The Study On PAN-based Carbon Fiber Modification And Properties Of Related Composite Materials

First, the PAN-based carbon fibers were oxidated by liquid-phase oxidation methods, and the optimum condition of carbon fiber oxidation process was determined. Second, the oxidated PAN-based carbon fibers were used to reinforce epoxy resin composite materials. And the mechanical properties of composite materials were determined to confirm the optimum technological condition of the composite materials forming.The results showed that the major factors affecting carbon fiber oxidation were oxidation time and oxidation temperature. In the microwave heating, the oxidation reaction was moderate and the own strength of carbon fibers changed rarely. Each factor affecting the results of experiment was discussed to determin the optimum technological condition of the PAN-based carbon fibers oxidation process by four factors-four levels orthogonal experiment. The results showed that: reaction temperature was 100℃, reaction time was 15 min, potessium dichromate potassium concentration was 20%,sulfuric acid concentration was 30%. By the optimum conditions of carbon fibers oxidation process, the results were obtained: weightlessness rate was 0.5775%; the contact angle between carbon fiber and epoxy resin was 56.10°;the phenolic group content of modified carbon fiber surface is 15.25 mmol/g, lactone based content was 5.75 mmol/g ,the carboxyl content was 2.21 mmol/g;tensile strength of modified carbon fiber was 3.12 GPa; carbon fiber-epoxy resin interface interlaminar shear strength was 118.12 MPa.Each factor affecting the results of experiment was discussed to determin the the optimum technological condition of composite materials pressing mould forming by four factors-four levels orthogonal experiment. The results showed that the main factors affecting mechanical properties of the composite materials were the carbon fibers content and molding temperature. The optimum conditions of the composite materials forming process were determined: the molding temperature was 160℃; the molding pressure was 12 MPa; the holding time was 30 min; In composite materials, carbon fibers content was 4%. By the optimum conditions of composite materials forming process, the results were obtained: tensile strength was 80.66 MPa; bending strength was 112.51 MPa; anti-impact intensity was 72.05 KJ/m2.FTIR analysis showed that the containing oxygen functional groups of carbon fiber surface were increased significantly such as hydroxy and carbonyl, improving the carbon fiber surface activity; XRD analysis showed that, after carbon fiber oxidation the internal structure was not changed; SEM analysis showed that oxidation process made the gully increased on carbon fiber surface, showing rough surface. Carbon fiber in composite materials scattered evenly. Composite materials tensile destroy section observation showed that though a little carbon is extracted, the damage zone was tidy relatively, explaining there was a good combination between enhance body carbon fiber and matrix epoxy resin. Impact section explained composite materials flush fracture interface was tidy relatively, it was tight relatively between enhance body carbon fiber and matrix epoxy resin. Carbon fiber has played a certain role and spreaded the strength. All of carbon fibers and epoxy resin played a load function.