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

Abstract

The invention discloses a modified carbon fiber, a carbon fiber composite material and a preparation method and application thereof, relates to the technical field of carbon fiber surface modification, and solves the problems that in the prior art, a carbon fiber modification method is single, and the damage condition of the carbon fiber composite material cannot be monitored in real time. The preparation method comprises the following steps: immersing desized carbon fiber cloth into conductive filler dispersion liquid, and drying to obtain conductive filler modified carbon fiber cloth; immersing the conductive filler modified carbon fiber cloth into a poly (3, 4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte for electrophoretic deposition; taking the conductive filler modified carbon fiber cloth as a negative electrode and a graphite plate as a positive electrode, and performing vacuum drying after deposition to obtain conductive polymer nanoparticle deposited carbon fibers; and preparing the carbon fiber composite material from the modified carbon fiber and epoxy resin. The synergistic effect of the conductive filler and the conductive polymer enhances the acting force between the carbon fiber and the resin, thereby enhancing the mechanical properties and damage detection capability of the material. The method can be applied to the field of damage detection.

Description

Technical Field

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

[0002] Carbon fiber materials have been widely used in aerospace, automobile, sports equipment, wind power generation and other fields due to their excellent mechanical properties, lightweight characteristics, good electrical conductivity and thermal stability. However, the surface of carbon fiber itself is relatively smooth and its chemical activity is low, resulting in weak interfacial bonding between it and matrix materials such as epoxy resin, thus limiting the application of carbon fiber composites in certain high-performance fields. In order to solve this problem, researchers have tried to modify carbon fiber through various methods. Common carbon fiber modification methods are mostly concentrated on surface modification (such as chemical treatment, plasma treatment, coating technology, etc.), among which chemical modification can improve the bonding and surface activity of carbon fiber, but the improvement effect on the mechanical properties such as strength and toughness of carbon fiber composites is relatively weak; plasma treatment can improve the surface activity of carbon fiber, but its modification depth is shallow, and it cannot significantly improve the internal structure and mechanical properties of carbon composites. At the same time, the instability and uncontrollability of the modification process make it impossible to guarantee the performance of carbon fiber composites under high-strength and high-load environments, affecting its reliability in high-end applications. In order to improve the shortcomings of the above-mentioned modification methods, some researchers have tried to perform secondary modification on carbon fiber to prepare carbon fiber composites, but the effect is still limited and needs further study.

[0003] The carbon fiber composite materials currently under study still face the risk of damage and aging. Therefore, real-time monitoring and detection of the damage state of carbon fiber composite materials without affecting the overall performance of the material has become an important research topic. The damage of carbon fiber composite materials usually manifests itself in various forms, mainly including cracks, delamination, fiber breakage, interface debonding, etc. At present, common carbon fiber composite material damage detection methods include ultrasonic detection, X-ray imaging, infrared thermal imaging, etc. Traditional ultrasonic detection methods are often used to detect damage such as cracks and delamination of carbon fiber composite materials, but their operation is complicated, requiring the detection personnel to have rich experience, and cannot be monitored in real time; X-ray imaging technology can effectively detect internal defects in carbon fiber composite materials, such as delamination and bubbles, but due to its high cost and the need for professional equipment, and can only be used in a static environment, it is not suitable for real-time monitoring; infrared thermal imaging technology can detect local temperature changes caused by damage, such as local debonding, crack extension, etc., but this method has high requirements on the surface flatness of the material, has poor detection effect on deep damage, and is difficult to quantitatively analyze the degree of damage. Therefore, the development of a carbon fiber composite material that can monitor damage in real time is of great significance to improving the safety and service life of carbon fiber materials. Summary of the invention

[0004] In order to solve the problem that the existing carbon fiber modification method is single and the carbon fiber composite material cannot monitor the damage in real time, the present invention proposes a modified carbon fiber, a carbon fiber epoxy resin composite material and a preparation method and application thereof. The technical solution of the present invention is as follows: A method for preparing modified carbon fiber comprises the following steps: S1: adding a conductive filler into deionized water and stirring, followed by ultrasonic treatment to obtain a uniformly dispersed conductive filler dispersion; immersing a desized carbon fiber cloth in the conductive filler dispersion, followed by drying to obtain a conductive filler-modified carbon fiber cloth; S2: Weigh poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate and add it into deionized water, and continue to add hydrochloric acid for stirring to obtain a uniformly dispersed poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte; S3: immersing the conductive filler modified carbon fiber cloth in poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte for electrophoretic deposition; using the conductive filler modified carbon fiber cloth as the negative electrode and the graphite plate as the positive electrode, vacuum drying after deposition to obtain a carbon fiber cloth with conductive polymer nanoparticles deposited; Furthermore, the desizing carbon fiber cloth is obtained by soaking the carbon fiber cloth in acetone, repeatedly washing with water and vacuum drying; the soaking temperature is 90-110° C.; the soaking time is 72-96 h; the drying temperature is 70-90° C.; the drying time is 5-8 h; Furthermore, the conductive filler in S1 is graphene oxide, carbon nanotubes or MXene; Furthermore, the stirring time in S1 is 2 to 48 h; Furthermore, the ultrasonic treatment time in S1 is 2 to 6 h; Further, the immersion time in S1 is 2 to 12 h; Further, the drying temperature in S1 is 70-90°C; Furthermore, the drying time in S1 is 5 to 8 hours; Furthermore, the stirring time in S2 is 2 to 4 h; Further, the concentration of the poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate aqueous solution in S2 is 3-6 g / L; Furthermore, the mass ratio of hydrochloric acid to poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate in S2 is 1:11-12; Furthermore, the electrophoretic deposition time in S3 is 10 to 25 min; Furthermore, the voltage in S3 is 10-20 V.

[0005] A modified carbon fiber is prepared by the above preparation method.

[0006] A carbon fiber composite material is prepared from the modified carbon fiber and epoxy resin. The preparation process comprises the following steps: putting 6 layers of modified carbon fiber cloth into a mold, vacuum injecting epoxy resin and curing agent diethylenetriamine into the mold, wherein the mass ratio of epoxy resin to curing agent diethylenetriamine is 100:10.8-12.8, and curing at 100-120°C for 1-4 hours to obtain a carbon fiber composite material.

[0007] An application of carbon fiber composite materials for damage detection in aerospace, automotive industry and biomedicine.

[0008] Compared with the prior art, the present invention solves the problem that the prior art carbon fiber modification method is single and the carbon fiber composite material cannot monitor the damage in real time. The specific beneficial effects are: 1. Secondary modification of carbon fiber improves the mechanical properties of carbon fiber composites: The present invention significantly improves the mechanical properties of carbon fiber materials by using the synergistic effect of modification with conductive fillers (including graphene oxide, carbon nanotubes, MXene, etc.) and electrophoretic deposition modification with poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate. The synergistic effect of poly (3,4-ethylenedioxythiophene) and conductive fillers increases the wettability of carbon fiber, so that the coating formed by the conductive filler wraps the carbon fiber, providing active sites for the deposition of poly (3,4-ethylenedioxythiophene). A large number of poly (3,4-ethylenedioxythiophene) nanoparticles are deposited on the carbon fiber cloth, thereby increasing the interaction between the carbon fiber and the resin, increasing the contact area between the carbon fiber and the resin, and forming a mechanical interlock at the interface, thereby improving the mechanical properties of the material.

[0009] 2. Real-time damage status of carbon fiber composite materials: The carbon fiber composite material prepared by modification of conductive filler / conductive polymer in the present invention has significant damage detection capability. Conductive filler and poly (3,4-ethylenedioxythiophene) are deposited on the carbon fiber, thereby increasing the surface area of ​​the carbon fiber and improving the conductive path of the material. A continuous electrical signal transmission path is formed at the fiber-resin-fiber interface. When the material is damaged, the resin matrix is ​​destroyed, causing the nanoparticles to fall off. At the same time, the fibers contact each other through the nanoparticles. The falling of nanoparticles causes the electrical signal of the carbon fiber composite material to change, so the damage of the material can be detected in real time.

[0010] 3. Environmental friendliness: The present invention uses water as a solvent in the preparation process, which has significant environmental friendliness advantages. Water as a solvent is not only clean, non-toxic and harmless, but also does not pollute the environment during use, which meets the requirements of modern green manufacturing. Compared with traditional solvents, water solvents have lower environmental risks and can effectively avoid the release of harmful chemicals, thereby reducing potential threats to the ecological environment and the health of operators. In addition, no special safety protection measures are required during the operation, which greatly simplifies the process flow and makes the whole process more convenient and safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of the preparation process of carbon fiber deposited with conductive polymer nanoparticles prepared in Example 1; Figure 2 This is an electron microscope image of the carbon fiber nanostructure deposited with conductive polymer nanoparticles prepared in Example 1; Figure 3 is the bending strength diagram of carbon fiber composite material; Figure 4 is the interlaminar shear strength diagram of carbon fiber composite materials; Figure 5 This is a damage detection diagram of the carbon fiber composite material prepared in Comparative Example 1; Figure 6 This is a damage detection diagram of the carbon fiber composite material prepared in Example 3. DETAILED DESCRIPTION

[0012] In order to make the technical solution of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the specification of the present invention. It should be noted that the following embodiments are only used to better understand the technical solution of the present invention and should not be understood as a limitation to the present invention.

[0013] Example 1. S1: The carbon fiber cloth was cut into a size of 100×100 mm, and the carbon fiber cloth was placed in acetone and soaked at 100°C for 72 h to remove the commercial sizing agent, and then repeatedly washed with water to remove excess acetone, and vacuum dried at 80°C for 5 h to obtain the desized carbon fiber cloth; S2: 1.2 g of graphene oxide was added to 1 L of deionized water and stirred for 2 h, followed by ultrasonic treatment for 3 h to obtain a uniformly dispersed graphene oxide dispersion; the desized carbon fiber cloth was immersed in the graphene oxide dispersion at 90 ° C for 2 h, followed by post-drying at 90 ° C for 5 h to obtain a graphene oxide modified carbon fiber cloth; S3: Weigh 3.5 g of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate and add it to 1 L of deionized water, then add 0.3 g of hydrochloric acid and stir for 2 h to obtain a uniformly dispersed poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte; S4: The graphene oxide modified carbon fiber cloth was immersed in poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte for electrophoretic deposition. The deposition time was 10 min and the deposition voltage was 15 V. The modified carbon fiber was used as the negative electrode and the graphite plate was used as the positive electrode. After deposition, it was vacuum dried at 80 °C for 5 h to obtain a carbon fiber cloth with conductive polymer nanoparticles deposited. S5: Take 6 layers of carbon fiber cloth deposited with conductive polymer nanoparticles, lay them out and put them into a mold, and then vacuum-inject epoxy resin and curing agent diethylenetriamine into the mold after removing bubbles, wherein the mass ratio of epoxy resin to curing agent diethylenetriamine is 100:10.8, and cure them at 100°C for 2 h and at 120°C for 2 h to obtain a carbon fiber composite material. Figure 1 Schematic diagram of the preparation process of carbon fiber deposited with conductive polymer nanoparticles; Figure 2 The electron microscope image of the nanostructure of the carbon fiber deposited with conductive polymer nanoparticles shows that the surface of the carbon fiber presents a rough and textured appearance, which can enhance the mechanical properties of the material. The mechanical properties of the carbon fiber composite material prepared in Example 1 were tested, and the bending strength, bending modulus and interlaminar shear of the carbon fiber composite material were measured to be 1510 MPa, 154 GPa and 72.9 MPa, respectively.

[0014] Example 2. S1: The carbon fiber cloth was cut into a size of 100×100 mm, and the carbon fiber cloth was placed in acetone and soaked at 100°C for 72 h to remove the commercial sizing agent, and then repeatedly washed with water to remove excess acetone, and vacuum dried at 80°C for 5 h to obtain the desized carbon fiber cloth; S2: 1g of carbon nanotubes was dissolved in 1L of deionized water, and then a dispersant was added and stirred for 48h and ultrasonicated for 4h to obtain a uniformly dispersed carbon nanotube dispersion; the desized carbon fiber was immersed in the uniformly dispersed carbon nanotube dispersion at 100℃ for 12h, and then dried at 90℃ for 5h to obtain a carbon nanotube-modified carbon fiber cloth; S3: Weigh 3.5 g of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate and add it to 1 L of deionized water, then add 0.3 g of hydrochloric acid and stir for 2 h to obtain a uniformly dispersed poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte; S4: The carbon fiber cloth modified with carbon nanotubes was immersed in poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte for electrophoretic deposition. The deposition time was 10 min, the deposition voltage was 15 V, the modified carbon fiber was used as the negative electrode, and the graphite plate was used as the positive electrode. After deposition, it was vacuum dried at 80 °C for 5 h to obtain the carbon fiber cloth with conductive polymer nanoparticles deposited. S5: Take 6 layers of carbon fiber cloth with conductive polymer nanoparticles deposited on it, lay it out and put it into the mold, remove bubbles from the epoxy resin and curing agent diethylenetriamine, and then vacuum inject it into the mold, wherein the mass ratio of epoxy resin to curing agent diethylenetriamine is 100:10.8, and cure it at 100°C for 2 h and at 120°C for 2 h to obtain a carbon fiber composite material. The mechanical properties of the carbon fiber composite material prepared in Example 4 were tested, and the bending strength, bending modulus and interlaminar shear of the carbon fiber composite material were measured to be 1555 MPa, 154 Gpa and 78.65 MPa, respectively.

[0015] Example 3. S1: The carbon fiber cloth was cut into a size of 100×100 mm, and the carbon fiber cloth was placed in acetone and soaked at 100°C for 72 h to remove the commercial sizing agent, and then repeatedly washed with water to remove excess acetone, and vacuum dried at 80°C for 5 h to obtain the desized carbon fiber cloth; S2: 1.5 g of MXene powder was dissolved in 1 L of deionized water, then ultrasonically treated for 4 h, and stirred for 4 h to obtain a uniformly dispersed MXene dispersion; the desized carbon fiber was immersed in the uniformly dispersed MXene at 90 ° C for 2 h, and then dried at 90 ° C for 5 h to obtain a MXene-modified carbon fiber cloth; S3: Weigh 3.5 g of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate and add it to 1 L of deionized water, then add 0.3 g of hydrochloric acid and stir for 2 h to obtain a uniformly dispersed poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte; S4: The MXene-modified carbon fiber cloth was immersed in poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte for electrophoretic deposition. The deposition time was 10 min, the deposition voltage was 15 V, the MXene-modified carbon fiber cloth was used as the negative electrode, and the graphite plate was used as the positive electrode. After deposition, it was vacuum dried at 80 °C for 5 h to obtain a carbon fiber cloth with conductive polymer nanoparticles deposited. S5: Take 6 layers of carbon fiber cloth with conductive polymer nanoparticles deposited on it, lay it out and put it into the mold, and then vacuum inject epoxy resin and curing agent diethylenetriamine into the mold after removing bubbles, wherein the mass ratio of epoxy resin to curing agent diethylenetriamine is 100:10.8, and cure it at 100°C for 2 h and at 120°C for 2 h to obtain a carbon fiber composite material. The mechanical properties of the carbon fiber composite material prepared in Example 5 were tested, and the bending strength, bending modulus and interlaminar shear of the carbon fiber composite material were measured to be 1635 Mpa, 166.5 Gpa and 82.35 Mpa, respectively.

[0016] Comparative Example 1. S1: The carbon fiber cloth was cut into a size of 100×100 mm; the carbon fiber cloth was placed in acetone and soaked at 100°C for 72 h to remove the commercial sizing agent, then repeatedly washed with water to remove excess acetone, and vacuum dried at 80°C for 5 h to obtain the desized carbon fiber cloth; S2: Take 6 layers of desizing carbon fiber cloth, lay them and put them into the mold, remove bubbles from the epoxy resin and curing agent diethylenetriamine, and then vacuum inject them into the mold, wherein the mass ratio of epoxy resin to curing agent diethylenetriamine is 100:10.8, and cure at 100°C for 2 h and at 120°C for 2 h to obtain a carbon fiber composite material. The mechanical properties of the carbon fiber composite material prepared in Comparative Example 1 were tested, and the bending strength, bending modulus and interlaminar shear of the carbon fiber composite material were measured to be 1313 MPa, 120.3 GPa and 67.8 MPa, 1555 MPa, 154 Gpa and 78.65 MPa, respectively.

[0017] Comparative Example 2. S1: Cut the carbon fiber cloth into a size of 100×100 mm; S2: Take 6 layers of carbon fiber cloth with conductive polymer nanoparticles deposited on it, lay it out and put it into the mold, and then vacuum inject epoxy resin and curing agent diethylenetriamine into the mold after removing bubbles, wherein the mass ratio of epoxy resin to curing agent diethylenetriamine is 100:10.8, and cure it at 100°C for 2 h and at 120°C for 2 h to obtain a carbon fiber composite material. The mechanical properties of the carbon fiber composite material prepared in Example 1 were tested, and the bending strength, bending modulus and interlaminar shear of the carbon fiber composite material were measured to be 1439 MPa, 140 GPa and 71 MPa, respectively.

[0018] Comparative Example 3. S1: The carbon fiber cloth was cut into a size of 100×100 mm; the carbon fiber cloth was placed in acetone and soaked at 100°C for 72 h to remove the commercial sizing agent, then repeatedly washed with water to remove excess acetone, and vacuum dried at 80°C for 5 h to obtain the desized carbon fiber cloth; S2: Weigh 3.5 g of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate and add it to 1 L of deionized water, then add 0.3 g of hydrochloric acid and stir for 2 h to obtain a uniformly dispersed poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte; S3: The desized carbon fiber cloth was immersed in poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate) electrolyte for electrophoretic deposition. The deposition time was 10 min and the deposition voltage was 15 V. The desized carbon fiber cloth was used as the negative electrode and the graphite plate was used as the positive electrode. After deposition, the desized carbon fiber cloth was vacuum dried at 80 °C for 5 h to obtain the desized electrodeposited carbon fiber cloth. S4: Take 6 layers of desizing electrodeposited carbon fiber cloth, lay them and put them into the mold, and vacuum inject epoxy resin and curing agent diethylenetriamine into the mold after removing bubbles, wherein the mass ratio of epoxy resin to curing agent diethylenetriamine is 100:10.8, and cure at 100°C for 2 h and at 120°C for 2 h to obtain a carbon fiber composite material. The mechanical properties of the carbon fiber composite material prepared in Example 2 were tested, and the bending strength, bending modulus and interlaminar shear of the carbon fiber composite material were measured to be 1370 MPa, 148 GPa and 70.5 MPa, respectively.

[0019] The mechanical properties of the carbon fiber composite materials prepared in Examples 1-3 and Comparative Examples 1-3 were tested. Figure 3 and Figure 4 As shown, the carbon fiber composites prepared using the modified carbon fibers of Examples 1-3 have an upward trend in bending strength, bending modulus, and interlaminar shear compared with Comparative Examples 1-3, proving that the modified carbon fibers prepared by the present invention can significantly improve the mechanical properties of the composite materials. This is attributed to the fact that poly(3,4-ethylenedioxythiophene) and conductive fillers increase the wettability of the carbon fibers, enhance the interaction between the fibers and the resin, and the coating formed by the conductive fillers wraps the carbon fibers, providing active sites for the deposition of poly(3,4-ethylenedioxythiophene). A large number of poly(3,4-ethylenedioxythiophene) nanoparticles are deposited on the fibers, increasing the contact area between the fibers and the resin, and forming a mechanical interlock at the interface, thereby improving the mechanical properties of the material.

[0020] The carbon fiber composite material prepared in Comparative Example 1 was subjected to a damage detection test. Figure 5 As shown in the figure, the resistance change rate in the early stage has basically no obvious change, indicating that in the early stage of damage, the resistance change rate cannot respond to material damage. The carbon fiber composite material prepared in Example 3 was subjected to damage detection test. Figure 6As shown in the figure, the carbon fiber composite material prepared by the modification of conductive filler / conductive polymer has significant damage detection ability. This is because the conductive filler and poly (3,4-ethylenedioxythiophene) are deposited on the fiber, which increases the surface area of ​​the carbon fiber, improves the conductive path of the material, and forms a continuous electrical signal transmission path at the fiber-resin-fiber interface. When the material is damaged, the resin matrix is ​​destroyed, causing the nanoparticles to fall off. At the same time, the fibers contact each other through the nanoparticles, and the shedding of the nanoparticles causes the electrical signal of the carbon fiber composite material to change, resulting in the composite material having excellent damage detection performance.

[0021] The application and design concept of the present invention are not limited to the above examples. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention. Any equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing modified carbon fiber, characterized in that: The following steps are involved: S1: adding a conductive filler into deionized water and stirring, followed by ultrasonic treatment to obtain a uniformly dispersed conductive filler dispersion; immersing a desized carbon fiber cloth in the conductive filler dispersion, followed by drying to obtain a conductive filler-modified carbon fiber cloth; S2: Weigh poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate and add it into deionized water, and continue to add hydrochloric acid for stirring to obtain a uniformly dispersed poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte; S3: The conductive filler-modified carbon fiber cloth is immersed in poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate electrolyte for electrophoretic deposition; the conductive filler-modified carbon fiber cloth is used as the negative electrode and the graphite plate is used as the positive electrode. After deposition, vacuum drying is performed to obtain a carbon fiber cloth with conductive polymer nanoparticles deposited thereon.

2. The method for preparing modified carbon fiber according to claim 1, characterized in that: The desized carbon fiber cloth is obtained by soaking the carbon fiber cloth in acetone, repeatedly washing with water and vacuum drying.

3. The method for preparing modified carbon fiber according to claim 2, characterized in that: The soaking temperature is 90-110° C.; the soaking time is 72-96 h; the drying temperature is 70-90° C.; and the drying time is 5-8 h.

4. The method for preparing modified carbon fiber according to claim 1, characterized in that: The conductive filler in S1 is graphene oxide, carbon nanotube or MXene.

5. The method for preparing modified carbon fiber according to claim 1, characterized in that: In the S1, the stirring time is 2 to 48 h; the ultrasonic treatment time is 2 to 6 h; the immersion time is 2 to 12 h; the drying temperature is 70 to 90° C.; and the drying time is 5 to 8 h.

6. The method for preparing modified carbon fiber according to claim 1, characterized in that: The stirring time in S2 is 2-4 h; the concentration of the poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate aqueous solution is 3-6 g / L; and the mass ratio of hydrochloric acid to poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate is 1:11-12.

7. The method for preparing modified carbon fiber according to claim 1, characterized in that: The electrophoretic deposition time in S3 is 10-25 min; the voltage is 10-20 V.

8. A modified carbon fiber, characterized in that: The method is prepared according to any one of claims 1 to 7.

9. A carbon fiber composite material, characterized in that: The modified carbon fiber and epoxy resin described in claim 8 are prepared, and the preparation process comprises the following steps: 6 layers of modified carbon fiber cloth are put into a mold, and epoxy resin and curing agent diethylenetriamine are vacuum injected into the mold, wherein the mass ratio of epoxy resin to curing agent diethylenetriamine is 100:10.8~12.8, and cured at 100~120°C for 1~4 hours to obtain a carbon fiber composite material.

10. An application of the carbon fiber composite material according to claim 9, characterized in that: Used for damage detection in aerospace, automotive industry and construction engineering.

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