Low-temperature-resistant anti-carburization carbon fiber reinforced composite material and preparation method thereof

Abstract

The application belongs to the technical field of composite materials, and particularly relates to a low-temperature-resistant anti-permeation carbon fiber reinforced composite material and a preparation method thereof. The preparation method comprises the following steps: dispersing polyamide acid grafted hydroxylated nano-silica in a solvent, adding nano-rubber and performing ultrasonic treatment to obtain a sizing agent; immersing carbon fibers after desizing in the sizing agent, taking out and drying to obtain sized carbon fibers; compounding polytrifluorochloroethylene resin and the sized carbon fibers to obtain a carbon fiber reinforced polytrifluorochloroethylene prepreg tape; compounding polyether sulfone resin, polyphenylene sulfide resin and the sized carbon fibers to obtain a carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape; stacking the carbon fiber reinforced polytrifluorochloroethylene prepreg tape in an inner layer and the carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape in an outer layer, and curing and forming, so that the carbon fiber composite material is obtained. The carbon fiber composite material can not only maintain high mechanical properties, but also has an ultra-low leakage rate under ultra-low temperature cycles.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon fiber reinforced composite materials, and particularly relates to a low-temperature-resistant anti-permeation carbon fiber reinforced composite material and a preparation method thereof. BACKGROUND

[0002] The development of space vehicle tank materials mainly experiences the stages of aluminum-magnesium alloy, aluminum-copper alloy, aluminum-lithium alloy, and finally develops towards carbon fiber composite materials. The specific strength and specific stiffness of carbon fiber composite materials are much higher than those of metals, and the carbon fiber composite materials have good fatigue resistance, vibration resistance, and good forming process, and are particularly suitable for application in large structures and integral structure forming, which can reduce the number of parts and connection processes, and are ideal materials for realizing high performance and light weight of aerospace advanced equipment structures. Compared with metal tanks, carbon fiber composite material tanks can reduce the weight of liquid oxygen tank structures by about 25%, and the larger the size of the low-temperature medium tank structure, the more obvious the weight reduction effect, and the overall launch cost is reduced. Therefore, the development of carbon fiber composite material tanks has become an inevitable trend.

[0003] Since the carbon fiber composite material exhibits certain oxidation resistance, but the key thermal properties such as ignition point, flash point and thermal decomposition temperature are lower than those of metal materials. When encountering high-energy instantaneous impact, the carbon fiber composite material may trigger a fire risk due to local rapid heating, and even may further cause an explosion accident. Therefore, improving the compatibility of carbon fiber composite materials with liquid oxygen is the primary core problem to be solved. In addition, due to the obvious difference between the thermal expansion coefficient of carbon fiber and the thermal expansion coefficient of the resin matrix, when the carbon fiber composite material cools from the forming temperature to room temperature, and is applied to low-temperature tanks such as liquid oxygen and liquid hydrogen, the thermal expansion mismatch will cause the deformation of carbon fiber and epoxy resin to be uncoordinated, resulting in high residual stress of the carbon fiber composite material at low temperature cooling, which is easy to produce microcracks at the resin matrix, carbon fiber and resin interface under the coupling action of internal mechanical stress. Under the continuous or cyclic action of low temperature and stress, the microcracks continuously expand until single-layer transverse cracks and interlayer cracks are formed, and then a leakage channel is formed to cause tank leakage; the leakage failure of the carbon fiber composite material low-temperature tank will occur before the structural load failure, which is extremely dangerous for flammable and explosive propellants such as liquid oxygen and liquid hydrogen. Therefore, how to effectively improve the liquid oxygen compatibility of carbon fiber composite materials, while effectively inhibiting the leakage problem of the carbon fiber composite materials in the ultra-low temperature medium, is the key to the application of carbon fiber composite materials in ultra-low temperature medium tanks.

[0004] In order to improve the low-temperature medium leakage resistance of carbon fiber composite materials, the prior art usually introduces flexible polymers (such as thermoplastic resins, nano rubber, etc.) or dopes nano materials (such as carbon nanotubes, silicon dioxide, etc.) in the resin matrix to improve the toughness of the resin matrix, so as to improve the crack propagation resistance and reduce the leakage risk. However, the above research and method cannot fundamentally solve the problem of microcrack caused by residual stress. The introduction of flexible polymers may increase the thermal expansion coefficient of the resin matrix. When the ambient temperature of the carbon fiber reinforced resin matrix composite material decreases from room temperature to ultra-low temperature, the temperature stress at the resin / fiber interface increases sharply due to the large thermal expansion coefficient of the resin matrix, which easily leads to the initiation of microcracks at the resin / fiber interface, resulting in an increase in the leakage rate. The nano materials in the resin matrix are prone to agglomeration, and if the surface lacks active functional groups, the interface bonding between the nano materials and the resin matrix will be weakened, resulting in a decrease in the mechanical properties of the carbon fiber composite material.

[0005] The thermal expansion coefficients of the commonly used epoxy resin matrix and carbon fiber are quite different, which will produce huge thermal stress, leading to the generation and propagation of microcracks. These microcracks will become the penetration channels of the medium (especially ultra-low temperature liquid and gas), causing the leakage rate to increase, which is extremely dangerous for flammable and explosive propellants (such as liquid oxygen and liquid hydrogen). Fluororesin is known for its extremely low permeability, excellent chemical inertness and high and low temperature resistance. However, there are two major technical bottlenecks in its compounding with carbon fiber: 1. Poor interfacial bonding: the surface energy of fluororesin is extremely low, which is a difficult-to-bond material, and the wettability and adhesion strength of carbon fiber are extremely poor, direct compounding will cause a serious decrease in mechanical properties. 2. Difficult to process: fluororesin has a high melting point and large melt viscosity, which makes it difficult to achieve good wetting of carbon fiber bundles, resulting in weak interfacial bonding ability and easy to produce pores.

[0006] In view of the above problems, how to effectively solve the liquid oxygen compatibility and leakage of carbon fiber composite materials in low temperature medium is a technical problem that needs to be solved urgently. SUMMARY

[0007] One of the purposes of the present application is to provide a preparation method of a low-temperature-resistant and anti-leakage carbon fiber reinforced composite material. The present application adopts a multi-level interface structure compatible with liquid oxygen and having high toughness, combined with a high anti-leakage thermoplastic resin, to prepare a carbon fiber reinforced fluororesin composite material which effectively prevents low-temperature medium leakage.

[0008] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0009] A preparation method of a low-temperature-resistant and anti-leakage carbon fiber reinforced composite material, comprising the following steps:

[0010] (1) dispersing polyamide acid grafted hydroxylated nano-silica in a solvent to obtain a polyamide acid grafted hydroxylated nano-silica solution, then adding nano-rubber and ultrasonically treating to obtain a sizing agent;

[0011] (2) desizing the carbon fiber to obtain desized carbon fiber, immersing the desized carbon fiber in the sizing agent obtained in step (1), taking out and drying to obtain sized carbon fiber;

[0012] (3) uniformly spreading polytrifluorochloroethylene resin on the sized carbon fiber obtained in step (2), hot-pressing and immersing, cooling and setting, and winding to obtain carbon fiber reinforced polytrifluorochloroethylene prepreg tape;

[0013] (4) blending polyether sulfone resin and polyphenylene sulfide resin, melting and plasticizing, coating on the sized carbon fiber obtained in step (2), hot-pressing and immersing, cooling and setting, and winding to obtain carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape;

[0014] (5) laying the carbon fiber reinforced polytrifluorochloroethylene prepreg tape in the inner layer and the carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape in the outer layer, and curing and forming to obtain the composite material.

[0015] Further, in step (1), the polyamide acid grafted hydroxylated nano-silica comprises the following steps:

[0016] adding condensing agent and catalyst into polyamide acid diluent to obtain a mixed solution, adding the mixed solution into hydroxylated nano-silica dispersion under nitrogen atmosphere, heating and stirring, centrifuging, washing, drying the reacted mixture to obtain polyamide acid grafted hydroxylated nano-silica.

[0017] The composite material of the present application comprises an anti-permeation layer and a load-bearing layer arranged in sequence from inside to outside; the anti-permeation layer is formed by laying the carbon fiber reinforced polytrifluorochloroethylene prepreg tape formed by impregnating polytrifluorochloroethylene on sized carbon fiber; and the load-bearing layer is formed by laying the carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape formed by impregnating polyether sulfone / polyphenylene sulfide resin on sized carbon fiber.

[0018] The surface of the sized carbon fiber of the present application has a multi-level reinforced interface layer, which is composed of polyamide acid (PAA) grafted hydroxylated nano-silica (OH-SiO2) and nano-rubber.

[0019] a. The polar groups (carboxyl, amido) in the molecular chain of polyamic acid (PAA) can form strong van der Waals forces and hydrogen bonds with the active groups on the surface of carbon fibers. In addition, during the hot-pressing and curing process, PAA is converted into polyimide (PI), and the PAA molecular chain can interdiffuse and entangle with the resin chains of polytrifluorochloroethylene resin (PCTFE), PES (polyether sulfone resin) / PPS (polyphenylene sulfide resin), etc., forming a gradient interpenetrating structure, which improves the binding ability of carbon fibers and PCTFE, PES / PPS, and forms a carbon fiber composite material with a laminated structure. That is, the introduction of polyamic acid grafted hydroxylated nano-silica not only improves the interfacial bonding of the resin matrix and carbon fibers, but also improves the density of the composite material, and improves its impermeability and compatibility after high and low temperature cycles.

[0020] b. Ordinary silica is prone to agglomeration in the resin matrix, leading to a decrease in the mechanical properties of the material and destroying the density of the material. In the present application, the carboxyl groups on the PAA chain react with the hydroxyl groups on the surface of the hydroxylated nano-silica, grafting the hydroxylated nano-silica onto the PAA, which stably exists in the sizing agent and is ultimately uniformly distributed on the surface of the carbon fibers, improving the strength and interfacial density of the material.

[0021] c. In the present application, the nano-rubber particles can be uniformly dispersed in the polyamic acid (PAA) grafted hydroxylated nano-silica solution, thereby effectively preventing agglomeration. During the subsequent hot-pressing and curing process, the PAA molecular chain will shrink and entangle, and the nano-rubber particles will be fixed in the formed polyimide (PI) network. This ensures that the nano-rubber particles are firmly fixed in the interfacial region of the fibers and the resin, and will not migrate or be lost during processing.

[0022] Further, the molar ratio of the polyamic acid, the condensing agent, and the catalyst is 1:(1.2-1.5):(0.1-0.2), the mass ratio of the mixed solution and the hydroxylated nano-silica dispersion liquid is (1-3):2; the concentration of the hydroxylated nano-silica dispersion liquid is 8-12wt%; the condensing agent is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, the catalyst is 4-N,N-dimethylpyridine, the solvent in the hydroxylated nano-silica dispersion liquid is N,N-dimethylformamide, and the concentration of the polyamic acid dilution liquid is 1-5wt%; the polyamic acid dilution liquid is obtained by diluting the polyamic acid stock solution with DMF.

[0023] Further, the temperature of the heating and stirring is 70-80℃, and the time is 20-24h.

[0024] Further, in step (1), the mass ratio of the nano rubber and the polyamide acid grafted hydroxylated nano silica solution is (0.5-3):(97-99.5); the concentration of the polyamide acid grafted hydroxylated silica solution is 1-3wt%; the solvent is N,N-dimethylformamide; and the nano rubber is a core-shell structure, the inner core is polybutadiene rubber, and the outer shell is polymethyl methacrylate, and the particle size is 50nm.

[0025] Further, in step (1), the ultrasonic treatment comprises: using 800-1000W power ultrasonic for 5-10min, and then using 300-500W power ultrasonic for 20-30min; the slurry temperature is controlled to be ≤40℃ during the ultrasonic treatment, and the absolute value of the Zeta potential of the dispersed slurry is greater than 35mV; in step (2), the temperature of the desmearing treatment is 350-450℃, and the time is 0.5-5min; the impregnation time is 25-30s; and the drying temperature is 140-180℃.

[0026] Further, in step (3), the temperature of the hot-pressing impregnation is 250-260℃, and the pressure is 0.5-2MPa; the temperature of the cooling and shaping is 10-20℃; in step (4), the temperature of the hot-pressing impregnation is 310-320℃, and the pressure is 1-3MPa; and the temperature of the cooling and shaping is 10-20℃.

[0027] Further, in step (5), the curing forming condition is: increasing the temperature from room temperature to 300-310℃ at a rate of 8-10℃ / min, and then maintaining at 0.5-1MPa, 4-5MPa and 2-3MPa respectively for 5-10min, and then decreasing to room temperature.

[0028] Further, in step (5), the thickness of the carbon fiber reinforced polytrifluorochloroethylene prepreg tape is 0.2-0.5mm, and the thickness of the carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape is 1.0-1.5mm.

[0029] The second object of the application is to provide a low-temperature-resistant anti-seepage carbon fiber reinforced composite material.

[0030] The low-temperature-resistant anti-seepage carbon fiber reinforced composite material is prepared by the above preparation method.

[0031] Compared with the prior art, the application has the following beneficial effects:

[0032] 1. This invention provides a low-temperature resistant, impermeable carbon fiber reinforced composite material that maintains high mechanical properties while exhibiting ultra-low leakage rate and compatibility under ultra-low temperature cycling. This composite material can be used as the lining or shell of a liquid hydrogen / liquid oxygen storage tank. After undergoing 50 thermal cycles from -196℃ to 120℃, the material meets the following requirements: (1) at 3MPa, the helium permeability in a liquid nitrogen environment is less than 1×10⁻⁶. -8 Pa·m 3 / s; (2) Interlaminar shear strength (ILSS) retention rate ≥90%; (3) Good liquid oxygen compatibility.

[0033] 2. This invention provides a method for preparing a low-temperature resistant and impermeable carbon fiber reinforced composite material. This preparation method is simple and easy to implement, suitable for industrialization and large-scale application. The development of this carbon fiber composite material can be used to prepare aerospace propellant tanks, high and low temperature tanks, etc., providing strong support for technological innovation and industrial upgrading in related fields. Detailed Implementation

[0034] The technical solution of the present invention will be further explained below with reference to specific embodiments, comparative examples, and test examples.

[0035] Unless otherwise specified, the raw materials and preparation methods used in the following examples, comparative examples, and experimental cases are all conventional materials and techniques in the art.

[0036] The hydroxylated nano-silica of this invention was purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd., model: XFnano-SiO2-20H: 20 nm.

[0037] The polyamic acid (PAA) stock solution of this invention was purchased from Shandong Liaocheng Tongda Chemical Co., Ltd. It is an N,N-dimethylformamide (DMF) system PAA solution with a solid content of 15wt%.

[0038] The nano-rubber particles of this invention were purchased from Shanghai Napai New Materials Co., Ltd. The nano-rubber particles have a core-shell structure, with a core of polybutadiene rubber and a shell of polymethyl methacrylate, and a particle size of 50 nm.

[0039] The polytrifluorochloroethylene resin (PCTFE) used in this invention was purchased from Zhengyu New Materials Technology Co., Ltd.

[0040] The polyethersulfone (PES) resin used in this invention was purchased from BASF AG.

[0041] The polyphenylene sulfide resin (PPS) used in this invention was purchased from Suzhou Napan New Materials Technology Co., Ltd.

[0042] The carbon fiber used in this invention was purchased from Jiangsu Hengshen Co., Ltd., and its model number is T1100.

[0043] Preparation Example

[0044] A method for preparing polyamic acid grafted hydroxylated nano-silica, comprising the following steps:

[0045] S1. Hydroxylated nano-silica (OH-SiO2) powder is added to a three-necked flask containing N,N-dimethylformamide (DMF), and is ultrasonically dispersed in an ice water bath for 60 min at a power of 600 W by using a probe-type ultrasonic instrument to obtain a semi-transparent or milky white OH-SiO2 dispersion (concentration of 10 wt%); nitrogen is continuously introduced into the system to remove air and moisture.

[0046] S2. A polyamic acid (PAA) stock solution is taken and diluted with DMF to obtain a PAA diluent of 5 wt%; in another container, a condensing agent 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC) and a catalyst 4-N,N-dimethylpyridine (DMAP) are added to the PAA diluent, wherein the molar ratio of PAA, EDC and DMAP is 1:1.5:0.1, and the mixture is stirred at room temperature for 30 min to obtain a mixed solution.

[0047] S3. The mixed solution in step S2 is slowly added to the OH-SiO2 dispersion using a constant pressure dropping funnel, and the mass ratio of the mixed solution to the OH-SiO2 dispersion is 1:1; the reaction is carried out at 70°C under nitrogen protection and continuous stirring at a stirring rate of 500 rpm for 20 h.

[0048] S4. The reaction product mixture is transferred to a centrifuge tube and centrifuged using a high-speed centrifuge at a speed of 10,000 rpm for 3 times, 5 min each time, and the precipitate is washed with acetone and ethanol alternately for 3 times; the finally obtained product is placed in a vacuum drying oven and dried at 80°C for 24 h to obtain polyamic acid grafted hydroxylated nano-silica.

[0049] Example 1

[0050] A method for preparing a low-temperature-resistant anti-carburization carbon fiber reinforced composite material, comprising the following steps:

[0051] (1) Polyamic acid grafted hydroxylated nano-silica is dispersed in DMF to obtain a polyamic acid grafted hydroxylated nano-silica solution of 2 wt%, and then nano rubber is added (the mass ratio of nano rubber to polyamic acid grafted hydroxylated nano-silica solution is 2:98); the slurry is subjected to stepwise ultrasonic dispersion treatment: first ultrasonic dispersion at a power of 900 W for 8 min, and then ultrasonic dispersion at a power of 400 W for 25 min; the slurry temperature is controlled to be ≤40°C during ultrasonic dispersion, and the absolute value of the Zeta potential of the slurry after dispersion is greater than 35 mV to obtain a sizing agent;

[0052] (2) The carbon fiber is desized at 400℃ for 1 min to obtain desized carbon fiber, and the desized carbon fiber is immersed in the sizing agent obtained in step (1) for 20 s, and then the solvent is volatilized at 150℃. The sized carbon fiber is obtained.

[0053] (3) The polytrifluorochloroethylene resin (PCTFE) is vacuum dried at 100℃ for 6 h, and then the PCTFE is uniformly spread on the sized carbon fiber developed in step (2), and immediately passed through a high-temperature hot roller, with the temperature set at 250℃, to make the molten resin roll and impregnate the sized carbon fiber under a pressure of 2 MPa, and then immediately passed through a cooling roller with a temperature of 20℃ to make the resin quench and set. The carbon fiber reinforced polytrifluorochloroethylene prepreg tape is obtained by winding.

[0054] (4) The polyether sulfone resin (PES) and polyphenylene sulfide resin (PPS) blended pellets are dried at 100℃ for 6 h. The dried blended resin is melted and plasticized by an extruder at a temperature of 310℃, and the melt is directly coated on the sized carbon fiber developed in step (2) through a slit die, and immediately passed through a high-temperature hot roller, with the temperature set at 310℃, to complete the impregnation under a pressure of 2 MPa. Then immediately passed through a cooling roller with a temperature of 10℃ to make the resin quench and set. The carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape is obtained by winding.

[0055] (5) The carbon fiber reinforced polytrifluorochloroethylene prepreg tape is laid in the inner layer (thickness 0.2 mm) as a barrier layer, and the carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape is laid in the outer layer (thickness 1.4 mm) as a load-bearing layer. The hot press molding process is used: from room temperature, the temperature is rapidly increased to 300℃ at a rate of 10℃ / min, and after reaching 300℃, it is kept at 0.5 MPa, 5 MPa and 2 MPa for 5 min respectively, and then reduced to room temperature. The low-temperature-resistant and anti-permeation carbon fiber reinforced composite material is obtained.

[0056] The embodiment also provides a low-temperature-resistant and anti-permeation carbon fiber reinforced composite material prepared by the above preparation method.

[0057] Example 2

[0058] A preparation method of a low-temperature-resistant and anti-permeation carbon fiber reinforced composite material, comprising the following steps:

[0059] (1) polyamide acid grafted hydroxylated nano-silica is dispersed in DMF to obtain a 1wt% polyamide acid grafted hydroxylated nano-silica solution, then nano-rubber is added (mass ratio of nano-rubber to polyamide acid grafted hydroxylated nano-silica solution is 0.5:99.5); the slurry is subjected to stepwise ultrasonic dispersion treatment: first ultrasonic dispersion is performed at 800W for 10min, then ultrasonic dispersion is performed at 300W for 30min; the slurry temperature is controlled to be ≤40℃ during ultrasonic dispersion, and the absolute value of Zeta potential of the slurry after dispersion is greater than 35mV, to obtain the sizing agent;

[0060] (2) carbon fibers are desized at 350℃ for 5min to obtain desized carbon fibers, the desized carbon fibers are immersed in the sizing agent obtained in step (1) for 20s, and then taken out, and the solvent is volatilized at 140℃, to obtain sized carbon fibers;

[0061] (3) PCTFE is vacuum dried at 100℃ for 6h, then the PCTFE is uniformly spread on the sized carbon fibers developed in step (2), and immediately passed through a high-temperature hot roller, the temperature is set to 255℃, the molten resin is rolled and impregnated on the sized carbon fibers under a pressure of 0.5MPa, and then immediately passed through a cooling roller, the temperature is 10℃, to make the resin quench and set; winding is performed to obtain a carbon fiber reinforced polytrifluorochloroethylene prepreg tape;

[0062] (4) PES and PPS blended granules are dried at 100℃ for 6h. The dried blended resin is melted and plasticized by an extruder at a temperature of 315℃, the melt is directly coated on the sized carbon fibers developed in step (2) through a slit die, and immediately passed through a high-temperature hot roller, the temperature is set to 315℃, and impregnation is completed under a pressure of 3MPa; then immediately passed through a cooling roller, the temperature is 20℃, to make the resin quench and set; winding is performed to obtain a carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape;

[0063] (5) the carbon fiber reinforced polytrifluorochloroethylene prepreg tape is laid in the inner layer (thickness is 0.5mm) as a barrier layer; the carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape is laid in the outer layer (thickness is 1.0mm) as a bearing layer; a hot-pressing forming process is used: rapidly heated to 305℃, after reaching 305℃, kept at 0.5MPa, 5MPa and 2MPa for 8min respectively, and then reduced to room temperature.

[0064] The embodiment also provides a low-temperature-resistant and anti-permeation carbon fiber reinforced composite material prepared by the above preparation method.

[0065] Example 3

[0066] A preparation method of a low-temperature-resistant and anti-permeation carbon fiber reinforced composite material, comprising the following steps:

[0067] (1) polyamide acid grafted hydroxylated nano-silica is dispersed in DMF to obtain a 2wt% polyamide acid grafted hydroxylated nano-silica solution, then nano-rubber is added (mass ratio of nano-rubber to polyamide acid grafted hydroxylated nano-silica solution is 3:97); the slurry is subjected to stepwise ultrasonic dispersion treatment: first ultrasonic dispersion is performed at 1000W for 5min, then ultrasonic dispersion is performed at 500W for 20min; the slurry temperature is controlled to be ≤40℃ during ultrasonic dispersion, and the absolute value of Zeta potential of the slurry after dispersion is greater than 35mV, to obtain the sizing agent;

[0068] (2) carbon fibers are desized at 450℃ for 0.5min to obtain desized carbon fibers, the desized carbon fibers are immersed in the sizing agent obtained in step (1) for 25s, and the solvent is volatilized at 180℃; to obtain sized carbon fibers;

[0069] (3) PCTFE is vacuum dried at 100℃ for 6h, then the PCTFE is uniformly spread on the sized carbon fibers developed in step (2), and immediately passed through a high-temperature hot roller, the temperature is set to 260℃, the molten resin is rolled and impregnated on the sized carbon fibers under a pressure of 1MPa, then immediately passed through a cooling roller, the temperature is 15℃, and the resin is rapidly cooled and shaped; winding is performed to obtain a carbon fiber reinforced polytrifluorochloroethylene prepreg tape;

[0070] (4) PES and PPS blended granules are dried at 100℃ for 6h. The dried blended resin is melted and plasticized by an extruder at a temperature of 320℃, the melt is directly coated on the sized carbon fibers developed in step (2) through a slit die, immediately passed through a high-temperature hot roller, the temperature is set to 320℃, and impregnation is completed under a pressure of 1MPa; then immediately passed through a cooling roller, the temperature is 15℃, and the resin is rapidly cooled and shaped; winding is performed to obtain a carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape;

[0071] (5) the carbon fiber reinforced polytrifluorochloroethylene prepreg tape is laid in the inner layer (thickness is 0.2mm) as a barrier layer; the carbon fiber reinforced polyether sulfone / polyphenylene sulfide resin prepreg tape is laid in the outer layer (thickness is 1.5mm) as a bearing layer; hot pressing and curing are performed: the temperature is rapidly increased to 310℃, after reaching 310℃, 0.5MPa, 5MPa and 2Mpa are maintained for 5min respectively, and then the temperature is reduced to room temperature; to obtain the product.

[0072] The embodiment also provides a low-temperature-resistant and anti-permeation carbon fiber reinforced composite material prepared by the above preparation method.

[0073] Comparative Example 1

[0074] Comparative Example 1 and Example 1 differ in that dispersing the polyamide acid grafted hydroxylated nano-silica in DMF in step (1) is replaced by dispersing the polyamide acid and nano-silica in DMF.

[0075] Comparative Example 2

[0076] Comparative Example 2 and Example 1 differ in that dispersing the polyamide acid grafted hydroxylated nano-silica in DMF in step (1) is replaced by dispersing the polyimide and hydroxylated nano-silica in DMF.

[0077] Comparative Example 3

[0078] Comparative Example 3 and Example 1 differ in that PCTFE in step (3) is replaced by epoxy resin.

[0079] Comparative Example 4

[0080] Comparative Example 4 and Example 1 differ in that step (4) is omitted and the carrier layer in step (5) is replaced by carbon fiber reinforced polytrifluorochloroethylene prepreg tape.

[0081] Test Example 1

[0082] The properties of the composite materials obtained in Examples 1-3 and Comparative Examples 1-4 of the present application were tested: the leakiness was tested by helium mass spectrometry leak detection, and the detection conditions were: liquid nitrogen environment, 3 MPa pressure; the interlaminar shear strength (ILSS) was characterized by ASTM 2344; after the material was cycled from -196°C to 120°C for 50 times, the leak rate, interlaminar shear strength of the material were tested again, and the liquid oxygen compatibility of the material was tested. The ILSS retention rate = (ILSS after 50 cycles / ILSS before cycling) x 100%; the results are shown in Table 1.

[0083] Table 1

[0084]

[0085] From the experimental results in Table 1, it can be seen that the carbon fiber composite material of the present application has an ultra-low leak rate and interlaminar shear strength. After 50 high-low temperature cycles from -196°C to 120°C, the leak rate of the carbon fiber composite material still maintains , the interlaminar shear strength (ILSS) retention rate is ≥ 90%; it has good liquid oxygen compatibility. Among them, the comprehensive performance of Examples 1-3 is generally better than that of Comparative Examples 1-4.

[0086] Compared with Example 1, the helium permeation rate, interlaminar shear strength and high-low temperature cycle performance of Comparative Example 1 are all poor. The specific analysis of the reasons is as follows: a series of chain reactions caused by the lack of hydroxyl groups on the surface of nano-silicon dioxide: the dispersibility and grafting reactivity with polyamic acid are poor, which directly weakens the interfacial bonding strength after sizing of carbon fibers. An insufficiently bonded interface cannot fully absorb external load energy, nor can it effectively inhibit the initiation and propagation of microcracks, which makes the composite more prone to interface failure and medium leakage under stress. Therefore, its initial ILSS value is low and the leakage rate is high. After cyclic loading or environmental aging, this inherent interface defect becomes a stress concentration point, leading to accelerated accumulation of damage, so the ILSS retention rate after cycling is significantly reduced, and the leakage phenomenon is further aggravated.

[0087] Compared with Example 1, the helium permeation rate of Comparative Example 2 is significantly reduced, and the interlaminar shear strength before and after cycling is significantly lower than that of Example 1. The reasons for the decrease are as follows: the hydrogen bond between polyimide and hydroxylated nano-silicon dioxide is mainly in the form of hydrogen bond, and no covalent bond is formed. Compared with a firm chemical bond, hydrogen bond as a weaker physical interaction has lower binding energy and is prone to dissociation under stress, which limits its reinforcing effect on the interface between carbon fiber and resin. This interface becomes a weak link under thermal cycling load (such as heat and force), and cannot effectively inhibit the initiation and propagation of microcracks, so the interfacial shear strength and the leakage rate will decrease before and after cycling, and the retention rate is low and the leakage rate increases significantly.

[0088] Compared with Example 1, the helium permeation rate and interlaminar shear strength of Comparative Example 3 before cycling are significantly reduced, and the helium permeation rate and interlaminar shear strength after cycling are the worst, and it does not have liquid oxygen compatibility. The reasons for the decrease are as follows: due to the use temperature of epoxy resin being much lower than 300℃, and being a thermosetting plastic, it does not have the ability of secondary molding. When it is co-molded with carbon fiber reinforced polyether sulfone / polyphenylene sulfide (PES / PPS) thermoplastic prepreg tape, the two cannot form a good interface fusion. Therefore, there is obvious interface separation in the obtained composite, including the carbon fiber / epoxy resin part and the carbon fiber / PES / PPS part. The bonding force of the two-phase interface of this structure is insufficient, leading to a significant decrease in interlaminar shear strength (ILSS); the epoxy resin itself does not have liquid oxygen compatibility, further limiting its applicability in a liquid oxygen environment; carbon fiber / epoxy resin as a barrier layer is prone to interface debonding under high-low temperature alternating stress, and cannot effectively block medium penetration, resulting in serious leakage after cycling.

[0089] Compared with example 1, the interlaminar shear strength (ILSS) of the product of comparative example 4 is always lower than that of example 1 due to the fact that the bulk mechanical property of polyphenylene sulfide (PPS) resin is significantly higher than that of polychlorotrifluoroethylene (PCTFE), and this gap still exists after the cycle test. In terms of the impermeability, PCTFE itself is an excellent impermeable material, so the final impermeability performance of the two is close.

[0090] The carbon fiber composite material prepared by the present application not only has ultra-low leakage rate under ultra-low temperature cycle, but also has high super mechanical property and compatibility. In summary, the sized carbon fiber of the present application has good interfacial bonding capacity in polytrifluorochloroethylene resin and polyether sulfone resin and polyphenylene sulfide resin mixed resin, forms a carbon fiber composite material with a multi-layer structure in the curing process, and the polyamide acid forms polyimide in the curing process, can uniformly fix silica and nano rubber on the surface of the carbon fiber, and more importantly, can further improve the strength of the composite material and its impermeability under high and low temperature cycle, interlaminar shear strength and the like.

[0091] The above is only the preferred embodiment of the present application, which is not limited to the above examples, and various modifications and changes can be made by those skilled in the art under the principle of the present application. Any modification, improvement, etc. shall be considered within the scope of protection of the present application.

[0092] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limited to the above examples. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A method for preparing a low-temperature resistant, impermeable carbon fiber reinforced composite material, characterized in that, Includes the following steps: (1) Add condensing agent and catalyst to polyamic acid dilution to obtain mixed solution; under nitrogen atmosphere, add the mixed solution to hydroxylated nano silica dispersion, heat and stir, centrifuge, wash and dry the mixture after reaction to obtain polyamic acid grafted hydroxylated nano silica; disperse polyamic acid grafted hydroxylated nano silica in solvent to obtain polyamic acid grafted hydroxylated nano silica solution, and then add nano rubber for ultrasonic treatment to obtain sizing agent; (2) The carbon fiber is desized to obtain desized carbon fiber, which is then immersed in the sizing agent obtained in step (1), removed and dried to obtain sized carbon fiber. (3) Spread polychlorotrifluoroethylene resin evenly onto the sized carbon fiber obtained in step (2), hot press impregnate, cool and shape, and wind up to obtain carbon fiber reinforced polychlorotrifluoroethylene prepreg tape. (4) After blending polyethersulfone resin and polyphenylene sulfide resin, melt plasticize them, coat them onto the sized carbon fiber obtained in step (2), hot press impregnate, cool and shape, and wind up to obtain carbon fiber reinforced polyethersulfone / polyphenylene sulfide resin prepreg tape. (5) Lay carbon fiber reinforced polychlorotrifluoroethylene prepreg tape in the inner layer and carbon fiber reinforced polyethersulfone / polyphenylene sulfide resin prepreg tape in the outer layer, and cure to form the desired shape. The molar ratio of the polyamic acid, condensing agent, and catalyst is 1:(1.2-1.5):(0.1-0.2), and the mass ratio of the mixed solution to the hydroxylated nano-silica dispersion is (1-3):2; the concentration of the hydroxylated nano-silica dispersion is 8-12 wt%; the condensing agent is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, the catalyst is 4-N,N-dimethylpyridine, the solvent in the hydroxylated nano-silica dispersion is N,N-dimethylformamide, and the concentration of the polyamic acid diluent is 1-5 wt%; the polyamic acid diluent is obtained by diluting the polyamic acid stock solution with DMF.

2. The method for preparing the low-temperature resistant and impermeable carbon fiber reinforced composite material according to claim 1, characterized in that, The heating and stirring temperature is 70-80℃, and the time is 20-24h.

3. The method for preparing the low-temperature resistant and impermeable carbon fiber reinforced composite material according to claim 1, characterized in that, In step (1), the mass ratio of the nano-rubber to the polyamic acid-grafted hydroxylated nano-silica solution is (0.5-3):(97-99.5); the concentration of the polyamic acid-grafted hydroxylated nano-silica solution is 1-3 wt%; the solvent is N,N-dimethylformamide; the nano-rubber has a core-shell structure, with a core of polybutadiene rubber and a shell of polymethyl methacrylate, and a particle size of 50 nm.

4. The method for preparing the low-temperature resistant and impermeable carbon fiber reinforced composite material according to claim 1, characterized in that, In step (1), the ultrasonic treatment includes: ultrasonication with 800-1000W power for 5-10 minutes, followed by ultrasonication with 300-500W power for 20-30 minutes; the slurry temperature is controlled to be ≤40℃ during the ultrasonic treatment; in step (2), the deslurry treatment temperature is 350-450℃ and the time is 0.5-5 minutes; the impregnation time is 25-30 seconds; and the drying temperature is 140-180℃.

5. The method for preparing the low-temperature resistant and impermeable carbon fiber reinforced composite material according to claim 1, characterized in that, In step (3), the temperature of hot pressing and impregnation is 250-260℃ and the pressure is 0.5-2MPa; the temperature of cooling and shaping is 10-20℃; in step (4), the temperature of hot pressing and impregnation is 310-320℃ and the pressure is 1-3MPa; the temperature of cooling and shaping is 10-20℃.

6. The method for preparing the low-temperature resistant and impermeable carbon fiber reinforced composite material according to claim 1, characterized in that, In step (5), the curing conditions are as follows: the temperature is increased from room temperature to 300-310℃ at a rate of 8-10℃ / min, and then maintained at 0.5-1MPa, 4-5MPa and 2-3MPa for 5-10min respectively, and then reduced to room temperature.

7. The method for preparing the low-temperature resistant and impermeable carbon fiber reinforced composite material according to claim 1, characterized in that, In step (5), the thickness of the carbon fiber reinforced polychlorotrifluoroethylene prepreg tape is 0.2-0.5 mm, and the thickness of the carbon fiber reinforced polyethersulfone / polyphenylene sulfide resin prepreg tape is 1.0-1.5 mm.

8. A low-temperature resistant and leak-proof carbon fiber reinforced composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

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