A composite expansion section of a solid rocket nozzle and its forming method

Abstract

The present application discloses a solid rocket nozzle composite expansion section and a forming method thereof, belonging to the technical field of composite expansion section forming, including: an ablation layer, the ablation layer includes a polyacrylonitrile carbon fiber / boron phenolic resin material layer, and is formed by premixing the acrylonitrile carbon fiber and the boron phenolic resin and molding by pressing; a heat insulation layer, the heat insulation layer includes a high silica cloth tape / boron phenolic resin material layer; the heat insulation layer is wound outside the ablation layer, and a multi-ring structure is formed at the connection interface between the ablation layer and the heat insulation layer. The present invention has the dual effects of anti-ablation and heat insulation, with a low ablation rate, and the structural connection is safe and reliable, the product interface size is stable, and the consistency is good.

Description

Technical Field

[0001] The present application relates to a composite expansion section of a solid rocket nozzle and a forming method thereof, belonging to the technical field of composite expansion section forming. Background Art

[0002] The expansion section is a key component in the nozzle of a solid rocket engine to improve the energy conversion efficiency, and it has to withstand high temperature, high pressure and high gas flow erosion during the operation of the engine. The fiber-reinforced resin-based expansion section has the advantages of high reliability, short production cycle, low cost, etc., and is widely used in high-performance solid rocket engines at home and abroad. At present, the preparation methods of fiber-reinforced resin-based expansion sections at home and abroad mainly include tape overlapping winding, tape diagonal winding, petal laying and molding. Among them, for the expansion section with short working time and not serious ablation, high silica fiber-reinforced resin or carbon fiber-reinforced resin materials are generally used and formed by molding; for the expansion section with serious ablation conditions and harsh working conditions, a carbon fiber phenolic / high silica fiber phenolic composite structure is generally adopted, with carbon fiber phenolic as the ablation layer material and high silica phenolic as the heat insulation layer material. This structure has the dual functions of anti-ablative heat insulation, and its forming processes include chopped fiber composite molding (QJ2727A-2014 "Specification for Carbon Fiber / Phenolic - High Silica Fiber / Phenolic Composite Molding Products") and tape winding (GJB3402-98 Specification for Carbon Cloth / Phenolic - High Silica Cloth / Phenolic Composite Winding Products) two ways.

[0003] For QJ2727A-2014, the cost is relatively low, but the process is relatively complex and it needs to be formed by at least two or three moldings. Moreover, although the viscose fiber carbon fiber used has good processability, its ablation resistance is average. In practical use, the thickness needs to be increased to improve its reliability, which increases the negative mass of the engine; for GJB3402-98, the cost is high, and the product has good mechanical properties, but the tape winding process requires strict program design for tape winding, the curing process control pressure is smaller than that of molding, the density of the carbon layer is generally low, and the residual carbon rate of the barium phenolic resin used for the tape is low. There are wrinkle marks at the interface between the two materials, the consistency is poor, and the tape layer falls off at the end of the work.

[0004] In view of this phenomenon, in this case, a carbon fiber / phenolic - high silica cloth / phenolic composite structure is designed as the expansion section of the solid rocket engine nozzle to realize its application in the solid rocket engine nozzle. Summary of the Invention

[0005] According to one aspect of the present application, a composite expansion section of a solid rocket nozzle is provided. This expansion section has the dual functions of anti-ablative heat insulation, low ablation rate, and the structure connection is safe and reliable, the product interface size is stable, and the consistency is good.

[0006] A solid rocket nozzle composite expansion section, characterized in that it comprises:

[0007] An ablation layer, the ablation layer includes a polyacrylonitrile carbon fiber / boron phenolic resin material layer, and is formed by premixing the acrylonitrile carbon fiber and the boron phenolic resin and molding by pressing;

[0008] A heat insulation layer, the heat insulation layer includes a high silica cloth tape / boron phenolic resin material layer;

[0009] The heat insulation layer is wound outside the ablation layer, and a multi-ring structure is formed at the connection interface between the ablation layer and the heat insulation layer.

[0010] Further, the multi-ring structure includes a plurality of alternately and continuously arranged grooves and protrusions at the connection interface between the ablation layer and the heat insulation layer;

[0011] The interval between adjacent multi-ring structures is 1 to 3 times the width of the heat insulation layer, the height of the multi-ring structure is 1.5 mm to 3 mm, and the width of the multi-ring structure is 1 / 8 to 1 / 10 of the height of the expansion section.

[0012] Further, the thicknesses of the ablation layer and the heat insulation layer are confirmed according to the actual working conditions of the expansion section, and according to the heat transfer path, the thickness of the ablation layer at the inlet part of the solid rocket nozzle is set to be gradually greater than the thickness of the ablation layer at the outlet part of the solid rocket nozzle.

[0013] Further, the thickness of the ablation layer at the inlet part of the solid rocket nozzle is greater than the thickness of the ablation layer at the outlet of the solid rocket nozzle.

[0014] According to another aspect of the present application, the present application also provides a forming method for a solid rocket nozzle composite expansion section, characterized in that it includes:

[0015] S1: Preparation of the ablation layer, weighing a quantitative amount of polyacrylonitrile carbon fiber and boron phenolic resin for pretreatment to obtain a polyacrylonitrile carbon fiber / boron phenolic resin premix, and then molding by pressing using a pressing mold and performing heat preservation treatment;

[0016] S2: After the heat preservation is completed, naturally cool down to room temperature, demold, and after demolding, obtain a polyacrylonitrile carbon fiber / boron phenolic resin blank. Clean the demolded polyacrylonitrile carbon fiber / boron phenolic resin blank, remove the excess flash, and after checking that the appearance is intact, load it into the winding mandrel;

[0017] S3: Preparation of the heat insulation layer, obtaining a high silica cloth tape / boron phenolic resin material layer;

[0018] S4: According to the set program, wind the high silica cloth tape / boron phenolic resin material layer outside the polyacrylonitrile carbon fiber / boron phenolic resin blank;

[0019] S5: After winding is completed, a polyacrylonitrile carbon fiber / boron phenolic resin blank coated with the high-silica cloth tape / boron phenolic resin material layer is obtained, and then it is cured and formed in an autoclave. The forming pressure in the autoclave is greater than or equal to 3.0 MPa;

[0020] S6: After curing is completed, demolding inspection is carried out and records are made.

[0021] Further, the preparation of the polyacrylonitrile carbon fiber / boron phenolic resin premix includes the following steps:

[0022] Step 1: Dry the polyacrylonitrile carbon fiber in an oven. The drying temperature is 90°C to 100°C, and the drying time is greater than or equal to 2 h;

[0023] Step 2: Dissolve the boron phenolic resin and let it stand for more than 24 h after dissolution;

[0024] Step 3: Mix the polyacrylonitrile carbon fiber and the dissolved boron phenolic resin in proportion, seal it, and let it stand for more than 24 h;

[0025] Step 4: Loosen the impregnated premix, and then air it for more than 24 h. The airing temperature is 15°C to 25°C, and the humidity is less than or equal to 45%;

[0026] Step 5: Dry the air-dried premix in an oven. The drying temperature is 80°C to 85°C, and the drying time is greater than or equal to 5 h. After drying, it is reserved for use.

[0027] Further, according to the mass ratio, the ratio of the polyacrylonitrile carbon fiber to the boron phenolic resin is 57:43.

[0028] Further, the ablation layer further includes a filler;

[0029] According to the mass ratio, the ratio of the polyacrylonitrile carbon fiber, the boron phenolic resin, and the filler is 55:42:3.

[0030] Further, before molding by using a compression molding die, it further includes: preheating the compression molding die. The preheating temperature is 100°C ± 5°C, and the preheating time is 1 h to 3 h;

[0031] Among them, the pressure in the compression molding is greater than or equal to 500 kg / cm 2 , the heat preservation temperature is 100°C ± 5°C, the heat preservation time is 1 h to 3 h, and the pressure application time is 25 min to 30 min after the mold is closed.

[0032] The beneficial effects that this application can produce include:

[0033] A composite expansion section of a solid rocket nozzle and its forming method provided by the present application. The expansion section has dual functions of anti-ablative heat insulation. The linear ablation rate of the ablation layer reaches 0.02 mm / s, which is at least 20% lower than that of the composite molding or cloth tape composite winding structure. At the same time, the bonding strength of the composite interface is not less than 10 MPa, the cost is at least 50% lower than that of the cloth tape composite winding structure, and the interface size of the product is stable and the consistency is good. Description of the Drawings

[0034] Figure 1 Schematic diagram of the structure of the nozzle expansion section of a solid rocket engine in an embodiment of the present application;

[0035] Figure 2 Schematic diagram of the forming tooling structure of the ablation layer of the nozzle expansion section of a solid rocket engine in an embodiment of the present application;

[0036] Figure 3 Schematic diagram of the structure of the nozzle expansion section of a solid rocket engine in Example 1 of the present application;

[0037] Figure 4 Schematic diagram of the structure of the nozzle expansion section of a solid rocket engine in Example 2 of the present application;

[0038] List of components and reference numerals: 1 - ablation layer; 2 - heat insulation layer; 3 - groove; 4 - boss; 5 - male mold; 6 - female mold; 7 - top plate. Detailed Description of the Embodiments

[0039] The present application will be described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0040] See Figure 1 , a composite expansion section of a solid rocket nozzle, characterized in that it includes:

[0041] An ablation layer 1, the ablation layer 1 includes a polyacrylonitrile carbon fiber / boron phenolic resin material layer, and is formed by premixing the acrylonitrile carbon fiber and the boron phenolic resin and molding by pressing;

[0042] A heat insulation layer 2, the heat insulation layer 2 includes a high silica cloth tape / boron phenolic resin material layer;

[0043] The heat insulation layer 2 is wound outside the ablation layer 1, and a multi-ring structure is formed at the connection interface between the ablation layer 1 and the heat insulation layer 2.

[0044] Specifically, during the operation of a solid rocket motor, the ablative layer 1 serves to resist ablation, withstand high temperatures, and the erosion of high-speed gas flows, ensuring the integrity and stability of the nozzle structure. The ablative layer 1 is made of a mixture of polyacrylonitrile carbon fiber and boron phenolic resin and is prepared by compression molding. This material combination has good ablation performance and mechanical properties. The main function of the thermal insulation layer 2 is to reduce the heat transfer to the interior of the nozzle, protecting the internal structure and components from the influence of high temperatures. The thermal insulation layer 2 is composed of a combination of high-silica cloth tape and boron phenolic resin and is wound around the outside of the ablative layer 1 to form a connecting interface with a multi-ring structure, which helps to improve the thermal protection effect of the nozzle while ensuring the stability and reliability of the structure;

[0045] Among them, polyacrylonitrile carbon fiber has extremely high tensile strength and modulus, can withstand large external forces, and at the same time, the fiber has a high thermal decomposition temperature and excellent high-temperature performance; boron phenolic resin has better heat resistance, instantaneous high-temperature resistance, heat-resistant oxidation performance, and neutron radiation protection and other excellent properties than ordinary phenolic resin. Due to the B-O bond energy being higher than the C-C bond energy, the heat resistance and ablation resistance of boron phenolic resin are much higher than those of ordinary phenolic resin. The B-O bond also has good flexibility. Therefore, the brittleness of boron phenolic resin is reduced and its mechanical properties are improved. The ablative layer 1 is made of a mixture of polyacrylonitrile carbon fiber and boron phenolic resin and is prepared by compression molding. This material combination has good ablation performance and mechanical properties.

[0046] The multi-ring structure includes a plurality of alternately continuous grooves 3 and protrusions 4 at the connection interface between the ablative layer 1 and the thermal insulation layer 2, which helps to enhance the connection strength and stability between the ablative layer 1 and the thermal insulation layer 2. At the same time, this structure helps to optimize the heat transfer path and improve the overall thermal insulation performance;

[0047] The interval between adjacent multi-ring structures is 1 to 3 times the width of the thermal insulation layer 2. The height of the multi-ring structure is 1.5 mm to 3 mm, and the width of the multi-ring structure is 1 / 8 to 1 / 10 of the height of the expansion section.

[0048] Among them, the height of the expansion section refers to Figure 1 the length in the oblique direction of the expansion section as shown, specifically the service length of the expansion section when the expansion section is provided on the solid rocket nozzle.

[0049] The thicknesses of the ablative layer 1 and the thermal insulation layer 2 are determined according to the actual working conditions of the expansion section. And according to the heat transfer path, the thickness of the ablative layer at the inlet part of the solid rocket nozzle is set to be gradually greater than the thickness of the ablative layer at the outlet part of the solid rocket nozzle.

[0050] The thickness of the ablative layer at the inlet part of the solid rocket nozzle is greater than the thickness of the ablative layer at the outlet of the solid rocket nozzle.

[0051] Specifically, the ablation layer 1 has a greater thickness at the inlet part of the solid rocket nozzle. This is to cope with the more intense high-temperature and high-speed gas flow erosion at the nozzle inlet. The thicker ablation layer 1 can provide better ablation resistance performance and a longer service life. In contrast, the ablation layer 1 has a smaller thickness at the outlet part of the solid rocket nozzle. This is because the gas flow velocity at the nozzle outlet is relatively low and the temperature is also relatively low, so there is no need for an overly thick ablation layer 1 to provide protection.

[0052] This application designs a nozzle expansion section of a high-performance solid rocket engine, with dual functions of ablation resistance and heat insulation. The linear ablation rate of the ablation layer 1 reaches 0.02 mm / s, which is at least 20% lower than the linear ablation rate of the composite molding or cloth tape composite winding structure. The bonding strength of the composite interface is not less than 10 MPa, and the cost is at least 50% lower than that of the cloth tape composite winding structure. Moreover, the interface size of the product is stable, with good consistency. The peak height of the composite interface fold does not exceed 2 mm, and the structural connection is safe and reliable. It has passed the ground test application and the effect is perfect.

[0053] Among them, the peak height of the composite interface fold refers to the maximum deviation of the wave peak from the average plane in the interface fold phenomenon caused by factors such as material heating, stress concentration, or other factors in the nozzle expansion section of the solid rocket engine. This parameter can reflect the stability and performance of the nozzle expansion section interface.

[0054] Physical properties such as the elastic modulus and Poisson's ratio of the material will affect its response to stress and temperature changes. Factors such as the structural design of the nozzle, the connection method, and the temperature control and pressure control during the manufacturing process will all have an impact on the peak height of the interface fold.

[0055] A forming method for a composite expansion section of a solid rocket nozzle, characterized by comprising:

[0056] S1: Preparation of the ablation layer. Weigh a certain amount of polyacrylonitrile carbon fiber and boron phenolic resin for pretreatment to obtain a polyacrylonitrile carbon fiber / boron phenolic resin premix, and then use a compression molding die for molding and perform heat preservation treatment;

[0057] Among them, the structure of the compression molding die is as Figure 2As shown in the figure, the compression molding die includes a male die 5, a female die 6 and a top plate 7 which are assembled with each other. The female die 6 is a die with a cavity, and the shape of this cavity is the same as that of the final product, i.e., the expansion section. During the molding process, the material to be processed is placed in the cavity of the female die 6. The male die 5 is a solid die, and its outer shape is opposite to the cavity of the female die 6, that is, corresponding to the shape of the final product. During the molding process, the male die 5 presses into the material in the female die 6, and the material is deformed by applying force to obtain the required product shape. The top plate 7 is an important component in the compression molding die, located at the top of the die, used to provide support and positioning during the pressing process, and help to push out the finished product during demolding.

[0058] S2: After the heat preservation is completed, it is naturally cooled to room temperature and demolded. After demolding, a polyacrylonitrile carbon fiber / boron phenolic resin blank is obtained. The demolded polyacrylonitrile carbon fiber / boron phenolic resin blank is cleaned, the excess flash is removed, and after checking that the appearance is intact, it is loaded into the winding mandrel;

[0059] S3: Preparation of the heat insulation layer to obtain a high silica cloth tape / boron phenolic resin material layer;

[0060] S4: According to the set program, the high silica cloth tape / boron phenolic resin material layer is wound on the outside of the polyacrylonitrile carbon fiber / boron phenolic resin blank;

[0061] S5: After winding is completed, a polyacrylonitrile carbon fiber / boron phenolic resin blank coated with the high silica cloth tape / boron phenolic resin material layer is obtained, and then it is cured and formed in a autoclave, and the autoclave forming pressure is greater than or equal to 3.0 MPa;

[0062] S6: After curing is completed, demolding inspection is carried out and records are made.

[0063] The preparation of the polyacrylonitrile carbon fiber / boron phenolic resin premix includes the following steps:

[0064] Step 1: The polyacrylonitrile carbon fiber is dried in an oven at a drying temperature of 90 °C to 100 °C and a drying time of greater than or equal to 2 h;

[0065] Step 2: The boron phenolic resin is dissolved and left standing for more than 24 h after dissolution;

[0066] Step 3: The polyacrylonitrile carbon fiber and the dissolved boron phenolic resin are mixed in proportion, sealed and left standing for more than 24 h;

[0067] Step 4: The impregnated premix is loosened and then left standing for more than 24 h at a standing temperature of 15 °C to 25 °C and a humidity of less than or equal to 45%;

[0068] Step Five: The air-dried premix is dried in an oven at a drying temperature of 80°C to 85°C for a drying time of 5 h or more, and then reserved for use after drying.

[0069] According to the mass ratio, the ratio of the polyacrylonitrile carbon fiber to the boron phenolic resin is 57:43.

[0070] The ablation layer 1 further includes a filler;

[0071] According to the mass ratio, the ratio of the polyacrylonitrile carbon fiber, the boron phenolic resin and the filler is 55:42:3.

[0072] Among them, the filler can be selected from inorganic fillers such as silica powder or alumina, or nano-fillers such as nano-silica or carbon nanotubes to further enhance or adjust the performance of the composite material.

[0073] Before molding by using a compression molding die, it further includes: preheating the compression molding die at a preheating temperature of 100°C ± 5°C for a preheating time of 1 h to 3 h;

[0074] Among them, the pressure in the compression molding is greater than or equal to 500 kg / cm 2 , the heat preservation temperature is 100°C ± 5°C, the heat preservation time is 1 h to 3 h, and the pressure application time is 25 min to 30 min after the mold is closed.

[0075] Example 1: It is required that the peak height of the interface fold of the nozzle expansion section of the solid rocket motor does not exceed 2 mm, the linear ablation rate of the ablation layer does not exceed 0.05 mm / s (oxyacetylene test), and the bonding strength of the composite interface is not less than 10 MPa; the normal working time of the motor is 26 s. The specific steps are as follows:

[0076] 1) Design of the expansion section structure:

[0077] As Figure 3 shown, this type of expansion section is composed of two parts, an ablation layer 1 and a heat insulation layer 2, where the interface is connected by a multi-ring structure. The interval of the multi-ring structure is generally 2 times the width of the heat insulation layer 2, the ring height is 1.5 mm, the width of the ring is 1 / 10 of the height of the expansion section, and the number of rings is 3. The ablation layer 1 is made of a polyacrylonitrile carbon fiber / boron phenolic resin premix material, and the heat insulation layer 2 is made of a high silica cloth tape / boron phenolic resin material.

[0078] Specifically, the groove width of the multi-ring structure is 40 mm, and the width of the convex platform of the multi-ring structure is 20 mm. Here, the groove and convex platform widths refer to the projected distance in the horizontal direction as Figure 3 described.

[0079] 2) Preparation of polyacrylonitrile carbon fiber / boron phenolic resin premix:

[0080] a) Prepare polyacrylonitrile carbon fiber with a length of 50 mm, dry it in an oven at a temperature of 90°C to 100°C for 2 h;

[0081] b) Dissolve boron phenolic resin in a solvent and let it stand for 24 h;

[0082] c) Mix according to the ratio of polyacrylonitrile carbon fiber: boron phenolic resin: filler = 55:42:3, seal it and let it stand for 24 h;

[0083] d) Loosen the impregnated premix manually or by equipment, then air dry it at room temperature for 24 h, with the temperature not lower than 15°C and the humidity not exceeding 45%;

[0084] e) Dry the air-dried premix in an oven at a temperature of 80°C to 85°C for 5 h; after drying, pack it in a clean premix bag or barrel.

[0085] 3) Molding of the expansion section:

[0086] a) Calculate the loading amount according to the designed density of the product, weigh 450 g of polyacrylonitrile carbon fiber / boron phenolic resin premix, and then pre-treat it in an oven for 35 min at a temperature of 90°C;

[0087] b) Clean the compression molding die and preheat it at 100°C ± 5°C for 2 h;

[0088] c) Uniformly load the pre-treated polyacrylonitrile carbon fiber / boron phenolic resin premix into the preheated die in multiple batches;

[0089] d) Close the die and apply pressure for molding on a four-column hydraulic press, with the pressure not less than 500 kg / cm 2 , the heat preservation temperature is 100°C ± 5°C, the time is 1 h, and the pressure application time is 25 min to 30 min after closing the die;

[0090] e) After the heat preservation is completed, naturally cool down to room temperature and demold;

[0091] f) Clean the demolded polyacrylonitrile carbon fiber / boron phenolic resin blank, remove the excess flash, and after checking the appearance is intact, load it into the winding mandrel;

[0092] g) Wind high silica cloth / boron phenolic resin on the polyacrylonitrile carbon fiber / boron phenolic resin blank according to the set program;

[0093] h) After winding, wrap the blank and then cure it in a autoclave. The autoclave molding pressure is 3.0 MPa;

[0094] i) After demolding and inspection after curing, the appearance is intact, without cracks or material shortages. After inspection, the internal structure of the product is intact, without cracks or bubbles, and the maximum height of the interface fold peak wave is 0.7 mm.

[0095] Example 2: It is required that the peak height of the interface fold of the nozzle expansion section of the solid rocket motor does not exceed 2 mm, the linear ablation rate of the ablation layer does not exceed 0.05 mm / s (oxyacetylene test), and the bonding strength of the composite interface is not less than 10 MPa; the normal working time of the engine is 38 s. The specific steps are as follows:

[0096] 1) Design of the expansion section structure:

[0097] As Figure 4 shown, this type of expansion section is composed of two parts: an ablation layer 1 and a heat insulation layer 2. Among them, the interface is connected by a multi-ring structure, and the interval is generally 2 times the width of the cloth belt. The ring height is 2 mm, the width of the ring is 1 / 8 of the height of the expansion section, and the number of rings is 5. The ablation layer 1 uses a polyacrylonitrile carbon fiber / boron phenolic resin premix material, and the heat insulation layer 2 uses a high silica cloth belt / boron phenolic resin material.

[0098] Specifically, the groove width of the multi-ring structure is 40 mm, and the width of the convex platform of the multi-ring structure is 50 mm. Here, the groove and convex platform widths refer to the projected distance in the horizontal direction as Figure 4 described.

[0099] 2) Preparation of polyacrylonitrile carbon fiber / boron phenolic resin premix:

[0100] a) Prepare polyacrylonitrile carbon fiber with a length of 55 mm, and dry it in an oven at a temperature of 90°C to 100°C for 3 h;

[0101] b) Dissolve the boron phenolic resin with a solvent and let it stand for 30 h;

[0102] c) Mix in the ratio of polyacrylonitrile carbon fiber: boron phenolic resin: filler = 55:42:3, seal it and let it stand for 32 h;

[0103] d) Loosen the impregnated premix manually or with equipment, and then air-dry it at room temperature for 30 h, with a temperature not lower than 15°C and a humidity not exceeding 45%;

[0104] e) Dry the air-dried premix in an oven at a temperature of 80°C to 85°C for 6 h; after drying, pack it in a clean premix bag or barrel.

[0105] 3) Molding of the expansion section:

[0106] a) Calculate the charging amount according to the designed density of the product, weigh 1500 g of polyacrylonitrile carbon fiber / boron phenolic resin premix, and then pre-treat it in an oven for 40 min at a temperature of 100 °C;

[0107] b) Clean the compression molding die and preheat it at 100 °C ± 5 °C for 3 h;

[0108] c) Uniformly load the pre-treated polyacrylonitrile carbon fiber / boron phenolic resin premix into the preheated die in multiple batches;

[0109] d) Close the die and apply pressure for molding on a four-column hydraulic press, with the pressure not less than 500 kg / cm 2 , the heat preservation temperature is 100 °C ± 5 °C, the time is 1 h, and the pressure application time is 25 min - 30 min after closing the die;

[0110] e) After the heat preservation is completed, naturally cool down to room temperature and demold;

[0111] f) Clean the demolded polyacrylonitrile carbon fiber / boron phenolic resin blank, remove the excess flash, and after checking that the appearance is intact, load it into the winding mandrel;

[0112] g) Wind the high silica cloth / boron phenolic resin on the polyacrylonitrile carbon fiber / boron phenolic resin blank according to the set program;

[0113] h) After winding is completed, wrap the blank and then cure it in a autoclave. The autoclave molding pressure is 3.5 MPa;

[0114] i) After curing is completed, demold and inspect. The appearance is intact, without cracks or material shortage. After inspection, the internal structure of the product is intact, without cracks or bubbles, and the maximum height of the interface fold peak is 1.2 mm.

[0115] The above are only several embodiments of the present application, and do not impose any form of limitation on the present application. Although the present application is disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the technical solution of the present application, makes some changes or modifications using the disclosed technical content, which are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A composite expansion section for a solid rocket nozzle, characterized in that: include: an ablation layer, the ablation layer comprising a polyacrylonitrile carbon fiber / boron phenolic resin material layer, and formed by premixing the acrylonitrile carbon fiber and the boron phenolic resin and molding; A heat-insulating layer, the heat-insulating layer comprising a high-silica cloth tape / boron phenolic resin material layer; The heat insulation layer is wound around the outside of the ablation layer, and the connection interface between the ablation layer and the heat insulation layer forms a multi-ring structure; The multi-ring structure comprises a plurality of alternately and continuously arranged grooves and bosses at the connection interface between the ablation layer and the heat insulation layer; and the plurality of alternately and continuously arranged grooves and bosses on the ablation layer are molded in a mold by the acrylonitrile carbon fiber and the boron phenolic resin premix; The interval between adjacent multi-ring structures is 1 to 3 times the width of the heat insulation layer, the height of the multi-ring structure is 1.5 mm to 3 mm, and the width of the multi-ring structure is 1 / 8 to 1 / 10 of the height of the expansion section; The method for forming the composite expansion section of the solid rocket nozzle comprises: S1: Preparation of the ablation layer, weighing a certain amount of polyacrylonitrile carbon fiber and boron phenolic resin for pretreatment to obtain a polyacrylonitrile carbon fiber / boron phenolic resin premix, and then molding it using a compression molding mold and performing heat preservation treatment; S2: After the heat preservation is completed, the product is naturally cooled to room temperature and demolded to obtain a polyacrylonitrile carbon fiber / boron phenolic resin blank. The demolded polyacrylonitrile carbon fiber / boron phenolic resin blank is cleaned and excess flash is removed. After the appearance is checked to be intact, the blank is loaded into a winding core mold; S3: Preparation of thermal insulation layer, obtaining high silica tape / boron phenolic resin material layer; S4: According to the set procedure, a high silica tape / boron phenolic resin material layer is wound around the outside of the polyacrylonitrile carbon fiber / boron phenolic resin blank; S5: After the winding is completed, a polyacrylonitrile carbon fiber / boron phenolic resin blank coated with the high-silica cloth tape / boron phenolic resin material layer is obtained, and then cured and formed in an autoclave, wherein the autoclave molding pressure is greater than or equal to 3.0 MPa; S6: After curing is completed, demoulding inspection is carried out and records are kept; The preparation of the polyacrylonitrile carbon fiber / boron phenolic resin premix comprises the following steps: Step 1: drying the polyacrylonitrile carbon fiber in an oven at a drying temperature of 90° C. to 100° C. for a drying time greater than or equal to 2 hours, wherein the length of the polyacrylonitrile carbon fiber is 35 mm to 60 mm; Step 2: dissolving the boron phenolic resin and standing it for more than 24 hours after dissolution; Step 3: Mix the polyacrylonitrile carbon fiber and the dissolved boron phenolic resin according to the proportion, seal and let stand for more than 24 hours; Step 4: Tear the premixed material loose, and then air it for more than 24 hours at a temperature of 15°C to 25°C and a humidity of less than or equal to 45%; Step 5: The dried premix is ​​dried in an oven at a temperature of 80°C to 85°C for a time of greater than or equal to 5 hours, and then set aside for use; The expansion section has the dual functions of anti-ablation and heat insulation. The linear ablation rate of the ablation layer reaches 0.02 mm / s, which is at least 20% lower than the linear ablation rate of the composite molding or tape composite winding structure. The composite interface bonding strength is not less than 10 MPa, and the cost is at least 50% lower than the tape composite winding structure. The product interface size is stable and consistent, the composite interface fold peak height does not exceed 2 mm, and the structural connection is safe and reliable. According to the mass ratio, the ratio of the polyacrylonitrile carbon fiber to the boron phenolic resin is 57:43; Among them, the pressure during compression molding is greater than or equal to 500kg / cm 2 , the insulation temperature is 100℃±5℃, the insulation time is 1h~3h, and the pressurization time is 25min~30min after mold closing.

2. A solid rocket nozzle composite expansion section according to claim 1, characterized in that: The thickness of the ablation layer and the thermal insulation layer are confirmed according to the actual working conditions of the expansion section, and according to the heat transfer path, the thickness of the ablation layer at the inlet part of the solid rocket nozzle is set to be gradually larger than the thickness of the ablation layer at the outlet part of the solid rocket nozzle.

3. A solid rocket nozzle composite expansion section according to claim 2, characterized in that: The thickness of the ablation layer at the inlet portion of the solid rocket nozzle is greater than the thickness of the ablation layer at the outlet portion of the solid rocket nozzle.

4. The method for forming a composite expansion section of a solid rocket nozzle according to claim 1, characterized in that: The ablative layer further comprises a filler; In terms of mass ratio, the ratio of the polyacrylonitrile carbon fiber, the boron phenolic resin and the filler is 55:42:

3.

5. The method for forming a composite expansion section of a solid rocket nozzle according to claim 1, characterized in that: Before the compression molding process is performed using the compression molding die, the method further includes: preheating the compression molding die at a temperature of 100° C.±5° C. for a period of 1 hour to 3 hours.

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