A method for forming a preform of an anti-ablation layer of a solid rocket engine rear head

Abstract

The present application discloses a method for forming a preform of an anti-ablative layer of a rear head of a solid rocket engine, which belongs to the technical field of manufacturing a preform of an anti-ablative layer of a rear head, and includes: step one: determining the structure of the anti-ablative layer according to the design requirements; the anti-ablative layer includes a plurality of layers of anti-ablative layer materials arranged in sequence, and each layer of the anti-ablative layer material has a different height; step two: using a forming mold to perform multi-stage pressurization forming and stitching treatment on the anti-ablative layer; wherein the stitching treatment is to physically connect the multi-layer anti-ablative layer materials, and the stitching method is to divide the anti-ablative layer into 4 to 8 petals, and stitch the overlapping parts of the anti-ablative layer along the dividing line with a dipped carbon fiber rope in a zigzag route, and the spacing between two adjacent stitching points is 10 to 20 mm. The present invention effectively ensures the integrity and reliability of the carbon fiber woven material, and further improves the anti-ablative performance of the anti-ablative layer.

Description

Technical Field

[0001] The present application relates to a method for forming a preform of an anti-ablation layer of a rear head of a solid rocket engine, and belongs to the technical field of manufacturing a preform of an anti-ablation layer of a rear head. Background Art

[0002] The anti-ablation insulation layer is one of the important components of the insulation shell of the solid rocket engine. It plays a very important protective role in medium and long-range rocket engines and engines with high overload and long flight time. The material is generally made of carbon fiber woven 2.5D material as the main body, impregnated with resin and rubber glue to form (made into ablative material sheets), and then cut and sewn according to the design size (in the case of multi-layer materials, they need to be sewn to make them an integrated state), and airbags are used for pressurization in the molding tool. Under normal circumstances, when airbags are used for pressurization, the airbag surface cannot fit well with the product surface, and when the airbag is pressurized and expanded, there will be a certain displacement with the film, and there is a possibility that the local fibers of the carbon fiber braid will move, which reduces the fiber density at that place, and there will be a serious risk of ablation. Summary of the invention

[0003] According to one aspect of the present application, a method for forming a preform of an anti-ablation layer of a rear head of a solid rocket engine is provided, which effectively ensures the integrity and reliability of the carbon fiber woven material and further improves the anti-ablation performance of the anti-ablation layer.

[0004] A method for forming a preform of an anti-ablation layer of a solid rocket engine rear head, characterized by comprising:

[0005] Step 1: Determine the structure of the anti-ablation layer according to the design requirements; the anti-ablation layer includes a plurality of layers of anti-ablation layer materials arranged in sequence, and each layer of the anti-ablation layer material has a different height;

[0006] Step 2: using a forming mold to perform multi-stage pressure forming and suturing on the anti-ablation layer;

[0007] Among them, the suturing process is to connect the multiple layers of the anti-ablation layer material by physical means. The suturing method is to divide the anti-ablation layer into 4 to 8 petals, and sew the overlapping parts of the anti-ablation layer along the dividing line in a zigzag route with a rubber-impregnated carbon fiber rope. The spacing between two adjacent suturing points is 10 to 20 mm.

[0008] Furthermore, the anti-ablation layer is a trumpet-shaped ring;

[0009] The thickness direction of the anti-ablation layer decreases from the inside to the outside of each layer of the anti-ablation layer material;

[0010] Along the flow direction of the gas, the thickness of the anti-ablation layer increases successively.

[0011] Furthermore, the step 2 includes:

[0012] Step 2.1, preheating the molding mold;

[0013] Step 2.2, laying the anti-ablation layer material in the molding die in sequence and compacting it;

[0014] Step 2.3, performing a first vacuum coating on the flattened anti-ablation layer material and the forming mold, and then preheating and pressing the anti-ablation layer to obtain a first preform;

[0015] Step 2.4, taking out the first preform, and using the impregnated carbon fiber rope to sew the first preform as a whole, so as to physically connect several layers of the anti-ablation layer material to obtain a second preform;

[0016] Step 2.5: placing the second preform into the molding die again, vacuum coating the second preform and the molding die for a second time, and then hot pressing to obtain a preform.

[0017] Furthermore, in step 2.1:

[0018] The molding die is preheated at a temperature of 55° C.-65° C. for at least 1 hour.

[0019] Furthermore, in step 2.3:

[0020] The vacuum degree during the first vacuum coating is not less than -0.099 MPa;

[0021] The pressure during the preheating and pressing is 0.5MPa-0.7MPa, wherein the pressure increasing rate is 0.05MPa per minute; at the same time, when the pressure is 0.5MPa, the heating is started, and the temperature is increased to 55°C-65°C at a rate of 1°C per minute, and then the first heat preservation and pressure holding is carried out, and the first heat preservation and pressure holding time is 1h-2h.

[0022] Further, the step 2.4 includes:

[0023] 2.4.1. The first preform is vertically divided into 4 to 8 petals along the axial direction, and a rubber-impregnated carbon fiber rope is used to pass through the overlapping parts of several layers of the anti-ablation layer material in a zigzag route along the dividing line, wherein the distance between two adjacent suture points is 10 mm to 20 mm;

[0024] 2.4.2. Use the impregnated carbon fiber rope to sew the completely overlapping parts of several layers of the anti-ablation layer material in a zigzag pattern for one circle.

[0025] Furthermore, in step 2.5:

[0026] The vacuum degree during the second vacuum coating is not less than -0.099 MPa;

[0027] The pressure during the hot pressing molding is 1.0MPa~1.5MPa, wherein the pressure increasing rate is 0.05MPa per minute; at the same time, when the pressure reaches 0.5MPa, the heating is started, and the temperature is increased to 55℃-65℃ at a rate of 1℃ per minute, and then the second heat preservation and pressure holding is carried out, and the second heat preservation and pressure holding time is 1h~2h.

[0028] Furthermore, in step 2.3 and step 2.5:

[0029] Before the first vacuum coating, a layer of polytetrafluoroethylene varnish cloth is laid between the anti-ablation layer material and the vacuum bag of vacuum coating;

[0030] Before the second vacuum coating, a layer of polytetrafluoroethylene varnished cloth is laid between the second preform and the vacuum bag of the vacuum coating.

[0031] Furthermore, it also includes post-processing of the preform;

[0032] Furthermore, the method further comprises step three: post-processing the preform;

[0033] Post-processing of prefabs includes:

[0034] 3.1. Check whether the thickness and size of the preform meet the requirements according to the design requirements;

[0035] 3.2. The preform is placed on a foam or polyurethane core, wrapped with a vacuum bag and stored in a vacuum bag to prevent the preform from being deformed when stored.

[0036] The beneficial effects of this application include:

[0037] The present application provides a method for forming a preform of an anti-ablation layer of a rear head of a solid rocket engine. The method adopts a stitching process to achieve the physical connection of multiple layers of anti-ablation layer materials, making them an effective whole. The method of heating and pressurizing under a vacuum state is adopted to effectively ensure the integrity and reliability of the carbon fiber woven material in the anti-ablation material, while removing excess small molecules in the sheet, thereby solving the risk of bulging caused by small molecules during later use. After two pre-pressing moldings, the carbon fiber rope of the stitched part can be effectively integrated with the preform. After the preform is formed, vacuum coating is adopted to ensure the stability of the preform's surface during long-term storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1This is a flow chart of the method for forming the preform of the anti-ablation layer of the rear head of the solid rocket engine of the present application;

[0039] Figure 2 This is a schematic diagram of the structure of the anti-ablation layer preform of a certain type of solid rocket engine rear head;

[0040] Figure 3 for Figure 2 Schematic diagram of the process design scheme for the ablation-resistant layer preform of a certain type of solid rocket engine;

[0041] Figure 4 This is a schematic diagram of the structure of the anti-ablation layer preform of a certain type of solid rocket engine rear head in Example 1;

[0042] Figure 5 This is a schematic diagram of the process design scheme for the anti-ablation layer preform of the rear head of a certain type of solid rocket engine in Example 1;

[0043] Figure 6 This is a schematic diagram of the structure of the anti-ablation layer preform of a certain type of solid rocket engine rear head in Example 2;

[0044] Figure 7 This is a schematic diagram of the process design scheme for the anti-ablation layer preform of a certain type of solid rocket engine rear head in Example 2. DETAILED DESCRIPTION

[0045] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0046] The anti-ablation layer is generally made of carbon fiber woven 2.5D material as the main body, which is formed by impregnation with resin and rubber glue, and then cut, stitched (in the case of multi-layer materials, stitching is required to make it an integrated state) and airbag pressurization. With airbag pressurization, the airbag profile cannot fit well with the product profile. When the airbag is compressed and expanded, there will be a certain displacement with the film. There is a local fiber movement of the carbon fiber woven fabric, which reduces the fiber density at that place, and there will be a serious risk of ablation. Furthermore, when stitching, since the thickness of the ablative material film is in an expanded state before pressing, it is related to the state of the carbon fiber woven body and is more than 2 times thicker than the theoretical thickness. If it is stitched before pressing, the length of the suture line will be increased. After the material is heated and pressed, the suture line will be in a free state, and the close fit between the multi-layer materials cannot be achieved, and the suture effect is lost.

[0047] like Figure 1 As shown, the present application provides a method for forming a preform of an anti-ablation layer of a rear head of a solid rocket engine, characterized in that it includes:

[0048] Step 1: If Figure 2-3As shown, the structure of the anti-ablation layer is determined according to the design requirements; the anti-ablation layer includes a plurality of layers of anti-ablation layer materials arranged in sequence, and each layer of the anti-ablation layer material has a different height;

[0049] It is worth noting that in Figure 2-3 In the figure, the material superposition direction of the structure drawing is opposite to that of the process drawing. This is mainly because when the propellant in the combustion chamber of a solid rocket engine burns, the airflow direction is along the large end of the anti-ablation layer to the small end, and the ablation direction is from the inside to the outside, which prevents the combustion gas from entering the middle of the two layers of material and causing the two to separate. There is a risk of clogging the nozzle roar path. The actual working conditions are implemented according to the process drawing.

[0050] The anti-ablation layer is a trumpet-shaped ring;

[0051] The thickness direction of the anti-ablation layer decreases from the inside to the outside of each layer of the anti-ablation layer material;

[0052] Along the gas flow direction (ablation is more serious at the tail end), the thickness of the anti-ablation layer increases successively.

[0053] Specifically, according to the working conditions and performance requirements of the rocket engine, determine the key parameters such as the heat flux density and ablation rate that the anti-ablation layer needs to withstand. Consider the overall structure and size of the engine to ensure that the anti-ablation layer can adapt to and effectively protect the rear head. Select materials with high thermal stability, ablation resistance and low thermal conductivity, such as carbon / carbon composites, ceramic-based composites, etc. Design a multi-layer anti-ablation layer with different heights of each layer to adapt to the uneven distribution of heat flux. Ensure that the inner layer material has high thermal resistance and good thermal stability to withstand the initial high temperature shock. The outer layer material may pay more attention to ablation resistance to extend the overall service life. The anti-ablation layer is a trumpet-shaped ring as a whole to adapt to the shape of the rear head of the rocket engine. The inner and outer diameters of the ring are determined according to the size of the rear head to ensure a close fit. In the thickness direction, the height of each layer of the anti-ablation layer material decreases from the inside to the outside, forming a stepped structure. This design helps to disperse the heat flow and reduce the heat load of a single layer. Since the ablation is more severe at the tail end of the combustion chamber, the thickness of the ablation layer increases successively along the direction of gas flow, which helps to reduce the overall weight while maintaining adequate protection.

[0054] Step 2: using a forming mold to perform multi-stage pressure forming and suturing on the anti-ablation layer;

[0055] Among them, the suturing process is to connect the multiple layers of the anti-ablation layer material by physical means. The suturing method is to divide the anti-ablation layer into 4 to 8 petals, and sew the overlapping parts of the anti-ablation layer along the dividing line in a zigzag route with a rubber-impregnated carbon fiber rope. The spacing between two adjacent suturing points is 10 to 20 mm.

[0056] Specifically, the method involves multiple key steps such as determination of the structure of the anti-ablation layer, multi-stage pressurization and suture processing. First, the structure and material of the anti-ablation layer are determined according to the working environment and performance requirements of the rear head of the solid rocket engine. Among them, the material is determined according to the actual working state, and the anti-ablation layer needs to have good anti-ablation performance, anti-scouring performance, light weight and high strength. The anti-ablation layer is composed of several layers of anti-ablation layer materials arranged in sequence. The height of each layer of anti-ablation layer material is different to adapt to the thermal environment and performance requirements of different parts. Then, the anti-ablation layer preform is fixed and formed by a forming mold. Among them, the shape and size of the forming mold can be matched with the actual shape and size of the rear head, and no limitation is made here. Further, the anti-ablation layer is subjected to multi-stage pressurization. By gradually increasing the pressure, the anti-ablation layer material gradually fits the mold to form the required shape and size. Multi-stage pressurization can ensure the close fit and uniform distribution between the anti-ablation layer materials. Suture processing is performed between the multiple layers of anti-ablation layer materials to enhance their integrity and stability.

[0057] It is worth noting that the suture process should be performed before or during the pressurization process to prevent the material from having gaps or falling off after being heated and pressed. The material and process of the suture line should meet the requirements of anti-ablation, anti-scouring, light weight and high strength.

[0058] The second step comprises:

[0059] Step 2.1, preheating the molding mold;

[0060] In step 2.1:

[0061] The molding die is preheated at a temperature of 55° C.-65° C. for at least 1 hour.

[0062] Furthermore, the preheating temperature of the molding die is set to 55°C-65°C. The selection of this temperature range is based on the thermal properties and molding requirements of the anti-ablation layer material. Preheating the mold can ensure that the temperature difference between the mold and the material will not be too large during the subsequent material pressing process, thereby avoiding cracks or deformation of the material due to thermal stress. At the same time, this temperature range also helps to improve the fluidity and plasticity of the material, making it easier to form the desired shape and size in the mold. The preheating time is at least 1 hour to ensure that the mold can reach a uniform preheating temperature across the entire surface. Long-term preheating can eliminate the temperature gradient inside the mold and bring it to a thermally stable state. This can further improve the uniformity and stability of the material during the molding process, thereby ensuring the quality and performance of the final product.

[0063] It is worth noting that during the preheating process, appropriate heating equipment should be used, such as ovens, flat vulcanizers, hydraulic presses, etc., to ensure that the mold can be heated evenly. After the preheating is completed, the temperature of the mold should be accurately measured using thermometers and other measuring tools to ensure that it reaches the predetermined preheating temperature and time requirements.

[0064] Step 2.2, laying the anti-ablation layer material in the molding die in sequence and compacting it;

[0065] Step 2.3, performing a first vacuum coating on the flattened anti-ablation layer material and the forming mold, and then preheating and pressing the anti-ablation layer to obtain a first preform;

[0066] In step 2.3:

[0067] The vacuum degree during the first vacuum coating is not less than -0.099 MPa;

[0068] The pressure during the preheating and pressing is 0.5MPa-0.7MPa, wherein the pressure increasing rate is 0.05MPa per minute; at the same time, when the pressure is 0.5MPa, the heating is started, and the temperature is increased to 55°C-65°C at a rate of 1°C per minute, and then the first heat preservation and pressure holding is carried out, and the first heat preservation and pressure holding time is 1h-2h.

[0069] Specifically, during vacuum coating, the vacuum degree should be no less than -0.099MPa. This vacuum degree is set to ensure that the air and volatiles inside the anti-ablation layer material can be effectively extracted during the pressing process, so as to avoid the formation of bubbles or voids inside the material, which will affect the quality and performance of the final product. The pressure during preheating pressing is set to 0.5MPa~0.7MPa. This pressure range is set to ensure that the anti-ablation layer material can fit tightly in the mold and form a good shape and size. At the same time, the pressure increase rate is controlled at 0.05MPa per minute to ensure that the pressure can be applied to the material evenly and stably to avoid cracks or deformation of the material due to sudden pressure changes. When the pressure reaches 0.5MPa, the heating system is started. The heating rate is set to 1°C per minute to ensure that the material can be heated evenly and slowly to avoid excessive thermal stress. The target temperature for heating is 55°C-65°C, and the selection of this temperature range is based on the thermal properties and molding requirements of the anti-ablation layer material. After reaching the predetermined temperature and pressure, the first heat preservation and pressure holding is carried out. The heat preservation and pressure holding time is set to 1h~2h. This time setting is to ensure that the material can be fully solidified under constant temperature and pressure to form a stable structure and performance. At the same time, the changes in temperature and pressure should be continuously monitored during the heat preservation and pressure holding process to ensure that they are always kept within the predetermined range.

[0070] It is worth noting that before vacuum coating and preheating and pressing, the mold and material should be clean and dry to avoid the influence of impurities and moisture on the molding process. The selection of heating and pressure increase rate should be adjusted according to the specific anti-ablation layer material and molding requirements. After the end of heat preservation and pressure holding, the temperature and pressure should be slowly reduced to avoid cracks or deformation of the material due to sudden temperature and pressure changes.

[0071] Step 2.4, taking out the first preform, and using the impregnated carbon fiber rope to sew the first preform as a whole, so as to physically connect several layers of the anti-ablation layer material to obtain a second preform;

[0072] The step 2.4 comprises:

[0073] 2.4.1. The first preform is vertically divided into 4 to 8 petals along the axial direction, and a rubber-impregnated carbon fiber rope is used to pass through the overlapping parts of several layers of the anti-ablation layer material in a zigzag route along the dividing line, wherein the distance between two adjacent suture points is 10 mm to 20 mm;

[0074] 2.4.2. Use the impregnated carbon fiber rope to sew the completely overlapping parts of several layers of the anti-ablation layer material in a zigzag pattern for one circle.

[0075] Specifically, first, the first preform is vertically divided into 4 to 8 petals along the axial direction. The purpose of equal division is to facilitate the subsequent suturing operation and ensure that the preform after suturing is more uniform and stable in structure. On each petal after equal division, the overlapping part of several layers of anti-ablation layer materials is passed through the zigzag route along the equal division line using the dipped carbon fiber rope. This suturing method can increase the number and distribution of suturing points, thereby improving the overall strength and stability of the preform. At the same time, the zigzag route can also effectively disperse the shear force of the suture line on the material to avoid damage to the material due to stress concentration. The spacing between two adjacent suturing points is set to 10mm to 20mm. The setting of this spacing is based on the performance of the anti-ablation layer material and the requirements of suturing strength. Too dense suturing points may cause the material to be too concentrated at the suture point, increasing the brittleness of the material; while too sparse suturing points may not provide sufficient suturing strength. After completing the axial equal division and zigzag suturing, it is also necessary to use the dipped carbon fiber rope to suturing the completely overlapping parts of several layers of anti-ablation layer materials in a zigzag route for one circle. The purpose of this step is to further enhance the integrity and stability of the preform, especially in the area where the materials completely overlap. Circumferential stitching can effectively prevent the materials from separating or deforming when subjected to external forces.

[0076] Among them, the dipped carbon fiber rope is a rope made by impregnating carbon fiber bundles in a specific resin and then undergoing processes such as weaving or winding. It is mainly composed of two parts: carbon fiber and resin. Carbon fiber provides high strength and high modulus, while the resin plays a role in bonding, protecting and enhancing the bonding force between fibers. Carbon fiber itself has extremely high strength, so the dipped carbon fiber rope also has excellent tensile strength. The high modulus of carbon fiber makes the dipped carbon fiber rope less likely to deform when subjected to force. The resin layer can protect the carbon fiber from erosion by environmental factors such as moisture and chemicals. The surface of the dipped carbon fiber rope is smooth and wear-resistant, suitable for various friction and wear environments. The combination of carbon fiber and certain resins can withstand high temperature environments, allowing the dipped carbon fiber rope to maintain good performance at high temperatures.

[0077] It is worth noting that during the stitching process, the quality of the glue-impregnated carbon fiber rope should be ensured to be good to avoid insufficient stitching strength due to insufficient glue during the stitching process. The tension and position of the stitching line should be evenly distributed to avoid stress concentration or deformation of the preform when subjected to force due to uneven tension or position deviation. After the stitching process is completed, the preform should be fully inspected to ensure that all stitching points are firm and reliable without omissions or looseness.

[0078] Step 2.5: placing the second preform into the molding die again, vacuum coating the second preform and the molding die for a second time, and then hot pressing to obtain a molded preform.

[0079] In step 2.5:

[0080] The vacuum degree during the second vacuum coating is not less than -0.099 MPa;

[0081] The pressure during the hot pressing molding is 1.0MPa~1.5MPa, wherein the pressure increasing rate is 0.05MPa per minute; at the same time, when the pressure reaches 0.5MPa, the heating is started, and the temperature is increased to 55℃-65℃ at a rate of 1℃ per minute, and then the second heat preservation and pressure holding is carried out, and the second heat preservation and pressure holding time is 1h~2h.

[0082] Specifically, during the second vacuum coating, the vacuum degree should be no less than -0.099MPa. This vacuum degree requirement is the same as the first vacuum coating in step 2.3, which is intended to ensure that the air and volatiles inside the anti-ablation layer material can be effectively extracted during the hot pressing process to avoid the formation of bubbles or voids inside the material, which will affect the quality and performance of the final product. The pressure during hot pressing is set to 1.0MPa to 1.5MPa. This pressure range is selected to ensure that the anti-ablation layer material can fit together tightly during the hot pressing process to form a solid overall structure. Compared with the preheating pressing in step 2.3, the pressure of hot pressing is higher to meet the molding requirements of the material at a higher temperature. The pressure increase rate is controlled at 0.05MPa per minute. This pressure increase rate is set to ensure that the pressure can be applied to the material evenly and stably to avoid cracks or deformation of the material due to sudden pressure changes. When the pressure reaches 0.5MPa, the heating system is started. The heating rate is set to 1°C per minute to ensure that the material can be heated evenly and slowly to avoid excessive thermal stress. The target temperature for heating is also 55°C-65°C. The selection of this temperature range is based on the thermal properties and molding requirements of the anti-ablation layer material. After reaching the predetermined temperature and pressure, the second heat preservation and pressure holding is carried out. The heat preservation and pressure holding time is set to 1h~2h to ensure that the material can be fully cured at a constant temperature and pressure to form a stable structure and performance.

[0083] It is worth noting that before the second vacuum coating and hot pressing molding, the mold and material should be clean and dry to avoid the influence of impurities and moisture on the molding process. The selection of heating and pressurization rates should be adjusted according to the specific anti-ablation layer material and molding requirements. Different materials may require different heating and pressurization rates to achieve the best molding effect. After the insulation and pressure are completed, the temperature and pressure should be slowly reduced to avoid cracks or deformation of the material due to sudden temperature and pressure changes. During the entire hot pressing molding process, the changes in temperature and pressure should be continuously monitored to ensure that they always remain within the predetermined range.

[0084] In steps 2.3 and 2.5:

[0085] Before the first vacuum coating, a layer of polytetrafluoroethylene varnish cloth is laid between the anti-ablation layer material and the vacuum bag of vacuum coating;

[0086] Before the second vacuum coating, a layer of polytetrafluoroethylene varnished cloth is laid between the second preform and the vacuum bag of the vacuum coating.

[0087] Specifically, PTFE (polytetrafluoroethylene) has extremely high temperature resistance and can remain stable in high temperature environments. The surface of PTFE has extremely low surface energy and hardly adheres to any substance, which makes it an ideal choice for preventing material adhesion. PTFE is an excellent electrical insulator and is suitable for occasions with special requirements for electrical performance. PTFE has good corrosion resistance to most chemicals and can protect the underlying material from erosion. A layer of PTFE varnished cloth needs to be laid between the anti-ablation layer material and the vacuum bag used for vacuum coating. The purpose of this step is to prevent the anti-ablation layer material from adhering to the vacuum bag during the vacuum coating process. Due to the non-stickiness of PTFE, it can effectively isolate the anti-ablation layer material and the vacuum bag, avoiding unnecessary adhesion during vacuuming and heating, thereby protecting the integrity of the material and the surface finish and better demolding. A layer of PTFE varnished cloth is also laid between the second preform (the anti-ablation layer material that has been preliminarily processed and sewn) and the vacuum bag used for vacuum coating. The purpose of this step is the same as in step 2.3, both of which are to prevent adhesion and ensure the smooth progress of the molding process. Since the conditions of the second vacuum encapsulation and hot pressing may be more severe (such as higher temperature and pressure), the use of PTFE varnished cloth is particularly important.

[0088] It is worth noting that according to the specific molding conditions and material requirements, select PTFE cloth with appropriate thickness, temperature resistance and corrosion resistance. When laying the PTFE cloth, make sure it is flat and wrinkle-free to avoid bubbles or wrinkles during the molding process, which will affect the quality and performance of the final product. During use, the integrity of the PTFE cloth should be checked regularly. If it is damaged or contaminated, it should be replaced in time.

[0089] Specifically, the present application involves a series of treatments for the anti-ablation layer material, including preheating the mold, material flattening and compacting, vacuum coating and preheating pressing, stitching, and vacuum coating and hot pressing again, so as to prepare an anti-ablation layer preform that meets the performance requirements.

[0090] Among them, preheating the mold can ensure that the temperature difference between the mold and the material will not be too large during the subsequent material pressing process, thereby avoiding cracks or deformation of the material due to thermal stress. Heat the molding mold to a predetermined temperature and maintain it for a period of time to ensure that the mold temperature is evenly distributed;

[0091] Ensure that each layer of anti-ablation layer material fits tightly in the mold to form a complete ablation layer structure. According to the design requirements, lay the anti-ablation layer material layer by layer in the preheated mold, and use appropriate tools or equipment to compact the material;

[0092] Through vacuum coating and preheating and pressing, the anti-ablation layer materials are more closely fitted together and initially formed into the required shape and size. The flattened anti-ablation layer materials and the mold are placed in the vacuum coating equipment, vacuum treated and preheated and pressed with a certain pressure;

[0093] Through stitching, several layers of anti-ablation layer materials are physically connected to enhance their integrity and stability. Take out the first preform obtained after the first vacuum coating and preheating pressing, and use the impregnated carbon fiber rope to stitch the whole body. The stitching line should be carried out along the inclined direction of the material to ensure that the stitched ablation layer becomes one and can better adapt to the flow direction of the high-temperature airflow;

[0094] By vacuum coating and hot pressing again, the stitched anti-ablation layer materials are more closely attached together and finally formed into the desired shape and size. The stitched second preform is placed in the molding mold again and vacuum coated for the second time. Then, hot pressing is performed at an appropriate temperature and pressure until a molded preform is obtained.

[0095] It is worth noting that during the entire molding process, process parameters such as temperature, pressure and time should be strictly controlled to ensure the quality and performance of the anti-ablation layer. During the suture process, it should be ensured that the material and process of the suture line meet the requirements of anti-ablation, anti-scouring, light weight and high strength. The preform after molding should be quality inspected, including appearance inspection, dimensional measurement and performance testing, to ensure that it meets the design requirements and quality standards.

[0096] The method further comprises step three: post-processing the preform;

[0097] Post-processing of prefabs includes:

[0098] 3.1. Check whether the thickness and size of the preform meet the requirements according to the design requirements;

[0099] 3.2. The preform is placed on a foam or polyurethane core, wrapped with a vacuum bag and stored in a vacuum bag to prevent the preform from being deformed when stored.

[0100] Specifically, ensuring that the thickness and size of the preform meet the design requirements is a key step to ensure the quality and performance of the final product. Use appropriate measuring tools (such as vernier calipers, micrometers, etc.) to measure the key parts of the preform, record the data and compare them with the design requirements. The accuracy of the measuring tools and the rationality of the measuring methods should be ensured during measurement to avoid misjudgment caused by measurement errors. Prevent the preform from deforming during parking or transportation and maintain the stability of its shape and size. According to the shape and size of the preform, select a suitable foam or polyurethane core as a support. Carefully put the preform on the core to ensure that it fits tightly and is not easy to slip. Put the core with the preform into a vacuum bag and close the opening of the vacuum bag. Use a vacuum pump to extract the air in the vacuum bag to form a negative pressure environment. Ensure that the negative pressure state in the vacuum bag is stable and seal the vacuum bag for storage. This can effectively prevent the preform from deforming due to external factors (such as gravity, temperature, etc.).

[0101] It is worth noting that when choosing a foam or polyurethane core, factors such as its density, hardness and shape should be considered to ensure that it can provide good support. When using a vacuum bag for wrapping, the airtightness and negative pressure resistance of the vacuum bag should be ensured to be good to avoid failure due to air leakage. During storage, the negative pressure state in the vacuum bag should be checked regularly to see if it is stable, and timely measures should be taken to deal with any possible abnormalities.

[0102] Example 1: Figure 4 As shown, the structure of the anti-ablation layer preform of the rear head of a solid rocket engine is shown.

[0103] A method for forming a preform of an anti-ablation layer of a solid rocket engine rear head, comprising:

[0104] (1) Process design:

[0105] According to the design requirements, the anti-ablation material is decomposed into three complete parts, that is, the anti-ablation layer material is three layers, and the anti-ablation layer is a trumpet-shaped ring; the height of the three layers of the anti-ablation layer material decreases from the inside to the outside in the thickness direction of the anti-ablation layer; along the energy transfer direction, the thickness of the anti-ablation layer decreases in sequence, such as Figure 5 As shown;

[0106] (2) Cutting of anti-ablation layer materials:

[0107] Re-check the thickness and size of the anti-ablation layer material that has been impregnated and meets the requirements to see if they meet the requirements; if they meet the requirements, cut them into a ring shape and mark them according to the process design plan;

[0108] (3) Mold preheating:

[0109] Preheat the forming mold (usually a female mold, the molding surface is consistent with the outer surface of the product) in an oven or on a flat vulcanizer or hydraulic press at 60°C for 2 hours;

[0110] (4) Laying:

[0111] Then, according to the process design plan, the cut trumpet-shaped rings (three-layer anti-ablation layer material) are laid in the mold in sequence (1#, 2#, 3#) and compacted;

[0112] (5) First pre-pressing:

[0113] The anti-ablation layer material and the forming mold are wrapped with a vacuum bag, and vacuum is drawn to ensure airtightness (vacuum degree is not greater than -0.099MPa). In order to prevent the anti-ablation layer material from adhering to the vacuum bag and making demoulding difficult, a layer of polytetrafluoroethylene paint cloth can be laid between the two. Then heat and pressurize in the autoclave to fix the shape. Then increase the pressure of the autoclave to 0.5MPa, and the pressure increase rate is 0.05MPa per minute. When the pressure reaches 0.5MPa, start heating, increase the temperature to 60℃ at a rate of 1℃ per minute, and then keep warm and pressurized for 1h. After the program is completed, turn off the heating, cool to room temperature, and then release the pressure and disassemble.

[0114] (6) Suture:

[0115] After the first pre-pressing is completed, the preform is taken out and the preform is stitched as a whole using a dipped carbon fiber rope; the purpose of stitching is to physically connect the multi-layer sheets. The preform is divided into 8 petals approximately equally, and the overlapping parts of the sheets are stitched together along the bisecting line using a dipped carbon fiber rope in a zigzag pattern, with the spacing between each two points being 10 to 20 mm; then the completely overlapping parts of the anti-ablation layer material are stitched in a zigzag pattern using a dipped carbon fiber rope;

[0116] (7) Second pressing:

[0117] After the stitching is completed, a vacuum bag is used to lay it out and wrap it together with the forming mold, and vacuum is drawn to ensure that there is no air leakage (the vacuum degree is not greater than -0.099MPa). In order to prevent the anti-ablation material from adhering to the vacuum bag and making it difficult to demould, a layer of polytetrafluoroethylene paint cloth can be laid between the two; then the pressure of the autoclave is increased to 1.5MPa, and the pressure increase rate is 0.05MPa per minute. When the pressure reaches 0.5MPa, the heating is started, and the temperature is increased to 60℃ at a rate of 1℃ per minute, and then the temperature and pressure are kept for 2h; after the program is completed, the heating is turned off, and the pressure is released and disassembled after cooling to room temperature;

[0118] (8) Inspection:

[0119] Check whether the thickness and related dimensions of the prefabricated body meet the requirements according to the design drawings;

[0120] (9) Packaging:

[0121] The preform is placed on a special foam or polyurethane core, then wrapped with a vacuum bag and stored in a vacuum to prevent the preform from deforming due to long-term storage.

[0122] Example 2: Figure 6 As shown, the structure of the anti-ablation layer preform of the rear head of a solid rocket engine is shown.

[0123] A method for forming a preform of an anti-ablation layer of a solid rocket engine rear head, comprising:

[0124] (1) Process design:

[0125] According to the design requirements, the anti-ablation material is decomposed into two complete parts, that is, the anti-ablation layer material is two layers, and the anti-ablation layer is a trumpet-shaped ring; the height of the two layers of the anti-ablation layer material decreases from the inside to the outside in the thickness direction of the anti-ablation layer; along the energy transfer direction, the thickness of the anti-ablation layer decreases successively, such as Figure 7 As shown;

[0126] (2) Cutting of anti-ablation layer materials:

[0127] Re-check the thickness and size of the anti-ablation layer material that has been impregnated and meets the requirements to see if they meet the requirements; if they meet the requirements, cut them into a ring shape and mark them according to the process design plan;

[0128] (3) Mold preheating:

[0129] Preheat the forming mold (usually a female mold, the molding surface is consistent with the outer surface of the product) in an oven or on a flat vulcanizer or hydraulic press at 65°C for 1 hour;

[0130] (4) Laying:

[0131] Then, according to the process design plan, the cut trumpet-shaped rings (two layers of anti-ablation layer materials) are laid in the mold in sequence (1#, 2#) and compacted;

[0132] (5) First pre-pressing:

[0133] The anti-ablation layer material and the forming mold are wrapped with a vacuum bag, and vacuum is drawn to ensure airtightness (vacuum degree is not greater than -0.099MPa). In order to prevent the anti-ablation layer material from adhering to the vacuum bag and making demoulding difficult, a layer of polytetrafluoroethylene paint cloth can be laid between the two. Then heat and pressurize in the autoclave to fix the shape. Then increase the pressure of the autoclave to 0.5MPa, and the pressure increase rate is 0.05MPa per minute. When the pressure reaches 0.7MPa, start heating, and increase the temperature to 65℃ at a rate of 1℃ per minute, and then keep warm and pressurized for 1h. After the program is completed, turn off the heating, cool to room temperature, and then release the pressure and disassemble.

[0134] (6) Suture:

[0135] After the first pre-pressing is completed, the preform is taken out and the preform is stitched as a whole using a dipped carbon fiber rope; the purpose of stitching is to physically connect the multi-layer sheets. The preform is divided into 6 petals approximately equally, and the overlapping parts of the sheets are stitched together along the bisecting line using a dipped carbon fiber rope in a zigzag pattern, with the spacing between each two points being 10 to 20 mm; then the completely overlapping parts of the anti-ablation layer material are stitched in a zigzag pattern using a dipped carbon fiber rope;

[0136] (7) Second pressing:

[0137] After the stitching is completed, a vacuum bag is used to lay it out and wrap it together with the forming mold, and vacuum is drawn to ensure that there is no air leakage (the vacuum degree is not greater than -0.099MPa). In order to prevent the anti-ablation material from adhering to the vacuum bag and making it difficult to demould, a layer of polytetrafluoroethylene paint cloth can be laid between the two; then the pressure of the autoclave is increased to 1.0MPa, and the pressure increase rate is 0.05MPa per minute. When the pressure reaches 0.5MPa, the heating is started, and the temperature is increased to 65℃ at a rate of 1℃ per minute, and then the temperature and pressure are kept for 2h; after the program is completed, the heating is turned off, and the pressure is released and disassembled after cooling to room temperature;

[0138] (8) Inspection:

[0139] Check whether the thickness and related dimensions of the prefabricated body meet the requirements according to the design drawings;

[0140] (9) Packaging:

[0141] The preform is placed on a special foam or polyurethane core, then wrapped with a vacuum bag and stored in a vacuum to prevent the preform from deforming due to long-term storage.

[0142] In the above, the solid rocket engine rear head anti-ablation layer preform provided by the present application realizes the physical connection of multiple layers of anti-ablation layer materials by stitching treatment, making it an effective whole; the method of heating and pressurizing under vacuum state effectively ensures the integrity and reliability of the carbon fiber woven material in the anti-ablation material, and removes the excess small molecules in the sheet, solving the risk of bulging caused by small molecules during later use; after two pre-pressing molding, the carbon fiber rope of the stitching part can be effectively integrated with the preform; after the preform is formed, vacuum coating is used to ensure the stability of the preform surface during long-term storage. At the same time, the oxyacetylene wire ablation rate of the anti-ablation layer described in the present application reaches 0.02mm / s, and the bonding strength with the insulation layer is greater than 3MPa.

[0143] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for forming a preform of an anti-ablation layer of a solid rocket engine rear head, characterized in that: include: Step 1: Determine the structure of the anti-ablation layer according to the design requirements; the anti-ablation layer includes a plurality of layers of anti-ablation layer materials arranged in sequence, and each layer of the anti-ablation layer material has a different height; Step 2: using a forming mold to perform multi-stage pressure forming and suturing on the anti-ablation layer; The stitching process is to physically connect the multiple layers of the anti-ablation layer material. The stitching method is to divide the anti-ablation layer into 4 to 8 petals, and stitch the overlapping parts of the anti-ablation layer along the bisection line in a zigzag pattern with a carbon fiber rope dipped in glue, and the spacing between two adjacent stitching points is 10 to 20 mm. The anti-ablation layer is a trumpet-shaped ring; The thickness direction of the anti-ablation layer decreases from the inside to the outside of each layer of the anti-ablation layer material; Along the gas flow direction, the thickness of the anti-ablation layer increases successively; The second step comprises: Step 2.1, preheating the molding mold; Step 2.2, laying the anti-ablation layer material in the molding die in sequence and compacting it; Step 2.3, performing a first vacuum coating on the flattened anti-ablation layer material and the forming mold, and then preheating and pressing the anti-ablation layer to obtain a first preform; Step 2.4, taking out the first preform, and using the impregnated carbon fiber rope to sew the first preform as a whole, so as to physically connect several layers of the anti-ablation layer material to obtain a second preform; Step 2.5, placing the second preform into the molding die again, vacuum coating the second preform and the molding die for a second time, and then hot pressing to obtain a molded preform; The pressure during the preheating and pressing is 0.5MPa-0.7MPa, wherein the pressure increasing rate is 0.05MPa per minute; at the same time, when the pressure is 0.5MPa, the heating is started, and the temperature is increased to 55°C-65°C at a rate of 1°C per minute, and then the first heat preservation and pressure holding is performed, and the first heat preservation and pressure holding time is 1h-2h; The pressure during the hot pressing molding is 1.0MPa-1.5MPa, wherein the pressure increasing rate is 0.05MPa per minute; at the same time, when the pressure reaches 0.5MPa, the heating is started, and the temperature is increased to 55°C-65°C at a rate of 1°C per minute, and then the second heat preservation and pressure holding is performed, and the second heat preservation and pressure holding time is 1h-2h; The multi-layer anti-ablative layer material is physically connected and integrated by stitching; the carbon fiber woven material in the anti-ablative material has integrity and reliability by heating and pressurizing under vacuum, and the excess small molecules in the sheet are removed to avoid the risk of bulging caused by small molecules during later use; after two pre-pressing moldings, the carbon fiber rope of the stitched part is better integrated with the preform, the oxyacetylene wire ablation rate of the anti-ablative layer reaches 0.02mm / s, and the bonding strength with the insulation layer is greater than 3MPa.

2. The method for forming a preform of an anti-ablation layer of a rear head of a solid rocket engine according to claim 1, characterized in that: In step 2.1: The molding die is preheated at a temperature of 55° C.-65° C. for at least 1 hour.

3. The method for forming a preform of an anti-ablation layer of a solid rocket engine rear head according to claim 1, characterized in that: In step 2.3: The vacuum degree during the first vacuum coating is not less than -0.099 MPa.

4. The method for forming a preform of an anti-ablation layer of a rear head of a solid rocket engine according to claim 1, characterized in that: The step 2.4 comprises: 2.4.

1. The first preform is vertically divided into 4 to 8 petals along the axial direction, and a rubber-impregnated carbon fiber rope is used to pass through the overlapping parts of several layers of the anti-ablation layer material in a zigzag route along the dividing line, wherein the distance between two adjacent suture points is 10 mm to 20 mm; 2.4.

2. Use the impregnated carbon fiber rope to sew the completely overlapping parts of several layers of the anti-ablation layer material in a zigzag pattern around the ring.

5. The method for forming a preform of an anti-ablation layer of a rear head of a solid rocket engine according to claim 1, characterized in that: In step 2.5: The vacuum degree during the second vacuum coating is not less than -0.099 MPa.

6. The method for forming a preform of an anti-ablation layer of a rear head of a solid rocket engine according to claim 1, characterized in that: In steps 2.3 and 2.5: Before the first vacuum coating, a layer of polytetrafluoroethylene varnish cloth is laid between the anti-ablation layer material and the vacuum bag of vacuum coating; Before the second vacuum coating, a layer of polytetrafluoroethylene varnished cloth is laid between the second preform and the vacuum bag of the vacuum coating.

7. The method for forming a preform of an anti-ablation layer of a rear head of a solid rocket engine according to claim 1, characterized in that: The method further comprises step three: post-processing the preform; Post-processing of prefabs includes: 3.

1. Check whether the thickness and size of the preform meet the requirements according to the design requirements; 3.

2. The preform is placed on a foam or polyurethane core, wrapped with a vacuum bag and stored in a vacuum bag to prevent the preform from being deformed when stored.

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