Tension control winding process of spaceflight carbon fiber composite launching canister

Abstract

The invention relates to the technical field of spaceflight material forming, in particular to a tension control winding process of a spaceflight carbon fiber composite launch canister, which comprises pretreatment, winding forming, curing and post-treatment. The method comprises the following steps: S1, coating a release agent and a modified coating after processing a core mold, carrying out plasma treatment and eliminating stress; the carbon fiber filaments are soaked in resin containing nanometer components, and are pre-stretched after a hot melting reaction; s2, closed-loop tension control is conducted, winding is conducted according to segmented angles, and modified resin is coated between layers to be overlapped in a crossed mode; s3, stepwise heating and curing, dynamically regulating the pressure and introducing inert gas; and S4, polishing after hydraulic demolding, carrying out sand blasting, carrying out transition layer and ceramic coating, and carrying out multi-dimensional detection. According to the process, the mechanical property and environmental adaptability of the launch canister are improved, the process precision is high, defects are reduced, the forming time is shortened, the rework rate and cost are reduced, the spaceflight requirement is met, and the process is suitable for batch production.

Description

Technical Field

[0001] This invention relates to the field of aerospace material molding technology, specifically to a tension-controlled winding process for a carbon fiber composite launch tube for aerospace applications. Background Technology

[0002] The aerospace industry has increasingly stringent requirements for composite material launch tubes, demanding both lightweight design to reduce launch load and extremely high strength, stiffness, and resistance to extreme environments. Carbon fiber winding technology is a core element determining these performance characteristics. However, current mainstream carbon fiber winding processes face numerous technical bottlenecks in application, making them difficult to adapt to the complex requirements of aerospace launches.

[0003] In the pretreatment stage, mandrels are often made of a single metal material and coated only with conventional release agents, leading to difficulties in demolding and a high risk of mandrel deformation. This is particularly problematic in high-precision launch tube fabrication, where dimensional deviations in the mandrel can result in uneven tube wall thickness, affecting overall strength. Carbon fiber pretreatment often involves a single impregnation, resulting in weak bonding between the matrix resin and the fiber. Furthermore, the lack of functional reinforcing components leads to low interlaminar shear strength in the composite material, making it unable to withstand the instantaneous impact during launch. Simultaneously, existing processes lack control over the chemical reactions during fiber pretreatment, making the resin prone to microscopic defects after curing, thus weakening material properties.

[0004] The tension control technology in the winding process is not perfect. Most systems use open-loop control, resulting in large tension fluctuations that can easily cause fiber breakage or loosening, leading to insufficient local strength in the launch tube. The winding profile design often uses a single angle or simple combination, failing to precisely adapt to the different stresses in different sections of the launch tube. This makes it impossible to achieve stress balance in all directions, and under alternating axial loads and radial pressures, local cracking is likely to occur. Furthermore, the lack of a dedicated bonding layer between layers results in a high risk of interlayer delamination, making it difficult to meet the requirements for long-term cyclic use.

[0005] The curing process often employs constant temperature and pressure. Rapid resin heating can easily generate bubbles, and internal stress accumulates during cooling, leading to warping and deformation of the launch tube after curing. The surface coatings used in post-processing are mostly made of a single material with limited high-temperature resistance and corrosion resistance. Under the high-temperature exhaust gases and extreme temperature differences of space, the coating is prone to peeling off, shortening the launch tube's lifespan. Furthermore, quality inspection standards are vague, and there is a lack of unified guidelines for judging and handling minor defects. Some latent defects may cause safety accidents during launch.

[0006] Existing processes do not fully integrate material chemical modification and process parameter optimization, failing to form a synergistic system of "material reinforcement - precise process - controllable performance". As a result, composite material launch tubes are deficient in terms of the balance between lightweight and high strength, adaptability to extreme environments, and service life, making it difficult to meet the urgent needs of the aerospace field for high-performance launch tubes. Therefore, it is urgent to develop a tension control winding process that is both innovative and practical. Summary of the Invention

[0007] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a tension-controlled winding process for aerospace carbon fiber composite launch tubes.

[0008] (II) Technical Solution A tension-controlled winding process for a carbon fiber composite launch tube for aerospace applications includes the following steps: S1. Pre-treatment before winding: Core mold preparation: The core mold is made of 7075 aluminum alloy substrate with dimensional accuracy of ±0.03mm and surface finish Ra≤0.4μm; silicone resin release agent and modified polytetrafluoroethylene coating are applied in sequence, and the core mold is cured at 25-30℃ for 1-2 hours, followed by plasma treatment. Carbon fiber pretreatment: Take T800 grade carbon fiber with a tensile strength ≥3800MPa, and first pass it through an epoxy resin matrix impregnation bath containing 0.5-2% nano silica and 0.3-0.8% silane coupling agent, with an impregnation amount of 30-40%; during hot melt impregnation at 80-100℃, the nano silica and epoxy resin undergo a cross-linking reaction, followed by pre-stretching with a tension of 30-50N to eliminate relaxation stress; S2. Filament winding: Tension control: A closed-loop system of servo motor + tension sensor is adopted, with circumferential winding tension of 200-300N, axial tension of 150-200N, and helical winding tension of 180-250N, and tension fluctuation within ±3N; fiber temperature is monitored synchronously, and automatic speed reduction and temperature control are implemented when the temperature exceeds 60℃. Line type and layer number control: Design the path in CAD, first 2-3 layers of circumferential winding, then 1-2 layers of axial winding, and finally 5-8 layers of spiral winding; odd-numbered layers and even-numbered layers cross in opposite directions, and 0.1-0.2mm of modified epoxy resin is applied between layers; S3. Curing process: Stepwise heating: room temperature → 50℃ → 100℃ → 150-180℃; vacuum bag pressurization 0.08-0.12MPa, while inert gas is introduced to prevent oxidation. In the later stage of curing, epoxy resin and carbon nanotubes undergo a bonding reaction. S4. Post-processing: Demolding and finishing: mechanically pull out the core mold, polish the outer surface, and apply an Al2O3-ZrO2 ceramic coating; Quality inspection: ultrasonic testing, X-ray flaw detection, infrared thermography; sampling hydrostatic test, axial tensile test.

[0009] Preferably, it also includes a temperature control and stirring system for the impregnation tank in S1: the impregnation tank adopts a double-jacketed heating system, and the temperature is controlled at 25-30℃; a built-in magnetic stirrer, combined with ultrasonic dispersion, ensures that the nano-silica and silane coupling agent are uniformly dispersed in the epoxy resin matrix.

[0010] Preferably, it also includes a redundant protection module for the tension control system in S2. This module contains dual tension sensors, which compare two sets of tension data in real time. When the difference exceeds 5N, an alarm is automatically triggered and the speed is reduced. At the same time, a mechanical tension buffer is set up. When the tension suddenly increases by more than 10% of the set value, the buffer absorbs the impact force instantly.

[0011] Preferably, the spiral winding angle adjustment in S2 adopts segmented program control. After every 3-5 layers of winding, the winding angle is automatically adjusted according to the stress simulation data of the launch tube section, with an adjustment interval of 5°-10°. In the transition section between the tube body and the flange, a gradual angle winding is adopted to avoid stress concentration, and the fiber coverage rate of the transition section is ≥99%.

[0012] Preferably, the system also includes a dynamic pressure adjustment mechanism for the curing process in S3. When the curing temperature rises to 50°C, the pressure is set to 0.05-0.08 MPa; when the temperature rises to 100°C, the pressure is increased to 0.08-0.12 MPa; during the constant temperature stage of 150-180°C, the pressure is finely adjusted by ±0.01 MPa every 2 hours to compensate for the pressure loss caused by resin shrinkage and ensure that the cylinder wall density is ≥98%.

[0013] Preferably, the process also includes a pretreatment step for the high-temperature resistant ceramic coating in step S4, wherein the outer surface of the launch tube is sandblasted before spraying to achieve a surface roughness Ra of 1.5-2.0 μm; then a transition layer is applied and baked at 150°C for 30 minutes.

[0014] Preferably, the process also includes stress relief treatment of the core mold in S1. After the core mold is processed, a low-temperature aging treatment is performed: the core mold is first heated to 120-150℃ and kept at that temperature for 4-6 hours, and then cooled to room temperature in the furnace; then vibration aging is performed to eliminate processing stress. The residual stress of the core mold is ≤50MPa, so as to avoid the deformation of the core mold during the winding process from affecting the dimensional accuracy of the launch tube.

[0015] Preferably, it also includes a precise calculation method for the number of winding layers in S2. Combined with the design load of the launch tube, it is calculated according to the formula "number of layers = (design load × safety factor) / (single layer fiber bearing strength × effective circumference of the tube)" with a safety factor of 1.8-2.2. The bearing strength of the single layer fiber is determined by test to ensure that the layer design meets the strength requirements while avoiding material waste.

[0016] Preferably, it also includes the defect classification and treatment standard in S4 for quality inspection. In ultrasonic testing, if the bubble diameter is ≤0.3mm and there are ≤2 bubbles within 100mm², no treatment is required; if the bubble diameter is 0.3-0.5mm and there are 2-3 bubbles within 100mm², local glue filling and curing are required; if the bubble diameter is >0.5mm or the delamination area is >8mm², the defective section needs to be cut off and rewound to ensure that the finished product qualification rate is ≥98%.

[0017] Preferably, the tension-controlled winding process of the aforementioned aerospace carbon fiber composite launch tube is suitable for launch tubes with an inner diameter of 150-450mm and a length of 1200-2800mm; the finished product density is 1.6-1.8g / cm³, which is 35-55% lighter than metal launch tubes, with a fatigue life of ≥1200 cycles of loading, and a dimensional change rate of ≤0.1% in an environment of -60℃ to 200℃, meeting the requirements for use in extreme aerospace environments.

[0018] (iii) Beneficial technical effects Compared with existing technologies, the beneficial effects of this invention are: 1. By introducing nano-silica and carbon nanotubes into the epoxy resin matrix, a stable bond between components is achieved through a specific chemical reaction, significantly improving the mechanical properties and interfacial bonding of the resin matrix and solving the problems of low interlayer shear strength and easy peeling in traditional processes. Simultaneously, the mandrel undergoes plasma treatment and stress relief treatment, effectively reducing the risk of deformation, ensuring the dimensional accuracy of the launch tube, and laying a solid foundation for subsequent winding molding. The overall material reinforcement effect is far superior to that of unmodified traditional processes.

[0019] 2. A closed-loop tension control system with redundant protection modules is adopted to achieve real-time and precise tension control and anomaly protection, preventing fiber breakage or loosening and ensuring a stable and controllable winding process. The segmented linear design and dynamic pressure curing mechanism adapt the winding angle to the stress differences in different sections of the launch tube. Combined with dynamic pressure adjustment during the curing process, internal stress and air bubble defects are effectively eliminated, improving the tube wall density and the balance of forces in all directions. Compared with traditional processes with fixed parameters, the process adaptability and finished product consistency are significantly improved.

[0020] 3. The high-temperature resistant ceramic coating, pretreated with sandblasting and featuring a transition layer design, combined with precise spraying technology, significantly enhances coating adhesion and resistance to high temperatures and corrosion, effectively resisting the erosion of the extreme aerospace environment. A comprehensive quality inspection and defect classification system accurately identifies and properly handles defects of different levels, reducing hidden risks and ensuring the long-term reliability of the launch tube. Compared to traditional processes with vague inspection standards, the safety and service life of the finished product are greatly improved. Attached Figure Description

[0021] Figure 1This is a flow chart of the tension-controlled winding process for a carbon fiber composite launch tube for aerospace applications proposed in this invention; Figure 2 This is a graph comparing the axial tensile strength and coating adhesion of the embodiments and comparative examples using a bar graph. Figure 3 This is a line graph comparing the strength retention rate after salt spray corrosion and the strength retention rate at 200℃ for the examples and comparative examples; Figure 4 This is a radar comparison chart created by standardizing the dimensions of the performance comparison data of the examples and comparative examples. Detailed Implementation

[0022] according to Figures 1 to 4 The specific embodiments of the present invention are as follows: Example 1 S1 Pre-treatment before winding Mandrel preparation: 7075 aluminum alloy rods were selected and machined into mandrels with an inner diameter of 200mm and a length of 1800mm using a CNC lathe. After machining, the dimensions were measured using a coordinate measuring machine, with dimensional accuracy controlled within ±0.03mm, and the surface finish was measured to be Ra=0.3μm using a laser interferometer. First, a silicone resin release agent was uniformly coated onto the mandrel surface using a pneumatic spraying process, with the coating thickness controlled at 7μm. The coating was then allowed to cure initially at 25℃ for 30 minutes. Next, a modified polytetrafluoroethylene coating containing 1% nano-alumina was applied, with a thickness of 4μm, and allowed to cure completely at 28℃ for 1.5 hours. Subsequently, the mandrel was placed in a plasma treatment device with a power of 400W and a treatment time of 8 minutes. After treatment, the contact angle of the mandrel surface decreased from 75° to 40°, improving the coating adhesion. Finally, stress relief treatment was carried out: the temperature was increased to 130℃ at a heating rate of 2℃ / min, held for 5 hours, cooled to room temperature in the furnace, and then subjected to vibration aging treatment. The frequency was set to 35Hz, the amplitude to 0.2mm, and the time to 45 minutes. The residual stress of the core mold was measured to be 42MPa by a stress tester.

[0023] Carbon fiber pretreatment: T800 grade carbon fiber with a tensile strength of 3800MPa was selected and installed on a pay-off frame before being introduced into the impregnation tank. The impregnation tank was heated by a double-layer jacket, with the temperature controlled at 28℃ (±1℃ error); it had a built-in magnetic stirrer at 400r / min, and an ultrasonic dispersion device with a power of 250W and a frequency of 25kHz. The epoxy resin matrix in the tank was E-51, containing 1.2% nano-silica with a particle size of 35nm and 0.5% silane coupling agent KH-550. The viscosity at 25℃ was measured by a rotational viscometer. Carbon fiber filaments pass through an impregnation tank at a speed of 0.5 m / min, with the impregnation amount controlled at 35%, verified by weighing. They then enter a hot-melt impregnation device at a temperature set to 90℃, allowing the nano-silica and epoxy resin to undergo a cross-linking reaction. After the reaction, a tension control system pre-stretches the fibers at a tension set to 40 N, with tension sensors monitoring in real time to ensure no fiber relaxation.

[0024] Winding Tension control: A closed-loop control system is composed of a servo motor and a tension sensor with an accuracy of ±0.1N. The system response time, measured by an oscilloscope, is 0.08 seconds. During circumferential winding, the tension is set at 250N; for axial winding, the tension is 180N; for helical winding, the tension is adjusted according to the section: 220N at the mid-section angle of 50° and 240N at the flanges at both ends, with tension fluctuations controlled within ±2N throughout the entire process. The system is equipped with a redundant protection module, with dual tension sensors comparing data in real time. An automatic alarm is triggered when the difference exceeds 3N. The mechanical tension buffer has an elastic coefficient of 8N / mm and is triggered when the tension suddenly increases by 10%, absorbing the impact force. Simultaneously, an infrared thermometer monitors the fiber temperature; when it exceeds 55℃, the servo motor automatically reduces its speed by 10% to ensure fiber temperature stability.

[0025] Line type and layer control: The winding path is designed using AutoCAD 2024 software, and the resulting CNC program is imported into the winding machine. First, two layers of circumferential winding are performed with a pitch of 8mm and a winding speed of 1m / min. Then, one layer of axial winding is performed, with a coverage density of 99% determined by image analysis. Finally, six layers of helical winding are performed. Every four layers, the angle is adjusted based on finite element analysis data from ANSYS 2023 software, with a transition section length of 80mm and an angle gradually changing from 50° to 75°. The multi-layer winding uses a cross-over method, with odd-numbered layers clockwise and even-numbered layers counterclockwise. A 0.15mm thick layer of modified epoxy resin containing 0.2% multi-walled carbon nanotubes is applied between layers using a micro-spraying device. The coating thickness is monitored in real-time by a laser thickness gauge. The number of winding layers is calculated according to the formula: the design axial load is 120kN, the radial pressure is 10MPa, the safety factor is 2.0, the single-layer fiber bearing strength is 1200MPa as determined by test, the effective circumference of the cylinder is 0.628m, and the calculated number of layers is 6, which is consistent with the actual number of winding layers.

[0026] Curing treatment The wound launch tube blank was placed in a curing oven, and a stepped heating method was used: starting from room temperature, the temperature was increased to 50°C at a rate of 3°C / min and held for 1 hour; then increased to 100°C at a rate of 4°C / min and held for 2 hours; finally, the temperature was increased to 160°C at a rate of 3°C / min and held for 6 hours. During the curing process, pressure was applied using a vacuum bag, with dynamic pressure adjustment: set at 0.07 MPa at 50°C, increased to 0.1 MPa at 100°C, and finely adjusted by +0.01 MPa every 2 hours at 160°C, with pressure sensors providing real-time pressure data. Simultaneously, 99.99% pure nitrogen gas was introduced at a flow rate of 2 L / min to prevent oxidation. In the later stages of curing, the epoxy resin and carbon nanotubes underwent a bonding reaction, which was detected by Fourier transform infrared spectroscopy, showing a reaction completion rate of 95%.

[0027] Post-processing Demolding and finishing: After curing, the core mold was removed using a hydraulic extraction device with a tensile force of 50kN. The demolding force was measured to be 8kN, with no damage to the core mold. The outer surface of the cylinder was ground with a 400-mesh abrasive wheel. After grinding, the dimensional accuracy was controlled within ±0.07mm by a laser diameter gauge. Burrs and excess resin were removed, with a residual amount ≤0.1mm. Surface pretreatment followed: Sandblasting was performed using 100-mesh abrasive particles at a pressure of 0.25MPa to achieve a surface roughness Ra=1.8μm. A 6μm thick TiN transition layer was then coated and baked at 150℃ for 30 minutes. Finally, an Al2O3-ZrO2 ceramic coating was applied using plasma spraying, with an Al2O3 content of 70% and a coating thickness of 15μm. The coating adhesion was measured to be 58MPa by the cross-cut adhesion test.

[0028] Quality Inspection: Internal defects were detected using a 3MHz ultrasonic detector, revealing one Class I bubble, 0.2mm in diameter, with only one bubble per 100mm², requiring no treatment. X-ray inspection at 300kV showed neat fiber arrangement and no breaks. Infrared thermal imaging with a resolution of 0.07℃ showed no curing defects. A water pressure test was conducted on samples: pressure 12MPa, held for 30 minutes; no leakage was detected by pressure sensor monitoring. Axial tensile testing was performed using a WDW-1000 universal testing machine, determining a tensile strength of 880MPa, meeting design requirements.

[0029] Example 2 Pre-treatment before winding Mandrel fabrication: A mandrel with an inner diameter of 150 mm and a length of 1200 mm was machined from 7075 aluminum alloy. The dimensional accuracy was controlled within ±0.03 mm using a coordinate measuring machine, and the surface finish was measured to be Ra=0.4 μm using a laser interferometer. First, a 5 μm thick silicone resin release agent was applied to the mandrel surface and allowed to cure initially at 25°C for 30 minutes. Then, a 3 μm thick modified polytetrafluoroethylene coating was applied and allowed to cure completely at 25°C for 30 minutes. The mandrel was then placed in a plasma treatment device with a power of 300 W and a treatment time of 5 minutes. After treatment, the contact angle of the mandrel surface decreased to 45°. Finally, stress relief treatment was performed: the mandrel was heated to 120°C at a heating rate of 2°C / min and held for 4 hours. After cooling to room temperature in the furnace, vibration aging treatment was performed with a frequency of 20 Hz, an amplitude of 0.1 mm, and a time of 30 minutes. The residual stress of the mandrel was measured to be 48 MPa using a stress tester.

[0030] Carbon fiber pretreatment: T800 grade carbon fiber with a tensile strength of 3800MPa was selected and introduced into the impregnation tank after being installed on the pay-off stand. The impregnation tank adopted a double-jacketed heating system, with the temperature controlled at 25℃, with an error of ±1℃; it had a built-in magnetic stirrer with a rotation speed of 300r / min, and was equipped with an ultrasonic dispersion device with a power of 200W and a frequency of 20kHz. The epoxy resin matrix in the tank contained 0.5% nano-silica with a particle size of 20nm and 0.3% silane coupling agent KH-550. The viscosity at 25℃ was measured by a rotational viscometer as follows: Carbon fiber filaments pass through an impregnation tank at a speed of 0.4 m / min, with the impregnation amount controlled at 30%, verified by weighing. They then enter a hot-melt impregnation device at a temperature set to 80℃ to induce a cross-linking reaction between the nano-silica and epoxy resin. After the reaction, a tension control system pre-stretches the fibers at a tension set to 30 N, with tension sensors monitoring in real time to ensure no fiber relaxation. The reaction completion rate was measured at 92%.

[0031] Winding Tension control: A closed-loop control system is composed of a servo motor and a tension sensor with an accuracy of ±0.1N. The system response time, measured by an oscilloscope, is 0.1 seconds. During circumferential winding, the tension is set to 200N; for axial winding, the tension is 150N; for helical winding, the tension is adjusted according to the section: 200N at the mid-section angle of 45° and 220N at the flanges at both ends, with tension fluctuations controlled within ±3N throughout the entire process. The system is equipped with a redundant protection module, with dual tension sensors comparing data in real time. An automatic alarm is triggered when the difference exceeds 5N. The mechanical tension buffer has an elastic coefficient of 5N / mm and is triggered when the tension suddenly increases by 10%, absorbing the impact force. Simultaneously, an infrared thermometer monitors the fiber temperature; if the temperature exceeds 55℃, the servo motor automatically reduces its speed by 10% to ensure fiber temperature stability.

[0032] Line type and layer control: The winding path is designed using AutoCAD 2024 software, and the resulting CNC program is imported into the winding machine. First, two layers of circumferential winding are performed with a pitch of 5mm and a winding speed of 0.8m / min. Then, one layer of axial winding is performed, with a coverage density of 98% determined by image analysis. Finally, five layers of helical winding are performed. Every three layers, the angle is adjusted based on finite element analysis data from ANSYS 2023 software, with a transition section length of 50mm and an angle gradually changing from 45° to 65°. The multi-layer winding uses a cross-over method, with odd-numbered layers clockwise and even-numbered layers counterclockwise. A 0.1mm thick layer of modified epoxy resin containing 0.2% multi-walled carbon nanotubes is applied between layers using a micro-spraying device. The coating thickness is monitored in real-time by a laser thickness gauge. The number of winding layers is calculated according to the formula: the design axial load is 80kN, the radial pressure is 8MPa, the safety factor is 1.8, the single-layer fiber bearing strength is 1150MPa as determined by test, the effective circumference of the cylinder is 0.471m, and the calculated number of layers is 5, which is consistent with the actual number of winding layers.

[0033] Curing treatment The wound launch tube blank was placed in a curing oven, and a stepped heating method was used: starting from room temperature, the temperature was increased to 50°C at a rate of 2°C / min and held for 1 hour; then increased to 100°C at a rate of 3°C / min and held for 2 hours; finally, the temperature was increased to 150°C at a rate of 2°C / min and held for 4 hours. During the curing process, pressure was applied using a vacuum bag, with dynamic pressure adjustment: set at 0.05 MPa at 50°C, increased to 0.08 MPa at 100°C, and finely adjusted by ±0.01 MPa every 2 hours at 150°C, with pressure sensor providing real-time pressure data. Simultaneously, 99.99% pure nitrogen gas was introduced at a flow rate of 1.5 L / min to prevent oxidation. In the later stages of curing, the epoxy resin and carbon nanotubes underwent a bonding reaction, which was detected by Fourier transform infrared spectroscopy, showing a reaction completion rate of 93%.

[0034] Post-processing Demolding and finishing: After curing, the core mold was removed using a hydraulic extraction device with a tensile force of 40kN. The demolding force was measured to be 7kN by a force gauge, and there was no damage to the core mold. The outer surface of the cylinder was ground with a 400-mesh abrasive wheel. After grinding, the dimensional accuracy was controlled within ±0.08mm by a laser diameter gauge. Burrs and excess resin were removed, with a residual amount ≤0.1mm. Subsequently, surface pretreatment was performed: sandblasting was performed using 80-mesh abrasive particles at a pressure of 0.2MPa to achieve a surface roughness Ra=1.5μm; a 5μm thick TiN transition layer was coated and baked at 150℃ for 30 minutes; finally, an Al2O3-ZrO2 ceramic coating was applied using a plasma spraying process, with an Al2O3 content of 70% and a coating thickness of 10μm. The coating adhesion was measured to be 55MPa by the cross-cut test.

[0035] Quality Inspection: Internal defects were detected using a 2MHz ultrasonic testing instrument, and no Class II or higher defects were found. X-ray flaw detection at 280kV showed that the fibers were neatly arranged and without breakage. Infrared thermal imager with a resolution of 0.08℃ was used for inspection, and no curing defects were found. Sampling was subjected to a hydrostatic test: pressure 10MPa, held for 30 minutes, and no leakage was detected by pressure sensor monitoring. Axial tensile testing was performed using a universal testing machine, and the tensile strength was determined to be 850MPa, meeting the design requirements.

[0036] Example 3 Pre-treatment before winding Mandrel fabrication: A mandrel with an inner diameter of 450 mm and a length of 2800 mm was machined from 7075 aluminum alloy. The dimensional accuracy was controlled within ±0.03 mm using a coordinate measuring machine, and the surface finish was measured to be Ra=0.3 μm using a laser interferometer. First, a 10 μm thick silicone resin release agent was coated onto the mandrel surface and allowed to cure initially at 25°C for 30 minutes. Then, a 5 μm thick modified polytetrafluoroethylene coating was applied and allowed to cure completely at 30°C for 1 hour. The mandrel was then placed in a plasma treatment device with a power of 500 W and a treatment time of 10 minutes. After treatment, the contact angle of the mandrel surface decreased to 38°. Finally, stress relief treatment was performed: the mandrel was heated to 150°C at a heating rate of 2°C / min and held for 6 hours. After cooling to room temperature in the furnace, vibration aging treatment was performed with a frequency of 50 Hz, an amplitude of 0.3 mm, and a time of 60 minutes. The residual stress of the mandrel was measured to be 45 MPa using a stress tester.

[0037] Carbon fiber pretreatment: T800 grade carbon fiber with a tensile strength of 3800MPa is selected and introduced into the impregnation tank after being installed on the pay-off stand. The impregnation tank adopts a double-jacketed heating system, with the temperature controlled at 30℃, with an error of ±1℃; it has a built-in magnetic stirrer with a rotation speed of 500r / min, and is equipped with an ultrasonic dispersion device with a power of 300W and a frequency of 30kHz. The epoxy resin matrix in the tank contains 2% nano-silica with a particle size of 50nm and 0.8% silane coupling agent KH-550. The viscosity at 25℃ is measured by a rotational viscometer as follows: Carbon fiber filaments pass through an impregnation tank at a speed of 0.6 m / min, with the impregnation amount controlled at 40%, verified by weighing. They then enter a hot-melt impregnation device at a temperature set to 100℃ to allow the nano-silica and epoxy resin to crosslink. After the reaction, a tension control system pre-stretches the fibers at a tension of 50 N, monitored in real-time by a tension sensor to ensure no fiber relaxation. The reaction completion rate was measured at 96%.

[0038] Winding Tension control: A closed-loop control system is composed of a servo motor and a tension sensor with an accuracy of ±0.1N. The system response time, measured by an oscilloscope, is 0.09 seconds. During circumferential winding, the tension is set to 300N; for axial winding, the tension is 200N; for helical winding, the tension is adjusted according to the section: 250N at a 60° angle in the middle of the cylinder and 250N at an 85° angle at both flange ends, with tension fluctuations controlled within ±2N throughout the entire process. The system is equipped with a redundant protection module, with dual tension sensors comparing data in real time. An automatic alarm is triggered when the difference exceeds 4N. The mechanical tension buffer has an elastic coefficient of 10N / mm and is triggered when the tension suddenly increases by 10%, absorbing the impact force. Simultaneously, an infrared thermometer monitors the fiber temperature; if the temperature exceeds 55℃, the servo motor automatically reduces its speed by 10% to ensure fiber temperature stability.

[0039] Line type and layer control: The winding path is designed using AutoCAD 2024 software, and the resulting CNC program is imported into the winding machine. First, three layers of circumferential winding are performed with a pitch of 10mm and a winding speed of 1.2m / min. Then, two layers of axial winding are performed, with a coverage density of 99% determined by image analysis. Finally, eight layers of helical winding are performed. Every five layers, the angle is adjusted based on finite element analysis data from ANSYS 2023 software, with a transition section length of 100mm and an angle gradually changing from 60° to 85°. The multi-layer winding uses a cross-over method, with odd-numbered layers clockwise and even-numbered layers counterclockwise. A 0.2mm thick layer of modified epoxy resin containing 0.2% multi-walled carbon nanotubes is applied between layers using a micro-spraying device. The coating thickness is monitored in real-time by a laser thickness gauge. The number of winding layers is calculated according to the formula: the design axial load is 200kN, the radial pressure is 15MPa, the safety factor is 2.2, the single-layer fiber bearing strength is 1250MPa as determined by test, the effective circumference of the cylinder is 1.413m, and the calculated number of layers is 8, which is consistent with the actual number of winding layers.

[0040] Curing treatment The wound launch tube blank was placed in a curing oven, and a stepped heating method was used: starting from room temperature, the temperature was increased to 50°C at a rate of 5°C / min and held for 1 hour; then increased to 100°C at a rate of 5°C / min and held for 2 hours; finally, the temperature was increased to 180°C at a rate of 5°C / min and held for 8 hours. During the curing process, pressure was applied using a vacuum bag, with dynamic pressure adjustment: set at 0.08 MPa at 50°C, increased to 0.12 MPa at 100°C, and finely adjusted by ±0.01 MPa every 2 hours at 180°C, with pressure sensors providing real-time pressure data. Simultaneously, 99.99% pure nitrogen gas was introduced at a flow rate of 2.5 L / min to prevent oxidation. In the later stages of curing, the epoxy resin and carbon nanotubes underwent a bonding reaction, which was detected by Fourier transform infrared spectroscopy, showing a reaction completion rate of 97%.

[0041] Post-processing Demolding and finishing: After curing, the core mold was removed using a hydraulic extraction device with a tensile force of 60kN. The demolding force was measured to be 9kN, with no damage to the core mold. The outer surface of the cylinder was ground with a 400-mesh abrasive wheel. After grinding, the dimensional accuracy was controlled within ±0.07mm by a laser diameter gauge. Burrs and excess resin were removed, with a residual amount ≤0.1mm. Surface pretreatment followed: Sandblasting was performed using 120-mesh abrasive particles at a pressure of 0.3MPa to achieve a surface roughness Ra=2.0μm. An 8μm thick TiN transition layer was then coated and baked at 150℃ for 30 minutes. Finally, an Al2O3-ZrO2 ceramic coating was applied using plasma spraying, with an Al2O3 content of 70% and a coating thickness of 20μm. The coating adhesion was measured to be 60MPa by the cross-cut adhesion test.

[0042] Quality Inspection: Internal defects were detected using a 5MHz ultrasonic testing instrument, and no Class II or higher defects were found. X-ray flaw detection at 320kV showed that the fibers were neatly arranged and without breakage. Infrared thermal imager with a resolution of 0.06℃ was used for inspection, and no curing defects were found. Sampling was subjected to a hydrostatic test: pressure 15MPa, held for 30 minutes, and no leakage was detected by pressure sensor monitoring. Axial tensile testing was performed using a universal testing machine, and the tensile strength was determined to be 900MPa, meeting the design requirements.

[0043] Comparative Example The specific steps for manufacturing aerospace-grade carbon fiber composite launch tubes using traditional winding processes are as follows: Pre-treatment before winding Mandrel fabrication: A mandrel with an inner diameter of 200 mm and a length of 1800 mm was machined from 6061 aluminum alloy. The dimensional accuracy was controlled within ±0.1 mm using ordinary calipers, and the surface finish was measured to be Ra=0.8 μm using a roughness tester. Only a 10 μm thick silicone resin release agent was applied to the mandrel surface, and it was cured at 25°C for 1 hour without plasma treatment or stress relief steps. The residual stress of the mandrel was measured to be 85 MPa using a stress tester.

[0044] Carbon fiber pretreatment: T700 grade carbon fiber with a tensile strength of 3200MPa was selected and directly introduced into the impregnation tank after being installed on the pay-off stand. The impregnation tank had no temperature control or stirring / dispersion device; the tank contained pure epoxy resin, and the viscosity at 25℃ was measured by a rotational viscometer to be [missing value]. The carbon fiber filaments passed through the impregnation tank at a speed of 0.5 m / min, with the impregnation amount controlled at 25%, verified by weighing. There were no hot-melt impregnation or pre-stretching steps; only natural air drying was performed. No resin cross-linking reaction control was performed, and the reaction completion rate was tested at 78%.

[0045] Winding Tension control: An open-loop tension control system is used, with no tension sensor feedback adjustment. During circumferential winding, the tension is set to 220N; the axial winding tension is 160N; the helical winding angle is fixed at 50° throughout the entire winding, with a tension set at 220N. Tension fluctuations throughout the winding are monitored to be ±12N. There is no redundant protection module or temperature monitoring; no speed reduction measures are implemented when the fiber temperature exceeds 65℃, occasionally resulting in fiber breakage.

[0046] Line type and layer control: The winding path is designed using simple drawing software, without any CNC program import, and the winding machine parameters are manually adjusted. First, two layers of circumferential winding are performed with a pitch of 8mm and a winding speed of 1m / min; then, one layer of axial winding is performed, with a coverage density of 90% determined by image analysis; finally, six layers of helical winding are performed, without segment angle adjustment or transition section design, and the angle is fixed at 50° throughout. The multi-layer winding design has no cross-overlapping, and there is no modified epoxy resin bonding layer between layers. The number of winding layers is set to 6 based on empirical values ​​and has not been verified through formula calculation.

[0047] Curing treatment The wound launch tube blank was placed in a conventional oven and heated at a constant temperature: starting from room temperature, the temperature was directly increased to 160°C at a rate of 10°C / min and held for 5 hours. During curing, pressure was applied using simple weights, maintaining a constant pressure of 0.1 MPa without dynamic adjustment or inert gas protection; air was in direct contact with the blank. There was no regulation of the bonding reaction between the epoxy resin and the reinforcing components, and the reaction completion rate was measured to be 76%.

[0048] Post-processing Demolding and finishing: After curing, the core mold was removed by mechanical hammering. Demolding force was not measured; 15% of the core molds showed slight damage, resulting in a demolding success rate of 85%. The outer surface of the cylinder was coarsely ground with a 200-mesh abrasive wheel. After grinding, dimensional accuracy was controlled within ±0.2mm using ordinary calipers, with burrs and excess resin residue exceeding 0.3mm. No surface sandblasting or transition layer treatment was applied; a single layer was directly coated using a brush. The coating has a thickness of 15 μm, and the coating adhesion strength was measured to be 32 MPa by cross-cut adhesion test.

[0049] Quality Inspection: Internal defects were only detected using a 2MHz ultrasonic testing instrument. There was no defect grading standard; only serious defects such as obvious delamination and large-sized bubbles were removed. No measures were taken to address minor defects. The finished product pass rate was 80%. X-ray flaw detection and infrared thermography were not performed. A hydrostatic test was conducted on samples: pressure 10MPa, held for 30 minutes; one sample showed leakage. An axial tensile test was performed using a universal testing machine, and the tensile strength was measured at 720MPa, which did not meet the design requirements.

[0050] The performance comparison between the examples and the comparative examples is shown in the table below: Table 1

[0051] The environmental adaptability and long-term use of the launch tubes in the examples and comparative examples are compared in the table below: Table 2

[0052] Compared with the comparative method that uses traditional open-loop control, no material modification, and simplified process, this invention achieves a comprehensive breakthrough in core performance, process precision, and environmental tolerance of aerospace carbon fiber composite launch tubes through precise material modification, closed-loop process control, and extreme environment adaptation design. It completely solves the industry pain points of traditional processes such as "large dimensional deviation, insufficient strength, weak resistance to extreme environments, and short lifespan".

[0053] In terms of core performance and process precision, the embodiment achieves a dimensional accuracy of ±0.07-0.08mm, far exceeding the ±0.2mm of the comparative example, thanks to core mold stress relief and plasma treatment, coupled with a closed-loop tension control system. The axial tensile strength is 850-900MPa, an increase of 18%-25% compared to the 720MPa of the comparative example. The cylinder wall density is 98.8%-99.5% vs 95.3%, which is due to the modification and enhancement of nano-silica and carbon nanotubes, the interlayer modified epoxy resin bonding layer, and dynamic pressure curing, which effectively improves the material interface bonding and structural integrity. The demolding success rate is 100%, a significant improvement compared to the 85% of the comparative example, avoiding core mold damage and process waste.

[0054] In terms of adaptability to extreme environments, the embodiments utilize sandblasting pretreatment, a TiN transition layer, and... The ceramic coating exhibits a dimensional change rate of only 0.04-0.06% under high and low temperature cycling, a reduction of 71%-81% compared to the comparative example's 0.21%. Its strength retention rate after salt spray corrosion is 95.8%-97.2%, and its high-temperature strength retention rate at 200℃ is 91.5%-93.1%, representing increases of 16%-18% respectively compared to the comparative example. Its low-temperature impact toughness is 47.2-49.8 kJ / m², 1.5-1.6 times that of the comparative example's 32.1 kJ / m², perfectly suited to the extreme temperature, humidity, and corrosive environments of aerospace.

[0055] In terms of long-term stability, the fatigue life of the embodiment is 1280-1400 cycles, which is 51%-65% higher than the comparative example's 850 cycles. The strength decay rate after 1000 cycles is only 2.8%-3.5%, far lower than the comparative example's 8.5%. This is attributed to the cross-layered winding design and interlayer bonding layer, which reduces the risk of interlayer delamination and ensures reliability for long-term cyclic use. Overall, this invention, through synergistic optimization of materials, processes, and performance, constructs a high-precision manufacturing system for aerospace-grade launch tubes, fully meeting the core requirements of lightweight, high strength, and adaptability to extreme environments.

[0056] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A tension-controlled winding process for a carbon fiber composite launch tube for aerospace applications, characterized in that, Includes the following steps: S1. Pre-treatment before winding: Core mold preparation: The core mold is made of 7075 aluminum alloy substrate with dimensional accuracy of ±0.03mm and surface finish Ra≤0.4μm; silicone resin release agent and modified polytetrafluoroethylene coating are applied in sequence, and the core mold is cured at 25-30℃ for 1-2 hours, followed by plasma treatment. Carbon fiber pretreatment: Take T800 grade carbon fiber with a tensile strength ≥3800MPa, and first pass it through an epoxy resin matrix impregnation bath containing 0.5-2% nano silica and 0.3-0.8% silane coupling agent, with an impregnation amount of 30-40%; during hot melt impregnation at 80-100℃, the nano silica and epoxy resin undergo a cross-linking reaction, followed by pre-stretching with a tension of 30-50N to eliminate relaxation stress; S2. Filament winding: Tension control: A closed-loop system of servo motor + tension sensor is adopted, with circumferential winding tension of 200-300N, axial tension of 150-200N, and helical winding tension of 180-250N, and tension fluctuation within ±3N; fiber temperature is monitored synchronously, and automatic speed reduction and temperature control are implemented when the temperature exceeds 60℃. Line type and layer number control: Design the path in CAD, first 2-3 layers of circumferential winding, then 1-2 layers of axial winding, and finally 5-8 layers of spiral winding; odd-numbered layers and even-numbered layers cross in opposite directions, and 0.1-0.2mm of modified epoxy resin is applied between layers; S3. Curing process: Stepwise heating: room temperature → 50℃ → 100℃ → 150-180℃; vacuum bag pressurization 0.08-0.12MPa, while inert gas is introduced to prevent oxidation. In the later stage of curing, epoxy resin and carbon nanotubes undergo a bonding reaction. S4. Post-processing: Demolding and finishing: mechanically pull out the core mold, polish the outer surface, and apply an Al2O3-ZrO2 ceramic coating; Quality inspection: ultrasonic testing, X-ray flaw detection, infrared thermography; sampling hydrostatic test, axial tensile test.

2. The tension-controlled winding process for the aerospace carbon fiber composite launch tube according to claim 1, characterized in that, It also includes the temperature control and stirring system of the impregnation tank in S1: the impregnation tank adopts double-jacket heating, and the temperature is controlled at 25-30℃; the built-in magnetic stirrer, combined with ultrasonic dispersion, ensures that the nano silica and silane coupling agent are uniformly dispersed in the epoxy resin matrix.

3. The tension-controlled winding process for the aerospace carbon fiber composite launch tube according to claim 1, characterized in that, It also includes a redundant protection module for the tension control system in S2. This module contains dual tension sensors that compare two sets of tension data in real time. When the difference exceeds 5N, it automatically triggers an alarm and reduces speed. At the same time, a mechanical tension buffer is set up. When the tension suddenly increases by more than 10% of the set value, the buffer instantly absorbs the impact force.

4. The tension-controlled winding process for the aerospace carbon fiber composite launch tube according to claim 1, characterized in that, The spiral winding angle adjustment in S2 adopts segmented program control. After every 3-5 layers of winding, the winding angle is automatically adjusted according to the stress simulation data of the launch tube section, with an adjustment interval of 5°-10°. In the transition section between the tube body and the flange, a gradual angle winding is adopted to avoid stress concentration, and the fiber coverage rate of the transition section is ≥99%.

5. The tension-controlled winding process for the aerospace carbon fiber composite launch tube according to claim 1, characterized in that, It also includes a dynamic pressure adjustment mechanism for the curing process in S3. When the curing temperature rises to 50°C, the pressure is set to 0.05-0.08MPa; when the temperature rises to 100°C, the pressure is increased to 0.08-0.12MPa; during the constant temperature stage of 150-180°C, the pressure is finely adjusted by ±0.01MPa every 2 hours to compensate for the pressure loss caused by resin shrinkage and ensure that the cylinder wall density is ≥98%.

6. The tension-controlled winding process for the aerospace carbon fiber composite launch tube according to claim 1, characterized in that, It also includes a pretreatment step for the high-temperature resistant ceramic coating in S4, where the outer surface of the launch tube is sandblasted before spraying to achieve a surface roughness Ra of 1.5-2.0 μm; Apply a transition layer and bake at 150°C for 30 minutes.

7. The tension-controlled winding process for the aerospace carbon fiber composite launch tube according to claim 1, characterized in that, It also includes stress relief treatment for the core mold in S1. After the core mold is processed, it is subjected to low temperature aging treatment: first, the core mold is heated to 120-150℃ and held for 4-6 hours, and then cooled to room temperature in the furnace; then vibration aging is performed to eliminate processing stress. The residual stress of the core mold is ≤50MPa, so as to avoid the core mold deformation during the winding process from affecting the dimensional accuracy of the launch tube.

8. The tension-controlled winding process for the aerospace carbon fiber composite launch tube according to claim 1, characterized in that, It also includes a precise calculation method for the number of winding layers in S2. Combined with the design load of the launch tube, it is calculated according to the formula "number of layers = (design load × safety factor) / (single layer fiber bearing strength × effective circumference of the tube)", with a safety factor of 1.8-2.

2. The load-bearing strength of a single layer of fiber is determined through testing to ensure that the layer design meets the strength requirements while avoiding material waste.

9. The tension-controlled winding process for the aerospace carbon fiber composite launch tube according to claim 1, characterized in that, It also includes the defect classification and handling standards in S4 for quality inspection. In ultrasonic testing, if the bubble diameter is ≤0.3mm and there are ≤2 bubbles within 100mm², no treatment is required; if the bubble diameter is 0.3-0.5mm and there are 2-3 bubbles within 100mm², local glue filling and curing are required; if the bubble diameter is >0.5mm or the delamination area is >8mm², the defective section needs to be cut off and rewound to ensure that the finished product qualification rate is ≥98%.

10. The tension-controlled winding process for aerospace carbon fiber composite launch tubes according to any one of claims 1-9, characterized in that, Suitable for launch tubes with an inner diameter of 150-450mm and a length of 1200-2800mm; finished product density is 1.6-1.8g / cm³, which is 35-55% lighter than metal launch tubes, with a fatigue life of ≥1200 cycles of loading, and a dimensional change rate of ≤0.1% in an environment of -60℃ to 200℃, meeting the requirements for use in extreme aerospace environments.

Images