A carbon fiber composite material for rail transit vehicles and its preparation process

Abstract

This invention discloses a carbon fiber composite material for rail transit vehicles and its preparation process, relating to the field of carbon fiber composite material technology. The method uses carbon fiber cloth as a matrix, depositing a polydopamine layer on its surface, then loading graphene epoxide, and using the polydopamine layer to grow manganese dioxide nanosheets in situ to obtain a carbon fiber matrix. Epoxy resin is then prepolymerized by pouring it into a mold, and the carbon fiber matrix is ​​laid flat in the prepolymerized resin. Epoxy resin is then poured in again, and the mixture is heated and cured under a pressure of 45–50 N to obtain the carbon fiber composite material. The carbon fiber composite material prepared by this method exhibits excellent mechanical properties, with improved tensile strength and interlaminar shear strength, and can be widely used in vehicles, ships, and other fields, demonstrating high practicality.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber composite materials technology, specifically a carbon fiber composite material for rail transit vehicles and its preparation process. Background Technology

[0002] With the advancement and development of science and technology, the research and development of new materials has become increasingly in-depth. In recent years, carbon fiber, as a high-strength, low-density, and high-modulus fiber-reinforced material, has become an important reinforcing material in high-end application fields due to its excellent wear resistance, heat resistance, and acid and alkali resistance. Among them, carbon fiber-epoxy resin composite materials have gradually become one of the preferred materials for aerospace, marine vessels, automobiles, and rail transportation.

[0003] In existing commercial preparations of carbon fiber-epoxy resin composites, the inertness of the carbon fiber surface leads to poor interfacial properties when carbon fiber or carbon fiber cloth is combined with resin, resulting in the composite material's mechanical properties failing to meet requirements. Therefore, based on this situation, this application discloses a carbon fiber composite material for rail transit vehicles and its preparation process to solve this technical problem. Summary of the Invention

[0004] The purpose of this invention is to provide a carbon fiber composite material for rail transit vehicles and its preparation process, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a preparation process for carbon fiber composite materials for rail transit vehicles, comprising the following steps:

[0006] Step (1): Mix Tris solution and dopamine to obtain dopamine solution; mix Tris solution and polyethyleneimine to obtain polyethyleneimine solution; mix dopamine solution and polyethyleneimine solution and stir evenly to obtain two-component impregnation solution;

[0007] Take carbon fiber cloth, heat treat it at 400-450℃ for 40-50 min, soak it in acetone for 12-16 h, take it out and dry it, then transfer it to a two-component impregnation solution and impregnate it for 20-24 h, wash it with deionized water, and vacuum dry it at 60-70℃ to obtain pretreated carbon fiber cloth.

[0008] Step (2): Mix graphene oxide with N,N-dimethylformamide and ultrasonically disperse for 20-30 min to obtain a graphene oxide dispersion;

[0009] The pretreated carbon fiber cloth was immersed in an epoxide graphene dispersion and stirred at 60-65°C for 4-6 hours. The product was collected by centrifugation, washed and dried to obtain the graphene-loaded carbon fiber cloth.

[0010] Step (3): Mix potassium permanganate and deionized water, stir at 350-450 rpm for 30-40 min to obtain potassium permanganate solution; immerse the graphene-loaded carbon fiber cloth in potassium permanganate solution, keep it at 150-160℃ for 5-6 h, wash and dry to obtain carbon fiber matrix;

[0011] Step (4): Mix epoxy resin, curing agent and reactive diluent, stir evenly, degas for 30-40 minutes to obtain epoxy resin solution; slowly pour epoxy resin solution into the bottom of mold, prepolymerize at 70-75℃ for 15-25 minutes, then lay several layers of carbon fiber matrix into mold, then pour epoxy resin solution, and cure under 45-50N pressure to obtain carbon fiber composite material.

[0012] In a more optimized scheme, in step (1), the concentration of dopamine solution is 2-3 mg / mL; the concentration of polyethyleneimine solution is 4-6 mg / mL; the preparation method of Tris solution is as follows: mix tris(hydroxymethyl)aminomethane and deionized water, stir until dissolved, and obtain 10 mM Tris solution, and adjust the pH to 8.5 with hydrochloric acid.

[0013] In a more optimized scheme, the preparation steps of graphene oxide in step (2) are as follows: graphene oxide is ultrasonically dispersed in N,N-dimethylformamide, potassium fluoride and potassium iodide are added, stirred evenly, epichlorohydrin is added, and the mixture is refluxed at 100-105℃ for 12-15h. The product is collected by centrifugation, washed and dried to obtain graphene oxide; the amount of graphene oxide and epichlorohydrin is 0.2g:40mL.

[0014] In a more optimized scheme, in step (2), the concentration of the epoxide graphene dispersion is 2-3 mg / mL.

[0015] In a more optimized scheme, in step (3), the mass concentration of the potassium permanganate solution is 0.02–0.03 wt%.

[0016] In a more optimized scheme, in step (4), the curing agent includes polyethyleneimine and triethylenetetramine, with a mass ratio of 6:4 for polyethyleneimine and triethylenetetramine; the mass ratio of epoxy resin, curing agent and reactive diluent is 10:7:1.

[0017] In a more optimized scheme, in step (1), the molecular weight of polyethyleneimine is 600-800; in step (3), the molecular weight of polyethyleneimine is 1200-1800.

[0018] In a more optimized scheme, the curing parameters in step (4) are: drying at 90-95℃ for 2-3 hours, and then drying at 110-120℃ for 4-5 hours.

[0019] A more optimized solution is a carbon fiber composite material for rail transit vehicles prepared according to any of the above-described preparation processes.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0021] This invention discloses a preparation process for carbon fiber composite materials for rail transit vehicles. The method uses carbon fiber cloth as the matrix, deposits a polydopamine layer on the surface of the carbon fiber cloth, loads graphene epoxide, and uses the polydopamine layer to grow manganese dioxide nanosheets in situ to obtain a carbon fiber matrix. Then, epoxy resin is poured into a mold for prepolymerization, and the carbon fiber matrix is ​​laid flat in the prepolymerized resin. Epoxy resin is poured in again, and the mixture is heated and cured. During curing, a pressure of 45-50N is applied to obtain the carbon fiber composite material. The carbon fiber composite material prepared by this method has excellent mechanical properties, with improved tensile strength and interlaminar shear strength, and can be widely used in vehicles, ships and other fields, showing high practicality.

[0022] This method first heat-treats the carbon fiber cloth at 400–450℃ for 40–50 min and then soaks it in acetone for 12–16 h to remove surface impurities. Next, it is impregnated in a two-component impregnation solution, which is an equal volume mixture of dopamine and polyethyleneimine solutions, to form a polyethyleneimine-polydopamine copolymer coating on the carbon fiber cloth surface. On one hand, the presence of this polyethyleneimine-polydopamine copolymer coating provides active sites for the subsequent loading of manganese dioxide nanosheets and epoxide graphene. On the other hand, the introduction of polyethyleneimine during polydopamine polymerization improves the stability and reactivity of the copolymer coating and mitigates the rigidity of the coating caused by simple polydopamine copolymerization, further enhancing interfacial properties. Simultaneously, the method limits the molecular weight of the polyethyleneimine to 600–800 to avoid uneven coating due to excessively high molecular weight.

[0023] It should be noted that when polymerizing a polyethyleneimine-polydopamine copolymer coating on the surface of conventional carbon fiber cloth, high molecular weight polyethyleneimine is usually chosen to increase the surface roughness of the carbon fiber cloth and form an uneven interface, thereby improving the interfacial anchoring performance between the carbon fiber cloth and the subsequent polymer. However, in this scheme, since in-situ growth and graphene oxide loading are required, low molecular weight polyethyleneimine is chosen. Small molecules are easier to spread on the surface of carbon fiber cloth, which is more conducive to the subsequent reaction process.

[0024] Based on this, the method first impregnates pretreated carbon fiber cloth in an epoxide graphene dispersion, and then loads epoxide graphene onto its surface. The reason for epoxide modification of graphene is that the polymer used in this method is epoxy resin, and the presence of epoxide graphene can further improve the interfacial performance. Next, the graphene-loaded carbon fiber cloth is impregnated in a potassium permanganate solution, and manganese dioxide nanosheets are grown in situ on the surface of the carbon fiber cloth. In this method, the processing order of epoxide graphene and manganese dioxide nanosheets is very important. The method loads epoxide graphene first, and then grows manganese dioxide nanosheets in situ. At this time, the epoxide graphene is perpendicular to the carbon fiber cloth interface, and the presence of manganese dioxide nanosheets can play a supplementary role. The two work together to further improve the anchoring effect between epoxy resin and carbon fiber cloth. If the order is reversed, the loading effect of epoxide graphene after in-situ growth of manganese dioxide nanosheets will be very poor, which will affect the interfacial performance of the product.

[0025] This invention discloses a preparation process for carbon fiber composite materials for rail transit vehicles. The process adjusts the surface modification process of carbon fiber cloth, which greatly improves the surface activity and wettability of carbon fiber cloth, resulting in excellent interfacial performance. The mechanical properties of the final carbon fiber composite material are improved, making it more practical. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In this embodiment, the Tris solution was prepared as follows: Tris(hydroxymethyl)aminomethane and deionized water were mixed and stirred until dissolved to obtain a 10 mM Tris solution, and the pH was adjusted to 8.5 with hydrochloric acid. The carbon fiber cloth was T700 orthogonally woven carbon fiber; the epoxy resin was E-51; and the reactive diluent was 660A epoxy reactive diluent. The polyethyleneimine was branched polyethyleneimine with a molecular weight of 600 or 1800, and the ratio of primary, secondary, and tertiary amine groups on the branched polyethyleneimine molecular chain was 1:2:1.

[0028] Example 1: A preparation process for carbon fiber composite materials for rail transit vehicles, comprising the following steps:

[0029] Step (1): Mix Tris solution and dopamine to obtain dopamine solution; the concentration of dopamine solution is 2 mg / mL. Mix Tris solution and polyethyleneimine (Mn = 600) to obtain polyethyleneimine solution; the concentration of polyethyleneimine solution is 4 mg / mL.

[0030] Equal volumes of dopamine solution and polyethyleneimine solution are mixed and stirred until homogeneous to obtain a two-component impregnation solution.

[0031] Take carbon fiber cloth, heat treat it at 450℃ for 40 min, soak it in acetone for 12 h, take it out and dry it, then transfer it to a two-component impregnation solution and impregnate it for 24 h, wash it with deionized water, and vacuum dry it at 60℃ to obtain pretreated carbon fiber cloth.

[0032] Step (2): The preparation steps of graphene oxide are as follows: 0.2g of graphene oxide is ultrasonically dispersed in N,N-dimethylformamide, 75.5g of potassium fluoride and 12g of potassium iodide are added, stirred evenly, and then 40mL of epichlorohydrin is added. The mixture is refluxed at 100℃ for 15h, the product is collected by centrifugation, washed and dried to obtain graphene oxide.

[0033] Epoxidized graphene was mixed with N,N-dimethylformamide and ultrasonically dispersed for 20 min to obtain an epoxidized graphene dispersion; the concentration of the epoxidized graphene dispersion was 2 mg / mL.

[0034] The pretreated carbon fiber cloth was immersed in an epoxide graphene dispersion, stirred at 65°C for 5 hours, centrifuged to collect the product, washed and dried to obtain the graphene-loaded carbon fiber cloth.

[0035] Step (3): Mix potassium permanganate and deionized water, and stir at 400 rpm for 30 min to obtain a potassium permanganate solution; the mass concentration of the potassium permanganate solution is 0.03 wt%.

[0036] Graphene-loaded carbon fiber cloth was impregnated in potassium permanganate solution and reacted at 150°C for 6 hours. After washing and drying, carbon fiber matrix was obtained.

[0037] Step (4): Mix 100g of epoxy resin, 70g of curing agent, and 10g of reactive diluent, stir evenly, and degas for 30 minutes to obtain epoxy resin solution; the mass ratio of epoxy resin, curing agent, and reactive diluent is 10:7:1. The curing agent includes polyethyleneimine (Mn=1800) and triethylenetetramine, with a mass ratio of polyethyleneimine (Mn=1800) to triethylenetetramine of 6:4.

[0038] The epoxy resin was slowly poured into the bottom of the mold and prepolymerized at 70°C for 15 minutes. Then, several layers of carbon fiber matrix were laid flat into the mold, followed by the pouring of epoxy resin. The mixture was cured under 50N pressure to obtain the carbon fiber composite material. The curing parameters were: drying at 90°C for 3 hours, and then drying at 120°C for 4 hours.

[0039] Example 2: A preparation process for carbon fiber composite materials for rail transit vehicles, comprising the following steps:

[0040] Step (1): Mix Tris solution and dopamine to obtain dopamine solution; the concentration of dopamine solution is 2 mg / mL. Mix Tris solution and polyethyleneimine (Mn = 600) to obtain polyethyleneimine solution; the concentration of polyethyleneimine solution is 4 mg / mL.

[0041] Equal volumes of dopamine solution and polyethyleneimine solution are mixed and stirred until homogeneous to obtain a two-component impregnation solution.

[0042] Take carbon fiber cloth, heat treat it at 450℃ for 45 min, soak it in acetone for 15 h, take it out and dry it, then transfer it to a two-component impregnation solution and impregnate it for 24 h, wash it with deionized water, and vacuum dry it at 65℃ to obtain pretreated carbon fiber cloth.

[0043] Step (2): The preparation steps of graphene oxide are as follows: 0.2g of graphene oxide is ultrasonically dispersed in N,N-dimethylformamide, 75.5g of potassium fluoride and 12g of potassium iodide are added, stirred evenly, and then 40mL of epichlorohydrin is added. The mixture is refluxed at 105℃ for 14h, the product is collected by centrifugation, washed and dried to obtain graphene oxide.

[0044] Epoxidized graphene was mixed with N,N-dimethylformamide and ultrasonically dispersed for 25 min to obtain an epoxidized graphene dispersion; the concentration of the epoxidized graphene dispersion was 2.5 mg / mL.

[0045] The pretreated carbon fiber cloth was immersed in an epoxide graphene dispersion, stirred at 65°C for 5 hours, centrifuged to collect the product, washed and dried to obtain the graphene-loaded carbon fiber cloth.

[0046] Step (3): Mix potassium permanganate and deionized water, and stir at 400 rpm for 35 min to obtain a potassium permanganate solution; the mass concentration of the potassium permanganate solution is 0.02 wt%.

[0047] Graphene-loaded carbon fiber cloth was impregnated in potassium permanganate solution and reacted at 150°C for 6 hours. After washing and drying, carbon fiber matrix was obtained.

[0048] Step (4): Mix 100g of epoxy resin, 70g of curing agent, and 10g of reactive diluent, stir evenly, and degas for 35 minutes to obtain epoxy resin solution; the mass ratio of epoxy resin, curing agent, and reactive diluent is 10:7:1. The curing agent includes polyethyleneimine (Mn=1800) and triethylenetetramine, with a mass ratio of polyethyleneimine (Mn=1800) to triethylenetetramine of 6:4.

[0049] The epoxy resin was slowly poured into the bottom of the mold and prepolymerized at 75°C for 15 minutes. Then, several layers of carbon fiber matrix were laid flat into the mold, followed by the pouring of epoxy resin. The mixture was cured under 50N pressure to obtain the carbon fiber composite material. The curing parameters were: drying at 90°C for 3 hours, and then drying at 120°C for 4 hours.

[0050] Example 3: A preparation process for carbon fiber composite materials for rail transit vehicles, comprising the following steps:

[0051] Step (1): Mix Tris solution and dopamine to obtain dopamine solution; the concentration of dopamine solution is 2 mg / mL. Mix Tris solution and polyethyleneimine (Mn = 600) to obtain polyethyleneimine solution; the concentration of polyethyleneimine solution is 4 mg / mL.

[0052] Equal volumes of dopamine solution and polyethyleneimine solution are mixed and stirred until homogeneous to obtain a two-component impregnation solution.

[0053] Take carbon fiber cloth, heat treat it at 450℃ for 50 min, soak it in acetone for 16 h, take it out and dry it, then transfer it to a two-component impregnation solution and impregnate it for 24 h, wash it with deionized water, and vacuum dry it at 70℃ to obtain pretreated carbon fiber cloth.

[0054] Step (2): The preparation steps of graphene oxide are as follows: 0.2g of graphene oxide is ultrasonically dispersed in N,N-dimethylformamide, 75.5g of potassium fluoride and 12g of potassium iodide are added, stirred evenly, and then 40mL of epichlorohydrin is added. The mixture is refluxed at 105℃ for 13h, the product is collected by centrifugation, washed and dried to obtain graphene oxide.

[0055] Epoxidized graphene was mixed with N,N-dimethylformamide and ultrasonically dispersed for 30 min to obtain an epoxidized graphene dispersion; the concentration of the epoxidized graphene dispersion was 3 mg / mL.

[0056] The pretreated carbon fiber cloth was immersed in an epoxide graphene dispersion, stirred at 65°C for 5 hours, centrifuged to collect the product, washed and dried to obtain the graphene-loaded carbon fiber cloth.

[0057] Step (3): Mix potassium permanganate and deionized water, and stir at 400 rpm for 40 min to obtain a potassium permanganate solution; the mass concentration of the potassium permanganate solution is 0.02 wt%.

[0058] Graphene-loaded carbon fiber cloth was impregnated in potassium permanganate solution and reacted at 150°C for 6 hours. After washing and drying, carbon fiber matrix was obtained.

[0059] Step (4): Mix 100g of epoxy resin, 70g of curing agent, and 10g of reactive diluent, stir evenly, and degas for 40 minutes to obtain epoxy resin solution; the mass ratio of epoxy resin, curing agent, and reactive diluent is 10:7:1. The curing agent includes polyethyleneimine (Mn=1800) and triethylenetetramine, with a mass ratio of polyethyleneimine (Mn=1800) to triethylenetetramine of 6:4.

[0060] The epoxy resin was slowly poured into the bottom of the mold and prepolymerized at 75°C for 15 minutes. Then, several layers of carbon fiber matrix were laid flat into the mold, followed by the pouring of epoxy resin. The mixture was cured under 50N pressure to obtain the carbon fiber composite material. The curing parameters were: drying at 90°C for 3 hours, and then drying at 120°C for 4 hours.

[0061] Comparative Example 1: A preparation process for carbon fiber composite materials for rail transit vehicles, comprising the following steps:

[0062] Step (1): Mix Tris solution and dopamine to obtain dopamine solution; the concentration of dopamine solution is 2 mg / mL. Mix Tris solution and polyethyleneimine (Mn = 1800) to obtain polyethyleneimine solution; the concentration of polyethyleneimine solution is 4 mg / mL.

[0063] Equal volumes of dopamine solution and polyethyleneimine solution are mixed and stirred until homogeneous to obtain a two-component impregnation solution.

[0064] Take carbon fiber cloth, heat treat it at 450℃ for 50 min, soak it in acetone for 16 h, take it out and dry it, then transfer it to a two-component impregnation solution and impregnate it for 24 h, wash it with deionized water, and vacuum dry it at 70℃ to obtain pretreated carbon fiber cloth.

[0065] Step (2): The preparation steps of graphene oxide are as follows: 0.2g of graphene oxide is ultrasonically dispersed in N,N-dimethylformamide, 75.5g of potassium fluoride and 12g of potassium iodide are added, stirred evenly, and then 40mL of epichlorohydrin is added. The mixture is refluxed at 105℃ for 13h, the product is collected by centrifugation, washed and dried to obtain graphene oxide.

[0066] Epoxidized graphene was mixed with N,N-dimethylformamide and ultrasonically dispersed for 30 min to obtain an epoxidized graphene dispersion; the concentration of the epoxidized graphene dispersion was 3 mg / mL.

[0067] The pretreated carbon fiber cloth was immersed in an epoxide graphene dispersion, stirred at 65°C for 5 hours, centrifuged to collect the product, washed and dried to obtain the graphene-loaded carbon fiber cloth.

[0068] Step (3): Mix potassium permanganate and deionized water, and stir at 400 rpm for 40 min to obtain a potassium permanganate solution; the mass concentration of the potassium permanganate solution is 0.02 wt%.

[0069] Graphene-loaded carbon fiber cloth was impregnated in potassium permanganate solution and reacted at 150°C for 6 hours. After washing and drying, carbon fiber matrix was obtained.

[0070] Step (4): Mix 100g of epoxy resin, 70g of curing agent, and 10g of reactive diluent, stir evenly, and degas for 40 minutes to obtain epoxy resin solution; the mass ratio of epoxy resin, curing agent, and reactive diluent is 10:7:1. The curing agent includes polyethyleneimine (Mn=1800) and triethylenetetramine, with a mass ratio of polyethyleneimine (Mn=1800) to triethylenetetramine of 6:4.

[0071] The epoxy resin was slowly poured into the bottom of the mold and prepolymerized at 75°C for 15 minutes. Then, several layers of carbon fiber matrix were laid flat into the mold, followed by the pouring of epoxy resin. The mixture was cured under 50N pressure to obtain the carbon fiber composite material. The curing parameters were: drying at 90°C for 3 hours, and then drying at 120°C for 4 hours.

[0072] Comparative Example 1 was a control experiment based on Example 3. The molecular weight of polyethyleneimine in the two-component impregnation solution in Comparative Example 1 was 1800.

[0073] Comparative Example 2: A preparation process for carbon fiber composite materials for rail transit vehicles, comprising the following steps:

[0074] Step (1): Mix Tris solution and dopamine to obtain dopamine solution; the concentration of dopamine solution is 2 mg / mL. Mix Tris solution and polyethyleneimine (Mn = 600) to obtain polyethyleneimine solution; the concentration of polyethyleneimine solution is 4 mg / mL.

[0075] Equal volumes of dopamine solution and polyethyleneimine solution are mixed and stirred until homogeneous to obtain a two-component impregnation solution.

[0076] Take carbon fiber cloth, heat treat it at 450℃ for 50 min, soak it in acetone for 16 h, take it out and dry it, then transfer it to a two-component impregnation solution and impregnate it for 24 h, wash it with deionized water, and vacuum dry it at 70℃ to obtain pretreated carbon fiber cloth.

[0077] Step (2): Mix potassium permanganate and deionized water, and stir at 400 rpm for 40 min to obtain a potassium permanganate solution; the mass concentration of the potassium permanganate solution is 0.02 wt%.

[0078] The pretreated carbon fiber cloth was immersed in potassium permanganate solution and reacted at 150°C for 6 hours. After washing and drying, carbon fiber cloth with in-situ grown manganese dioxide nanosheets was obtained.

[0079] Step (3): The preparation steps of graphene oxide are as follows: 0.2g of graphene oxide is ultrasonically dispersed in N,N-dimethylformamide, 75.5g of potassium fluoride and 12g of potassium iodide are added, stirred evenly, and then 40mL of epichlorohydrin is added. The mixture is refluxed at 105℃ for 13h, the product is collected by centrifugation, washed and dried to obtain graphene oxide.

[0080] Epoxidized graphene was mixed with N,N-dimethylformamide and ultrasonically dispersed for 30 min to obtain an epoxidized graphene dispersion; the concentration of the epoxidized graphene dispersion was 3 mg / mL.

[0081] Carbon fiber cloth with in-situ grown manganese dioxide nanosheets was impregnated in a dispersion of graphene epoxide, stirred at 65°C for 5 h, and the product was collected by centrifugation, washed and dried to obtain the carbon fiber matrix.

[0082] Step (4): Mix 100g of epoxy resin, 70g of curing agent, and 10g of reactive diluent, stir evenly, and degas for 40 minutes to obtain epoxy resin solution; the mass ratio of epoxy resin, curing agent, and reactive diluent is 10:7:1. The curing agent includes polyethyleneimine (Mn=1800) and triethylenetetramine, with a mass ratio of polyethyleneimine (Mn=1800) to triethylenetetramine of 6:4.

[0083] The epoxy resin was slowly poured into the bottom of the mold and prepolymerized at 75°C for 15 minutes. Then, several layers of carbon fiber matrix were laid flat into the mold, followed by the pouring of epoxy resin. The mixture was cured under 50N pressure to obtain the carbon fiber composite material. The curing parameters were: drying at 90°C for 3 hours, and then drying at 120°C for 4 hours.

[0084] Comparative Example 2 was a control experiment based on Example 3. In Comparative Example 2, the sample was first immersed in potassium permanganate solution and then immersed in epoxide graphene dispersion.

[0085] Comparative Example 3: A preparation process for a carbon fiber composite material for rail transit vehicles, comprising the following steps:

[0086] Step (1): Mix Tris solution and dopamine to obtain dopamine solution; the concentration of dopamine solution is 2 mg / mL. Mix Tris solution and polyethyleneimine (Mn = 600) to obtain polyethyleneimine solution; the concentration of polyethyleneimine solution is 4 mg / mL.

[0087] Equal volumes of dopamine solution and polyethyleneimine solution are mixed and stirred until homogeneous to obtain a two-component impregnation solution.

[0088] Take carbon fiber cloth, heat treat it at 450℃ for 50 min, soak it in acetone for 16 h, take it out and dry it, then transfer it to a two-component impregnation solution and impregnate it for 24 h, wash it with deionized water, and vacuum dry it at 70℃ to obtain pretreated carbon fiber cloth.

[0089] Step (2): Mix potassium permanganate and deionized water, and stir at 400 rpm for 40 min to obtain a potassium permanganate solution; the mass concentration of the potassium permanganate solution is 0.02 wt%.

[0090] The pretreated carbon fiber cloth was immersed in potassium permanganate solution and reacted at 150°C for 6 hours. After washing and drying, the carbon fiber matrix was obtained.

[0091] Step (3): Mix 100g of epoxy resin, 70g of curing agent, and 10g of reactive diluent, stir evenly, and degas for 40 minutes to obtain epoxy resin solution; the mass ratio of epoxy resin, curing agent, and reactive diluent is 10:7:1. The curing agent includes polyethyleneimine (Mn=1800) and triethylenetetramine, with a mass ratio of polyethyleneimine (Mn=1800) to triethylenetetramine of 6:4.

[0092] The epoxy resin was slowly poured into the bottom of the mold and prepolymerized at 75°C for 15 minutes. Then, several layers of carbon fiber matrix were laid flat into the mold, followed by the pouring of epoxy resin. The mixture was cured under 50N pressure to obtain the carbon fiber composite material. The curing parameters were: drying at 90°C for 3 hours, and then drying at 120°C for 4 hours.

[0093] Comparative Example 3 is a control experiment based on Example 3, except that the step of "immersion in epoxide graphene dispersion" is omitted in Comparative Example 3.

[0094] Comparative Example 4: A preparation process for carbon fiber composite materials for rail transit vehicles, comprising the following steps:

[0095] Step (1): Mix Tris solution and dopamine to obtain dopamine solution; the concentration of dopamine solution is 2 mg / mL. Mix Tris solution and polyethyleneimine (Mn = 600) to obtain polyethyleneimine solution; the concentration of polyethyleneimine solution is 4 mg / mL.

[0096] Equal volumes of dopamine solution and polyethyleneimine solution are mixed and stirred until homogeneous to obtain a two-component impregnation solution.

[0097] Take carbon fiber cloth, heat treat it at 450℃ for 50 min, soak it in acetone for 16 h, take it out and dry it, then transfer it to a two-component impregnation solution and impregnate it for 24 h, wash it with deionized water, and vacuum dry it at 70℃ to obtain pretreated carbon fiber cloth.

[0098] Step (2): The preparation steps of graphene oxide are as follows: 0.2g of graphene oxide is ultrasonically dispersed in N,N-dimethylformamide, 75.5g of potassium fluoride and 12g of potassium iodide are added, stirred evenly, and then 40mL of epichlorohydrin is added. The mixture is refluxed at 105℃ for 13h, the product is collected by centrifugation, washed and dried to obtain graphene oxide.

[0099] Epoxidized graphene was mixed with N,N-dimethylformamide and ultrasonically dispersed for 30 min to obtain an epoxidized graphene dispersion; the concentration of the epoxidized graphene dispersion was 3 mg / mL.

[0100] The pretreated carbon fiber cloth was immersed in an epoxide graphene dispersion, stirred at 65°C for 5 hours, centrifuged to collect the product, washed and dried to obtain the graphene-loaded carbon fiber cloth.

[0101] Step (3): Mix 100g of epoxy resin, 70g of curing agent, and 10g of reactive diluent, stir evenly, and degas for 40 minutes to obtain epoxy resin solution; the mass ratio of epoxy resin, curing agent, and reactive diluent is 10:7:1. The curing agent includes polyethyleneimine (Mn=1800) and triethylenetetramine, with a mass ratio of polyethyleneimine (Mn=1800) to triethylenetetramine of 6:4.

[0102] Epoxy resin was slowly poured into the bottom of the mold and prepolymerized at 75°C for 15 minutes. Then, several layers of graphene-loaded carbon fiber cloth were laid flat into the mold, followed by the pouring of epoxy resin. The mixture was then cured under 50N pressure to obtain the carbon fiber composite material. The curing parameters were: drying at 90°C for 3 hours, and then drying at 120°C for 4 hours.

[0103] Comparative Example 4 is a control experiment based on Example 3, but the step of "immersion in potassium permanganate solution" is omitted in Comparative Example 4.

[0104] Testing experiment:

[0105] Carbon fiber composite materials prepared in Examples 1-3 and Comparative Examples 1-4 were used as samples, with a sample thickness of 2 mm. The flexural strength of the samples was tested according to the method disclosed in ASTM D7264 at a test temperature of 25°C. The interlaminar shear strength was tested according to ASTM D2344 at a test speed of 1 mm / min. Specific data are shown in Table 1.

[0106] Table 1

[0107]

[0108] Conclusion: This invention discloses a preparation process for carbon fiber composite materials for rail transit vehicles. The scheme adjusts the surface modification process of carbon fiber cloth, which greatly improves the surface activity and wettability of carbon fiber cloth, resulting in excellent interfacial performance. The mechanical properties of the final carbon fiber composite material are improved, and its practicality is enhanced.

[0109] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A preparation process for carbon fiber composite materials for rail transit vehicles, characterized in that: Includes the following steps: Step (1): Mix Tris solution and dopamine to obtain dopamine solution; The Tris solution and polyethyleneimine were mixed to obtain a polyethyleneimine solution; Dopamine solution and polyethyleneimine solution are mixed and stirred evenly to obtain a two-component impregnation solution; Take carbon fiber cloth, heat treat it at 400-450℃ for 40-50 min, soak it in acetone for 12-16 h, take it out and dry it, then transfer it to a two-component impregnation solution and impregnate it for 20-24 h, wash it with deionized water, and vacuum dry it at 60-70℃ to obtain pretreated carbon fiber cloth. Step (2): Mix graphene oxide with N,N-dimethylformamide and ultrasonically disperse for 20-30 min to obtain a graphene oxide dispersion; The pretreated carbon fiber cloth was immersed in an epoxide graphene dispersion and stirred at 60-65°C for 4-6 hours. The product was collected by centrifugation, washed and dried to obtain the graphene-loaded carbon fiber cloth. Step (3): Mix potassium permanganate and deionized water to obtain potassium permanganate solution; immerse the graphene-loaded carbon fiber cloth in potassium permanganate solution, keep it at 150-160℃ for 5-6 hours, wash and dry to obtain carbon fiber matrix; Step (4): Mix epoxy resin, curing agent and reactive diluent, stir evenly, degas for 30-40 minutes to obtain epoxy resin solution; slowly pour epoxy resin solution into the bottom of mold, prepolymerize at 70-75℃ for 15-25 minutes, then lay several layers of carbon fiber matrix into mold, then pour epoxy resin solution, and cure under 45-50N pressure to obtain carbon fiber composite material; In step (1), the molecular weight of polyethyleneimine is 600-800.

2. The preparation process of carbon fiber composite material for rail transit vehicles according to claim 1, characterized in that: In step (1), the concentration of dopamine solution is 2-3 mg / mL; the concentration of polyethyleneimine solution is 4-6 mg / mL.

3. The preparation process of a carbon fiber composite material for rail transit vehicles according to claim 1, characterized in that: In step (2), the preparation steps of graphene oxide are as follows: graphene oxide is ultrasonically dispersed in N,N-dimethylformamide, potassium fluoride and potassium iodide are added, stirred evenly, epichlorohydrin is added, and the mixture is refluxed at 100-105℃ for 12-15h. The product is collected by centrifugation, washed and dried to obtain graphene oxide.

4. The preparation process of carbon fiber composite material for rail transit vehicles according to claim 1, characterized in that: In step (2), the concentration of the epoxide graphene dispersion is 2-3 mg / mL.

5. The preparation process of a carbon fiber composite material for rail transit vehicles according to claim 1, characterized in that: In step (3), the mass concentration of the potassium permanganate solution is 0.02–0.03 wt%.

6. The preparation process of carbon fiber composite material for rail transit vehicles according to claim 1, characterized in that: In step (4), the curing agent includes polyethyleneimine and triethylenetetramine, with a mass ratio of 6:4 for polyethyleneimine and triethylenetetramine; the mass ratio of epoxy resin, curing agent and reactive diluent is 10:7:

1.

7. The preparation process of carbon fiber composite material for rail transit vehicles according to claim 6, characterized in that: In step (4), the molecular weight of polyethyleneimine is 1200 to 1800.

8. The preparation process of carbon fiber composite material for rail transit vehicles according to claim 1, characterized in that: In step (4), the curing parameters are: drying at 90-95℃ for 2-3 hours, and then drying at 110-120℃ for 4-5 hours.

9. A carbon fiber composite material for rail transit vehicles prepared by the preparation process according to any one of claims 1 to 8.

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