Fabrication And Interfacial Properties Of Carbon Fiber/epoxy Composite

A novel method of surface modification for carbon fiber is proposed: through the sol-gelprocess using a silane coupling agent, tetraethoxysilane as the precursor, and P-toluene sulfonicacid as the catalyst, a surface layer with membrane-grain structure is formed after cured. Usingthe prepared surface agent to modify the carbon fiber, and investigating the effects of surfaceagent to the morphology and mechanical properties of carbon fiber. On this basis, we preparedthe carbon fiber/epoxy composite to study the interfacial properties.According to the research on the preparing technique of surface modifier, the results showthat the method obtained a well dispersed and uniform-size nano-SiO₂with a membrane-grainstructure in situ. the size of the membrane-grain are in the range of20-30nm. The infraredabsorption band of Si-O-Si and Si-OH was observed, it means the covalent bond exists betweenthe nano-SiO2and silane coupling agents. Through the testing of linear thermal expansion, foundthat the thermal expansion coefficient of surface modifier was between carbon fiber and epoxyresin, which provides the possibility of reducing the residual stress on the carbon fiber compositeinterface. The appearance of this surface modifier provide a new option to carbon fiber treating.Treating carbon fiber by the surface modification and characterizing the modificationeffects, the results show that: the surface treatment have a certain effects on the morphology andmechanical properties of carbon fiber. The fiber surface changed to be roughness withnano-SiO2,which is treated by no aging surface modifier, However, the carbon fiber treated bythe aging surface modifier, the nano-SiO₂particles is coated in the membrane structure and thegroove on the surface was filled. The tensile strength of carbon fibers which was treated by thesurface modifier was improved significantly. We conclude that the prepared modifier have theeffect o repair the defects on the fiber.On the basis of above studies, a further investigation of interfacial properties was carriedout, we use the modified carbon fiber and epoxy resin to prepare composites, the results show that: through the various methods of surface treatment of carbon fiber composite, the interfaceperformance has improved at various degrees, the fiber sample pretreated by HNO₃modified bythe aging surface modifier composite whose interfacial shear strength（IFSS） reached26.74MPa,the IFSS of acetone treated carbon fiber composite was only13.52MPa; this method has notbeen reported before, which provides a new way of improving interface performance of carbonfiber composite.