Modified carbon fiber, preparation method thereof and carbon fiber reinforced composite material

Abstract

The invention discloses a modified carbon fiber and a preparation method thereof and a carbon fiber reinforced composite material, and belongs to the technical field of composite material interface modification.The preparation method of the modified carbon fiber comprises the following steps that after the surface of the carbon fiber is treated, the carbon fiber is mixed with dopamine, the mixture is added into a buffer solution for ultrasonic treatment, and the carbon fiber is obtained; the dopamine modified carbon fiber is obtained; the preparation method comprises the following steps: dispersing dopamine modified carbon fibers in an organic solvent containing polyvinylpyrrolidone, then sequentially adding pentaerythritol tetra-3-mercaptopropionate and isophorone diisocyanate, and carrying out a reaction so as to obtain the modified carbon fibers. The prepared modified carbon fiber is high in strength retention and free of obvious surface defects, and the modified carbon fiber and epoxy resin can be prepared into a carbon fiber reinforced composite material with improved interface strength and mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of composite material interface modification, in particular to a modified carbon fiber and a preparation method thereof, and a carbon fiber reinforced composite material. Background Art

[0002] In the past few decades, the increasing demand for new and advanced materials in the automotive and aerospace fields, such as lightweight and high strength, has led engineers and scientists to use polymer composites as a substitute for metal parts. Carbon fiber reinforced composites (CFRP) have light weight, high tensile strength, corrosion resistance, and excellent fatigue resistance. Generally, the final mechanical properties of composites are closely related to the reinforcement, the matrix, and the interface between the two. The interface is the "bridge" for bonding and load transfer between carbon fiber and epoxy resin. Good interfacial compatibility can improve the composite performance of carbon fiber and matrix, and can effectively transfer external stress from the interface to the carbon fiber to reduce stress concentration. However, the fiber surface is smooth, without extra active functional groups, and presents a certain chemical inertness. This leads to poor interfacial adhesion when carbon fiber is composited with epoxy resin, which seriously limits the application of composite materials. In order to solve the above problems, researchers have conducted a lot of exploration and research on the modification methods of carbon fiber surface. Mainly focused on: changing the chemical composition of CF surface, using a lot of energy to destroy the dense graphite layer, and improving the surface roughness of CF.

[0003] On the one hand, almost all of these modification methods will have varying degrees of negative impact on the strength of the carbon fiber itself: strong acid or strong alkali is required to corrode the surface of the carbon fiber; on the other hand, most modification methods have complicated steps, long reaction cycles, and expensive reagents, which are not conducive to industrialization. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing modified carbon fiber to solve the problems raised in the above background technology.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions: A method for preparing modified carbon fiber comprises the following steps: After treating the surface of the carbon fiber, the carbon fiber is mixed with dopamine and added into a buffer solution for ultrasonic treatment to obtain dopamine-modified carbon fiber; The dopamine-modified carbon fiber is dispersed in an organic solvent containing polyvinyl pyrrolidone, and then pentaerythritol tetrakis-3-mercaptopropionate and isophorone diisocyanate are added in sequence to react to obtain the modified carbon fiber.

[0006] Preferably, the method for treating the surface of the carbon fiber is: washing away the sizing agent and pollutants on the surface of the carbon fiber with acetone.

[0007] Preferably, the mass ratio of the carbon fiber to dopamine is (8-12):(1.5-2.5).

[0008] Preferably, the mass ratio of polyvinyl pyrrolidone to carbon fiber is (1-5):(8-12).

[0009] Preferably, the mass ratio of pentaerythritol tetrakis-3-mercaptopropionate, isophorone diisocyanate and carbon fiber is (7.3-14.6):(6.7-13.3):(8-12).

[0010] Preferably, the organic solvent is ethanol; Another object of the present invention is to provide a modified carbon fiber prepared by the preparation method described in the claim.

[0011] Another object of the present invention is to provide an application of the modified carbon fiber in reinforcing epoxy resin.

[0012] Another object of the present invention is to provide a carbon fiber reinforced composite material, which includes epoxy resin and the above-mentioned modified carbon fiber.

[0013] Preferably, the preparation method of the carbon fiber reinforced composite material comprises the following steps: mixing an epoxy resin, a curing agent and a defoaming agent, then mixing them with the modified carbon fiber, and performing a curing treatment to obtain the carbon fiber reinforced composite material; wherein the mass ratio of the modified carbon fiber, epoxy resin, curing agent and defoaming agent is (0.8-1.2):(0.8-1.2):(0.8-1.2):(0.05-0.15).

[0014] The preparation method of the modified carbon fiber provided by the present invention has mild experimental conditions, high conversion efficiency, short reaction time, low cost, and has industrial application prospects; the steps are simple, the process is simple, no high-precision equipment is required, and it is clean and environmentally friendly; the modified carbon fiber prepared by the present invention has high strength retention and no obvious defects on the surface, and can be prepared with epoxy resin to prepare a carbon fiber reinforced composite material with improved interface strength and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a scanning electron microscope (SEM) image of the modified carbon fiber prepared in an embodiment of the present invention; Figure 2 The figure is a comparison diagram of the interlaminar shear strength of the carbon fiber reinforced composite material before and after modification; in the figure, Untreated CF is an unmodified carbon fiber reinforced composite material, CF-PDA is a dopamine-modified carbon fiber reinforced composite material, and CF-SN is a carbon fiber reinforced composite material prepared in an embodiment of the present invention; Figure 3: is a comparison chart of the tensile strength of the carbon fiber reinforced composite material before and after modification; in the figure, Untreated CF is an unmodified carbon fiber reinforced composite material, CF-PDA is a dopamine-modified carbon fiber reinforced composite material, and CF-SN is a carbon fiber reinforced composite material prepared in an embodiment of the present invention; Figure 4 This is the tensile fracture interface diagram of the unmodified carbon fiber reinforced composite material; Figure 5 This is a tensile fracture interface diagram of a carbon fiber reinforced composite material prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] In an embodiment of the present invention, in order to improve the interface strength between carbon fiber and epoxy resin and improve the mechanical properties of the composite material, a method for preparing a modified carbon fiber and a carbon fiber reinforced composite material is provided, which specifically comprises the following steps: S1. Wash the sizing agent and contaminants on the surface of the carbon fiber with acetone; then, let it stand for 20-28 hours, rinse with deionized water, and vacuum dry; place the cleaned 8-10mm long 8-12g carbon fiber tow at the bottom of the beaker, add 1.5-2.5g dopamine, and pour in 750-1250mL of prepared Tris-HCl buffer solution. Ultrasonicate at 20-35℃ water temperature for 12-24h. Then, rinse the carbon fiber with deionized water several times until the solution is clear, and then vacuum dry to obtain dopamine-modified carbon fiber.

[0018] S2. Disperse 1-5g of polyvinyl pyrrolidone (PVP) in 500mL of ethanol solvent under magnetic stirring at 25-35°C to obtain an ethanol solution containing polyvinyl pyrrolidone; then disperse the dopamine-modified carbon fiber obtained above in the ethanol solution containing polyvinyl pyrrolidone; then add monomers 7.3-14.6g of pentaerythritol tetra-3-mercaptopropionate (PETMP) and 6.7-13.3g of isophorone diisocyanate (IPDI) in sequence, and place in a 20-30°C water bath for reaction for 6-24h. After the reaction is completed, rinse the carbon fiber with ethanol and deionized water several times, and then vacuum dry to obtain modified carbon fiber modified with mercapto-isocyanate microspheres.

[0019] S3. Preparation of carbon fiber reinforced composite materials: Wipe the mold clean with ethanol, evenly apply the release agent, and heat it in a 50-70℃ oven for 20-40min to fully wet the mold. Pour the weighed epoxy resin into a beaker, add the curing agent, and stir it magnetically for 20-40min; then add the silicone defoamer, stir it magnetically for 0.5-1.5h, put it in a 70℃ oven and let it stand for 1-3h to defoam, then take it out, mix it with the above-mentioned modified carbon fiber, pour it into the mold, and place it in a flat vulcanizer at 25℃ for 20-28h for curing to obtain a carbon fiber reinforced composite material. Among them, the mass ratio of modified carbon fiber, epoxy resin, curing agent, and defoaming agent is (0.8-1.2):(0.8-1.2):(0.8-1.2):(0.05-0.15).

[0020] The following embodiments are some specific implementation cases and application cases of the present invention in practical applications, but are not limited thereto.

[0021] Embodiment 1: This embodiment provides a method for preparing a modified carbon fiber and a carbon fiber reinforced composite material, which specifically comprises the following steps: S1. Place 8g of carbon fiber with a length of 8mm in a 1000mL beaker containing 200mL of acetone, and heat it in a water bath at 20℃ for 10h to remove the surface sizing agent and pollutants. Subsequently, let it stand for 24h, rinse the carbon fiber with deionized water several times, and finally dry it in a vacuum drying oven at 60℃ for 4h. Use a volumetric flask to measure 1000mL of deionized water and pour it into a beaker, add 1.21g of trishydroxymethylaminomethane (Tris) reagent and fully dissolve it, add 1mol / L dilute hydrochloric acid dropwise, adjust the pH value of the solution to 8.5, and obtain a Tris-HCl buffer solution. Place the cleaned 8g carbon fiber tow with a length of 8mm at the bottom of the beaker, add 1.5g of dopamine, and pour in 750mL of the prepared Tris-HCl buffer solution. Place the above solution in an ultrasonic device (800W, 40KHz), and control the ultrasonic water temperature at 30℃ with circulating water. Subsequently, the carbon fiber was rinsed with deionized water for multiple times until the solution was clear, and then placed in a vacuum oven at 50°C for drying for 2 h to obtain dopamine-modified carbon fiber.

[0022] S2. Disperse 1g of polyvinyl pyrrolidone (PVP) in 500mL of ethanol solvent under magnetic stirring at 25°C to obtain an ethanol solution containing polyvinyl pyrrolidone; then, place the dopamine-modified carbon fiber obtained above in a beaker, and add the above ethanol solution containing polyvinyl pyrrolidone to magnetically stir at room temperature; then, add monomers 7.3g of pentaerythritol tetra-3-mercaptopropionate (PETMP) and 6.7g of isophorone diisocyanate (IPDI) in sequence, and place in a 20°C water bath to react for 6h. After the reaction is completed, rinse the carbon fiber with ethanol and deionized water several times, and then place it in a vacuum oven at 50°C to dry for 2h to obtain modified carbon fiber modified with mercapto-isocyanate microspheres.

[0023] S3. Preparation of carbon fiber reinforced composite materials: Wipe the mold clean with ethanol, evenly apply the release agent, and heat it in a 50°C oven for 40 minutes to fully wet the mold. Pour 12g of epoxy resin into a beaker, add 12g of curing agent, and stir magnetically for 30 minutes; then add 1.5g of silicone defoamer, stir magnetically for 1 hour, put it in a 70°C oven for 2 hours to defoam, then take it out, mix it with 8g of the above-mentioned modified carbon fiber, pour it into the mold, and place it in a flat vulcanizer at 25°C for 24 hours for curing to obtain a carbon fiber reinforced composite material.

[0024] Embodiment 2: This embodiment provides a method for preparing a modified carbon fiber and a carbon fiber reinforced composite material, which specifically comprises the following steps: S1. Place 12g of carbon fiber with a length of 10mm in a 1000mL beaker containing 400mL of acetone, and heat it in a water bath at 30℃ for 10h to remove the surface sizing agent and pollutants. Subsequently, let it stand for 24h, rinse the carbon fiber with deionized water several times, and finally dry it in a vacuum drying oven at 60℃ for 4h. Use a volumetric flask to measure 1000mL of deionized water and pour it into a beaker, add 1.21g of trishydroxymethylaminomethane (Tris) reagent and fully dissolve it, add 1mol / L dilute hydrochloric acid dropwise, adjust the pH value of the solution to 8.5, and obtain a Tris-HCl buffer solution. Place the cleaned 12g carbon fiber tow with a length of 10mm at the bottom of the beaker, add 2g of dopamine, and pour in 1000mL of the prepared Tris-HCl buffer solution. Place the above solution in an ultrasonic device (800W, 40KHz), and control the ultrasonic water temperature at 32℃ with circulating water. Subsequently, the carbon fiber was rinsed with deionized water for multiple times until the solution was clear, and then placed in a vacuum oven at 50°C for drying for 2 h to obtain dopamine-modified carbon fiber.

[0025] S2. Disperse 2g of polyvinyl pyrrolidone (PVP) in 500mL of ethanol solvent under magnetic stirring at 25°C to obtain an ethanol solution containing polyvinyl pyrrolidone; then, place the dopamine-modified carbon fiber obtained above in a beaker, and add the above ethanol solution containing polyvinyl pyrrolidone to magnetically stir at room temperature; then, add monomers 14.6g of pentaerythritol tetra-3-mercaptopropionate (PETMP) and 13.3g of isophorone diisocyanate (IPDI) in sequence, and place in a 30°C water bath to react for 12h. After the reaction is completed, rinse the carbon fiber with ethanol and deionized water several times, and then place it in a vacuum oven at 50°C to dry for 2h to obtain modified carbon fiber modified with mercapto-isocyanate microspheres.

[0026] S3. Preparation of carbon fiber reinforced composite materials: Wipe the mold clean with ethanol, evenly apply the release agent, and heat it in a 60°C oven for 30 minutes to fully wet the mold. Pour 8g of epoxy resin into a beaker, add 8g of curing agent, and stir magnetically for 30 minutes; then add 0.5g of silicone defoamer, stir magnetically for 1 hour, put it in a 70°C oven for 2 hours to defoam, then take it out, mix it with 12g of the above-mentioned modified carbon fiber, pour it into the mold, and place it in a flat vulcanizer at 25°C for 24 hours for curing to obtain a carbon fiber reinforced composite material.

[0027] Embodiment 3: This embodiment provides a method for preparing a modified carbon fiber and a carbon fiber reinforced composite material, which specifically comprises the following steps: S1. Place 10g of carbon fiber with a length of 9mm in a 1000mL beaker containing 300mL of acetone, and heat it in a water bath at 25℃ for 10h to remove the surface sizing agent and pollutants. Subsequently, let it stand for 24h, rinse the carbon fiber with deionized water several times, and finally dry it in a vacuum drying oven at 60℃ for 4h. Use a volumetric flask to measure 1000mL of deionized water and pour it into a beaker, add 1.21g of trishydroxymethylaminomethane (Tris) reagent and fully dissolve it, add 1mol / L dilute hydrochloric acid dropwise, adjust the pH value of the solution to 8.5, and obtain a Tris-HCl buffer solution. Place the cleaned 9mm long 10g carbon fiber tow at the bottom of the beaker, add 2g of dopamine, and pour in 1000mL of the prepared Tris-HCl buffer solution. Place the above solution in an ultrasonic device (800W, 40KHz), and control the ultrasonic water temperature at 35℃ with circulating water. Subsequently, the carbon fiber was rinsed with deionized water for multiple times until the solution was clear, and then placed in a vacuum oven at 50°C for drying for 2 h to obtain dopamine-modified carbon fiber.

[0028] S2. Disperse 5g of polyvinyl pyrrolidone (PVP) in 500mL of ethanol solvent under magnetic stirring at 25°C to obtain an ethanol solution containing polyvinyl pyrrolidone; then, place the dopamine-modified carbon fiber obtained above in a beaker, and add the above ethanol solution containing polyvinyl pyrrolidone to magnetically stir at room temperature; then, add monomers 10.9g of pentaerythritol tetra-3-mercaptopropionate (PETMP) and 10.1g of isophorone diisocyanate (IPDI) in sequence, and place in a 28°C water bath to react for 6h. After the reaction is completed, rinse the carbon fiber with ethanol and deionized water several times, and then place it in a vacuum oven at 50°C to dry for 2h to obtain modified carbon fiber modified with mercapto-isocyanate microspheres.

[0029] S3. Preparation of carbon fiber reinforced composite materials: Wipe the mold clean with ethanol, evenly apply the release agent, and heat it in a 60°C oven for 30 minutes to fully wet the mold. Pour 10g of epoxy resin into a beaker, add 10g of curing agent, and stir magnetically for 30 minutes; then add 1g of silicone defoamer, stir magnetically for 1 hour, put it in a 70°C oven for 2 hours to defoam, then take it out, mix it with 10g of the above-mentioned modified carbon fiber, pour it into the mold, and place it in a flat vulcanizer at 25°C for 24 hours for curing to obtain a carbon fiber reinforced composite material.

[0030] Embodiment 4: This embodiment provides a method for preparing a modified carbon fiber and a carbon fiber reinforced composite material, which specifically comprises the following steps: S1. Place 11g of carbon fiber with a length of 9mm in a 1000mL beaker containing 400mL of acetone, and heat it in a water bath at 30℃ for 11h to remove the surface sizing agent and pollutants. Subsequently, let it stand for 24h, rinse the carbon fiber with deionized water several times, and finally place it in a vacuum drying oven at 60℃ for 4h. Use a volumetric flask to measure 2000mL of deionized water and pour it into a beaker, add 2.42g of trishydroxymethylaminomethane (Tris) reagent and fully dissolve it, add 1mol / L dilute hydrochloric acid dropwise, adjust the pH value of the solution to 8.5, and obtain a Tris-HCl buffer solution. Place the cleaned 9mm long 11g carbon fiber tow at the bottom of the beaker, add 2.5g of dopamine, and pour in 1250mL of the prepared Tris-HCl buffer solution. Place the above solution in an ultrasonic device (800W, 40KHz), and control the ultrasonic water temperature at 20℃ with circulating water. Subsequently, the carbon fiber was rinsed with deionized water for multiple times until the solution was clear, and then placed in a vacuum oven at 50°C for drying for 2 h to obtain dopamine-modified carbon fiber.

[0031] S2. Disperse 4g of polyvinyl pyrrolidone (PVP) in 500mL of ethanol solvent under magnetic stirring at 35°C to obtain an ethanol solution containing polyvinyl pyrrolidone; then, place the dopamine-modified carbon fiber obtained above in a beaker, and add the above ethanol solution containing polyvinyl pyrrolidone to magnetically stir at room temperature; then, add monomers 13.1g of pentaerythritol tetrakis-3-mercaptopropionate (PETMP) and 12.1g of isophorone diisocyanate (IPDI) in sequence, and place in a 30°C water bath to react for 24h. After the reaction is completed, rinse the carbon fiber with ethanol and deionized water several times, and then place it in a vacuum oven at 50°C to dry for 2h to obtain modified carbon fiber modified with mercapto-isocyanate microspheres, and its scanning electron microscope (SEM) image is as follows Figure 1 shown.

[0032] S3. Preparation of carbon fiber reinforced composite materials: Wipe the mold clean with ethanol, evenly apply the release agent, and heat it in a 70°C oven for 20 minutes to fully wet the mold. Pour 10g of epoxy resin into a beaker, add 10g of curing agent, and stir magnetically for 30 minutes; then add 1g of silicone defoamer, stir magnetically for 1 hour, put it in a 70°C oven for 2 hours to defoam, then take it out, mix it with 10g of the above-mentioned modified carbon fiber, pour it into the mold, and place it in a flat vulcanizer at 25°C for 24 hours for curing to obtain a carbon fiber reinforced composite material.

[0033] Comparative Example 1: This comparative example provides a method for preparing an unmodified carbon fiber reinforced composite material, which specifically comprises the following steps: S1. Place 11g of carbon fiber with a length of 9mm in a 1000mL beaker containing 400mL of acetone, and heat it in a 30℃ water bath for 11h to remove the surface sizing agent and pollutants. Then, let it stand for 24h, rinse the carbon fiber with deionized water several times, and finally dry it in a vacuum drying oven at 60℃ for 4h.

[0034] S2. Preparation of unmodified carbon fiber reinforced composite materials: Wipe the mold clean with ethanol, evenly apply the release agent, and heat it in a 70°C oven for 20 minutes to fully wet the mold. Pour 10g of epoxy resin into a beaker, add 10g of curing agent, and stir magnetically for 30 minutes; then add 1g of silicone defoamer, stir magnetically for 1 hour, put it in a 70°C oven to defoam for 2 hours, then take it out, and then mix it with 10g of the above-mentioned unmodified carbon fiber after cleaning, pour it into the mold, and place it in a flat vulcanizer at 25°C for 24 hours for curing to obtain an unmodified carbon fiber reinforced composite material.

[0035] Comparative Example 2: This comparative example provides a method for preparing a dopamine-modified carbon fiber and a dopamine-modified carbon fiber reinforced composite material, which specifically comprises the following steps: S1. Place 11g of carbon fiber with a length of 9mm in a 1000mL beaker containing 400mL of acetone, and heat it in a water bath at 30℃ for 11h to remove the surface sizing agent and pollutants. Subsequently, let it stand for 24h, rinse the carbon fiber with deionized water several times, and finally place it in a vacuum drying oven at 60℃ for 4h. Use a volumetric flask to measure 2000mL of deionized water and pour it into a beaker, add 2.42g of trishydroxymethylaminomethane (Tris) reagent and fully dissolve it, add 1mol / L dilute hydrochloric acid dropwise, adjust the pH value of the solution to 8.5, and obtain a Tris-HCl buffer solution. Place the cleaned 9mm long 11g carbon fiber tow at the bottom of the beaker, add 2.5g of dopamine, and pour in 1250mL of the prepared Tris-HCl buffer solution. Place the above solution in an ultrasonic device (800W, 40KHz), and control the ultrasonic water temperature at 20℃ with circulating water. Subsequently, the carbon fiber was rinsed with deionized water for multiple times until the solution was clear, and then placed in a vacuum oven at 50°C for drying for 2 h to obtain dopamine-modified carbon fiber.

[0036] S2. Dopamine modified carbon fiber reinforced composite material: Wipe the mold clean with ethanol, evenly apply the release agent, and heat it in a 70°C oven for 20 minutes to fully wet the mold. Pour 10g of epoxy resin into a beaker, add 10g of curing agent, and stir magnetically for 30 minutes; then add 1g of silicone defoamer, stir magnetically for 1 hour, put it in a 70°C oven to defoam for 2 hours, then take it out, mix it with 10g of the above-mentioned dopamine-modified carbon fiber, pour it into the mold, and place it in a flat vulcanizer at 25°C for 24 hours for curing to obtain a dopamine modified carbon fiber reinforced composite material.

[0037] The interlaminar shear strength and tensile strength of the carbon fiber reinforced composite material (CF-SN) prepared in Example 4, the unmodified carbon fiber reinforced composite material (Untreated CF) prepared in Comparative Example 1, and the dopamine-modified carbon fiber reinforced composite material (CF-PDA) prepared in Comparative Example 2 were tested. The results are as follows: Figure 2 and Figure 3 In addition, the tensile fracture interfaces of the unmodified carbon fiber reinforced composite material and the carbon fiber reinforced composite material prepared in Example 4 are respectively as shown in Figure 4 and Figure 5 shown.

[0038] Through the above comparative experiments, it can be known that the interfacial performance between the carbon fiber modified by the in-situ growth of raspberry-shaped microspheres by mercapto-isocyanate click polymerization and the epoxy resin is better, and compared with the unmodified carbon fiber reinforced composite material, the interlaminar shear strength and tensile strength of the carbon fiber reinforced composite material prepared in the embodiment of the present invention are improved, and the mechanical properties are improved.

[0039] Based on the above-mentioned ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above-mentioned description. The technical scope of the present invention is not limited to the contents of the specification.

Claims

1. A method for preparing modified carbon fiber, characterized in that: The following steps are involved: After treating the surface of the carbon fiber, the carbon fiber is mixed with dopamine and added into a buffer solution for ultrasonic treatment to obtain dopamine-modified carbon fiber; The dopamine-modified carbon fiber is dispersed in an organic solvent containing polyvinyl pyrrolidone, and then pentaerythritol tetrakis-3-mercaptopropionate and isophorone diisocyanate are added in sequence to react to obtain the modified carbon fiber.

2. The method for preparing modified carbon fiber according to claim 1, characterized in that: The method for treating the surface of the carbon fiber is to wash away the sizing agent and pollutants on the surface of the carbon fiber with acetone.

3. The method for preparing modified carbon fiber according to claim 1 or 2, characterized in that: The mass ratio of the carbon fiber to dopamine is (8-12):(1.5-2.5).

4. The method for preparing modified carbon fiber according to claim 1, characterized in that: The mass ratio of the polyvinyl pyrrolidone to the carbon fiber is (1-5):(8-12).

5. The method for preparing modified carbon fiber according to claim 1, characterized in that: The mass ratio of pentaerythritol tetrakis-3-mercaptopropionate, isophorone diisocyanate and carbon fiber is (7.3-14.6):(6.7-13.3):(8-12).

6. The method for preparing modified carbon fiber according to claim 1, characterized in that: The organic solvent is ethanol.

7. A modified carbon fiber prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the modified carbon fiber as claimed in claim 7 in reinforcing epoxy resin.

9. A carbon fiber reinforced composite material comprising epoxy resin, characterized in that: Also included is the modified carbon fiber as described in claim 7.

10. The carbon fiber reinforced composite material according to claim 9, characterized in that: The preparation method of the carbon fiber reinforced composite material comprises the following steps: mixing an epoxy resin, a curing agent and a defoaming agent, then mixing them with the modified carbon fiber, and performing a curing treatment to obtain the carbon fiber reinforced composite material; wherein the mass ratio of the modified carbon fiber, the epoxy resin, the curing agent and the defoaming agent is (0.8-1.2):(0.8-1.2):(0.8-1.2):(0.05-0.15).

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