A method for preparing a carbon fiber flame-retardant reinforced epoxy resin composite material

Abstract

The application discloses a preparation method of carbon fiber flame-retardant reinforced epoxy resin composite material and belongs to the technical field of polymer composite material preparation. The application takes carbon fiber, phytic acid, chitosan, epoxy resin and a curing agent thereof as raw materials, carries out high-temperature desizing and alkali activation treatment on the original carbon fiber, constructs a phytic acid / chitosan composite coating on the surface of the carbon fiber through step-by-step coating, prepares flame-retardant modified carbon fiber fillers, finally mixes the fillers with the epoxy resin and the curing agent, and through stirring, defoaming and stage temperature rising curing, the carbon fiber flame-retardant reinforced epoxy resin composite material is prepared. Compared with the unmodified carbon fiber reinforced epoxy resin composite material, the composite material prepared by the application has synchronous improvement of mechanical properties and flame-retardant properties, higher tensile strength and breaking strain, significant improvement of the limiting oxygen index, obvious improvement of heat release and smoke production performance, and the preparation process is simple and the raw materials are environment-friendly, so the application can be widely applied in the fields of electronic packaging, aerospace, automobile manufacturing and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer composite material preparation technology, specifically to a method for preparing carbon fiber flame-retardant reinforced epoxy resin composite material. Background Technology

[0002] Epoxy resin (EP) is widely used in key fields such as electronic packaging, aerospace, automotive manufacturing, and high-performance composite materials due to its excellent mechanical strength, good adhesion, chemical stability, and low curing shrinkage. However, epoxy resin has inherent high flammability, releasing a large amount of heat and smoke during combustion, posing a serious fire safety hazard. This defect greatly limits its application in scenarios with strict fire safety requirements. Therefore, effectively improving the flame retardant properties of epoxy resin while maintaining its excellent overall performance is one of the core challenges in the current materials research and development field.

[0003] Currently, the main approaches to improving the flame retardant properties of epoxy resins are divided into additive and reactive flame retardant technologies. Additive flame retardants are simple to process, but they have problems such as easy migration and potential degradation of the long-term performance of the matrix. Reactive flame retardants achieve a long-lasting flame retardant effect through chemical bonding, but they require high precision in molecular design and synthesis processes. In recent years, bio-based flame retardants such as phytic acid (PA) and chitosan (CS) have received widespread attention due to their environmentally friendly, renewable, and low-toxicity properties. Both can exert a phosphorus-nitrogen synergistic flame retardant effect, playing a flame-retardant role in both the gas and condensed phases, providing a new approach for the development of green flame retardant systems.

[0004] Carbon fiber (CF), as a high-performance reinforcement, is often used to improve the mechanical properties of epoxy resins. However, the surface of raw carbon fiber is inert, resulting in weak interfacial bonding with the resin matrix, leading to low stress transfer efficiency and insufficient reinforcement effect. Modifying the surface of carbon fiber, introducing active functional groups, or constructing composite coatings are effective means to improve its interfacial compatibility and adhesion with the matrix, and may also bring additional functionality to the matrix.

[0005] Existing research primarily focuses on the application of bio-based flame retardants or their reinforcing effects on carbon fibers. There is a lack of systematic research on the synergistic use of phytic acid and chitosan for carbon fiber surface modification, constructing novel fillers that combine interfacial reinforcement and high-efficiency flame retardancy, and systematically studying their synergistic effects on the mechanical, thermal stability, and flame retardant properties of epoxy composites. Therefore, developing a phytic acid / chitosan composite coating-modified carbon fiber-reinforced epoxy resin composite material to simultaneously optimize its mechanical and flame-retardant properties is of significant technical necessity and application value for promoting the development of high-performance, environmentally friendly composite materials. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, the present invention aims to provide a method for preparing carbon fiber flame-retardant reinforced epoxy resin composite materials. This invention modifies the surface of carbon fibers to construct a phytic acid / chitosan composite coating. The prepared modified carbon fiber filler possesses both reinforcing and flame-retardant functions. When combined with epoxy resin, it can simultaneously improve the mechanical properties and flame-retardant properties of the material. Furthermore, the preparation process is simple, the raw materials are environmentally friendly, and it is suitable for industrial production.

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

[0008] A method for preparing a carbon fiber flame-retardant reinforced epoxy resin composite material includes the following steps:

[0009] 1) Preparation of activated carbon fiber: The raw carbon fiber is subjected to high temperature heat treatment to remove the sizing agent on the surface, and after cooling, washing and drying, desizing carbon fiber is obtained; then activated carbon fiber is obtained by alkaline treatment.

[0010] 2) Preparation of phytic acid / chitosan composite coating modified carbon fiber: The activated carbon fiber is reacted with phytic acid solution and chitosan solution in sequence to build a phytic acid / chitosan composite coating layer by layer on the surface of the activated carbon fiber. After washing and drying, flame-retardant modified carbon fiber filler is obtained.

[0011] 3) Preparation of epoxy resin composite material: Flame-retardant modified carbon fiber filler is mixed with epoxy resin and curing agent, stirred and degassed, and then poured into a mold. The carbon fiber flame-retardant reinforced epoxy resin composite material is prepared by a staged temperature rise curing process.

[0012] Preferably, the high-temperature heat treatment method in step 1) is as follows: the original carbon fiber is laid flat in a ceramic boat and placed in a tube furnace at 500°C for 1 hour to remove the sizing agent.

[0013] Preferably, the alkaline treatment in step 1) is as follows: after the desized carbon fiber is refluxed with NaOH aqueous solution at 100°C for 24 hours, it is repeatedly washed with deionized water until the filtrate is neutral, filtered and dried to obtain activated carbon fiber, which introduces oxygen-containing functional groups on its surface and increases its roughness, providing active sites for subsequent coating.

[0014] Preferably, in step 2), the activated carbon fibers are reacted sequentially with phytic acid solution and chitosan solution: the activated carbon fibers are added to deionized water and ultrasonically dispersed for 20 minutes, then phytic acid aqueous solution is added and reacted at room temperature for 4 hours to allow the phytic acid to fully combine with the functional groups on the surface of the activated carbon fibers; excess phytic acid is removed by centrifugation and washing; the treated carbon fibers are redispersed in deionized water and ultrasonically dispersed for 20 minutes, then chitosan solution and acetic acid aqueous solution are added and reacted at room temperature for another 2 hours to achieve secondary coating of chitosan on the surface of the carbon fibers; after centrifugation and washing, the carbon fibers are dried in an oven at 50°C for 24 hours and then ground to obtain flame-retardant modified carbon fiber filler.

[0015] Preferably, in step 3), the flame-retardant modified carbon fiber filler and epoxy resin are mixed and stirred at 50°C for 30 minutes, a curing agent accounting for 6% of the mass of epoxy resin is added and stirred for another 30 minutes, and after ultrasonic water bath degassing for 20 minutes, it is poured into a mold preheated at 80°C for 10 minutes, pre-cured at 80°C for 1 hour, and then cured at 140°C for 1 hour. After naturally cooling to room temperature, the carbon fiber flame-retardant reinforced epoxy resin composite material is obtained.

[0016] Preferably, in step 2), the phytic acid solution is an aqueous solution of phytic acid with a concentration of 40 mg / ml; the chitosan solution is a chitosan solution with a concentration of 10 mg / ml; and the solvent is an aqueous solution of acetic acid with a volume fraction of 22%.

[0017] Preferably, in step 3), the mass ratio of flame-retardant modified carbon fiber filler to epoxy resin is 1%-20%.

[0018] The beneficial effects of this invention are as follows:

[0019] 1. The present invention achieves a combination of high-temperature desizing, alkaline activation and stepwise coating of phytic acid / chitosan in the modification process of carbon fiber. Alkaline activation introduces oxygen-containing functional groups into the carbon fiber surface and increases roughness, providing sufficient active sites for the coating of phytic acid and chitosan. The phytic acid / chitosan composite coating is uniformly loaded on the carbon fiber surface without obvious agglomeration, and the modification effect is stable.

[0020] 2. The flame-retardant modified carbon fiber filler prepared by this invention has both mechanical reinforcement and flame retardant functions. After being compounded with epoxy resin, the filler and the matrix achieve a strong interfacial bond through hydrogen bonding, chemical bonding or physical entanglement. The rigid carbon fiber effectively bears and transfers the load, while the phosphorus-based component of phytic acid and the nitrogen-containing structure of chitosan exert a phosphorus-nitrogen synergistic flame retardant effect.

[0021] 3. The mechanical properties of the carbon fiber flame-retardant reinforced epoxy resin composite material prepared by this invention are significantly improved. The tensile strength and fracture strain are significantly increased compared with the unmodified carbon fiber reinforced composite material. Moreover, the glass transition temperature increases with the increase of filler content. The glass transition temperature reaches 150.71℃ when the filler content is 20%, and the thermal stability is significantly enhanced.

[0022] 4. The composite material of the present invention has excellent flame retardant properties. The high-temperature char rate increases significantly with the increase of filler content. The phytic acid / chitosan composite coating and carbon fiber work together to form a dense and stable char layer, which delays the transfer of heat and combustible gas. When the filler content is 20%, the composite material passes the UL-94V-0 vertical burning rating, the limiting oxygen index is significantly improved, and the heat release and smoke production performance are significantly improved.

[0023] 5. The preparation process of this invention is simple and controllable. The raw materials are environmentally friendly bio-based flame retardants phytic acid and chitosan, which do not produce any toxic or harmful substances. It is suitable for industrial-scale production. The prepared composite material can be widely used in fields such as electronic packaging, aerospace, and automobile manufacturing, where there are high requirements for the mechanical properties and flame retardant properties of materials. Attached Figure Description

[0024] Figure 1 The images are SEM images of carbon fibers before and after modification, where: (a) is carbon fiber after high-temperature treatment and desizing, (b) is carbon fiber after alkaline activation (O-CF), (c) is carbon fiber modified with phytic acid / chitosan composite coating (PA / CS@CF), and (d) is a photograph of the carbon fibers before and after modification.

[0025] Figure 2 The elemental energy spectrum mapping analysis diagram for PA / CS@CF;

[0026] Figure 3 The diagrams show the structural characterization of the carbon fiber modified material, where: (a) is the Fourier transform infrared spectrum (FT-IR), and (bf) is the X-ray photoelectron spectrum (XPS).

[0027] Figure 4 DSC curves of PA / CS@CF-EP composites with different contents;

[0028] Figure 5 TG and DTG curves for PA / CS@CF-EP composites with different contents;

[0029] Figure 6 Mechanical property curves of PA / CS@CF-EP composites with different contents;

[0030] Figure 7 SEM images of cross sections of PA / CS@CF-EP composites with different contents are shown, where: (a) is 1% content, (b) is 5% content, (c) is 10% content, and (d) is 20% content;

[0031] Figure 8 Images of vertical burning (UL-94) tests on PA / CS@CF-EP composites with different contents.

[0032] Among them: CF - original carbon fiber; desized-CF - desized carbon fiber; O-CF - surface activated carbon fiber; PA / CS@CF - phytic acid / chitosan composite coated modified carbon fiber; PA - phytic acid; CS - chitosan; EP - epoxy resin; PA / CS@CF - EP - carbon fiber flame retardant reinforced epoxy resin composite material. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0034] A method for preparing a carbon fiber flame-retardant reinforced epoxy resin composite material includes the following steps:

[0035] 1. Preparation of activated carbon fibers

[0036] The raw carbon fiber (CF) was laid flat in a ceramic boat and placed in a tube furnace. The temperature was raised to 500°C and held at that temperature for 1 hour. The sizing agent on the surface of the carbon fiber was removed under an air atmosphere. After naturally cooling to room temperature, it was washed three times with deionized water and dried in an oven to obtain desized carbon fiber (CF).

[0037] Weigh 20.0g of the above desized carbon fiber-CF into a beaker, add 200ml of 15% NaOH aqueous solution, place the beaker in a 100℃ oil bath and connect a reflux condenser, and react for 24 hours. After the reaction is completed, wash the product repeatedly with deionized water until the filtrate is neutral. After filtration and drying, surface-activated carbon fiber O-CF is obtained.

[0038] 2. Preparation of phytic acid / chitosan composite coating modified carbon fiber PA / CS@CF

[0039] Take 2g of activated carbon fiber O-CF and add it to 200ml of deionized water. Disperse it by sonication for 20 minutes to ensure uniform dispersion of the carbon fiber. Then add 150ml of phytic acid PA aqueous solution with a concentration of 40mg / ml and stir at room temperature for 4 hours to allow phytic acid PA to fully combine with the functional groups on the surface of activated carbon fiber desized-CF. After the reaction is completed, centrifuge the solution and wash it with deionized water several times to remove excess unbound phytic acid PA from the surface.

[0040] The carbon fibers treated with phytic acid (PA) were redispersed in 200 ml of deionized water and ultrasonically dispersed for 20 minutes. Then, 100 ml of a 10 mg / ml chitosan (CS) solution (with 22% acetic acid aqueous solution as the solvent) was added, and the mixture was stirred and reacted at room temperature for 2 hours to achieve secondary coating of chitosan (CS) on the surface of the carbon fibers. After the reaction was completed, the mixture was centrifuged and washed with deionized water to remove excess chitosan (CS). The resulting solid was dried in a 50°C oven for 24 hours and then ground to obtain the final phytic acid / chitosan composite coating modified carbon fiber filler PA / CS@CF.

[0041] 3. Preparation of carbon fiber flame-retardant reinforced epoxy resin composite PA / CS@CF-EP

[0042] According to the design ratio of phytic acid / chitosan composite coating modified carbon fiber filler PA / CS@CF to epoxy resin EP by 1%, 5%, 10%, and 20% of the total mass, the phytic acid / chitosan composite coating modified carbon fiber filler and 50 g of epoxy resin were added to a beaker and mixed and stirred at 50°C for 30 minutes to ensure that the filler and epoxy resin were initially and uniformly mixed. Then, 6% of the total mass of epoxy resin was added as curing agent, and stirring was continued for 30 minutes to ensure that the curing agent and the mixture were fully integrated.

[0043] The above mixture was transferred to an ultrasonic water bath for 20 minutes to remove air bubbles. The bubble-free mixture was then poured into a high-temperature mold that had been preheated to 80°C for 10 minutes. The mold was then placed in an oven and cured according to a staged temperature increase program: first, pre-curing at 80°C for 1 hour, followed by curing at 140°C for 1 hour. After curing, the oven heating was turned off, and the sample was allowed to cool naturally to room temperature inside the oven. After demolding, carbon fiber flame-retardant reinforced epoxy resin composite PA / CS@CF-EP samples with different filler contents were obtained.

[0044] Through such Figure 1 The SEM images are shown in the figure. Figure 1 The high-temperature treated CF surface is smooth and clean, indicating that the desizing process of holding at 500℃ for 1 hour in a tubular furnace effectively removes the sizing agent. Figure 1 b shows that the O-CF surface treated with NaOH exhibits obvious etching texture, indicating that the hydroxylation modification by refluxing at 100℃ with 15% NaOH solution for 24 hours successfully increased the surface roughness of the carbon fibers, providing adhesion sites for subsequent coating. Figure 1 c shows that the PA / CS@CF surface after coating has a distinct coating layer, indicating that the stepwise coating process of PA and CS can form a continuous modified layer on the carbon fiber surface. Figure 1Thermogravimetric analysis revealed that PA / CS@CF and Desized-CF exhibited significantly different thermogravimetric behaviors. This difference stemmed from the characteristic decomposition of the PA and CS coatings during heating, indirectly confirming the successful loading of the PA / CS composite coating onto the carbon fiber surface. The effective carbon fiber surface modification and PA / CS composite coating process provide a reliable modified filler basis for the subsequent preparation of high-performance PA / CS@CF-EP composite materials.

[0045] like Figure 2 Elemental energy dispersive spectroscopy (EDS) analysis of PA / CS@CF showed that O, P, and N elements were uniformly distributed on the surface of PA / CS@CF, proving that the PA / CS coating layer was uniformly loaded on the carbon fiber surface without obvious agglomeration or local deficiencies. This provides a reliable modified filler basis for the subsequent preparation of high-performance PA / CS@CF-EP composite materials.

[0046] like Figure 3 Fourier transform infrared spectroscopy analysis showed that the carbon fiber surface after desizing was clean with fewer characteristic peaks; however, after sodium hydroxide treatment, its spectrum showed obvious characteristic peaks of oxygen-containing functional groups in a specific wavenumber range, confirming the success of surface hydroxylation modification. Furthermore, after stepwise coating with phytic acid and chitosan, the resulting PA / CS@CF spectrum clearly showed characteristic absorption peaks belonging to the phosphorus-oxygen double bonds of phytic acid and the amino functional groups of chitosan, confirming that the composite coating was successfully constructed on the carbon fiber surface. X-ray photoelectron spectroscopy (XPS) Figure 3 (b) The analysis provided further direct evidence for this. XPS full spectrum showed characteristic signals of four elements—carbon, oxygen, nitrogen, and phosphorus—in PA / CS@CF. Through fine fitting analysis of the high-resolution spectra of each element: the C1s spectrum revealed that carbon atoms were in multiple chemical environments; the characteristic peaks in the N1s spectrum confirmed the successful grafting of chitosan; the typical bimodal structure in the P2p spectrum corresponded to the phosphate groups in phytic acid; and the O1s spectrum comprehensively reflected the formation of oxygen-containing functional groups and the organic coating layer on the surface. These results systematically verified the existence of the PA / CS composite coating from the perspectives of elemental composition and chemical state.

[0047] like Figure 4The DSC curves of PA / CS@CF modified epoxy resins with different contents are shown in the figure. It can be seen from the figure that the glass transition temperature of pure epoxy resin is approximately 137.2℃. When the PA / CS@CF content is 1%, 5%, 10%, and 20%, the glass transition temperatures of the PA / CS@CF-EP composites are 137.97℃, 148.35℃, 149.58℃, and 150.71℃, respectively. The glass transition temperatures of the epoxy resin composites are all higher than those of pure epoxy resin, and the glass transition temperature increases with increasing PA / CS@CF content, reaching its highest value at a PA / CS@CF content of 20%. On the one hand, the PA (containing phosphate groups) and CS (containing amino / hydroxyl groups) on the surface of the hydroxylated carbon fibers interact with the EP molecular chains through hydrogen bonds, chemical bonds, or physical entanglement, restricting the thermal motion of the EP chain segments. On the other hand, the dispersed phase formed by the rigid carbon fibers and fillers in the matrix constitutes a "physical cross-linking network," further hindering chain segment movement. As the filler content increases, this "restriction of chain segment movement" effect becomes more significant. Therefore, higher temperatures are required for sufficient movement of molecular chain segments. Ultimately, this manifests as a gradual increase in glass transition temperature with increasing filler content, indicating that PA / CS@CF filler can enhance the molecular chain rigidity and thermal stability of the EP matrix.

[0048] Figure 5 The TG and DTG curves of the PA / CS@CF composite material are shown. Compared with pure epoxy resin, the initial decomposition temperature of the composite material shows a slight decreasing trend with the increase of PA / CS@CF filler content. This is mainly due to the relatively low thermal stability of some functional groups in PA and CS, which preferentially decompose in the early stage of heating, thus slightly inducing early degradation of the matrix. The initial decomposition stage is earlier, but the high-temperature thermal stability and char formation ability of the composite material are significantly enhanced. The maximum decomposition rate temperature remains stable, while the termination decomposition stage shows a delayed trend. The char residue of the material at high temperature increases significantly with the increase of filler content. This is attributed to the synergistic catalytic char formation of phosphorus components in PA and nitrogen-containing structures in CS during pyrolysis, and the construction of a denser and more stable char layer supported by the rigid skeleton of surface-hydroxylated carbon fibers. This char layer effectively delays the transfer of heat and combustible gases during thermal decomposition, thereby improving the overall thermal stability and flame retardant properties of the composite material.

[0049] like Figure 6The influence of PA / CS@CF filler content on the tensile properties of epoxy resin composites is shown. The tensile properties of the composites exhibit a significant filler content dependence, showing a trend of first increasing and then decreasing. When PA / CS@CF filler is added at a lower proportion, the tensile strength and fracture strain of the composites are significantly improved, reaching peak values ​​at a specific addition amount. This is mainly attributed to the strong interfacial bond formed between the surface-modified carbon fibers and the epoxy resin matrix. On the one hand, the fibers, as rigid reinforcements, effectively bear and transfer loads; on the other hand, the PA / CS composite coating on the surface interacts strongly with the matrix through physicochemical processes, dissipating energy during deformation through mechanisms such as interfacial friction and fiber pull-out, thereby simultaneously improving the strength and toughness of the composites. When the addition amount of PA / CS@CF exceeds a certain threshold, the tensile strength and fracture strain of the composites begin to decrease. This is because excessive filler is difficult to disperse uniformly in the matrix, easily agglomerates, forms stress concentration points, and introduces defects at the interface. These factors disrupt the continuity of the matrix, leading to uneven stress distribution, thus weakening the material's load-bearing capacity and deformation capacity. Correspondingly, it can be inferred from the fracture behavior of the material that an appropriate amount of filler promotes the transformation of the matrix from brittle to ductile, while excessive filler may lead to an increase in the tendency for brittle fracture.

[0050] Figure 7 The cross-sectional morphology of epoxy resin composites with different PA / CS@CF filler contents (1%, 5%, 10%, 20%) is shown. Figure 7 As shown in Figure a, when the filler content is 1%, PA / CS@CF is sparsely dispersed in the matrix with no agglomeration and good dispersibility. However, there are a few voids at the fiber-epoxy resin interface, which may limit the load transfer efficiency and have a limited contribution to the improvement of mechanical properties. Figure 7 Section b represents the cross-section with a filler content of 5%. It is evident that the dispersion uniformity of PA / CS@CF is significantly improved, the fiber-epoxy resin interface is tightly bonded, and porosity is virtually eliminated. This is attributed to the physical anchoring effect resulting from the increased surface roughness of the fiber after NaOH activation treatment, and the chemical bonding effect brought about by the PA / CS coating. These factors synergistically achieve simultaneous optimization of "dispersion-interfacial bonding," laying the structural foundation for effective load transfer. When the filler content increases to 10% ( Figure 7 c) PA / CS@CF is densely distributed in the matrix and still maintains good dispersion, with excellent interfacial bonding with epoxy resin and no obvious defects. This ratio can be regarded as the optimal balance point between filler "dispersion" and "interfacial bonding", constructing a highly efficient fiber-reinforced network, corresponding to the best performance of the composite material's mechanical properties. However, when the filler content is further increased to 20% ( Figure 7d) Obvious local fiber agglomeration was observed, with numerous voids and microcracks at the interface. This is because high filler content increases the difficulty of filler dispersion, and the "concentration entropy reduction effect" leads to deterioration of dispersibility. Agglomerates become stress concentration points, thereby impairing the final mechanical properties of the composite material.

[0051] Figure 8 The results of vertical burning (UL-94) tests on epoxy resin composites with different PA / CS@CF contents are presented. Samples containing pure epoxy resin and 1% PA / CS@CF continued to burn after ignition and failed to meet any UL-94 rating. When the addition amount increased to 5%, the material showed some flame retardant tendency, but still did not meet the rating standards. The composite material with 10% PA / CS@CF showed clear self-extinguishing properties in the test, achieving a V-1 rating. The sample with 20% PA / CS@CF showed excellent flame retardant properties; its flame self-extinguished rapidly after secondary ignition, successfully achieving the highest V-0 rating.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon fiber flame-retardant reinforced epoxy resin composite material, characterized in that, Includes the following steps: 1) Preparation of activated carbon fiber: The original carbon fiber is subjected to high temperature heat treatment to remove the sizing agent on the surface, and after cooling, washing and drying, desizing carbon fiber is obtained. Activated carbon fibers are then obtained through alkaline treatment. 2) Preparation of phytic acid / chitosan composite coating modified carbon fiber: The activated carbon fiber is reacted with phytic acid solution and chitosan solution in sequence to build a phytic acid / chitosan composite coating layer by layer on the surface of the activated carbon fiber. After washing and drying, flame-retardant modified carbon fiber filler is obtained. 3) Preparation of epoxy resin composite material: Flame-retardant modified carbon fiber filler is mixed with epoxy resin and curing agent, stirred and degassed, and then poured into a mold. The carbon fiber flame-retardant reinforced epoxy resin composite material is prepared by a staged temperature rise curing process.

2. The method for preparing carbon fiber flame-retardant reinforced epoxy resin composite material according to claim 1, characterized in that, Step 1) High-temperature heat treatment method: The original carbon fiber is laid flat in a ceramic boat and placed in a tube furnace at 500℃ for 1 hour to remove the sizing agent.

3. The method for preparing carbon fiber flame-retardant reinforced epoxy resin composite material according to claim 1, characterized in that, The alkaline treatment method in step 1) is as follows: after reflux reaction of desized carbon fiber with NaOH aqueous solution at 100°C for 24 hours, the filtrate is repeatedly washed with deionized water until it is neutral, filtered and dried to obtain activated carbon fiber.

4. The method for preparing carbon fiber flame-retardant reinforced epoxy resin composite material according to claim 1, characterized in that, In step 2), the activated carbon fibers are reacted sequentially with phytic acid solution and chitosan solution: the activated carbon fibers are added to deionized water and ultrasonically dispersed for 20 minutes, then phytic acid aqueous solution is added and reacted at room temperature for 4 hours. After centrifugation and washing, excess phytic acid is removed. The treated carbon fibers are redispersed in deionized water and ultrasonically dispersed for 20 minutes, then chitosan solution and acetic acid aqueous solution are added and reacted at room temperature for another 2 hours. After centrifugation and washing, the carbon fibers are dried in an oven at 50°C for 24 hours and then ground to obtain flame-retardant modified carbon fiber filler.

5. The method for preparing carbon fiber flame-retardant reinforced epoxy resin composite material according to claim 1, characterized in that, In step 3), the flame-retardant modified carbon fiber filler and epoxy resin are mixed and stirred at 50°C for 30 minutes. Then, a curing agent accounting for 6% of the mass of the epoxy resin is added and stirred for another 30 minutes. After ultrasonic water bath degassing for 20 minutes, the mixture is poured into a mold preheated at 80°C for 10 minutes. After pre-curing at 80°C for 1 hour and curing at 140°C for 1 hour, the mixture is naturally cooled to room temperature and demolded to obtain a carbon fiber flame-retardant reinforced epoxy resin composite material.

6. The method for preparing carbon fiber flame-retardant reinforced epoxy resin composite material according to claim 1, characterized in that, In step 2), the phytic acid solution is an aqueous solution of phytic acid with a concentration of 40 mg / ml; the chitosan solution is a chitosan solution with a concentration of 10 mg / ml, and the solvent is an aqueous solution of acetic acid with a volume fraction of 22%.

7. The method for preparing carbon fiber flame-retardant reinforced epoxy resin composite material according to claim 1, characterized in that, In step 3), the mass ratio of flame-retardant modified carbon fiber filler to epoxy resin is 1%-20%.

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