High-density anti-seepage carbon fiber composite material for ultralow-temperature high-strain environment and preparation method thereof

Abstract

The invention belongs to the technical field of carbon fiber composite materials, and particularly relates to a high-density anti-seepage carbon fiber composite material for an ultralow-temperature high-strain environment and a preparation method thereof. The preparation method of the composite material comprises the following steps: adding peroxide, triallyl isocyanurate and a compatilizer into fluororesin, uniformly mixing, dispersing in a mixed solvent, coating to form a film, and drying to obtain fluororesin prepreg; evaporating Al2O3 on one surface of the fluororesin prepreg to obtain the fluororesin prepreg deposited with Al2O3; the Al2O3 layer is attached to the fluororesin prepreg, and the Al2O3 layer is clamped between the two layers of fluororesin prepreg; forming a fluororesin / Al2O3 / fluororesin sandwich anti-seepage unit; the treated carbon fiber prepreg is laid on the outer side of the anti-seepage unit; and carrying out hot-pressing curing and cryogenic-rebound densification treatment to obtain the composite material. The composite material disclosed by the invention can still maintain good ultra-low permeability, stripping resistance and crack resistance in an ultralow-temperature and high-strain environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of resin-based carbon fiber composite materials, and particularly relates to a high-density anti-permeation carbon fiber composite material for an ultralow-temperature high-strain environment and a preparation method thereof. BACKGROUND

[0002] Liquid hydrogen storage systems are the key core of promoting hydrogen energy utilization, especially in the fields of aerospace, heavy traffic, etc. One of the ultimate challenges it faces is mainly that the liquid hydrogen molecule has a small radius and strong diffusivity. In the deep cryogenic environment, the storage container material not only withstands the extreme low-temperature embrittlement test, but also continuously experiences severe low-temperature-thermal cycling and periodic high hoop strain and bending strain due to the internal liquid hydrogen filling, emptying and pressure fluctuation. The superimposition of low-temperature-thermal cycling and high strain easily induces microcracks, interlaminar cracks and through permeation channels in conventional resin-based composite materials, resulting in leakage failure in the case of sufficient strength margin.

[0003] Although the existing metal liner and all-metal scheme can reduce leakage, they have high quality, prominent welding and fatigue problems, high cost and manufacturing complexity. In addition, if a single polymer is used to prepare the inner liner, the inner liner strength and interface compatibility are insufficient, efficient co-curing with the load-bearing layer is difficult, and the overall performance of the composite material cannot be improved in the ultralow-temperature high-strain environment.

[0004] Therefore, there is an urgent need for an integrated composite material structure that can maintain ultralow leakage and interface stability under ultralow-temperature and high hoop strain / bending conditions, and can be compatible with existing AFP / ATL, autoclave or VARI engineering equipment to achieve batch manufacturing. SUMMARY

[0005] One of the purposes of the present application is to provide a preparation method of a high-density anti-permeation carbon fiber composite material for an ultralow-temperature high-strain environment. The present application proposes a multi-scale architecture composed of a "fluororesin / Al2O3 / fluororesin" sandwich anti-permeation unit and a high-toughness load-bearing layer (carbon fiber prepreg). An integrated process of synchronous vulcanization-curing is adopted to simultaneously complete the vulcanization crosslinking and curing-densification of the fluororesin prepreg and the carbon fiber prepreg in the same molding cycle, to form a dense crosslinked phase and a gradient transition in situ at the interface, and to realize low permeation, interface stability and high strain adaptation under liquid hydrogen working conditions by cooperating with deep cryogenic-rebound densification post-processing.

[0006] To achieve the above-mentioned purposes, the present application adopts the following technical solutions: A preparation method of a high-density anti-permeation carbon fiber composite material for an ultralow-temperature high-strain environment, comprising the following steps: (1) Preparation of fluororesin prepreg: adding peroxide, triallyl isocyanurate and compatibilizer into fluororesin, mixing uniformly, dispersing in mixed solvent, coating into film, drying to obtain fluororesin prepreg; The peroxide, triallyl isocyanurate (TAIC) and compatibilizer are introduced into the fluororesin prepreg, and the synergistic optimization of molecular and macroscopic properties can be achieved through chemical crosslinking and interface regulation. The peroxide generates free radicals during heating, which initiates the crosslinking reaction of fluororesin molecular chain and constructs a dense three-dimensional network structure. TAIC, as a multifunctional crosslinking agent, its isocyanuric acid ring structure endows the resin with high rigidity and low temperature toughness, improving the dimensional stability and anti-brittle ability of the system. The compatibilizer improves the polarity matching and chemical bonding of the fluororesin and the reinforcing fiber interface, significantly improves the interface wettability and adhesion strength. Under the synergistic action of the three, the resin system forms a flexible and adjustable polarity crosslinked network, which significantly enhances the anti-permeation, crack resistance and interface stability of the composite material in deep low temperature and high strain environment, providing high reliability matrix support for the composite material serving in liquid oxygen environment.

[0007] (2) Depositing Al2O3 on one side of the fluororesin prepreg obtained in step (1) to obtain fluororesin prepreg with deposited Al2O3; (3) Laminating the fluororesin prepreg with deposited Al2O3 obtained in step (2) and the fluororesin prepreg obtained in step (1) to sandwich the Al2O3 layer between the two layers of fluororesin prepreg; hot pressing to form a fluororesin / Al2O3 / fluororesin sandwich anti-permeation unit; (4) Plasma or gas phase fluorination treatment of carbon fiber prepreg to obtain treated carbon fiber prepreg; (5) Laying the treated carbon fiber prepreg obtained in step (4) on the fluororesin / Al2O3 / fluororesin sandwich anti-permeation unit obtained in step (3); hot pressing and curing to obtain a molded part; (6) Heat preservation treatment of the molded part of step (5) to obtain.

[0008] The fluororesin / Al2O3 / fluororesin sandwich anti-permeation unit realizes excellent anti-permeation and interface stability through the organic and inorganic multi-layer coupling structure. The outer fluororesin provides low permeability and chemical inertness, the intermediate Al2O3 layer forms a dense barrier layer and conducts heat, and the inner fluororesin enhances the compatibility with the carbon fiber matrix, forming an "rigid-flexible cooperative" interface system. The polar bonding between Al2O3 and fluororesin and the stress buffering of the flexible chain of fluororesin make the structure stable in liquid oxygen, deep cryogenic and thermal cycling environments. After being combined with the carbon fiber thermosetting prepreg, the sandwich unit can effectively block gas permeation and interface crack propagation, and improve the thermal stress distribution. The fluororesin / Al2O3 / fluororesin sandwich anti-permeation unit itself has weak load-bearing capacity and mainly bears the functions of anti-permeation and liquid oxygen compatibility; while the carbon fiber thermosetting prepreg has excellent mechanical properties, but has the problem of insufficient anti-permeation performance. After being combined, the sandwich unit constructs a dense multi-layer barrier system, effectively preventing liquid oxygen and low-temperature medium from permeating; the carbon fiber prepreg layer provides high strength and high modulus support to ensure the load-bearing and stability of the overall structure. Through interface matching and thermal force coupling optimization, the composite system realizes the functional complementation of the anti-permeation layer and the load-bearing layer, significantly improves the liquid oxygen compatibility, thermal stability and cyclic fatigue life of the material, and constructs an integrated high-reliability composite system with anti-permeation, liquid oxygen compatibility and high load-bearing performance.

[0009] Further, in step (1), the mass ratio of the fluororesin, peroxide, triallyl isocyanurate, compatibility agent, and mixed solvent is 100: (0.5-1): 3: (1-5): 100.

[0010] Further, in step (1), the temperature of the drying is 80-140°C, and the drying is performed until the residual solvent is ≤1 wt%.

[0011] Further, in step (1), the fluororesin is a vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer, the peroxide is vulcanizing agent bis 25; the compatibility agent is glycidyl methacrylate grafted vinylidene fluoride; and the mixed solvent is prepared by mixing acetone and ethyl acetate in a mass ratio of (3-1): 1.

[0012] Further, in step (1), the thickness of the fluororesin prepreg is 80-150 μm; in step (2), the thickness of the deposited Al2O3 is 5-20 μm; and in step (5), the thickness of the formed piece is 1.5-2.5 mm.

[0013] Further, in step (2), during the deposition, the temperature of the fluororesin prepreg is 80-120°C, and the deposition rate is 0.05-0.5 μm / min.

[0014] Further, in step (3), the hot-pressing condition is: 70-120°C, 0.1-0.3 MPa, 5-15 min.

[0015] Further, in step (4), the carbon fiber prepreg is a carbon fiber reinforced thermosetting prepreg.

[0016] Further, in step (5), the hot-pressing curing condition is: 0.5-0.8 MPa, 180-200°C, 1-2 h, then heated to 190-220°C, and continued to be treated at this temperature for 1-2 h.

[0017] Further, in step (6), the specific condition of the heat preservation treatment is: -196°C~25°C cycle 3-5 times, the heating rate is 10-15°C / min, the cooling rate is 10-15°C / min, 0.2-0.5 MPa, 40-90°C, 30-90 min each time.

[0018] In step (5) of the application, the purpose of laying the carbon fiber prepreg on the fluororesin / Al2O3 / fluororesin sandwich impermeable unit is to bear the load. The heat preservation treatment (deep cooling-rebound densification treatment) in step (6): the deep cooling treatment is mainly to release the residual stress in the composite material; the purpose of densification is to compress the composite material to reduce the porosity.

[0019] The second purpose of the application is to provide a high-dense impermeable carbon fiber composite material for ultra-low temperature and high-strain environment.

[0020] The high-dense impermeable carbon fiber composite material for ultra-low temperature and high-strain environment is prepared by the above preparation method.

[0021] Further, the composite material can be used for storing any one of liquid oxygen, liquid hydrogen, liquid natural gas, liquid petroleum gas and liquid nitrogen; when applied, the fluororesin / Al2O3 / fluororesin sandwich impermeable unit directly contacts the storage medium on the side, and the thermosetting carbon fiber prepreg bearing layer is on the outside, so as to form a rigid transition structure with rigid outside and soft inside.

[0022] Compared with the prior art, the application has the following beneficial effects: 1. The present application provides a kind of high-density impermeable carbon fiber composite for ultra-low temperature high strain environment, which is a high-performance composite material specially designed for ultra-low temperature application scenarios such as liquid hydrogen storage, effectively replacing the epoxy / composite or metal lining material used in traditional hydrogen storage tank, with the advantages of lightweight, high strength, one-piece molding, etc. The present application realizes ultra-low permeability, anti-peeling and anti-cracking under low temperature and high strain through the synergistic effect of "fluororesin / Al2O3 / fluororesin" sandwich unit and gradient compatibility, deep cooling-rebound densification, especially suitable for the storage of liquid hydrogen, liquid oxygen and other media. Specifically, (1) the sandwich unit of the present application has good buffering capacity, and the gradient compatible overlayer formed after laying-curing inhibits stress concentration; the resulting carbon fiber composite material still does not produce through cracks / peeling under ultra-low temperature high strain environment. (2) The carbon fiber composite material of the present application has good high strain adaptability: the near inner surface ± 45 ° oriented layer and the flexible fluororesin interlayer cooperate to maintain ultra-low permeability and structural integrity under > 8000 με strain.

[0023] 2. The present application also provides a preparation method of high-density impermeable carbon fiber composite for ultra-low temperature high strain environment, which is strong in operability and has significant advantages in process compatibility and long-term reliability, which helps to realize batch manufacturing; It can be compatible with existing AFP / ATL, autoclave or VARI engineering equipment, avoiding the huge cost of developing a new production line, providing technical support for realizing large-scale, low-cost and high-quality production of liquid hydrogen storage tank. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure of the present specification. The present application can also be implemented or applied by means of other different specific embodiments, and various modifications or changes can be made to the details in the specification without departing from the spirit of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art.

[0025] The fluororesin of the present application is a terpolymer of vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene, purchased from Shanghai Yingqu Chemical Technology Co., Ltd., model TFE101; The peroxide of the present application is vulcanizing agent double 25, purchased from Hubei Tianmen Hengfa Chemical Technology Co., Ltd., purity 93%; The triallyl isocyanurate of the present application is purchased from Shanghai Tuorui New Material Technology Co., Ltd., with a purity of 99%; The compatilizer of the present application is glycidyl methacrylate grafted polyvinylidene fluoride (GMA-g-PVDF) with a grafting rate of 30%, which is purchased from Dongguan Kadar Plastic Raw Material Co., Ltd. The carbon fiber prepreg of the present application is a carbon fiber reinforced thermosetting prepreg, which is purchased from Jiangsu Hengshen Co., Ltd. and the model is CJ003-12KHF60C.

[0026] Example 1 A preparation method of a high-dense anti-permeation carbon fiber composite material for an ultralow-temperature high-strain environment, comprising the following steps: (1) Preparation of fluororesin prepreg: fluororesin is used as the matrix, and peroxide (vulcanizing agent double 25), triallyl isocyanurate (TAIC), and compatilizer (GMA-g-PVDF) are added thereto and uniformly mixed, and then dispersed in a mixed solvent of acetone / ethyl acetate (the mass ratio of the two is 1:1), wherein the mass ratio of fluororesin, peroxide, triallyl isocyanurate, compatilizer, and mixed solvent is 100:0.8:3:3:100; then coating and blade coating to form a wet film, and drying at 100°C until the residual solvent is ≤1wt%, to obtain a fluororesin prepreg with a thickness of 100 μm; (2) Evaporation deposition is performed on one side of the fluororesin prepreg obtained in step (1) to deposit a dense layer of aluminum oxide (Al2O3); wherein the temperature of the fluororesin prepreg substrate is 100°C, the deposition rate is 0.1 μm / min, and the deposition thickness is 10 μm; to obtain a fluororesin prepreg with deposited Al2O3; (3) The fluororesin prepreg with deposited Al2O3 obtained in step (2) is laminated with the fluororesin prepreg obtained in step (1) face to face, so that the Al2O3 layer is sandwiched between the two layers of fluororesin prepreg; hot pressing lamination is performed at 100°C and 0.2 MPa for 15 min to form a fluororesin / Al2O3 / fluororesin sandwich anti-permeation unit; (4) Plasma treatment is performed on the carbon fiber reinforced thermosetting prepreg, specifically: using a gas mixture of argon and oxygen at a volume ratio of 2:1, and simultaneously introducing a solvent vapor of methanol and water at a volume ratio of 10:1, at a power of 180W, and treating at room temperature for 2 min to obtain a treated carbon fiber prepreg (as a load-bearing layer); (5) Laminating and synchronous vulcanization-curing: laying the treated carbon fiber prepreg obtained in step (4) on the fluororesin / Al2O3 / fluororesin sandwich impermeable unit obtained in step (3), and the laying mode is [±45 / 0 / 90]2s (first, a laying containing +45°, -45°, 0° and 90° directions is carried out; then, the laying sequence is repeated once to form an 8-layer sequence; finally, the 8-layer sequence is symmetrically laid to obtain a composite laminated plate having a total of 16 layers and being symmetrical about the middle plane); the vulcanization crosslinking of the fluororesin and the curing / densification of the load-bearing layer are simultaneously completed in the same hot-pressing / autoclave molding process, the interface in-situ crosslinking and gradient transition are realized, secondary heating and interface weakening are avoided, and the autoclave molding conditions are 0.6 MPa, 180℃ for 2 h, then the temperature is increased to 200℃, and the molding is continued at this temperature for 2 h to obtain a molded part having a thickness of 1.8 mm; (6) Cryogenic-rebound densification treatment: the molded part is cycled 5 times at -196℃ to 25℃, the temperature increasing rate is 10℃ / min, and the temperature decreasing rate is 10℃ / min; and the free volume is rearranged and the sub-micron connected pores are compacted under 50℃ and 0.5 MPa external pressure for 90 min.

[0027] The embodiment also provides a high-density impermeable carbon fiber composite material for an ultralow-temperature high-strain environment, which is prepared by the above preparation method. The high-density impermeable carbon fiber composite material obtained by the method can be used for storing liquid hydrogen. In application, the fluororesin / Al2O3 / fluororesin sandwich impermeable unit directly contacts the storage medium on the side, and the thermosetting carbon fiber prepreg load-bearing layer is on the outside to form a stiffness transition structure with outer rigidity and inner flexibility.

[0028] Embodiment 2 A preparation method of a high-density impermeable carbon fiber composite material for an ultralow-temperature high-strain environment, comprising the following steps: (1) Preparation of fluororesin prepreg: fluororesin is used as a matrix, and peroxide (vulcanizing agent bis 25), triallyl isocyanurate (TAIC) and a compatibilizer (GMA-g-PVDF) are added and uniformly mixed, and then dispersed in a mixed solvent of acetone / ethyl acetate (the mass ratio of the two is 3:1), wherein the mass ratio of the fluororesin, the peroxide, the triallyl isocyanurate, the compatibilizer and the mixed solvent is 100:0.5:3:1:100; then coating and blade film forming are carried out to obtain a wet film, and the wet film is dried at 100℃ until the residual solvent is ≤1wt%, to obtain a fluororesin prepreg having a thickness of 100 μm; (2) The fluororesin prepreg obtained in step (1) is subjected to evaporation and deposition on one side to deposit a dense layer of aluminum oxide (Al2O3); the fluororesin prepreg substrate temperature is 80°C, the deposition rate is 0.3 μm / min, and the deposition thickness is 8 μm; a fluororesin prepreg with deposited Al2O3 is obtained; (3) The fluororesin prepreg with deposited Al2O3 obtained in step (2) is laminated with the fluororesin prepreg obtained in step (1) face to face, with the Al2O3 layer sandwiched between the two layers of fluororesin prepreg; hot pressing lamination is performed at 70°C and 0.3 MPa for 15 min to form a fluororesin / Al2O3 / fluororesin sandwich impermeable unit; (4) The carbon fiber reinforced thermosetting prepreg is subjected to plasma treatment, specifically: using a gas mixture of argon and oxygen at a volume ratio of 2:1, while introducing a solvent vapor of methanol and water at a volume ratio of 10:1, at a power of 180W, room temperature treatment for 2 min, to obtain a treated carbon fiber prepreg (as a load-bearing layer); (5) Lamination and simultaneous vulcanization-curing: the treated carbon fiber prepreg obtained in step (4) is laid on the fluororesin / Al2O3 / fluororesin sandwich impermeable unit obtained in step (3), and the laying mode is [±45 / 0 / 90]2s; the vulcanization and crosslinking of the fluororesin and the curing / densification of the load-bearing layer are simultaneously completed in the same hot pressing / autoclave molding process, realizing in-situ crosslinking and gradient transition at the interface, avoiding secondary heating and interface weakening, and the autoclave molding conditions are: 0.5 MPa, 200°C for 1 h, then heated to 220°C and continued to treat for 1 h, to obtain a molded part with a thickness of 1.9 mm; (6) Cryogenic-rebound densification treatment: the molded part is cycled 5 times at -196°C~25°C, with a heating rate of 15°C / min and a cooling rate of 15°C / min; and heat preservation at 60°C and 0.2 MPa external pressure for 90 min, to rearrange the free volume and compact the sub-micron connected pores.

[0029] The embodiment also provides a high-density impermeable carbon fiber composite material for use in an ultralow-temperature high-strain environment, which is prepared by the above preparation method. The high-density impermeable carbon fiber composite material obtained by the present application can be used for storing liquid hydrogen. In application, the fluororesin / Al2O3 / fluororesin sandwich impermeable unit directly contacts the storage medium on the side, and the thermosetting carbon fiber prepreg load-bearing layer is on the outside, to form a stiffness transition structure with rigid outside and soft inside.

[0030] Example 3 A preparation method of a high-density impermeable carbon fiber composite material for use in an ultralow-temperature high-strain environment, comprising the following steps: (1) Preparation of fluororesin prepreg: fluororesin as matrix, adding peroxide (vulcanizing agent bis 25), triallyl isocyanurate (TAIC), and compatibilizer (GMA-g-PVDF) uniformly, dispersing in a mixed solvent of acetone / ethyl acetate (mass ratio of 2:1), the mass ratio of fluororesin, peroxide, triallyl isocyanurate, compatibilizer, and mixed solvent is 100:1:3:5:100; then coating and film drawing to form a wet film, drying at 100°C until the residual solvent is ≤1wt%, obtaining fluororesin prepreg with a thickness of 100 μm; (2) Evaporating on one side of the fluororesin prepreg obtained in step (1) to deposit a dense layer of aluminum oxide (Al2O3); the fluororesin prepreg substrate temperature is 120°C, the deposition rate is 0.5 μm / min, and the deposition thickness is 12 μm; obtaining fluororesin prepreg with deposited Al2O3; (3) Laminating the fluororesin prepreg with deposited Al2O3 obtained in step (2) with the fluororesin prepreg obtained in step (1) face to face, with the Al2O3 layer sandwiched between the two layers of fluororesin prepreg; hot pressing at 120°C and 0.1 MPa for 10 min to form a fluororesin / Al2O3 / fluororesin sandwich impermeable unit; (4) Plasma treatment of carbon fiber reinforced thermosetting prepreg: using a gas mixture of argon and oxygen at a volume ratio of 2:1, and introducing a solvent vapor of methanol and water at a volume ratio of 10:1, at a power of 180W, treating at room temperature for 2 min to obtain the treated carbon fiber prepreg (as the load-bearing layer); (5) Laminating and simultaneous vulcanization-curing: laying the treated carbon fiber prepreg on the fluororesin / Al2O3 / fluororesin sandwich impermeable unit obtained in step (3), the laying mode is [±45 / 0 / 90]2s; simultaneously completing the vulcanization and crosslinking of fluororesin and the curing / densification of the load-bearing layer in the same hot pressing / autoclave molding process, realizing in-situ crosslinking and gradient transition at the interface, avoiding secondary heating and interface weakening, the autoclave molding conditions are 0.8 MPa, 190°C for 1.5 h, then increasing the temperature to 210°C and continuing to treat at this temperature for 1.5 h, obtaining a molded part with a thickness of 1.7 mm; (6) Cryogenic-rebound densification treatment: cycling the molded part at -196°C~25°C for 5 times, the heating rate is 12°C / min and the cooling rate is 15°C / min; holding at 40°C and 0.4 MPa external pressure for 90 min to rearrange the free volume and compact the submicron interconnected pores.

[0031] The embodiment also provides a high-density anti-permeation carbon fiber composite material for an ultralow-temperature high-strain environment, which is prepared by the preparation method.

[0032] Comparative Example 1 The difference between the present comparative example 1 and the embodiment 1 is that the triallyl isocyanurate is omitted in the preparation of the fluororesin prepreg in step (1), and the other conditions are the same as those in the embodiment 1.

[0033] Comparative Example 2 The difference between the present comparative example 2 and the embodiment 1 is that the Al2O3 and the fluororesin are directly mixed, that is, steps (2) and (3) are omitted, and step (1) is adjusted as follows: the fluororesin is used as a matrix, and the Al2O3, the peroxide (vulcanizing agent Bis 25), the triallyl isocyanurate (TAIC) and the compatilizer (GMA-g-PVDF) are added and uniformly mixed, and then the mixture is dispersed in a mixed solvent of acetone / ethyl acetate (the mass ratio of the two is 1:1), and then a wet film is formed by coating and film scraping, and the wet film is dried at 100°C until the residual solvent is less than or equal to 1 wt%, to obtain a fluororesin prepreg with a thickness of 100 μm; the fluororesin prepreg prepared above is used to replace the sandwich anti-permeation unit in step (5).

[0034] Comparative Example 3 A preparation method of a high-density anti-permeation carbon fiber composite material for an ultralow-temperature high-strain environment, comprising the following steps: (1) Preparation of a fluororesin prepreg: the fluororesin is used as a matrix, and the peroxide (vulcanizing agent Bis 25), the triallyl isocyanurate (TAIC) and the compatilizer (GMA-g-PVDF) are added and uniformly mixed, and then the mixture is dispersed in a mixed solvent of acetone / ethyl acetate (the mass ratio of the two is 1:1), and then a wet film is formed by coating and film scraping, and the wet film is dried at 100°C until the residual solvent is less than or equal to 1 wt%, to obtain a fluororesin prepreg with a thickness of 100 μm; the fluororesin prepreg is treated at 0.6 MPa and 180°C for 2 h, and then the temperature is increased to 200°C and the treatment is continued at this temperature for 2 h, to obtain a vulcanized fluororesin prepreg; (2) Evaporation deposition is performed on one side of the vulcanized fluororesin prepreg obtained in step (1) to deposit a dense layer of aluminum oxide (Al2O3); wherein the temperature of the fluororesin prepreg substrate is 100°C, the deposition rate is 0.1 μm / min, and the deposition thickness is 10 μm; to obtain a fluororesin prepreg with deposited Al2O3; (3) The Al2O3-deposited fluororesin prepreg obtained in step (2) is laminated with the vulcanized fluororesin prepreg obtained in step (1) face to face, with the Al2O3 layer sandwiched between the two layers of fluororesin prepreg; hot pressing lamination is performed at 100°C and 0.2 MPa for 15 min to form a fluororesin / Al2O3 / fluororesin sandwich impermeable unit; (4) Plasma treatment is performed on the carbon fiber-reinforced thermosetting prepreg, specifically: using a gas mixture of argon and oxygen at a volume ratio of 2:1, while introducing solvent vapor of a mixture of methanol and water at a volume ratio of 10:1, at a power of 180W, room temperature treatment for 2 min, to obtain the treated carbon fiber prepreg (as the load-bearing layer); (5) The treated carbon fiber prepreg obtained in step (4) is laid on the fluororesin / Al2O3 / fluororesin sandwich impermeable unit obtained in step (3), with the layup mode being [±45 / 0 / 90]2s; treatment is performed at 0.6 MPa and 180°C for 2 h, then the temperature is raised to 200°C and treatment is continued at this temperature for 2 h, to obtain a molded part with a thickness of 2.0 mm; (6) Cryogenic-rebound densification treatment: the molded part is cycled 5 times at -196°C to 25°C, with a heating rate of 10°C / min and a cooling rate of 10°C / min; heat preservation is performed at 50°C and 0.5 MPa external pressure for 90 min, to rearrange the free volume and compact the sub-micron connected pores, and the product is obtained.

[0035] Comparative Example 4 The difference between this comparative example 4 and example 1 is that step (6) is omitted.

[0036] Test Example 1 The properties of the composite materials obtained in examples 1-3 and comparative examples 1-4 of the present application are tested: leakage is detected by helium mass spectrometry, with detection conditions being: liquid nitrogen environment, 3 MPa pressure; peel resistance (interlaminar shear strength) is characterized by ASTM 2344; the results are shown in Table 1 below. After the material is cycled 20 times at -196°C to 150°C and 8000 me, it is tested again, and the results are shown in Table 2 below, with crack resistance being observed by microscope whether cracks are generated and whether through cracks are formed.

[0037] Table 1 Test results of the properties of the composite material before cycling Table 2 Test results of the properties of the composite material after 20 cycles As can be seen from Tables 1 and 2, the high-density impermeable carbon fiber composite material obtained in Examples 1-3 of the present application has good permeation resistance, anti-stripping performance, and can still maintain good anti-permeation performance, interlaminar shear strength, and structural integrity of the surface of the carbon fiber composite material, and prevent the carbon fiber composite material from cracking after 20 cycles at -196℃ to 150℃ and 8000 me (under the environment of ultra-low temperature and high strain). The permeation rate and interlaminar shear strength of Comparative Examples 1-4 under the environment of ultra-low temperature and high strain are not as good as Example 1. This may be due to the combined effect of the fluororesin / Al2O3 / fluororesin sandwich unit, the gradient compatible transition layer, and the cryogenic-rebound densification treatment of the composite material obtained in the present application, thereby realizing the combination of ultra-low permeability, anti-stripping and anti-cracking performance of the composite material under the environment of low temperature and high strain.

[0038] The above embodiments are only preferred embodiments of the present application, and cannot be used to limit the scope of protection of the present application. Any non-essential changes and substitutions made by those skilled in the art on the basis of the present application shall fall within the scope of protection of the present application.

Claims

1. A method for the production of high-density impermeable carbon fiber composites for ultra-low temperature high strain environments, characterized by, It comprises the following steps: (1) Preparation of fluororesin prepreg: adding peroxide, triallyl isocyanurate and compatibilizer into fluororesin, mixing uniformly, dispersing in mixed solvent, coating into film, drying to obtain fluororesin prepreg; (2) Depositing Al2O3 on one side of fluororesin prepreg obtained in step (1) to obtain fluororesin prepreg with deposited Al2O3; (3) Bonding fluororesin prepreg with deposited Al2O3 obtained in step (2) and fluororesin prepreg obtained in step (1) to sandwich Al2O3 layer between the two layers of fluororesin prepreg; hot pressing to form fluororesin / Al2O3 / fluororesin sandwich impermeable unit; (4) Treating carbon fiber prepreg by plasma or gas phase fluorination to obtain treated carbon fiber prepreg; (5) Laying treated carbon fiber prepreg obtained in step (4) on fluororesin / Al2O3 / fluororesin sandwich impermeable unit obtained in step (3); hot pressing and curing to obtain shaped piece; (6) Heat treating shaped piece of step (5) to obtain the product.

2. The method for preparing high-density, impermeable carbon fiber composite material for ultra-low temperature, high-strain environments according to claim 1, characterized in that, In step (1), the mass ratio of fluororesin, peroxide, triallyl isocyanurate, compatibilizer and mixed solvent is 100: (0.5-1): 3: (1-5):

100.

3. The method for preparing high-density, impermeable carbon fiber composite material for ultra-low temperature, high-strain environments according to claim 1, characterized in that, In step (1), the fluororesin is vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene terpolymer, the peroxide is vulcanizing agent bis 25, the compatibilizer is glycidyl methacrylate grafted vinylidene fluoride, and the mixed solvent is prepared by mixing acetone and ethyl acetate in a mass ratio of (3-1):

1.

4. The method for preparing high-density, impermeable carbon fiber composite material for ultra-low temperature, high-strain environments according to claim 1, characterized in that, In step (1), the thickness of fluororesin prepreg is 80-150 μm; in step (2), the thickness of deposited Al2O3 is 5-20 μm; in step (5), the thickness of shaped piece is 1.5-2.5 mm.

5. The method for preparing high-density, impermeable carbon fiber composite material for ultra-low temperature, high-strain environments according to claim 1, characterized in that, In step (2), during deposition, the temperature of fluororesin prepreg is 80-120°C, and the deposition rate is 0.05-0.5 μm / min.

6. The method for preparing high-density, impermeable carbon fiber composite material for ultra-low temperature, high-strain environments according to claim 1, characterized in that, In step (3), the hot pressing conditions are: treating at 70-120°C, 0.1-0.3 MPa for 5-15 min.

7. The method for preparing high-density, impermeable carbon fiber composite material for ultra-low temperature, high-strain environments according to claim 1, characterized in that, In step (4), the carbon fiber prepreg is carbon fiber reinforced thermosetting prepreg.

8. The method for preparing high-density, impermeable carbon fiber composite material for ultra-low temperature, high-strain environments according to claim 1, characterized in that, In step (5), the hot pressing and curing conditions are: treating at 0.5-0.8 MPa, 180-200°C for 1-2 h, then increasing the temperature to 190-220°C and continuing to treat at this temperature for 1-2 h.

9. The method for preparing high-density, impermeable carbon fiber composite material for ultra-low temperature, high-strain environments according to claim 1, characterized in that, In step (6), the specific conditions of heat treatment are: cycling at -196°C~25°C for 3-5 times, the heating rate is 10-15°C / min, the cooling rate is 10-15°C / min; each time at 0.2-0.5 MPa, 40-90°C for 30-90 min.

10. A highly dense impermeable carbon fiber composite material for ultra-low temperature and high strain environment, characterized by, The preparation method of any one of claims 1-9 is used.

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