A method for improving the interfacial bonding properties of carbon fiber reinforced epoxy resin matrix composites

Abstract

This invention provides a method for improving the interfacial bonding performance of carbon fiber reinforced epoxy resin matrix composites, belonging to the field of carbon fiber surface modification technology. The method for preparing modified carbon fibers in this invention includes the following steps: using air as the plasma gas medium to perform plasma treatment on carbon fibers to obtain plasma-surface modified carbon fibers; immersing the plasma-surface modified carbon fibers in a polyamide-amine dendritic macromolecule (PAMAM) solution for reaction to obtain the modified carbon fibers. This invention prepares modified carbon fibers by combining plasma treatment and surface grafting treatment, thereby improving the interfacial bonding strength of carbon fiber reinforced epoxy resin matrix composites while maintaining the stability of the original tensile properties of the carbon fibers.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber surface modification technology, and in particular to a method for improving the interfacial bonding performance of carbon fiber reinforced epoxy resin matrix composites. Background Technology

[0002] Carbon fiber is a high-performance material with a carbon content exceeding 90%, and its molecular structure is similar to that of disordered graphite. As a commonly used reinforcing material, carbon fiber possesses high strength, high stiffness, low density, and excellent corrosion resistance, while also exhibiting outstanding thermal, electrical, and chemical properties. Composite materials formed by combining carbon fiber with epoxy resin are lightweight, high-strength, offer good design flexibility, strong fatigue resistance, and good corrosion resistance, and are suitable for large-area monolithic molding. Therefore, carbon fiber is receiving increasing attention and application in various fields such as aerospace, electronics and information technology, transportation, metallurgy and chemical engineering, and medical and health care.

[0003] During the production of carbon fiber, it undergoes high-temperature carbonization treatment exceeding 1000℃ in an inert gas environment. This process releases non-carbon elements (such as oxygen and nitrogen) from the fiber and causes the lattice structure of carbon atoms to transform into a disordered graphite structure. As a result, the carbon fiber surface becomes relatively smooth, lacking active functional groups, and therefore exhibits inertness and low reactivity. This characteristic leads to poor bonding performance between carbon fiber and resin, insufficient interfacial bonding force, and thus reduces the interlaminar shear strength of carbon fiber reinforced resin matrix composites, affecting their performance. Therefore, before bonding carbon fiber with resin, the carbon fiber surface needs to be treated to improve its surface roughness and chemical activity, thereby improving its bonding effect with epoxy resin.

[0004] Plasma treatment is an emerging carbon fiber modification technology that has attracted much attention in recent years. Plasma is an ionized mixture containing ions, electrons, free radicals, and excited molecules and atoms, which can interact with the carbon fiber surface to generate highly reactive substances. During plasma treatment of carbon fibers, the different properties of the gases used may generate free radicals, ions, and metastable substances, thereby initiating ablation, cross-linking, or oxidation reactions. During the treatment process, plasma etches the carbon fiber surface to change its morphology, thus increasing the fiber surface roughness. Oxidation reactions also occur, generating active oxygen-containing functional groups to increase the fiber surface activity, thereby improving the physical intercalation and chemical bonding between the fiber and the resin, and enhancing the interfacial adhesion. Simultaneously, plasma treatment of carbon fibers only affects the fiber surface and does not significantly alter the overall properties, maintaining the original internal properties of the fiber. Therefore, plasma treatment has become a widely used method for carbon fiber surface modification with very significant treatment effects.

[0005] However, plasma-treated carbon fibers have a time-dependent effect, and the treated surface may gradually lose its activity over time. Therefore, in order to prevent the plasma-treated carbon fibers from failing, an additional surface treatment is required. Summary of the Invention

[0006] Based on the above, the purpose of this invention is to provide a method for improving the interfacial bonding performance of carbon fiber reinforced epoxy resin matrix composites. This invention utilizes a combination of plasma treatment and surface grafting treatment to enhance the interfacial bonding strength between carbon fiber and epoxy resin matrix composites, while simultaneously maintaining the stability of the original tensile properties of the carbon fiber.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] One of the technical solutions of this invention is a method for preparing modified carbon fiber, comprising the following steps:

[0009] Using air as the plasma gas medium, carbon fibers are subjected to plasma treatment to obtain plasma-modified carbon fibers.

[0010] The plasma-modified carbon fiber was immersed in a PAMAM solution to react and obtain the modified carbon fiber.

[0011] The second technical solution of the present invention is to prepare modified carbon fiber by the above preparation method.

[0012] The third technical solution of the present invention is a method for improving the interfacial bonding performance of carbon fiber reinforced epoxy resin matrix composites, wherein the carbon fiber is modified by the above-mentioned preparation method.

[0013] The fourth technical solution of the present invention is a carbon fiber reinforced epoxy resin matrix composite material, the raw materials of which include the above-mentioned modified carbon fiber and epoxy resin.

[0014] The principle of this invention is as follows:

[0015] First, vacuum plasma is used to modify the surface of carbon fibers. The modified carbon fiber surface is rich in oxygen-containing functional groups such as -OH, -COOH, and C=O. Simultaneously, the surface roughness increases, enhancing the chemical bonding and mechanical interlocking between the fiber and epoxy resin. This results in increased interfacial shear strength and improved interfacial bonding performance of the carbon fiber-reinforced epoxy resin composite. Furthermore, plasma treatment maintains the original tensile properties of the carbon fiber without affecting its overall performance.

[0016] Subsequently, PAMAM solution was used to perform surface grafting modification on the carbon fibers. After this modification, the carbon fiber surface gained nitrogen-containing functional groups rich in -C-NH2, while the content of oxygen-containing functional groups such as -OH, -COOH, and C=O also increased. PAMAM molecules were adsorbed onto the carbon fiber surface during the treatment, resulting in a slight decrease in the surface roughness, but overall it remained consistent with that before the surface grafting treatment.

[0017] The present invention discloses the following technical effects:

[0018] This invention uses vacuum plasma to modify the surface of carbon fibers, combining the characteristics of physical and chemical modification. It can not only generate oxygen-containing functional groups on the surface of carbon fibers, but also increase the surface roughness of the fibers, thereby strengthening the bonding ability between the fibers and epoxy resin, and thus enhancing the interfacial properties.

[0019] This invention employs surface grafting treatment to fill the fine grooves on the surface of carbon fibers, while simultaneously generating nitrogen-containing and oxygen-containing functional groups on the carbon fiber surface. This further enhances the surface activity of carbon fibers based on plasma treatment, compensates for the time-limited nature of vacuum plasma treatment, and thus further strengthens the bonding ability between carbon fibers and epoxy resin, thereby enhancing the interfacial properties of the composite material.

[0020] After modifying the fibers using the method of this invention, not only is the interfacial strength of the carbon fiber reinforced epoxy resin matrix composite material improved, but the original overall properties of the carbon fiber, such as tensile properties, are also kept unaffected.

[0021] The method provided by this invention is simple and efficient, can introduce more active functional groups on the surface of carbon fibers, and can avoid the problem of short aging of carbon fibers after plasma treatment. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram illustrating the preparation of the modified carbon fiber of the present invention;

[0024] Figure 2 Schematic diagram for preparing PAMAM solution;

[0025] Figure 3 These are macroscopic morphology images of the modified and unmodified carbon fibers in Example 1. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] Surface grafting is a commonly used method for modifying carbon fiber surfaces. Surface grafting (such as grafting polymers, functional molecules, or other active ingredients) can add stable chemical structures to these active groups. These structures not only reduce the exposure of surface-active groups, preventing further oxidation or hydrolysis by airborne molecules, but also, to a certain extent, "seal" or "protect" the surface-active groups through chemical reactions. This enhances the stability of the carbon fiber surface, slows down the degradation of surface-active groups over time, and thus mitigates or solves the aging problem. Surface grafting refers to modifying the carbon fiber surface to allow for the grafting or in-situ growth of compounds or polymers with specific functional groups. It can also connect nanoparticles to form an effective interfacial transition layer, thereby enhancing the interfacial adhesion of carbon fiber-reinforced polymer matrix composites. This treatment not only introduces functional groups, improving surface roughness and wettability, but also avoids damage to the carbon fiber and even enhances its strength to a certain extent. Therefore, similar to plasma treatment, it does not negatively affect the tensile properties of the carbon fiber and can effectively improve interfacial bonding.

[0032] The first aspect of this invention provides a method for preparing modified carbon fibers, comprising the following steps:

[0033] Using air as the plasma gas medium, carbon fibers are subjected to plasma treatment to obtain plasma-modified carbon fibers.

[0034] The plasma-modified carbon fiber was immersed in a PAMAM solution to react and obtain the modified carbon fiber.

[0035] In some embodiments of the present invention, the plasma treatment specifically involves: placing carbon fibers in a vacuum plasma chamber, evacuating the chamber to a pressure of 0.2–0.5 mbar, a treatment power of 100–300 W, a gas flow rate of 5–10 sccm, and a treatment time of 0.5–10 min.

[0036] In some embodiments of the present invention, the concentration of the PAMAM solution is 2 × 10⁻⁶. -4 mol / L—20×10 -4 mol / L. The preparation method of PAMAM solution in this invention is as follows: PAMAM is dissolved in DMF, sonicated, and then condensing agent HATU is added at a ratio of 45 mg per 270 mL of solution, followed by sonication.

[0037] In some embodiments of the present invention, the concentration of the PAMAM solution is 2 × 10⁻⁶. -4 mol / L—15×10 -4 mol / L.

[0038] In some embodiments of the present invention, the concentration of the PAMAM solution is 10 × 10⁻⁶. -4 mol / L—15×10 - 4 mol / L.

[0039] This invention does not impose any special limitation on the amount of PAMAM solution used, as long as it is sufficient to completely immerse the carbon fiber.

[0040] In some embodiments of the present invention, the reaction is carried out at room temperature for 4 hours.

[0041] In some embodiments of the present invention, after the reaction is completed, the process further includes a cleaning and drying step; the drying is vacuum drying, the temperature of which is 50°C and the time is 24 hours.

[0042] A second aspect of the present invention provides a modified carbon fiber prepared by the above-described preparation method.

[0043] A third aspect of the present invention provides a method for improving the interfacial bonding performance of carbon fiber reinforced epoxy resin matrix composites, wherein the carbon fiber is modified using the above-described preparation method.

[0044] A fourth aspect of the present invention provides a carbon fiber reinforced epoxy resin-based composite material, the raw materials of which include the above-mentioned modified carbon fiber and epoxy resin.

[0045] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0046] To better understand this invention, the following embodiments further illustrate its content; however, the invention is not limited to these embodiments. A schematic diagram of the preparation of modified carbon fiber in this invention is shown below. Figure 1 .

[0047] In this embodiment, the epoxy resin used is E54 epoxy resin, and the curing temperature of the epoxy resin and the modified carbon fiber composite is 180°C, and the curing time is 3 hours.

[0048] In the following examples and comparative examples, the mass ratio of epoxy resin to modified carbon fiber is equal to the mass ratio of epoxy resin to unmodified carbon fiber, which is 1:3.

[0049] Example 1

[0050] The preparation steps for modified carbon fiber are as follows:

[0051] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.25 mbar. Air is used as the plasma gas medium with a flow rate of 7 sccm, a treatment power of 300 W, and a treatment time of 0.5 min.

[0052] (2) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 2×10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0053] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in the prepared PAMAM / DMF solution and then placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain the modified carbon fibers.

[0054] After heating and curing the epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 106.54 MPa, which is 23.85% higher than that of the unmodified interfacial shear strength in Comparative Example 1.

[0055] Example 2

[0056] The preparation steps for modified carbon fiber are as follows:

[0057] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.25 mbar. Air is used as the plasma gas medium with a flow rate of 7 sccm, a treatment power of 300 W, and a treatment time of 3 min.

[0058] (2) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 6×10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0059] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in the prepared PAMAM / DMF solution and placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain modified carbon fibers.

[0060] After heating and curing the epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 118.23 MPa, which is 37.44% higher than that of the unmodified interfacial shear strength in Comparative Example 1.

[0061] Example 3

[0062] The preparation steps for modified carbon fiber are as follows:

[0063] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.25 mbar. Air is used as the plasma gas medium with a flow rate of 8 sccm, a treatment power of 300 W, and a treatment time of 3 min.

[0064] (2) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 10 × 10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0065] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in the prepared PAMAM / DMF solution and placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain modified carbon fibers.

[0066] After heating and curing the epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 128.53 MPa, which is 49.42% higher than that of the unmodified interfacial shear strength in Comparative Example 1.

[0067] Example 4

[0068] The preparation steps for modified carbon fiber are as follows:

[0069] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.3 mbar. Air is used as the plasma gas medium with a flow rate of 7 sccm, a treatment power of 300 W, and a treatment time of 3 min.

[0070] (2) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 15 × 10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0071] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in the prepared PAMAM / DMF solution and placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain modified carbon fibers.

[0072] After heating and curing the epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 124.21 MPa, which is 44.40% higher than that of the unmodified interfacial shear strength in Comparative Example 1.

[0073] Example 5

[0074] The preparation steps for modified carbon fiber are as follows:

[0075] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.25 mbar. Air is used as the plasma gas medium with a flow rate of 7 sccm, a treatment power of 300 W, and a treatment time of 5 min.

[0076] (2) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 10 × 10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0077] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in the prepared PAMAM / DMF solution and placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain modified carbon fibers.

[0078] After heating and curing the epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 116.46 MPa, which is 35.39% higher than that of the unmodified interfacial shear strength in Comparative Example 1.

[0079] Example 6

[0080] The preparation steps for modified carbon fiber are as follows:

[0081] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.25 mbar. Air is used as the plasma gas medium with a flow rate of 8 sccm, a treatment power of 300 W, and a treatment time of 9 min.

[0082] (2) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 6×10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0083] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in the prepared PAMAM / DMF solution and placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain modified carbon fibers.

[0084] After heating and curing the epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 135.63 MPa, which is 57.67% higher than that of the unmodified interfacial shear strength in Comparative Example 1.

[0085] Example 7

[0086] The preparation steps for modified carbon fiber are as follows:

[0087] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.25 mbar. Air is used as the plasma gas medium with a flow rate of 7 sccm, a treatment power of 300 W, and a treatment time of 9 min.

[0088] (2) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 10 × 10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0089] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in the prepared PAMAM / DMF solution and placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain modified carbon fibers.

[0090] After heating and curing the epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 140.73 MPa, which is 63.60% higher than that of the unmodified interfacial shear strength in Comparative Example 1.

[0091] Example 8

[0092] The preparation steps for modified carbon fiber are as follows:

[0093] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.3 mbar. Air is used as the plasma gas medium with a flow rate of 7 sccm, a treatment power of 300 W, and a treatment time of 9 min.

[0094] (2) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 15 × 10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0095] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in the prepared PAMAM / DMF solution and placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain modified carbon fibers.

[0096] After heating and curing the epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 137.85 MPa, which is 60.25% higher than that of the unmodified interfacial shear strength in Comparative Example 1.

[0097] Comparative Example 1

[0098] After heating and curing unmodified carbon fibers with epoxy resin, a micro-debonding test was conducted, and the interfacial shear strength was found to be 86.02 MPa.

[0099] The carbon fibers obtained above have not undergone modification treatment, and their interfacial bonding performance with epoxy resin is poor.

[0100] Comparative Example 2

[0101] (1) Plasma treatment of carbon fiber surface. The carbon fiber was placed in a plasma chamber, and the chamber was evacuated to a pressure of 0.25 mbar. Air was used as the plasma gas medium, with a gas flow rate of 7 sccm, a treatment power of 300 W, and a treatment time of 1 min. Plasma-modified carbon fiber was obtained.

[0102] After heating and curing the plasma-modified carbon fiber with epoxy resin, a micro-debonding test was conducted, and the interfacial shear strength was found to be 95.09 MPa, which is 10.54% higher than that of the unmodified interfacial shear strength in Comparative Example 1.

[0103] The carbon fibers obtained above have not undergone surface grafting treatment; after plasma treatment alone, the interfacial bonding performance between the fibers and epoxy resin is only slightly improved.

[0104] Comparative Example 3

[0105] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.25 mbar. Air is used as the plasma gas medium with a flow rate of 7 sccm, a treatment power of 300 W, and a treatment time of 15 min.

[0106] (2) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 10 × 10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0107] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in the prepared PAMAM / DMF solution and placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain modified carbon fibers.

[0108] After heating and curing epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 95.68 MPa, which is 11.23% higher than that of the unmodified interfacial shear strength.

[0109] The carbon fibers obtained above were severely damaged due to the excessively long plasma treatment time, making them unsuitable as reinforcing materials.

[0110] Comparative Example 4

[0111] (1) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 2×10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0112] (2) Surface grafting treatment of carbon fibers. The carbon fibers were placed in a prepared PAMAM / DMF solution and placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain the modified carbon fibers.

[0113] After heating and curing the modified carbon fiber with epoxy resin, a micro-debonding test was conducted, and the interfacial shear strength was found to be 96.53 MPa, which is 12.22% higher than that of the unmodified interfacial shear strength.

[0114] The carbon fibers obtained above were not subjected to plasma treatment; after only surface grafting treatment, the interfacial bonding performance between the fibers and epoxy resin was only slightly improved.

[0115] Comparative Example 5

[0116] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.25 mbar. Argon is used as the plasma gas medium with a flow rate of 7 sccm, a treatment power of 300 W, and a treatment time of 0.5 min.

[0117] (2) Preparation of PAMAM / DMF solution. Dissolve PAMAM in DMF to prepare a solution with a concentration of 2×10⁻⁶. -4 Add mol / L PAMAM / DMF solution, sonicate for 5 min, then add condensing agent HATU at a ratio of 45 mg per 270 mL solution, and sonicate for 5 min.

[0118] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in the prepared PAMAM / DMF solution and placed in a desiccator to react at room temperature for 4 hours. After the reaction was completed, the carbon fibers were rinsed once with DMF solvent and three times with deionized water. Then, they were placed in a vacuum drying oven and dried at 50°C for 24 hours to obtain modified carbon fibers.

[0119] After heating and curing epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 98.45 MPa, which is 14.45% higher than that of the unmodified interfacial shear strength.

[0120] The carbon fibers obtained above use argon as the plasma gas medium, which results in limited improvement in interfacial bonding performance.

[0121] Comparative Example 6

[0122] (1) Plasma treatment of carbon fiber surface. The carbon fiber is placed in the plasma chamber and the chamber is evacuated to a pressure of 0.25 mbar. Air is used as the plasma gas medium with a flow rate of 7 sccm, a treatment power of 300 W, and a treatment time of 0.5 min.

[0123] (2) Preparation of maleic anhydride xylene solution. Dissolve 7g of maleic anhydride in 100mL of xylene in a water bath at 60℃ to obtain maleic anhydride xylene solution.

[0124] (3) Surface grafting treatment of carbon fibers. The carbon fibers treated with plasma in step (1) were placed in a prepared maleic anhydride xylene solution and sonicated for 30 min. Then, the carbon fibers were wrapped with tin foil and placed in a high-temperature oven at 170°C. After reacting for 7 min, the mixture was cooled to obtain crude carbon fibers grafted with maleic anhydride to the plasma-treated product. The obtained crude carbon fibers were added to the precipitant acetone and allowed to stand for 24 hours. The solvent was then removed, and the mixture was dissolved in xylene. After dissolution, the mixture was poured into acetone to precipitate, and this process was repeated twice. Subsequently, most of the solvent was evaporated under an infrared lamp, and the mixture was vacuum dried at 50°C to constant weight to obtain grafted maleic anhydride carbon fibers.

[0125] After heating and curing epoxy resin and modified carbon fiber, a micro-debonding test was conducted, and the interfacial shear strength was found to be 100.45 MPa, which is 16.78% higher than that of the unmodified interfacial shear strength.

[0126] The carbon fibers obtained above are surface grafted with maleic anhydride, which only provides limited improvement in interfacial bonding performance.

[0127] Examples 1 to 8 show that when the plasma treatment time for carbon fibers is 9 min, the concentration of PAMAM / DMF solution in the surface grafting treatment is 10 × 10⁻⁶. -4 At a concentration of mol / L, the carbon fiber reinforced epoxy resin matrix composite exhibited the highest interfacial shear strength of 140.73 MPa, representing a 63.60% increase compared to the 86.02 MPa of untreated carbon fiber. Composite panels prepared by compression molding of treated carbon fiber and epoxy resin showed the best interfacial bonding performance and the most significant improvement in interfacial properties.

[0128] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A carbon fiber reinforced epoxy resin matrix composite, characterized by, The raw materials include modified carbon fiber and epoxy resin; the preparation steps of the modified carbon fiber are as follows: (1) carbon fiber surface plasma treatment: the carbon fiber is placed in a plasma cavity, the cavity is vacuumed to 0.25 mbar, air is used as the plasma gas medium, the gas flow is 7 sccm, the treatment power is 300 W, and the treatment time is 9 min; (2) Preparation of PAMAM / DMF solution: PAMAM was dissolved in DMF to prepare PAMAM / DMF solution with a concentration of 10 x 10 -4 mol / L, and sonicated for 5 min. Then, 45 mg of condensing agent HATU was added according to the proportion of 1 mg per 270 mL of solution, and sonicated for 5 min. (3) carbon fiber surface grafting treatment: the carbon fiber treated by plasma in step (1) is placed in the prepared PAMAM / DMF solution, is placed in a dryer to react for 4 h at room temperature, is washed once with a solvent DMF and three times with deionized water after the reaction, and is then placed in a vacuum drying box to be dried at 50 DEG C for 24 h, so that the modified carbon fiber is obtained.

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