Process for machining flanged composite pipe without liner for liquid hydrogen environment

Abstract

The application provides a processing technology of a flange-equipped inner-liner-free composite pipeline for a liquid hydrogen environment, and relates to the technical field of liquid hydrogen transportation. The processing technology comprises the following steps: S1: after carbon fiber surface felt is impregnated with a liquid hydrogen resin system, heating pre-curing is performed, the carbon fiber surface felt is laid on the surface of a core mold, and is rolled into a cylinder to form a permeation prevention layer; S2: a fiber woven cloth impregnated with the liquid hydrogen resin system is laid by adopting a ring winding mode to form a transition layer; S3: a strength layer is formed on the surface of the transition layer by adopting a ring carbon fiber laying and winding combined mode, and carbon fibers are laid between the strength layers to form a flange layer; and S4: high-temperature curing is performed on the pipeline. The liquid hydrogen environment flange-equipped inner-liner-free composite pipeline prepared by the application has good mechanical properties, can avoid the generation of micro-cracks under the joint action of a high temperature difference and a high pressure difference, and can prevent the occurrence of liquid hydrogen permeation during use.

Description

Technical Field

[0001] This invention relates to the field of liquid hydrogen transportation technology, and more specifically, to a processing technology for flanged, unlined composite material pipelines for use in liquid hydrogen environments. Background Technology

[0002] Hydrogen is a highly flammable gas, colorless, transparent, odorless, tasteless, and sparingly soluble in water. It is the least dense gas known in the world, allowing it to penetrate the crystal lattice of many metals, causing "hydrogen embrittlement." This necessitates the use of special materials and more complex designs for hydrogen storage tanks and pipelines. Currently, in actual production and transportation, the pipelines used for transporting hydrogen often lack proper sealing or are not designed with corresponding leak-proof structures. This leads to hydrogen leaks that cannot be detected and repaired in a timely manner, increasing the likelihood of hydrogen embrittlement and resulting in more localized leaks. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a processing technology for flanged, unlined composite material pipelines for liquid hydrogen environments, resolving the issue of hydrogen leakage due to permeation during liquid hydrogen transportation. The invention provides an unlined composite material pipeline for liquid hydrogen environments, which utilizes winding and impregnation processes to form an anti-seepage layer, a transition layer, a strength layer, and a flange layer, respectively. Pre-curing with heat allows the liquid hydrogen resin system to fully fuse with the carbon fiber surface felt. Finally, high-temperature curing further ensures the anti-seepage layer, transition layer, strength layer, and flange layer are fully fused and interwoven, forming an organic whole. A flanged, unlined composite material pipeline was prepared, forming a series of protective layers. During liquid hydrogen transportation, these layers not only prevent hydrogen permeation but also complement the impermeable layers, further enhancing the impermeability. The strength layer acts as a bridging element, preventing direct contact between the strength layer and the impermeable layer, which could lead to delamination and hydrogen leakage over time. The strength layer envelops and reinforces the transition and impermeable layers, possessing tensile and burst-resistant properties matching those of the impermeable and transition layers. This ensures that the impermeable, transition, strength, and flange layers have matching toughness, preventing delamination and thus preventing hydrogen leakage during long-term liquid hydrogen transportation.

[0004] This invention provides a processing method for flanged, unlined composite material pipelines for use in liquid hydrogen environments, the processing method comprising the following steps:

[0005] S1: After impregnating the carbon fiber surface felt with liquid hydrogen resin system, it is pre-cured by heating at 50℃-90℃. The pre-cured carbon fiber surface felt is laid flat on the surface of the mandrel and rolled into a cylinder as the mandrel rotates to form a waterproof layer.

[0006] S2: A fiber woven fabric impregnated with a liquid hydrogen resin system is laid in a circumferential winding manner on the surface of the impermeable layer to form a transition layer.

[0007] S3: A strength layer is formed on the surface of the transition layer by a combination of circumferential carbon fiber lay-up and winding, and carbon fibers are laid between the strength layers to form a flange layer.

[0008] S4: The pipeline is cured at 100-150℃ using a vacuum method, and the core mold is removed to form a flanged, unlined composite material pipeline for use in a liquid hydrogen environment.

[0009] The liquid hydrogen resin system, by mass parts, includes 100 parts of bisphenol F epoxy resin and bisphenol A epoxy resin, 20-30 parts of epoxy reactive diluent, 10-30 parts of toughening agent, and 20-50 parts of curing agent. The mass ratio of bisphenol F epoxy resin to bisphenol A epoxy resin is 50-70:30-50.

[0010] Compared with the prior art, the present invention achieves at least one of the following beneficial effects:

[0011] (1) The processing technology of the flanged unlined composite material pipeline for liquid hydrogen environment of the present invention, through the cooperation and interaction of the anti-seepage layer, transition layer, strength layer and flange layer, forms a matching toughness and will not peel off, so that the pipeline can transport liquid hydrogen for a long time without hydrogen leakage.

[0012] (2) The liquid hydrogen resin system of the present invention is obtained by compounding bisphenol F epoxy resin, bisphenol A epoxy resin, epoxy reactive diluent, toughening agent and curing agent. It can ensure the mechanical properties of the resin system, improve the toughness of the resin system, reduce the generation of microcracks in the resin system under the combined action of high temperature difference and high pressure difference, and avoid the occurrence of liquid hydrogen permeation during use below -100℃.

[0013] (3) The present invention modifies the carbon fiber surface felt. The present invention uses concentrated nitric acid to perform surface oxidation modification on the carbon fiber surface felt to improve the surface roughness of the carbon fiber surface felt, so as to introduce a large amount of sodium molybdate on the surface of the carbon fiber surface felt, and obtain carbon fiber surface felt with sodium molybdate particles on the surface, thereby improving the hydrogen permeation barrier. At the same time, the modified carbon fiber surface felt has a stronger interaction with the liquid hydrogen resin system, stronger interfacial adhesion, and improved compatibility between the carbon fiber surface felt and the liquid hydrogen resin system.

[0014] (4) In this invention, ferric oxide-modified graphene oxide is added to bisphenol F epoxy resin and bisphenol A epoxy resin. Magnetic Fe3O4-modified graphene oxide is used to modify bisphenol F epoxy resin and bisphenol A epoxy resin respectively. Under the action of a magnetic field, the graphene oxide can be orderly dispersed in the resin without agglomeration. This can further improve the mechanical strength and toughness of bisphenol F epoxy resin and bisphenol A epoxy resin.

[0015] (5) The toughening agent of this invention is a core-shell particle; the outer shell material of the core-shell particle is polyvinyl butyral or polymethyl methacrylate; the core material is nano-alumina or nano-silica. The outer shell material has good compatibility with bisphenol F epoxy resin and bisphenol A epoxy resin, which can ensure the degree of crosslinking of epoxy resin, and at the same time help the core-shell particles to be uniformly dispersed in the resin, thereby improving the toughness of the resin system. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0017] Figure 1 An exemplary embodiment of the present invention is shown in the diagram of a flanged, unlined composite material piping structure for use in a liquid hydrogen environment.

[0018] Explanation of reference numerals in the attached figures:

[0019] 1-Impermeable layer; 2-Transition layer; 3-Strength layer; 4-Flange layer; 401-First limiting groove; 402-Second limiting groove; 403-Sealing groove. Detailed Implementation

[0020] To more clearly illustrate the overall concept of the present invention, a detailed description will be provided below with reference to the accompanying drawings and examples.

[0021] Numerous specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention may be practiced in other ways different from those described herein, and therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below. In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0022] In an exemplary embodiment of the present invention, the manufacturing process of a flanged, unlined composite material pipeline for a liquid hydrogen environment includes the following steps:

[0023] S1: After impregnating the carbon fiber surface felt with liquid hydrogen resin system, it is pre-cured by heating at 50℃-90℃. The pre-cured carbon fiber surface felt is laid flat on the surface of the mandrel and rolled into a cylinder as the mandrel rotates to form a waterproof layer.

[0024] S2: A fiber woven fabric impregnated with a liquid hydrogen resin system is laid in a circumferential winding manner on the surface of the impermeable layer to form a transition layer.

[0025] S3: A strength layer is formed on the surface of the transition layer by a combination of circumferential carbon fiber lay-up and winding, and carbon fibers are laid between the strength layers to form a flange layer.

[0026] S4: The pipeline is cured at 100-150℃ using a vacuum method, and the core mold is removed to form a flanged, unlined composite material pipeline for use in a liquid hydrogen environment.

[0027] The liquid hydrogen resin system, by mass parts, includes 100 parts of bisphenol F epoxy resin and bisphenol A epoxy resin, 20-30 parts of epoxy reactive diluent, 10-30 parts of toughening agent, and 20-50 parts of curing agent. The mass ratio of bisphenol F epoxy resin to bisphenol A epoxy resin is 50-70:30-50.

[0028] Optionally, the inner diameter of the pipeline is 400-500mm, the thickness of the seepage prevention layer is 2-5mm, the thickness of the transition layer is 1-3mm, and the thickness of the strength layer is 2-5mm.

[0029] Optionally, the carbon fiber surface felt in step S1 may be modified, and the modification process may include the following steps:

[0030] S10: Immerse the carbon fiber surface felt in an organic solvent and then dry it to obtain a clean carbon fiber surface felt. For example, the organic solvent is a mixed solution of ethanol, acetone, and tetrahydrofuran, wherein the ethanol, acetone, and tetrahydrofuran are mixed in a volume ratio of 1:1:1 to 1:3:3. This removes stains from the carbon fiber surface, laying the foundation for improving the bonding ability with the liquid hydrogen resin system.

[0031] S11: The clean carbon fiber surface felt is oxidized and etched in concentrated nitric acid. Then, the oxidized and etched carbon fiber surface felt is placed in a mixed solution of silane coupling agent and sodium molybdate to obtain a carbon fiber surface felt with sodium molybdate grains on its surface. For example, in step S11, the mass concentration of concentrated nitric acid is 30-60%, and the oxidation etching temperature is 50-90℃. During oxidation etching, by controlling the concentration and temperature of concentrated nitric acid, the excellent mechanical properties of the carbon fiber surface felt itself are not affected, ensuring the matching performance of subsequent protective layers. Simultaneously, the surface oxidation modification of the carbon fiber surface felt using concentrated nitric acid increases its surface roughness, introducing a large amount of sodium molybdate onto the surface, resulting in a carbon fiber surface felt coated with sodium molybdate particles. This improves its hydrogen permeation resistance. Furthermore, the modified carbon fiber surface felt has a stronger interaction with the liquid hydrogen resin system, resulting in stronger interfacial adhesion and improved compatibility between the carbon fiber surface felt and the liquid hydrogen resin system.

[0032] The mass ratio of silane coupling agent to sodium molybdate is 1:1-3. The silane coupling agent improves the uniformity of sodium molybdate bonding to the surface of the oxidized and etched carbon fiber surface mat. However, if the content of silane coupling agent is too high, it will result in a large amount of sodium molybdate on the surface of the carbon fiber surface mat, which will reduce the bonding strength between the carbon fiber surface mat and the liquid hydrogen resin system to some extent.

[0033] S12: The carbon fiber surface felt obtained in step S11 is placed in a vacuum drying oven for constant temperature drying to obtain a carbon fiber surface felt with sodium molybdate particles coated on the surface.

[0034] Optionally, the isothermal drying temperature in step S12 is 100-150℃. By performing isothermal drying within this temperature range, the bonding strength between the sodium molybdate particles and the carbon fiber surface felt can be further improved, laying the foundation for ensuring the bonding strength with the liquid hydrogen resin system in the future.

[0035] Optionally, bisphenol F epoxy resin and bisphenol A epoxy resin are modified respectively; the modification method is: adding iron oxide-modified graphene oxide to bisphenol F epoxy resin and bisphenol A epoxy resin respectively.

[0036] The amount of graphene oxide added was 2-5%. Magnetic Fe3O4-modified graphene oxide was used to modify bisphenol F epoxy resin and bisphenol A epoxy resin, respectively. Under the action of a magnetic field, graphene oxide could achieve orderly dispersion in the resin without agglomeration. This further improved the mechanical strength and toughness of bisphenol F epoxy resin and bisphenol A epoxy resin.

[0037] Optionally, the epoxy reactive diluent is one or more selected from alkyl glycidyl ethers, acrylates, acetates, and caprolactone. This invention, by adding a certain proportion of epoxy reactive diluent, can reduce the viscosity of materials during the reaction process while ensuring the crosslinking density of the resin, thereby improving the degree of reaction and dispersion of each substance.

[0038] Optionally, the alkyl group in the alkyl glycidyl ether is butyl, octyl, ethyl, or phenyl;

[0039] Optionally, the acrylate is methyl methacrylate, cyclohexane acrylate, glyceryl triacrylate, allyl acrylate, 1,6-hexanediol diacrylate, or vinyl acrylate;

[0040] Optionally, the acetate is vinyl acetate;

[0041] Optionally, the caprolactone is γ-caprolactone, δ-caprolactone, or ε-caprolactone.

[0042] Optionally, the toughening agent is a core-shell particle; the outer shell material of the core-shell particle is polyvinyl butyral or polymethyl methacrylate; the core material is nano-alumina or nano-silica. For example, the mass ratio of the outer shell material to the core material is 5-8:2-4. The outer shell material is a polymer with good compatibility with epoxy resin, and its addition will not significantly reduce the crosslinking density of the resin, and it helps to uniformly disperse the core-shell particles in the resin, solving the problem that the toughening effect is affected by the aggregation of bisphenol F epoxy resin and bisphenol A epoxy resin.

[0043] Optionally, the curing agent is a composite of aliphatic amine aromatic curing agent and polyether amine curing agent; for example, the aliphatic amine aromatic curing agent is diethyltoluenediamine or m-phenylenediamine. The curing agent can introduce flexible segments into the crosslinked network, improve the flexibility of the network chain molecules, and further enhance the toughness of the epoxy resin.

[0044] In an exemplary embodiment of the present invention, the main difference from the above embodiments lies in that the flange layer includes a first limiting groove, a second limiting groove, and a sealing groove, wherein the sealing groove is formed on the end face of the flange layer connection end. Further, the flange layer is disposed at one end of the pipeline. The first limiting groove can be threaded and is formed on the outer surface of the flange layer. The second limiting groove can be a recess, formed on the inner surface of the flange layer. During pipeline processing, the strength layer is snapped into the recess. The outer and inner surfaces of the flange layer are further fixed by the first and second limiting grooves. Through high-temperature curing, the anti-seepage layer, transition layer, strength layer, and flange layer are fully fused and interwoven to form an organic whole, improving the matching between the flange layer and the strength layer and preventing peeling. Therefore, hydrogen leakage will not occur during long-term transport of liquid hydrogen. The sealing groove can be a semi-circular annular groove. The semi-circular annular groove is used to install a circular sealing ring, which can achieve a tight connection and seal at the joint end face.

[0045] Optionally, an elastomer is embedded in the flange layer. The elastomer, by weight, comprises 80-90 parts of hydrogenated styrene-butadiene block copolymer, 10-20 parts of fluorosilicone rubber, 5-10 parts of polyurethane, and 4-7 parts of polyether diol. The elastomer is obtained by melt-mixing the hydrogenated styrene-butadiene block copolymer, fluorosilicone rubber, polyurethane, polyether diol, and vulcanizing agent. This elastomer exhibits good low-temperature resistance and a certain degree of shrinkage elasticity, which can further improve the sealing performance of the joint end face.

[0046] Example 1

[0047] Anti-seepage layer 1#

[0048] S10: Immerse the carbon fiber in a mixed solution of organic solvents ethanol, acetone and tetrahydrofuran in a volume ratio of 1:1:1, and then dry it to obtain a clean carbon fiber surface felt.

[0049] S11: The clean carbon fiber surface felt is placed in concentrated nitric acid with a mass concentration of 30-60% and oxidized and etched at 50°C. Then, the oxidized and etched carbon fiber surface felt is placed in a mixed solution of silane coupling agent and sodium molybdate, wherein the mass ratio of silane coupling agent to sodium molybdate is 1:1, to obtain a carbon fiber surface felt with sodium molybdate grains on the surface.

[0050] S12: Place the carbon fiber surface felt obtained in step S11 in a vacuum drying oven and dry it at a constant temperature of 100°C to obtain a carbon fiber surface felt with sodium molybdate particles coated on the surface.

[0051] S1: After impregnating the carbon fiber surface felt coated with sodium molybdate particles into the liquid hydrogen resin system, it is pre-cured at 50°C. The pre-cured carbon fiber surface felt is then laid flat on the surface of the mandrel and rolled into a cylinder as the mandrel rotates, forming a waterproof layer. The liquid hydrogen resin system, by mass parts, includes 50 parts of bisphenol F epoxy resin, 50 parts of bisphenol A epoxy resin, and 20 parts of epoxy reactive diluent, wherein the epoxy reactive diluent is ethyl glycidyl ether: methyl methacrylate: γ-caprolactone added in a mass ratio of 10:5:5; 10 parts of toughening agent core-shell particles, wherein the outer shell material of the core-shell particles is polyvinyl butyral, and the core material is nano-alumina; and 20 parts of curing agent, a composite of diethyltoluene diamine and polyether amine curing agent.

[0052] Seepage barrier layer #2

[0053] S10: Immerse the carbon fiber in a mixed solution of organic solvents ethanol, acetone and tetrahydrofuran in a volume ratio of 1:2:1, and then dry it to obtain a clean carbon fiber surface felt.

[0054] S11: The clean carbon fiber surface felt is placed in concentrated nitric acid with a mass concentration of 30-60% and oxidized and etched at 70°C. Then, the oxidized and etched carbon fiber surface felt is placed in a mixed solution of silane coupling agent and sodium molybdate, wherein the mass ratio of silane coupling agent to sodium molybdate is 1:2, to obtain a carbon fiber surface felt with sodium molybdate grains on the surface.

[0055] S12: Place the carbon fiber surface felt obtained in step S11 in a vacuum drying oven and dry it at a constant temperature of 130°C to obtain a carbon fiber surface felt with sodium molybdate particles coated on the surface.

[0056] S1: After impregnating the carbon fiber surface felt coated with sodium molybdate particles into the liquid hydrogen resin system, it is pre-cured at 70°C. The pre-cured carbon fiber surface felt is then laid flat on the surface of the mandrel and rolled into a cylinder as the mandrel rotates, forming an impermeable layer. The liquid hydrogen resin system, by mass parts, includes 70 parts of bisphenol F epoxy resin, 30 parts of bisphenol A epoxy resin, and 30 parts of epoxy reactive diluent, wherein the epoxy reactive diluent is phenyl glycidyl ether: methyl methacrylate: γ-caprolactone added in a mass ratio of 10:5:5; 30 parts of toughening agent core-shell particles, wherein the outer shell material of the core-shell particles is polyvinyl butyral, and the core material is nano-alumina; and 50 parts of curing agent are a composite of diethyltoluene diamine and polyether amine curing agents.

[0057] Anti-seepage layer #3

[0058] S10: Immerse the carbon fiber in a mixed solution of organic solvents ethanol, acetone and tetrahydrofuran in a volume ratio of 1:3:3, and then dry it to obtain a clean carbon fiber surface felt.

[0059] S11: The clean carbon fiber surface felt is placed in concentrated nitric acid with a mass concentration of 30-60% and oxidized at 90°C. Then, the oxidized carbon fiber surface felt is placed in a mixed solution of silane coupling agent and sodium molybdate, wherein the mass ratio of silane coupling agent to sodium molybdate is 1:3, to obtain a carbon fiber surface felt with sodium molybdate grains on the surface.

[0060] S12: Place the carbon fiber surface felt obtained in step S11 in a vacuum drying oven and dry it at a constant temperature of 150°C to obtain a carbon fiber surface felt with sodium molybdate particles coated on the surface.

[0061] S1: After impregnating the carbon fiber surface felt coated with sodium molybdate particles into the liquid hydrogen resin system, it is pre-cured at 90℃. The pre-cured carbon fiber surface felt is then laid flat on the surface of the mandrel and rolled into a cylinder as the mandrel rotates, forming an impermeable layer. The liquid hydrogen resin system, by mass parts, includes 60 parts of bisphenol F epoxy resin, 40 parts of bisphenol A epoxy resin, and 25 parts of epoxy reactive diluent, wherein the epoxy reactive diluent is ethyl glycidyl ether: glyceryl triacrylate: vinyl acetate added in a mass ratio of 10:5:5; 20 parts of toughening agent core-shell particles, wherein the outer shell material of the core-shell particles is polyvinyl butyral, and the core material is nano-alumina; and 50 parts of curing agent, a composite of diethyltoluene diamine and polyether amine curing agent.

[0062] Wherein, the bisphenol F epoxy resin and the bisphenol A epoxy resin are modified epoxy resins; the modification method is as follows: 2% of iron oxide-modified graphene oxide is added to the bisphenol F epoxy resin; 5% of iron oxide-modified graphene oxide is added to the bisphenol A epoxy resin.

[0063] Seepage barrier layer #4

[0064] Based on the No. 3 impermeable layer, the main difference is that 5% of iron oxide-modified graphene oxide is added to the bisphenol F epoxy resin; and 5% of iron oxide-modified graphene oxide is added to the bisphenol A epoxy resin.

[0065] Seepage barrier layer #5

[0066] The main difference between this layer and the first layer is that the carbon fiber surface felt in step S1 was not modified.

[0067] Example 2

[0068] Elastomer 1#

[0069] The elastomer, by weight, comprises 80 parts of hydrogenated styrene-butadiene block copolymer, 10 parts of fluorosilicone rubber, 5 parts of polyurethane, 4 parts of polyether diol, and 3 parts of vulcanizing agent. The materials are melt-mixed and shaped to obtain elastomer #1.

[0070] Elastomer #2

[0071] The elastomer, by weight, comprises 90 parts of hydrogenated styrene-butadiene block copolymer, 20 parts of fluorosilicone rubber, 10 parts of polyurethane, 7 parts of polyether diol, and 3 parts of vulcanizing agent. The materials are melt-mixed and shaped to obtain elastomer #2.

[0072] Example 3

[0073] Flange-equipped, unlined composite material piping for liquid hydrogen environments #1

[0074] S2: A fiber woven fabric impregnated with liquid hydrogen resin system is laid in a circumferential winding manner on the surface of the impermeable layer 1# to form a transition layer; wherein, the liquid hydrogen resin system includes 50 parts of bisphenol F epoxy resin and 50 parts of bisphenol A epoxy resin, 20 parts of methyl methacrylate, 10 parts of core-shell particles, the outer shell material is polyvinyl butyral, the core material is nano alumina, and 20 parts of diethyltoluene diamine.

[0075] S3: A strength layer is formed on the surface of the transition layer by a combination of circumferential carbon fiber lay-up and winding, and carbon fibers are laid between the strength layers to form a flange layer.

[0076] S4: The pipeline is cured at 100℃ using a vacuum method, and the core mold is removed to form a flanged, unlined composite material pipeline #1 for use in a liquid hydrogen environment.

[0077] Flange-equipped, unlined composite material piping for liquid hydrogen environments #2

[0078] S2: A fiber woven fabric impregnated with liquid hydrogen resin system is laid in a circumferential winding manner on the surface of the impermeable layer 2# to form a transition layer; wherein, the liquid hydrogen resin system includes 70 parts of bisphenol F epoxy resin and 30 parts of bisphenol A epoxy resin, 25 parts of ethyl glycidyl ether, 20 parts of core-shell particles, the outer shell material is polymethyl methacrylate, the core material is nano silica, and 30 parts of diethyltoluene diamine.

[0079] S3: A strength layer is formed on the surface of the transition layer by a combination of circumferential carbon fiber lay-up and winding, and carbon fibers are laid between the strength layers to form a flange layer.

[0080] S4: The pipeline is cured at 120℃ using a vacuum method, and the core mold is removed to form a flanged, unlined composite material pipeline #2 for use in a liquid hydrogen environment.

[0081] Flange-equipped, unlined composite material piping for liquid hydrogen environments #3

[0082] S2: A fiber woven fabric impregnated with liquid hydrogen resin system is laid in a circumferential winding manner on the surface of the seepage-proof layer 3# to form a transition layer; wherein, the liquid hydrogen resin system includes 60 parts of bisphenol F epoxy resin and 40 parts of bisphenol A epoxy resin, 30 parts of ethyl glycidyl ether, 30 parts of core-shell particles, the outer shell material is polymethyl methacrylate, the core material is nano silica, and 50 parts of diethyltoluene diamine.

[0083] S3: A strength layer is formed on the surface of the transition layer using a combination of circumferential carbon fiber lay-up and winding. Carbon fibers are then laid between the strength layers to form a flange layer. (Reference) Figure 1 As shown, the pipeline includes, from the inside out, an impermeable layer 1, a transition layer 2, and a strength layer 3. The flange layer 4 is located at one end of the pipeline and is disposed between the strength layers 3. An elastomer 1# (not shown in the figure) is embedded in the flange layer 4. The flange layer 4 includes a first limiting groove 401, a second limiting groove 402, and a sealing groove 403. The sealing groove 403 is formed on the end face of the flange layer 4 connection end. The sealing groove 403 is a semi-circular annular groove. The semi-circular annular groove is used to install a circular sealing ring, which can achieve a tight connection and sealing of the joint end face. Furthermore, the flange layer 4 is located at one end of the pipeline. The first limiting groove 401 is threaded and is located on the outer surface of the flange layer. The second limiting groove 402 is a groove and is located on the inner surface of the flange layer 4. During pipeline processing, multiple layers of the strength layer 3 can be set. The strength layer 3 is snapped into the groove. The outer and inner surfaces of the flange layer are further fixed by the first and second limiting grooves. Through high-temperature curing, the anti-seepage layer, transition layer, strength layer and flange layer are fully fused and interwoven to form an organic whole.

[0084] S4: The pipeline is cured at 150℃ using a vacuum method, and the core mold is removed to form a flanged, unlined composite material pipeline #3 for use in a liquid hydrogen environment.

[0085] Flange-equipped, unlined composite material piping for liquid hydrogen environments, #4

[0086] Based on the 3# flanged unlined composite material pipeline for liquid hydrogen environment, the main difference is that the flange layer has an embedded elastomer 2#.

[0087] 5# Flange-equipped, unlined composite material piping for liquid hydrogen environments

[0088] Based on the No. 1 flanged unlined composite material pipeline for liquid hydrogen environment, the main difference is the use of the No. 4 anti-seepage layer.

[0089] Flange-equipped, unlined composite material piping for liquid hydrogen environments, #6

[0090] Based on the No. 1 flanged unlined composite material pipeline for liquid hydrogen environment, the main difference is the use of the No. 5 anti-seepage layer.

[0091] D1 Flange-equipped, unlined composite piping for liquid hydrogen environments

[0092] Based on the No. 1 flanged unlined composite material pipeline for liquid hydrogen environment, the main difference is that no transition layer is laid.

[0093] D2 Flange-equipped, unlined composite piping for liquid hydrogen environments

[0094] Based on the No. 1 flanged unlined composite material pipeline for liquid hydrogen environment, the main difference is that no toughening additives are added to the liquid hydrogen resin system impregnated with the No. 1 anti-seepage layer.

[0095] The performance of the above-mentioned flanged unlined composite material pipelines 1#-6# and D1-D2 for liquid hydrogen environment was tested at room temperature (25℃). The hydrogen permeability coefficient was tested according to GB / T1038-2000, as shown in Table 1.

[0096] Table 1

[0097]

[0098]

[0099] Referring to Table 1, it can be seen that the flanged, unlined composite material pipeline for liquid hydrogen environments prepared by this invention has a tensile strength of 60-70 MPa at room temperature and a fracture toughness of not less than 5 MPa·m. 1 / 2 The hydrogen permeability coefficient is no higher than 5×10 -15 .

[0100] The performance of flanged, unlined composite piping (numbers 1-6) in a liquid hydrogen environment was tested at -196°C, for example, in a liquid nitrogen environment. See Table 2 for reference.

[0101] Table 2

[0102]

[0103]

[0104] Referring to Table 2, it can be seen that at -196℃, the flanged, unlined composite material pipeline for liquid hydrogen environments prepared by this invention has a tensile strength of 70-90 MPa and a fracture toughness of not less than 3 MPa·m. 1 / 2 The hydrogen permeability coefficient is no higher than 11×10 -15 .

[0105] In summary, the flanged, unlined composite material pipeline for liquid hydrogen environments prepared by this invention has good mechanical properties, can avoid the generation of microcracks under the combined action of high temperature difference and high pressure difference, and prevent liquid hydrogen permeation during use.

[0106] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A processing method for a flanged, unlined composite material pipeline for use in liquid hydrogen environments, characterized in that, The processing technology includes the following steps: S1: After impregnating the carbon fiber surface felt with the liquid hydrogen resin system, it is pre-cured by heating at 50℃-90℃. The pre-cured carbon fiber surface felt is laid flat on the surface of the core mold and rolled into a cylinder as the core mold rotates to form a waterproof layer. S2: A fiber woven fabric impregnated with a liquid hydrogen resin system is laid in a circumferential winding manner on the surface of the impermeable layer to form a transition layer; S3: A strength layer is formed on the surface of the transition layer by a combination of circumferential carbon fiber lay-up and winding, and carbon fibers are laid between the strength layers to form a flange layer; S4: The pipeline is cured at 100-150℃ using a vacuum method, and the core mold is removed to form a flanged, unlined composite material pipeline for use in a liquid hydrogen environment. The liquid hydrogen resin system, by mass parts, includes 100 parts of bisphenol F epoxy resin and bisphenol A epoxy resin, 20-30 parts of epoxy reactive diluent, 10-30 parts of toughening agent, and 20-50 parts of curing agent. The mass ratio of bisphenol F epoxy resin to bisphenol A epoxy resin is 50-70:30-50.

2. The processing technology according to claim 1, characterized in that, The carbon fiber surface felt in step S1 is modified by the following steps: S10: Immerse the carbon fiber surface felt in an organic solvent and then dry it to obtain a clean carbon fiber surface felt; S11: The clean carbon fiber surface felt is placed in concentrated nitric acid for oxidation etching, and then the oxidized carbon fiber surface felt is placed in a mixed solution of silane coupling agent and sodium molybdate to obtain a carbon fiber surface felt with sodium molybdate grains on the surface. S12: Place the carbon fiber surface felt obtained in step S11 into a vacuum drying oven for constant temperature drying to obtain a carbon fiber surface felt with sodium molybdate particles coated on the surface. The mass ratio of silane coupling agent to sodium molybdate is 1:1-3.

3. The processing technology according to claim 2, characterized in that, The temperature for constant temperature drying in step S12 is 100-150℃.

4. The processing technology according to claim 2, characterized in that, In step S11, the concentration of concentrated nitric acid is 30-60%, and the oxidation etching temperature is 50-90℃.

5. The processing technology according to claim 1, characterized in that, Bisphenol F epoxy resin and bisphenol A epoxy resin were modified respectively; the modification method was to add iron oxide-modified graphene oxide to bisphenol F epoxy resin and bisphenol A epoxy resin respectively. The amount of graphene oxide added is 2-5%.

6. The processing technology according to claim 1, characterized in that, The epoxy reactive diluent is one or more of alkyl glycidyl ether, acrylate, acetate, and caprolactone.

7. The processing technology according to claim 6, characterized in that, The alkyl group in the alkyl glycidyl ether is butyl, octyl, ethyl or phenyl; And / or the acrylate is methyl methacrylate, cyclohexane acrylate, glyceryl triacrylate, allyl acrylate, 1,6-hexanediol diacrylate or vinyl acrylate; And / or the acetate ester is vinyl acetate; And / or the caprolactone is γ-caprolactone, δ-caprolactone, or ε-caprolactone.

8. The processing technology according to claim 1, characterized in that, The toughening agent is a core-shell particle; the outer shell material of the core-shell particle is polyvinyl butyral or polymethyl methacrylate; the core material is nano-alumina or nano-silica.

9. The processing technology according to claim 1, characterized in that, The flange layer includes a first limiting groove, a second limiting groove, and a sealing groove, wherein the sealing groove is formed on the end face of the flange layer connection end.

10. The processing technology according to claim 1, characterized in that, The flange layer is embedded with an elastomer, which, by mass parts, comprises 80-90 parts of hydrogenated styrene-butadiene block copolymer, 10-20 parts of fluorosilicone rubber, 5-10 parts of polyurethane, and 4-7 parts of polyether diol.

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