Carbon fiber modified and patch-wound reinforced solid rocket motor casing and its manufacturing method

Abstract

This invention discloses a method for manufacturing a solid rocket motor casing with modified carbon fiber and reinforced by patch winding. The method includes the following steps: preparing a base sizing agent; preparing crystalline polyetheretherketone (PEEK)-grafted carbon nanotubes; preparing a final sizing agent: dispersing raw carbon nanotubes, carboxylated carbon nanotubes, or PEEK-grafted carbon nanotubes in NM under ultrasonic conditions, followed by pouring in the base sizing agent and ultrasonically dispersing to obtain the final sizing agent; modifying the carbon fiber using the final sizing agent; winding the casing spirally followed by circumferentially to form a stepped structure with a gradually decreasing height from the body to the end cap, followed by primary curing; filling the stepped height difference with two-stage fan-shaped two-layer patches, and then spirally winding the entire casing again, followed by secondary curing to obtain the solid rocket motor casing. This invention can improve the stress distribution of the casing, reduce stress concentration, and enhance heat resistance, thereby improving the safety and reliability of the rocket motor.

Description

Technical Field

[0001] This invention belongs to the field of solid rocket motor casings, specifically relating to a carbon fiber modified and patch-wound reinforced solid rocket motor casing and its manufacturing method. Background Technology

[0002] The fabrication of rocket engine casings made of carbon fiber composites typically employs a winding process, where pre-impregnated epoxy resin-coated carbon fiber tape is wound onto a mandrel. During fiber winding, a large number of helical layers concentrate in the cylindrical portion. The presence of these helical layers results in an inefficient distribution of fiber material in this area, with many fibers failing to fully utilize their load-bearing capacity. This leads to uneven stress distribution and the potential for excessively high localized stress, compromising the casing's safety. Furthermore, the low utilization efficiency of fiber material in the cylindrical portion increases both material costs and the overall weight of the container in order to meet the required performance.

[0003] Using a reasonable spiral wound reinforcement method can effectively solve the above problems. However, this raises the issue of curing. A single curing cycle leads to incomplete curing of the internal spiral and circumferential layers, severely impacting the shell's mechanical properties and airtightness. Therefore, a two-stage curing method is employed to address this issue. Traditional carbon fiber epoxy resin composites, to a certain extent, meet the high strength and high modulus requirements of rocket engine shells, but their insufficient heat resistance affects the structure's safety and reliability. Because two-stage curing requires higher temperatures, traditional carbon fiber epoxy resin materials do not meet the requirements of two-stage curing. Modification of the carbon fiber matrix material is necessary to improve its heat resistance.

[0004] Therefore, it is of great significance to find a more effective way to reinforce the end cap section to improve its safety and to effectively modify the carbon fiber composite material to improve its heat resistance. Summary of the Invention

[0005] The purpose of this invention is to provide a carbon fiber modified and patch-wound reinforced solid rocket motor casing and its manufacturing method.

[0006] The technical solution to achieve the purpose of this invention is: a method for manufacturing a solid rocket motor casing with carbon fiber modification and patch winding reinforcement, comprising the following steps:

[0007] Step (1): Prepare the base slurry;

[0008] Step (2): Prepare crystalline polyetheretherketone-grafted carbon nanotubes;

[0009] Step (3): Preparation of final sizing agent: Disperse the original carbon nanotubes, carboxylated carbon nanotubes or polyether ether ketone grafted carbon nanotubes in NM under ultrasonic conditions, then pour in the sizing agent prepared in step (1), and disperse it again under ultrasonic conditions to obtain the final sizing agent;

[0010] Step (4): Modify the carbon fiber using the final sizing agent prepared in step (3) to obtain modified carbon fiber;

[0011] Step (5): The shell is first spiral wound and then circumferential wound to form a stepped structure with the height gradually decreasing from the cylinder to the head section, and then cured once; the stepped height difference is filled by two-segment fan-shaped two-layer patches, and the entire shell is spiral wound and cured a second time to obtain the solid rocket motor shell.

[0012] Further, step (1) specifically involves: synthesizing polyether ether ketone-1,3-dithionecyclopentane PEEKDith with different molecular weights and carbonyl contents by protecting the carbonyl group to avoid unnecessary reactions; synthesizing polyether ether ketone-1,3-dioxolane PEEKDith-2.5-100 through a substitution reaction; dissolving it in N-methylpyrrolidone; and reacting it at room temperature for 2 ± 0.2 h under magnetic stirring to prepare a base slurry.

[0013] Furthermore, step (2) specifically includes the following steps:

[0014] Step (21): PEEKDith-2.0-20 was dissolved in tetrahydrofuran (THF) under magnetic stirring, and then NaBH4 and anhydrous methanol were added sequentially. After reacting at room temperature for 10±1 h, a mixture was obtained and poured into ethanol, resulting in a white precipitate. The precipitate was boiled and washed several times in ethanol and then dried at 100±5 °C to obtain white PEEKDith-2.0-20-OH powder. PEEKDith-2.0-144-OH powder was obtained in the same way.

[0015] Step (22): The CNTs were oxidized to obtain carboxylated carbon nanotubes CNT-COOH; the carboxylated carbon nanotubes CNT-COOH were added to anhydrous N-methylpyrrolidone NMP to obtain a CNT-COOH suspension. After ultrasonic dispersion, DCC and DMAC were added, and then ultrasonic treatment was carried out at 40±2℃ for 2±0.2h to obtain an ultrasonically treated CNT-COOH suspension.

[0016] Step (23): Dissolve the PEEKDith-2.0-20-OH powder or PEEKDith-2.0-144-OH powder prepared in step (21) in THF, then add DCC and pour it into the ultrasonically prepared CNT-COOH suspension under ultrasonic stirring. React at 50-60℃ for 70±5h, heat under reflux for 24±2h, and filter to obtain the crude CNT product grafted with PEEK-1,3-dithiacyclopentane. Wash the crude CNT product grafted with PEEK-1,3-dithiacyclopentane under reflux conditions with NMP, THF and DMF to remove excess polymer, and dry to obtain the CNT grafted with PEEK-1,3-dithiacyclopentane.

[0017] Step (24): Under 400W ultrasonic conditions, PEEK-1,3-dithiacyclopentane-grafted CNTs were added to chloroform and ultrasonically dispersed for 2±0.2 hours. Then, dimethyl sulfoxide (DMSO) and 2-iodo-2-methylpropane were added sequentially, and ultrasonic treatment was carried out at 60±2℃ for 24±2 hours. After ultrasonic treatment, the mixture was heated to 65±1℃ and held for 48±1 hours to obtain a crude product of crystalline PEEK-grafted CNTs. The crude product of crystalline PEEK-grafted CNTs was washed multiple times with methanol and dried at 80±2℃ to obtain crystalline PEEK-grafted CNTs, namely CNT-gPEEK-20 or CNT-gPEEK-144.

[0018] Step (25): Disperse the raw carbon nanotubes Raw-CNT, CNT-COOH and CNT-gPEEK-20 or CNT-gPEEK-144 in NMP under ultrasonic conditions for 2 hours, then slowly pour the base slurry into the above suspension, and then ultrasonically disperse for another 2 hours to obtain the final slurry.

[0019] Further, step (4) specifically involves: passing unsized carbon fibers through a sizing tank containing the final sizing agent at a speed of 0.1±0.02 m / min, followed by vacuum drying at 160±5℃; passing sized carbon fibers sequentially through a 1 mol / L hydrogen chloride solution and deionized water, and finally vacuum drying at 80±2℃ to obtain modified carbon fibers.

[0020] Furthermore, step (5) specifically involves:

[0021] Step (51): Using a wet winding process, the modified carbon fiber bundle obtained in step (4) is unfolded, mixed with liquid polyether ether ketone matrix resin by impregnation in a resin tank, and directly drawn out and wound on the mandrel installed on the winding machine tooling; during the winding process, a constant tension of 2.5N is applied to the fiber bundle, and the heating temperature is set to 120-180℃.

[0022] Step (52): Calculate the winding angle of the spiral winding, calculate the thickness of the spiral winding layer of the cylinder section, the thickness of the circumferential winding layer, and determine the layup sequence scheme; perform the winding of the innermost complete spiral layer and the winding of the circumferential layer of the middle cylinder section to obtain the semi-finished shell;

[0023] Step (53): Place the semi-finished shell into the curing chamber for the first vacuum curing treatment;

[0024] Step (54): After the first curing is completed, the area to be patched in the end cap section is polished and shot blasted. Two layers of patch reinforcement are applied to the end cap section. Each layer of patch reinforcement is in two sections, and each section consists of multiple fan-shaped patches. After patch reinforcement, carbon fiber epoxy resin material is used to spirally wind the shell as a whole.

[0025] Step (55): After the final spiral winding is completed, a second curing process is performed.

[0026] Furthermore, in step (52), the thickness of the spiral winding layer in the cylinder section is 1.5±0.1mm, and the thickness of the circumferential winding layer is 2.2±0.1mm; the spiral winding layer is determined to be 2 layers and the circumferential winding layer is determined to be 2 layers, and the layup sequence is determined to be {[(15.1°), (-15.1°)], (90°)2}.

[0027] Further, the curing in step (53) is as follows: from room temperature, the temperature is increased to 250±10℃ at a heating rate of 40~50℃ / h, and kept at the temperature for 2-4 hours. After curing, the temperature is naturally cooled to room temperature. During the curing process, the shell is kept rotating uniformly at a speed of 2±0.1r / min.

[0028] Furthermore, in step (54), the surface is polished using 320-grit sandpaper and the polisher speed is 800-1200 rpm.

[0029] When sandblasting, select plastic granules as the sandblasting medium, set the sandblasting distance to 15-20 cm, and the sandblasting pressure to 0.2-0.4 MPa;

[0030] The overall spiral winding angle is 40±2°, the winding layer is 2 layers, and the winding thickness is 1.5±0.1mm.

[0031] Further, step (55) curing specifically involves placing the entire shell in a curing chamber, raising the temperature from room temperature to 90℃-120℃ at a rate of 25℃~30℃ / h, holding the temperature for 2-4 hours, and then allowing it to cool naturally to room temperature before demolding.

[0032] A carbon fiber modified and patch-wound reinforced solid rocket motor casing is prepared using the method described above.

[0033] Compared with the prior art, the significant advantages of this invention are:

[0034] (1) Performance improvement after carbon fiber / polyetheretherketone modification: Compared with traditional methods, the novel chemical grafting method proposed in this invention overcomes the problem that crystalline polyetheretherketone is difficult to directly graft onto carbon nanotubes at room temperature, providing a new approach for nano-reinforced carbon fiber / polyetheretherketone composite materials; under this method, the heat resistance of the composite material is improved from about 120° to about 250° compared with traditional epoxy resin-based composite materials, meeting the temperature requirements for secondary curing, and the curing effect is outstanding.

[0035] (2) Uniform strength distribution: Compared with the traditional circumferential spiral alternating winding, the fiber winding and patching process in this invention has fewer circumferential-spiral line alternations, the stress on the composite layer is smaller, the container can withstand greater pressure in the circumferential direction, and the burst pressure of the end cap section is effectively improved. In addition, the two-stage fan-shaped patching layout in this invention effectively reduces the stress concentration problem at the critical point of circumferential winding and spiral winding. Under this winding method, the burst pressure of the shell is increased from 18MPa to 21MPa, with an improvement of about 16%, which is quite significant. Furthermore, the mass of the container is reduced by 15% while the burst pressure remains unchanged due to the patching reinforcement.

[0036] (3) High airtightness and high material utilization: The mechanical properties of the shell are improved by secondary curing and the porosity inside the shell is reduced. At the same time, the reasonable layup and patch design also reduces the winding cost. Attached Figure Description

[0037] Figure 1 This is a flowchart of the fiber modification process in this invention.

[0038] Figure 2 The diagram shows the principle of the formation process of polyether ether ketone sizing agent in this invention; (1) is the reaction of soluble polyether ether ketone with carbon nanotubes to obtain PEEK-CNT sizing agent; (2) is the reaction of soluble polyether ether ketone with carbon nanotubes to obtain PEEK-aCNT sizing agent; (3) is the further reaction of intermediate products to obtain PEEK-gCNT.

[0039] Figure 3(a) is a schematic diagram of the shell winding and patch reinforcement of the present invention.

[0040] Figure 3(b) is a side view of the patch layer.

[0041] Figure 3(c) is a schematic diagram of wet winding.

[0042] Explanation of reference numerals in the attached figures:

[0043] 3-1-Helical winding layer, 3-2-Circular winding layer, 3-3-Helical winding layer, 3-4-Patch layer, 3-5-Joint. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings.

[0045] A method for manufacturing a solid rocket motor casing reinforced with carbon fiber modification and patch winding includes the following steps:

[0046] Step 1): Preparation of soluble polyetheretherketone and grafting of crystalline polyetheretherketone onto carbon nanotubes (CNTs):

[0047] Polyetheretherketone-1,3-dithionecyclopentane (PEEKDith) with different molecular weights and carbonyl contents was synthesized by protecting the carbonyl groups to prevent unnecessary reactions. The naming convention, PEEKDith-2.5-100, indicates a 1,2-ethylenedithiol content of 0.25 mol and a polyetheretherketone melt flow index of 100. PEEKDith-2.5-100 was substituted to synthesize polyetheretherketone-1,3-dioxolane, which was then dissolved in N-methylpyrrolidone and reacted at room temperature for 2 hours under magnetic stirring to prepare a base sizing agent. A sizing agent with a solid content of 0.75 wt% was selected for subsequent modification operations.

[0048] Using synthesized PEEKDith-2.0-20 and PEEKDith-2.0-144 as raw materials, hydroxyl-containing PEEKDith was synthesized. The procedure was as follows: First, PEEKDith-2.0-20 was dissolved in tetrahydrofuran (THF) under magnetic stirring. Then, NaBH4 and anhydrous methanol were added sequentially to the solution. After reacting at room temperature for 10 h, the mixture was poured into ethanol, resulting in a white precipitate. Finally, the precipitate was boiled and washed three times in ethanol, and then dried overnight at 100 °C to obtain a white PEEKDith-2.0-20-OH powder. PEEKDith-2.0-144-OH was obtained using the same method.

[0049] Carboxylated carbon nanotubes (CNT-COOH) were obtained by oxidizing CNTs. CNT-COOH was slowly added to anhydrous N-methylpyrrolidone (NMP) to obtain a CNT-COOH suspension. After ultrasonic dispersion for 2 hours, DCC and DMAC were added, followed by ultrasonic treatment at 40°C for 2 hours. PEEKDith-2.0-20-OH / PEEKDith-2.0-144-OH was dissolved in THF, and then DCC was added. The solution was rapidly poured into the CNT-COOH suspension under ultrasonic stirring and reacted at 50-60°C for approximately 70 hours. The polymer solution was then refluxed for 24 hours. The crude product was obtained after filtration. The crude product was washed with NMP, THF, and DMF under reflux to remove excess polymer. After drying, PEEK-1,3-dithiacyclopentane-grafted CNTs were obtained. PEEK-1,3-dithiacyclopentane-grafted CNTs were slowly added to chloroform under 400 W ultrasonication. After ultrasonic dispersion for 2 hours, dimethyl sulfoxide (DMSO) and 2-iodo-2-methylpropane were added sequentially, followed by ultrasonic treatment at 60 °C for 24 hours. After ultrasonic treatment, the flask was heated to 65 °C and maintained for 48 hours. The mixture was then poured into methanol. The crude product was washed three times with methanol and dried at 80 °C to obtain crystalline PEEK-grafted CNTs. The samples were named CNT-gPEEK-20 and CNT-gPEEK-144.

[0050] Step 2): Preparation of sizing agent and sizing treatment:

[0051] Raw carbon nanotubes (Raw-CNT), CNT-COOH, or CNT-gPEEK-20 were dispersed in NMP under ultrasonic conditions for 2 hours. Then, a base sizing agent was slowly poured into the suspension, followed by ultrasonic dispersion for another 2 hours to obtain the final sizing agent. A schematic diagram of this chemical reaction is shown below. Figure 2 As shown.

[0052] Unsized carbon fibers are passed through a sizing agent (sizing tank length 1.0 m) at a low speed of approximately 0.1 m / min, followed by vacuum drying at 160 °C. Sizing carbon fibers are then passed sequentially through a 1 mol / L hydrogen chloride solution and deionized water, and finally vacuum dried at 80 °C to obtain modified carbon fibers. The flow chart is shown below. Figure 1 As shown.

[0053] Step 3) Fiber composite material winding, patching, and curing process

[0054] This invention employs a wet winding process. Modified polyetheretherketone (PEEK) / carbon fiber unidirectional bundles are unfurled using a fiber spreading device, then mixed with liquid PEEK matrix resin in a resin bath. The mixture is then directly drawn from the impregnation device and wound onto a mandrel already mounted on the winding machine fixture via a winding nozzle. The winding speed is set to 0.8 m / min. The winding forming device is shown in Figure 3(c). In the tension control and heating device, a constant tension of 2.5 N and a temperature of 120-180℃ are set. This tension is applied to the fiber bundle during winding to ensure uniform impregnation with PEEK resin and tight winding onto the mandrel. The nozzle controls the direction of the carbon fiber tape, ensuring the accuracy and consistency of the winding process.

[0055] The winding process of rocket engine casings includes precisely calculated circumferential winding and helical winding. The winding angle is calculated based on the geodesic winding formula according to the isopolar hole structure. The calculation yields α = 15.1°, where r0 is the polar aperture radius and r is the radius of a circle at any latitude;

[0056] Using improved mesh theory, we calculated the thickness of the helical winding layer in the cylinder section to be 1.5 mm and the thickness of the circumferential winding layer to be 2.2 mm. Using MATLAB software combined with cubic spline function method and geometric method, we determined the optimal layup sequence for the two helical winding layers and the two circumferential winding layers. Furthermore, based on finite element simulation, the layup sequence was determined to be {[(15.1°), (-15.1°)], (90°)²}. Before patch reinforcement, the modified wound shell was placed in a curing chamber for a first vacuum curing treatment. The specific parameters for the curing process were: heating from room temperature to 250°C at a rate of 40–50°C / h, holding at that temperature for 2–4 hours, and then allowing it to cool naturally to room temperature after curing. Throughout the curing process, the composite shell was kept rotating uniformly at a speed of 2 rpm to ensure the curing effect.

[0057] After the initial curing is complete, the patch area needs to be sanded before application. Use 320-grit sandpaper to gently sand the surface, reducing the sander speed to 800-1200 rpm. For sandblasting, select a plastic granule blasting medium, increasing the blasting distance to 15-20 cm while reducing the blasting pressure to 0.2-0.4 MPa. For the end cap section, apply a two-section, fan-shaped, two-layer patch reinforcement with a thickness of 2.2 mm, as shown in Figures 3(a) and 3(b). Then, reinforce the shell with carbon fiber epoxy resin using an overall spiral winding reinforcement. The spiral winding angle is 40°, with two layers and a winding thickness of 1.5 mm.

[0058] After the final spiral winding is completed, a second curing process is carried out. The entire shell is placed in the curing chamber. The specific parameters for this curing process are: from room temperature, the temperature is increased to 90℃ to 120℃ at a heating rate of 25℃~30℃ / h, and the temperature is maintained for 2 hours to 4 hours. After curing, the shell is naturally cooled to room temperature before demolding.

[0059] This method achieves two key advantages: firstly, the strength of the wound cylinder section is equal to or greater than that of traditional winding methods; secondly, the use of multi-layer patch reinforcement ensures a tight fit, reducing gaps at the transition between the end cap and the cylinder section during manufacturing, thus minimizing stress concentration. A final spiral winding reinforces the entire shell, enhancing its mechanical properties. Furthermore, this winding, patching, and curing process increased the burst pressure of the shell from 18 MPa to 21 MPa, a significant increase of approximately 16%. Moreover, using patch reinforcement reduced the container's mass by 15% while maintaining the same burst pressure.

Claims

1. A method for manufacturing a solid rocket motor casing reinforced with carbon fiber modification and patch winding, characterized in that, Includes the following steps: Step (1): Prepare the base slurry; Step (2): Prepare crystalline polyetheretherketone-grafted carbon nanotubes; Step (3): Preparation of final sizing agent: Disperse the original carbon nanotubes, carboxylated carbon nanotubes or polyether ether ketone grafted carbon nanotubes in NMP under ultrasonic conditions, then pour in the sizing agent prepared in step (1), and disperse it again under ultrasonic conditions to obtain the final sizing agent. Step (4): Modify the carbon fiber using the final sizing agent prepared in step (3) to obtain modified carbon fiber; Step (5): The shell is first spiral wound and then circumferential wound to form a stepped structure with the height gradually decreasing from the cylinder to the head section, and then cured once; the stepped height difference is filled by two-segment fan-shaped two-layer patches, and the entire shell is spiral wound and cured a second time to obtain the solid rocket motor shell. Step (1) specifically involves: synthesizing polyether ether ketone-1,3-dithionecyclopentane PEEKDith with different molecular weights and carbonyl contents by protecting the carbonyl groups to prevent unnecessary reactions; synthesizing polyether ether ketone-1,3-dioxolane PEEKDith-2.5-100 through a substitution reaction; dissolving it in N-methylpyrrolidone; and reacting it at room temperature for 2 ± 0.2 h under magnetic stirring to prepare a base slurry. Step (5) specifically involves: Step (51): Using a wet winding process, the modified carbon fiber bundle obtained in step (4) is unfolded, mixed with liquid polyether ether ketone matrix resin by impregnation in a resin tank, and directly drawn out and wound on the mandrel installed on the winding machine tooling; during the winding process, a constant tension of 2.5N is applied to the fiber bundle, and the heating temperature is set to 120-180℃. Step (52): Calculate the winding angle of the spiral winding, calculate the thickness of the spiral winding layer of the cylinder section, the thickness of the circumferential winding layer, and determine the layup sequence scheme; perform the winding of the innermost complete spiral layer and the winding of the circumferential layer of the middle cylinder section to obtain the semi-finished shell; Step (53): Place the semi-finished shell into the curing chamber for the first vacuum curing treatment; Step (54): After the first curing is completed, the area to be patched in the end cap section is polished and shot blasted. Two layers of patch reinforcement are applied to the end cap section. Each layer of patch reinforcement is in two sections, and each section consists of multiple fan-shaped patches. After patch reinforcement, carbon fiber epoxy resin material is used to spirally wind the shell as a whole. Step (55): Perform a second curing process after the final spiral winding is completed; In step (52), the thickness of the spiral winding layer in the cylinder section is 1.5±0.1mm, and the thickness of the circumferential winding layer is 2.2±0.1mm; the spiral winding layer is determined to be 2 layers and the circumferential winding layer is determined to be 2 layers, and the layup sequence is determined to be {[(15.1°), (-15.1°)], (90°)2}; The overall spiral winding angle is 40±2°, the winding layer is 2 layers, and the winding thickness is 1.5±0.1mm.

2. The method according to claim 1, characterized in that, Step (2) specifically includes the following steps: Step (21): PEEKDith-2.0-20 was dissolved in tetrahydrofuran (THF) under magnetic stirring, and then NaBH4 and anhydrous methanol were added sequentially. After reacting at room temperature for 10±1 h, a mixture was obtained and poured into ethanol, resulting in a white precipitate. The precipitate was boiled and washed several times in ethanol and then dried at 100±5 °C to obtain white PEEKDith-2.0-20-OH powder. PEEKDith-2.0-144-OH powder was obtained in the same way. Step (22): Oxidize CNTs to obtain carboxylated carbon nanotubes CNT-COOH; Carboxylated carbon nanotubes (CNT-COOH) were added to anhydrous N-methylpyrrolidone (NMP) to obtain a CNT-COOH suspension. After ultrasonic dispersion, DCC and DMAC were added, and then the suspension was ultrasonically treated at 40±2℃ for 2±0.2h to obtain an ultrasonically treated CNT-COOH suspension. Step (23): Dissolve the PEEKDith-2.0-20-OH powder or PEEKDith-2.0-144-OH powder prepared in step (21) in THF, then add DCC and pour it into the ultrasonically prepared CNT-COOH suspension under ultrasonic stirring. React at 50-60℃ for 70±5h, heat under reflux for 24±2h, and filter to obtain the crude CNT product grafted with PEEK-1,3-dithiacyclopentane. Wash the crude CNT product grafted with PEEK-1,3-dithiacyclopentane under reflux conditions with NMP, THF and DMF to remove excess polymer, and dry to obtain the CNT grafted with PEEK-1,3-dithiacyclopentane. Step (24): Under 400W ultrasonic conditions, PEEK-1,3-dithiacyclopentane-grafted CNTs were added to chloroform and ultrasonically dispersed for 2±0.2 hours. Then, dimethyl sulfoxide (DMSO) and 2-iodo-2-methylpropane were added sequentially, and ultrasonic treatment was carried out at 60±2℃ for 24±2 hours. After ultrasonic treatment, the mixture was heated to 65±1℃ and held for 48±1 hours to obtain a crude product of crystalline PEEK-grafted CNTs. The crude product of crystalline PEEK-grafted CNTs was washed multiple times with methanol and dried at 80±2℃ to obtain crystalline PEEK-grafted CNTs, namely CNT-gPEEK-20 or CNT-gPEEK-144. Step (25): Disperse the raw carbon nanotubes Raw-CNT, CNT-COOH and CNT-gPEEK-20 or CNT-gPEEK-144 in NMP under ultrasonic conditions for 2 hours, then slowly pour the base slurry into the above suspension, and then ultrasonically disperse for another 2 hours to obtain the final slurry.

3. The method according to claim 2, characterized in that, Step (4) is as follows: Unsized carbon fibers pass through a sizing tank containing the final sizing agent at a speed of 0.1±0.02 m / min, and are then vacuum dried at 160±5℃; sized carbon fibers are passed through a 1mol / L hydrogen chloride solution and deionized water in sequence, and are finally vacuum dried at 80±2℃ to obtain modified carbon fibers.

4. The method according to claim 3, characterized in that, The curing process in step (53) is as follows: the temperature is increased from room temperature to 250±10℃ at a heating rate of 40-50℃ / h, and kept at that temperature for 2-4 hours. After curing, the temperature is naturally cooled to room temperature. During the curing process, the shell is rotated uniformly at a speed of 2±0.1r / min.

5. The method according to claim 4, characterized in that, In step (54), use 320-grit sandpaper to polish the surface and the sander speed is 800-1200 rpm. When sandblasting, select plastic granules as the sandblasting medium, set the sandblasting distance to 15-20 cm, and the sandblasting pressure to 0.2-0.4 MPa.

6. The method according to claim 5, characterized in that, Step (55) Curing is specifically as follows: Place the entire shell in the curing chamber, raise the temperature from room temperature to 90℃-120℃ at a heating rate of 25℃~30℃ / h, keep it at the temperature for 2-4 hours, and after curing, let it cool naturally to room temperature before demolding.

7. A carbon fiber modified and patch-wound reinforced solid rocket motor casing, characterized in that, Prepared using the method described in any one of claims 1-6.

Images