A lightweight, low-ablation nozzle expansion section and a preparation method thereof

Abstract

The present invention provides a method for preparing a lightweight, low-ablation nozzle expansion section, comprising: mixing high-residue carbon phenolic resin, polyacrylonitrile-based short-cut carbon fiber and solvent in proportion to form a premix; after the premix is ​​desolventized, it is loaded into an expansion section preform curing tooling, and cured by heating and pressurizing a press to form a preform blank; the preform blank is machined to obtain a preform; the composite expansion section preform is woven on the outside of the preform and the large end of the expansion section by a carbon cloth / mesh tire + needle punching molding process, and after it is made, it is impregnated with phenolic resin, and then in the expansion section integral molding tooling, it is cured by heating and pressurizing a press to form a composite expansion section product; the expansion section blank is partially machined in the subsequent nozzle production and assembled with the nozzle shell. The present invention solves the problems of low material strength of the winding expansion section, large ablation amount under high temperature and high pressure working environment, and heavy nozzle weight, and meets the performance requirements of solid rocket engines for high impact-to-mass ratio nozzles.

Description

Technical Field

[0001] The present invention relates to the field of solid rocket engine nozzles, and in particular to a lightweight, low-ablation nozzle expansion section and a preparation method thereof. Background Art

[0002] Currently, the expansion section of solid rocket motor nozzles in standard batch production in China is mostly made of a carbon cloth / high-silica cloth reinforced phenolic resin composite wound product. This composite wound expansion section experiences significant ablation under high-temperature, high-pressure, and intense operating conditions. This requires increasing the material's design thickness to ensure ablation resistance during prolonged erosion. This often results in an excessively high negative mass for the expansion section, failing to meet nozzle weight reduction requirements. Therefore, expansion sections with lightweight, long-term, low-ablation performance are an essential choice for advanced, high-performance nozzles.

[0003] Existing lightweight, low-ablation expander technologies include: Patent CN111997781A utilizes a composite expander molding method based on a semi-cured RTM process to produce a double-layer composite nozzle expander. The inner layer is a 2.5D carbon fiber fabric-reinforced resin-based composite ablative layer, while the outer layer is a high-silica fiber tape-wound thermal insulation layer. This expander manufacturing method, fabricated from a 2.5D carbon fiber preform, results in varying resistance to ablation and debonding during high-pressure engine operation due to the warp and weft yarns being exposed to the combustion gases. This can easily result in a wavy ablation morphology and poor ablation uniformity. Furthermore, this method involves multiple molding techniques, including RTM tooling design, tape winding, and autoclave curing. The molding process also requires different tooling, resulting in a complex process and numerous factors affecting product quality. Patent CN106116623A addresses the drawbacks of existing diffuser sections, such as heavy weight and high cost, by using a vapor deposition method to impregnate the carbon fiber fabric, followed by pyrolysis to produce a C / C blank. The blank is then immersed in a xylene solution of polycarbosilane, and finally undergoes a series of operations including physical pressure curing, high-temperature cracking, and mechanical processing to obtain an expansion section of the desired size. This preparation process requires the use of special equipment such as vapor deposition equipment and high-temperature cracking furnaces, and the impregnation-curing-cracking process must be repeated 5-7 times to achieve the required product density. The entire process is complex, with high equipment requirements and high process costs. The CN209011969U patent introduces a relatively thin and lightweight carbon / silicon carbide composite winding material at the rear end of the expansion section based on a carbon cloth-high silica cloth / phenolic winding expansion section to reduce the overall weight. Ultimately, it is still a winding expansion section. Compared with the needle-punched preform, the shear performance of the composite material between the layers of the winding process is poor. The thin-walled structure design of the winding expansion section is prone to structural delamination after high-temperature carbonization.

[0004] Most existing expansion section materials are prepared using carbon cloth / high-silica cloth reinforced phenolic resin composite winding technology. In actual engine applications, there are two main deficiencies: first, the "step" effect at the small end of the expansion section (where it connects with the throat liner) is significant, resulting in a high ablation rate, which reduces the specific impulse efficiency of the expansion section and may even cause structural damage to the expansion section. On the other hand, the expansion section outlet cone is a thin-walled structure, and the composite materials produced by traditional winding processes have the problem of low interlayer performance. Structural delamination is prone to occur after high-temperature carbonization. In order to reduce the impact of the carbonization zone, a design approach of increasing the wall thickness is required, but this will result in a significant increase in the passive mass of the expansion section. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a lightweight, low-ablation nozzle expansion section to solve the problems of the existing wound expansion section, such as low material strength, large ablation in high-temperature and high-pressure working environments, the need for thicker winding thickness to meet anti-ablation requirements, and the resulting heavy nozzle weight, so as to meet the performance requirements of advanced solid rocket engines for high impact-to-mass ratio nozzles.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a lightweight, low-ablation nozzle expansion section, comprising:

[0007] S1: Preparation of the small end of the expansion section: high carbon residue phenolic resin, polyacrylonitrile-based chopped carbon fibers and solvent are mixed in proportion to form a premix. After the premix is ​​desolventized, it is loaded into the expansion section preform curing tooling, and heated and pressurized in a press to form a preform blank. The preform blank is then machined to obtain a preform;

[0008] S2: Preparation of the large end of the expansion section: The composite expansion section preform is woven on the outside of the preform and the large end of the expansion section using carbon cloth / mesh + needle punching technology. After it is made, it is impregnated with phenolic resin and then placed in the overall expansion section molding tooling. It is heated and pressurized by a press to solidify into a composite expansion section product. In the subsequent nozzle production, the expansion section blank is locally machined and assembled into place with the nozzle shell.

[0009] Furthermore, the solvent in S1 is industrial alcohol, wherein the mass ratio of high carbon residue phenolic resin, polyacrylonitrile-based chopped carbon fibers and solvent is 1:1.4-1.6:2.8-3.2.

[0010] Furthermore, the premix in S1 is desolventized at 70-80° C. to maintain the volatile matter x content in the premix at 3.0%≤x≤5.5%.

[0011] Furthermore, the S1 press heating and curing step is as follows: heating from room temperature to 80-90°C within 50-60 minutes, maintaining for 120-130 minutes; then heating to 100-110°C within 50-60 minutes, maintaining for 90-100 minutes; finally heating to 170-180°C within 140-150 minutes, maintaining for 150-160 minutes; the press press curing step is as follows: pressurizing 1.0-1.5M at 80-90°C Pa mold closing; pressurize to 3.0-3.5MPa at 100-110℃; keep warm at 100-110℃ for 60-70min, release air for 1-2min, and pressurize to 6.0-6.5MPa; keep warm at 100-110℃ for 90-100min, release air for 1-2min, and then pressurize to 10.0-10.5MPa, and maintain the pressure until the end of the program. After the curing is completed, the cured tooling is naturally cooled to room temperature, and the small-end prefabricated part is demoulded and taken out.

[0012] Furthermore, the carbon cloth in S2 is T800 polyacrylonitrile-based carbon fiber twill cloth, and the mesh is T700 polyacrylonitrile-based carbon fiber, wherein the carbon cloth and the carbon fiber mesh are alternately stacked, and the laying direction is parallel to the busbar direction of the expansion section, and is fixedly formed into a composite expansion section integral preform with a conical structure through a needle punching process.

[0013] Furthermore, after the composite expansion section preform in S2 is molded, the preform is subjected to a dehumidification treatment at 105-110° C. / 2 h.

[0014] Furthermore, the S2 medium press heating and curing step is as follows: heating from room temperature to 100-110°C within 80-90 minutes, maintaining for 240-250 minutes; then heating to 120-130°C within 30-40 minutes, maintaining for 120-130 minutes; finally heating to 170-180°C within 170-180 minutes, maintaining for 150-160 minutes; the press press curing step is as follows: when heating to 100-110°C, pressurizing 0.3-0.4MPa and closing the mold; keeping warm at 100-110°C and curing When the expansion section is bundled, pressurize it by 1.0-1.2MPa; when the temperature is raised to 120-130℃, release the air for 1-2min and then pressurize it by 2.0-2.2MPa; when keeping it at 120-130℃ for 60-70min, release the air for 1-2min and pressurize it by 3.0-3.2MPa; when keeping it at 120-130℃ for 120-130min, release the air for 1-2min and pressurize it by 4.0-4.2MPa, and maintain the pressure until the end of the program. After the curing is completed, the overall molded tooling of the expansion section is naturally cooled to room temperature, and the expanded section product is demoulded and taken out.

[0015] Based on the same concept, the present invention also provides a lightweight, low-ablation nozzle expansion section.

[0016] The above one or more technical solutions of the present invention have the following technical effects:

[0017] An embodiment of the present invention provides a lightweight, low-ablation nozzle expansion section and a method for preparing the same. The expansion section's double-layer structure and dimensions are rationally designed based on the functional requirements of different sections of the expansion section. This achieves lightweighting while meeting the varying performance requirements of different sections, thereby increasing the engine's payload. Compared to conventional carbon cloth / high-silicon-oxide cloth-reinforced phenolic resin composite wound expansion sections, and improved carbon / silicon carbide composite wound expansion sections based on these wound expansion sections, the composite nozzle expansion section, through a zoned functional design, exhibits superior ablation resistance in the main ablation zone at the small end, while maintaining good overall structural stability and low density in other non-ablation zones. The expansion section's overall preform is formed using carbon cloth and needle punching, significantly improving interlaminar shear strength and avoiding the risk of structural delamination that can occur in thin-walled wound expansion section designs after high-temperature carbonization. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0019] Figure 1 A flow chart for preparing a lightweight, low-ablation nozzle expansion section;

[0020] Figure 2 .Diagram of curing fixture for the prefabricated part at the small end of the expansion section;

[0021] Figure 3 .Schematic diagram of the prefabricated structure of the small end of the expansion section;

[0022] Figure 4 .Composite expansion section overall prefabricated body diagram;

[0023] Figure 5 .Integral molded tooling drawing of the composite expansion section;

[0024] Figure 6 .Compound expansion section product drawing (blank);

[0025] Among them, 1. male mold, 2. ring, 3. screw, 4. female mold, 5. spacer, 6. top cover, 7. female mold, 8. male mold, 9. screw, 10. chassis. DETAILED DESCRIPTION

[0026] Example 1

[0027] like Figure 1As shown, a method for preparing a lightweight, low-ablation nozzle expansion section includes:

[0028] S1: Preparation of the small end of the expansion section: high carbon residue phenolic resin, polyacrylonitrile-based chopped carbon fibers and solvent are mixed in proportion to form a premix. After the premix is ​​desolventized, it is loaded into the expansion section preform curing tooling, and heated and pressurized in a press to form a preform blank. The preform blank is then machined to obtain a preform;

[0029] Specifically, the solvent is industrial alcohol, wherein the mass ratio of high carbon residue phenolic resin, polyacrylonitrile-based chopped carbon fibers and solvent is 1:1.4-1.6:2.8-3.2, wherein the mixing order is firstly mixing the high carbon residue phenolic resin and industrial alcohol by mechanical stirring according to the above ratio, and then adding the polyacrylonitrile-based chopped carbon fibers, repeatedly kneading and squeezing, so that the resin solution and the carbon fibers are fully mixed to form a premix, and the premix is ​​desolventized at 70-80°C, and can be placed in an oven for desolventization, or other methods can be used for desolventization, and the volatile matter x content in the premix is ​​maintained at 3.0%≤x≤5.5%. The volatile matter test method of the premix is ​​as follows: take a certain amount (20-40g) of the premix, weigh m1, put it into a (103-107)°C oven, keep it warm for (29-31)min, take it out and let it cool to room temperature, and then weigh m2. The volatile matter x is calculated as: After the premix is ​​desolventized and qualified, weigh an appropriate amount of premix and put it into Figure 1The preform for the small end of the expansion section is molded in the preform curing fixture shown. The preform curing fixture includes a spacer, a female mold, a male mold, and a collar. The female mold and collar are connected using screws, and the other fixtures are connected through fittings. Before the premix is ​​molded, the female mold and the pad are connected by fitting, and the female mold and the collar are connected by screws to form a cavity between the pad, the female mold and the collar. The weighed premix is ​​evenly spread into the cavity, and finally the male mold is covered to complete the molding of the expansion section small end preform; the expansion section small end preform curing tooling after molding is placed on the press and prepared for curing. The press heating and curing steps are: heating from room temperature to 80-90℃ within 50-60min, maintaining for 120-130min; then heating to 100-110℃ within 50-60min, maintaining for 90-100min; finally heating within 140-150min To 170-180℃, maintain for 150-160min; the pressurizing and curing steps are as follows: pressurizing 1.0-1.5MPa and closing the mold at 80-90℃; pressurizing 3.0-3.5MPa at 100-110℃; keeping warm at 100-110℃ for 60-70min, releasing air for 1-2min, and pressurizing 6.0-6.5MPa; keeping warm at 100-110℃ for 90-100min, releasing air for 1-2min and then pressurizing 10.0-10.5MPa, and maintaining the pressure until the end of the program. After the curing is completed, the cured tooling is naturally cooled to room temperature, and the small-end prefabricated blank is removed from the mold; the prefabricated blank is obtained by the machine. Figure 3 The preformed product shown.

[0030] S2: Preparation of the expansion section large end: A composite expansion section preform is woven on the outside of the preform and the expansion section large end using a carbon cloth / mesh tire + needle punching process. After being formed, it is impregnated with phenolic resin and then placed in the expansion section integral molding tool. It is heated and pressurized in a press to solidify into a composite expansion section product. In the subsequent nozzle production, the expansion section blank is partially machined and assembled into the nozzle shell.

[0031] Specifically, the carbon cloth is T800 polyacrylonitrile-based carbon fiber twill, and the mat is T700 polyacrylonitrile-based carbon fiber. The carbon cloth and carbon fiber mat are alternately layered, with the ply direction parallel to the expansion section's busbars. A needling process forms a tapered composite expansion section preform. After compression molding, the composite expansion section preform is subjected to a dehumidification treatment at 105-110°C / 2 hours. After dehumidification, the preform is vacuum-baged to create a sealed space, with a vacuum port reserved at the small end and several glue inlets at the large end. Prior to impregnation, the vacuum bag's vacuum level is tested, requiring it to maintain a continuous vacuum level of ≤-0.07 MPa. Weigh a certain amount of phenolic resin and place it in a clean container. Then connect the phenolic resin in the container and the preform inlet through a PE injection hose. When the vacuum degree meets the requirements, open the preform inlet valve. The phenolic resin begins to be slowly sucked into the preform under vacuum suction until the preform is completely soaked with phenolic resin. The preform resin impregnation process is completed. The preform impregnated with resin is placed in the composite expansion section integral molding tooling for heating and pressurizing curing. The integral molding tooling is as follows: Figure 5 As shown, it consists of a female mold, a male mold, a chassis, a top cover, and screws. First, connect the male mold and the chassis with screws, then install the impregnated preform on the male mold, and then close the female mold and the top cover in sequence to complete the molding. The molded tooling is placed on the press and ready for curing. The press heating and curing steps are: heating from room temperature to 100-110℃ within 80-90min, and maintaining for 240-250min; then heating to 120-130℃ within 30-40min, and maintaining for 120-130min; finally heating to 170-180℃ within 170-180min, and maintaining for 150-160min; the press press curing steps are: heating to 100-110℃ and maintaining for 240-250min. Pressurize 0.3-0.4MPa to close the mold; at the end of the insulation at 100-110℃, pressurize 1.0-1.2MPa; when the temperature rises to 120-130℃, release air for 1-2min and then pressurize 2.0-2.2MPa; when the temperature is kept at 120-130℃ for 60-70min, release air for 1-2min and pressurize 3.0-3.2MPa; when the temperature is kept at 120-130℃ for 120-130min, release air for 1-2min and pressurize 4.0-4.2MPa, and maintain the pressure until the end of the program. After the curing is completed, the entire molded tooling of the expansion section is naturally cooled to room temperature, and the expansion section product is demoulded and taken out. Figure 6 shown.

[0032] The oxyacetylene wire ablation rate of the polyacrylonitrile-based carbon fiber / high carbon residue phenolic resin material (implementing the standard GJB 323B) is 0.02-0.03 mm / s, which is 50% lower than the ablation rate of the traditional wound expansion segment material (0.05-0.06). In addition, compared with the wound expansion segment, the carbon fiber / phenolic material has a simpler preparation process and greatly improved quality controllability.

Claims

1. A method for preparing a lightweight, low-ablation nozzle expansion section, It is characterized in that include: S1: Preparation of the small end of the expansion section: high carbon residue phenolic resin, polyacrylonitrile-based short carbon fibers and solvent are mixed in proportion to form a premix, and after the premix is ​​desolventized, it is loaded into the expansion section preform curing tooling, and heated and pressurized by a press to form a preform blank, and the preform blank is machined to obtain a preform; S2: Preparation of the large end of the expansion section: The composite expansion section preform is woven on the outside of the preform and the large end of the expansion section using carbon cloth / mesh tire + needle punching molding process. After being made, it is impregnated with phenolic resin and then placed in the expansion section integral molding tooling. It is heated and pressurized by a press to solidify into a composite expansion section product. In the subsequent nozzle production, the expansion section blank is partially machined and assembled into place with the nozzle shell.

2. The method for preparing the lightweight, low-ablation nozzle expansion section according to claim 1, Features: The solvent in S1 is industrial alcohol, wherein the mass ratio of high carbon residue phenolic resin, polyacrylonitrile-based chopped carbon fibers and solvent is 1:1.4-1.6:2.8-3.

2.

3. The method for preparing the lightweight, low-ablation nozzle expansion section according to claim 1, Features: The premix in S1 is desolventized at 70-80° C. to maintain the volatile matter x content in the premix at 3.0%≤x≤5.5%.

4. The method for preparing the lightweight, low-ablation nozzle expansion section according to claim 1, Features: The step of heating and curing in the press in S1 is: heating from room temperature to 80-90°C within 50-60min, and maintaining for 120-130min; then heating to 100-110°C within 50-60min, and maintaining for 90-100min; finally heating to 170-180°C within 140-150min, and maintaining for 150-160min; the step of press curing is: pressurizing at 1.0-1.5MPa at 80-90°C Close the mold; pressurize at 3.0-3.5MPa at 100-110℃; keep warm at 100-110℃ for 60-70min, release air for 1-2min, and pressurize at 6.0-6.5MPa; keep warm at 100-110℃ for 90-100min, release air for 1-2min and then pressurize at 10.0-10.5MPa, and keep the pressure until the end of the program. After curing, the cured tooling is naturally cooled to room temperature, and the small-end prefabricated blank is demoulded and taken out.

5. The method for preparing the lightweight, low-ablation nozzle expansion section according to claim 1, Features: The carbon cloth in S2 is T800 polyacrylonitrile-based carbon fiber twill cloth, and the mesh is T700 polyacrylonitrile-based carbon fiber, wherein the carbon cloth and the carbon fiber mesh are alternately stacked, and the stacking direction is parallel to the direction of the expansion section generatrix, and is fixed by a needle punching process to form a composite expansion section integral preform with a conical structure.

6. The method for preparing the lightweight, low-ablation nozzle expansion section according to claim 1, Features: After the composite expansion section preform in S2 is molded, the preform is subjected to dehumidification treatment at 105-110° C. / 2 h.

7. The method for preparing the lightweight, low-ablation nozzle expansion section according to claim 1, Features: The S2 press heating and curing steps are: heating from room temperature to 100-110°C within 80-90 minutes, maintaining for 240-250 minutes; then heating to 120-130°C within 30-40 minutes, maintaining for 120-130 minutes; finally heating to 170-180°C within 170-180 minutes, maintaining for 150-160 minutes; the press press curing steps are: when the temperature is raised to 100-110°C, pressurize 0.3-0.4MPa to close the mold; when the temperature is kept at 100-110°C, , pressurize to 1.0-1.2MPa; when the temperature rises to 120-130℃, release air for 1-2min and then pressurize to 2.0-2.2MPa; when keeping warm at 120-130℃ for 60-70min, release air for 1-2min and pressurize to 3.0-3.2MPa; when keeping warm at 120-130℃ for 120-130min, release air for 1-2min and pressurize to 4.0-4.2MPa, and keep the pressure until the end of the program. After the curing is completed, the overall molding tooling of the expansion section is naturally cooled to room temperature, and the expansion section product is demolded and taken out.

8. A lightweight, low-ablation nozzle expansion section, Features: The lightweight, low-ablation expansion segment is prepared by any one of the methods of claims 1-7.

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