio can be increased. The curing schedule varies depending on the resin-to-curing agent ratio and production time.

[0046] The reason for removing the female mold after the mold temperature drops to room temperature in step 11) is that some water molecules are generated during the curing process of the product. After the female mold is assembled, the water molecules are difficult to be discharged, and the female mold needs to be removed.

[0047] Demolding is performed after the post-curing described in step 12) is completed, which is also a part of the curing, that is, to expel water vapor and increase the degree of curing of the product.

[0048] The removal of burrs and polishing of the end surface of the product described in step 12) refers to the presence of resin-rich areas on the end surface due to the position of the fabric in the mold cavity. In order to ensure the flatness of the end surface of the product, polishing or machining is reserved for the process.

[0049] The drilling and painting treatments described in step 13) refer to other process requirements required for application on the product.

[0050] The present invention also relates to a low-density heat-proof structural composite material, which is obtained by the molding method of the above-mentioned low-density heat-proof structural composite material. The low-density heat-proof structural composite material has a surface layer of a 2.5D quartz fiber preform, and the quartz fiber in the fabric serves as an ablation layer, and its thickness is controlled to be 1 / 3 of the total thickness of the preform. The inner insulation structure layer is a quartz fiber mesh with a needle-punched structure, and the thickness is 2 / 3 of the total thickness. The density of the mixed woven quartz fabric is 1.0-1.1, meeting its low density requirements; under the conditions of a combustion chamber of 1.2±0.05MPa, a residual oxygen coefficient of 0.6±0.05, a temperature condition of 1600℃, and a test time of 60s, the average ablation rate is 0.019mm / s, and it has excellent ablation resistance and heat insulation properties.

[0051] The prefabricated fiber fabrics used in traditional processes have a single structure, poor thermal insulation performance, high density and high quality, unstable apparent quality, and general processability, so the quality of the product is difficult to guarantee. The present invention adopts a mixed weaving method that combines weaving and needle punching to obtain an integrated heat-proof structural fabric with different structural layers. The internal structure of the preform can be changed by weaving to control the density of the product. And unlike traditional glass fiber, a special glass fiber - quartz fiber is selected. Compared with ordinary glass fiber, the needle of this material has better temperature resistance and lower density. The present invention uses RTM molding method, which is convenient to mold and has good processability. The molded product has low density, good heat protection performance, uniform appearance and stable quality.

[0052] Compared with the prior art, the present invention has the following advantages:

[0053] 1. The molding method of a low-density heat-proof structural composite material described in the present invention, wherein the mixed weaving method refers to a mixture of methods of weaving fibers. Taking into account the advantages and disadvantages of different fiber weaving methods, the mixed weaving of acupuncture and suture methods is the innovation of the present invention. After the final RTM molding, its density is about 0.8, which is lower than the density of 1.2 of heat-proof materials prepared by general vacuum introduction. While meeting the design weight, thickness and strength requirements, it can also meet its heat-proof performance requirements. The present invention obtains a continuous fabric preform integrating heat protection and heat insulation by stitching and needle-punching through a reasonable design of the heat-proof structural layer and the heat-insulating structural layer. The product prepared by RTM molding has low density, high interlayer strength, and effectively guaranteed heat-proof performance.

[0054] 2. The appearance quality of heat-resistant structural products prepared by traditional vacuum induction molding methods is relatively poor, and the thickness cannot be effectively controlled, which affects the assembly of heat-resistant products with structural parts. The key innovation of the molding method of a low-density heat-resistant structural composite material described in the present invention is to control the weaving method and parameters while meeting its thickness and heat-resistant requirements, so as to achieve the low-density requirements of the fiber preform, and the ablation layer and the heat-insulating layer are an integrated structure; the RTM molding method is simple and convenient, with better processability, and the appearance quality of the prepared products is high. The inner and outer surfaces of the heat-resistant structural material do not require additional post-processing, which facilitates assembly with structural parts, effectively saving manpower and time costs.

[0055] 3. The present invention provides a molding method for a low-density heat-resistant structural composite material, wherein the phenolic resin is a specially prepared phenolic resin material in a mass ratio of 1000:(30-50). Under the specially prepared ratio, the viscosity after mixing is 10-30 mPa·s, which has a very low viscosity, a long operating window time, and excellent processability.

[0056] 4. The low-density heat-resistant structural composite material described herein is produced through a closed mold process. It exhibits high apparent quality, utilizes a low-viscosity resin, has a long operating window, is easy to operate, and exhibits excellent processability. Furthermore, RTM-molded products exhibit high quality stability. This low-density heat-resistant structural composite material exhibits excellent appearance quality, and its innovative molding process utilizes secondary degassing of the low-viscosity resin, simplifying the process and reducing product defects.

[0057] 5. The low-density heat-resistant structural composite material described herein utilizes a weaving method combining needle punching and stitching to create a quartz fiber preform fabric with an integrated ablative layer and thermal insulation layer. This fabric exhibits enhanced interlayer continuity, excellent surface quality, low density, heat-resistant performance, and interlayer strength. This invention offers excellent designability, allowing the preform's internal structure to be modified through weaving, controlling the product's thickness, density, and heat-resistant performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a diagram of an RTM molding die for a molding method of a low-density heat-resistant structural composite material according to the present invention;

[0059] Figure 2 2 is a cross-sectional view of a quartz fiber preform fabric of a low-density heat-resistant structural composite material prepared in an experimental example of the present invention;

[0060] Figure 3 This is a diagram of an airtightness inspection system for a molding method of a low-density heat-resistant structural composite material according to the present invention;

[0061] Figure 4 This is a diagram of a glue injection system for a molding method of a low-density heat-resistant structural composite material according to the present invention;

[0062] Figure 5 This is a process flow chart of a molding method of a low-density heat-resistant structural composite material according to the present invention. DETAILED DESCRIPTION

[0063] The present invention is further described in detail below by way of examples, but these examples should not be considered as limiting the present invention.

[0064] Example:

[0065] A method for forming a low-density heat-resistant structural composite material comprises the following steps:

[0066] 1) Clean the mold surface with acetone, alcohol or other cleaning agents to remove dirt and dust. After drying at room temperature, apply mold release agent 5 times on the mold.

[0067] 2) Place a layer of PTFE release cloth on the contact surface of the female mold and the male mold with the product, and then apply 5 coats of release agent on the surface of the release cloth;

[0068] 3) Based on the product operating temperature conditions of 1600°C and ablation time of ≤60s, a fabric proportional structure design is performed. A quartz fiber preform fabric is obtained by mixed weaving through needling and stitching to obtain an ablation structure layer and a thermal insulation structure layer. The thickness of the ablation layer is controlled to be 1 / 3 of the total thickness of the preform, and the thickness of the thermal insulation structure layer is controlled to be 2 / 3 of the total thickness of the preform. The ablation structure layer and the thermal insulation structure layer are an integrated structure. After obtaining the fabric material, the quartz fiber preform fabric is placed on the male mold. After the fabric is placed in the desired position, the fabric surface is leveled.

[0069] 4) Install the silicone rubber sealing strips and silicone rubber sealing blocks into the sealing grooves of the base plate, male mold, and female mold, and fill the gaps with vulcanized silicone; hoist and install the female mold, and fix and tighten the female molds and the female molds with pins and bolts;

[0070] 5) Phenolic resin, resin curing agent and hydrochloric acid catalyst are prepared in a mass ratio of 1000:30:10 and stirred evenly;

[0071] The phenolic resin is selected from the hybrid IPC resin with the brand name AGPF-50;

[0072] The hydrochloric acid catalyst is selected from hydrochloric acid with a mass fraction of 38%;

[0073] 6) Install the mold and pressure tank vacuum valve, and connect the pressure tank and mold vacuum tube;

[0074] 7) Check the air tightness of the pressure tank, pipeline and mold. If the air tightness is good, close all connecting valves;

[0075] 8) Slowly inject the resin prepared in step 5) into the pressure tank, connect the vacuum pump and the pressure tank pipeline, and vacuum the prepared resin to remove bubbles; after the completion, turn off the vacuum pump, release the pressure, unplug the vacuum air pipe, connect the vacuum pipe to the nitrogen bottle air pipe, open the pressure tank injection valve and the mold glue inlet, so that the resin flows smoothly into the mold, maintain the filling pressure, and close the glue outlet valve when resin flows out of the glue outlet; after all the glue outlet valves of the mold are closed, start to remove bubbles from the resin in the mold cavity. When removing bubbles, open the mold glue outlet valves in sequence, and stop when no excess bubbles are discharged from all the glue outlets;

[0076] 9) Close the pressure tank valve, close the pressure tank outlet valve, open the pressure tank feed port, pour the discharged resin into the pressure tank, close the pressure tank feed port, connect the vacuum pipeline, and vacuum the resin in the pressure tank to remove bubbles; after the resin in the pressure tank is de-bubbled, release the vacuum pressure, connect the nitrogen bottle, open the nitrogen bottle valve, the pressure tank outlet and the mold inlet, and remove bubbles again. Stop the operation when no obvious large bubbles or dense small bubbles are seen at the outlet.

[0077] 10) Close all valves, remove the vacuum pipe, push the mold into the curing oven, and heat and cure the product according to the resin curing system;

[0078] Curing system: heat the mold to 80℃, keep it warm for 32h, cool it down to room temperature, leave it for 24h, heat it up again for (40±5)℃×(4-4.5)h, (60±5)℃×(4-4.5)h, (80±5)℃×(4-4.5)h, (100±5)℃×(6-6.5)h, and then cool it down to room temperature;

[0079] 11) After the heat curing is completed, wait until the mold temperature drops to room temperature, remove the mold outer mold, place it in a cool place for 24 hours, and then perform post-curing heating;

[0080] 12) After post-curing is completed, demould the product, take it out and place it on the work surface, use an air grinder to remove the burrs of the product and polish the end surface of the product;

[0081] 13) Use CNC machine tools to drill holes in the product as needed, use an air blow gun to clean the surface of the product after drilling, and then spray paint the surface of the product after cleaning.

[0082] The low-density heat-resistant structural composite material has the following technical indicators:

[0083] 1. The surface layer of this product is a 2.5D quartz fiber preform. The quartz fiber in the fabric is type B. Its thickness as the ablation layer is controlled to be 1 / 3 of the total thickness of the preform. The inner insulation structure layer is a needle-punched quartz fiber mesh with a thickness of 2 / 3 of the total thickness.

[0084] 2. The molded product has excellent heat insulation capabilities. In a quartz lamp ablation test under the conditions of a combustion chamber of 1.25MPa, a residual oxygen coefficient of 0.65, a temperature of 1600℃, and a combustion time of 60s, the average ablation rate obtained in the test is 0.019mm / s;

[0085] 3. The density of this product is low, and the density after molding is 0.8~1.0g / cm 3 Between, with lighter structural weight.

[0086] Figure 2 This is a cross-sectional view of a quartz fiber preform fabric of a low-density heat-resistant structural composite material prepared in an experimental example.

[0087] The results show that:

[0088] The molded products are compared to the previous products. The temperature resistance of the products in the comparative example can only reach 800°C. The products prepared using this molding method can reach a temperature resistance of 1600°C, which has a higher temperature resistance level. After adding short-cut fibers and quartz mesh to fill the interlayers, Z-PIN technology is used for puncture, which can more effectively increase the interlayer performance and at the same time has better mechanical properties. In summary, the heat-resistant layer products molded using this method have higher designability, lower density of the molded products, better heat insulation performance, and higher overall structural strength. The molding method is simpler and the product quality is more stable.

[0089] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. Various process solutions that have no substantial difference from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A method for forming a low-density heat-resistant structural composite material, characterized by: The following steps are involved: 1) Clean the mold surface with acetone, alcohol or other cleaning agents to remove dirt and dust. After drying at room temperature, apply mold release agent 5 times on the mold. 2) Place a layer of PTFE release cloth on the contact surface of the female mold and the male mold with the product, and then apply 5 coats of release agent on the surface of the release cloth; 3) obtaining a quartz fiber preform fabric by a combination of needling and stitching to obtain an ablative structural layer and a thermal insulation structural layer, wherein the thickness of the ablative layer is controlled to be 1 / 3 of the total thickness of the preform, and the thickness of the thermal insulation structural layer is controlled to be 2 / 3 of the total thickness of the preform, and the ablative structural layer and the thermal insulation structural layer are an integrated structure; after obtaining the fabric material, the quartz fiber preform fabric is placed on a male mold, the fabric is placed in the desired position, and the fabric surface is leveled; The quartz fiber is selected from one of 2.5D type A quartz fiber, 2.5D type B quartz fiber or 2.5D type C quartz fiber; 4) Install the silicone rubber sealing strips and silicone rubber sealing blocks into the sealing grooves of the base plate, male mold, and female mold, and fill the gaps with vulcanized silicone; hoist and install the female mold, and fix and tighten the female molds and the female molds with pins and bolts; 5) Phenolic resin, resin curing agent and hydrochloric acid catalyst are prepared in a mass ratio of 1000: (30-50): (5-10) and stirred evenly; 6) Install the mold and pressure tank vacuum valve, and connect the pressure tank and mold vacuum tube; 7) Check the air tightness of the pressure tank, pipeline and mold. If the air tightness is good, close all connecting valves; 8) Slowly inject the resin prepared in step 5) into the pressure tank, connect the vacuum pump and the pressure tank pipeline, and vacuum the prepared resin to remove bubbles; after the completion, turn off the vacuum pump, release the pressure, unplug the vacuum air pipe, connect the vacuum pipe to the nitrogen bottle air pipe, open the pressure tank injection valve and the mold glue inlet, so that the resin flows smoothly into the mold, maintain the filling pressure, and close the glue outlet valve when resin flows out of the glue outlet; after all the glue outlet valves of the mold are closed, start to remove bubbles from the resin in the mold cavity. When removing bubbles, open the mold glue outlet valves in sequence, and stop when no excess bubbles are discharged from all the glue outlets; 9) Close the pressure tank valve, close the pressure tank outlet valve, open the pressure tank feed port, pour the discharged resin into the pressure tank, close the pressure tank feed port, connect the vacuum pipeline, and vacuum the resin in the pressure tank to remove bubbles; after the resin in the pressure tank is de-bubbled, release the vacuum pressure, connect the nitrogen bottle, open the nitrogen bottle valve, the pressure tank outlet and the mold inlet, and remove bubbles again. Stop the operation when no obvious large bubbles or dense small bubbles are seen at the outlet. 10) Close all valves, remove the vacuum pipe, push the mold into the curing oven, and heat and cure the product according to the resin curing system; 11) After the heat curing is completed, wait until the mold temperature drops to room temperature, remove the mold outer mold, place it in a cool place for 24 hours, and then perform post-curing heating; 12) After post-curing is completed, demould the product, take it out and place it on the work surface, use an air grinder to remove the burrs of the product and polish the end surface of the product; 13) Use CNC machine tools to drill holes in the product as needed, use an air blow gun to clean the surface of the product after drilling, and then spray paint the surface of the product after cleaning; The obtained low-density heat-proof structural composite material has a surface layer of a 2.5D quartz fiber preform. The quartz fiber in the fabric serves as an ablation layer, and its thickness is controlled to be 1 / 3 of the total thickness of the preform. The inner thermal insulation structure layer is a needle-punched quartz fiber mesh with a thickness of 2 / 3 of the total thickness. The density of the mixed woven quartz fabric is 1.0-1.1, meeting its low density requirements. Under the conditions of a combustion chamber of 1.2±0.05MPa, a residual oxygen coefficient of 0.6±0.05, a temperature of 1600℃, and a test time of 60s, the average ablation rate is 0.019mm / s.

2. The method for forming a low-density heat-resistant structural composite material according to claim 1, characterized in that: The quartz fiber described in step 3) is selected from 2.5D B-type quartz fiber.

3. The method for forming a low-density heat-resistant structural composite material according to claim 1, characterized in that: The product curing system described in step 10) is: the mold is heated to 80°C, kept warm for 32 hours, cooled to room temperature, left for 24 hours, heated again for (40±5)°C×(4-4.5) hours, (60±5)°C×(4-4.5) hours, (80±5)°C×(4-4.5) hours, (100±5)°C×(6-6.5) hours, and then cooled to room temperature.

4. A low-density heat-resistant structural composite material, characterized by: The low-density heat-proof structural composite material is obtained by the molding method of any one of claims 1-3, wherein the surface layer is a 2.5D quartz fiber preform, the quartz fiber in the fabric serves as an ablation layer, and its thickness is controlled to be 1 / 3 of the total thickness of the preform, the inner thermal insulation structure layer is a quartz fiber mesh with a needle-punched structure, the thickness of which is 2 / 3 of the total thickness, and the density of the mixed woven quartz fabric is 1.0-1.1, meeting its low density requirement; under the conditions of a combustion chamber of 1.2±0.05MPa, a residual oxygen coefficient of 0.6±0.05, a temperature condition of 1600°C, and a test time of 60s, the average ablation rate is 0.019mm / s.

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