Characterization Of The Surface Properties Of The T-700 Carbon Fiber And Study Of The Interface Properties Of The Fiber Reinforced Composite

Carbon fiber and its composites have been widely used in aerospace, weapon manufacture, automobile parts and many other fields, because of its high strength, high modulus and excellent fatigue performance. As the representative of the new high performance fiber, T700 carbon fiber has more widely application prospect. There are great gaps at the performances between the domestic carbon fiber and the imported carbon fiber, which are mainly due to the differences in surface properties and interface properties of them. In order to give domestic carbon fiber production some useful referrence and guidance, the surface properties and the interface properties of the imported T700 carbon fiber have been systematically analyzed in this paper.The surface performances include physical performances and chemic performances have been characterized first. The surface tensionmeter was used to test the surface energy and wetting property of T700 carbon fiber. The results showed that the surface energy of the fiber was 49.15mJ·m-2 which indicated the surface was non-polar and inert. The contact angle between the fiber and epoxy resin was 55.90°. The atom force microscope(AFM) was used to test the roughness of T700 carbon fiber. The surface of the fiber was very smooth and there was no apparent groove and defect on it. The thickness of the coating layer on the surface of the fiber was about 35.5nm and the uniformity of it was not ideal enough. The chemical component of the fiber surface was tested by X-ray photoelectron spectroscopy(XPS). The results showed that there were four kinds of chemical elements(C, O, N, Si) on the surface of the fiber and their contents were 72.79%, 25.78%, 0.48% and 0.95% separately. Meanwhile, there were three kinds of function groups(-C-C-, -C-O-, -C=O) on the surface of the fiber and their contents were 44.83%, 47.02% and 8.15% separately. The heat-resistance properties of the surface coating of the fiber were tested by TG. The results showed that the initial decomposition temperature of the coating was 256.8℃.Then, the interface performances include physical performances and chemic performances have been studied and characterized. The interfacial shear strength of the T700 carbon fiber reinforced composite is about 48.54MPa. The fiber and the matrix resin in the composite were very different in modulus and there was no effective transition layer. Under certain conditions, an effective chemical reaction could take place between the surface of the T700 carbon fiber and the coating, they had good reactivities with each other. After heat-aging treatment, the interfacial shear strength of the fiber reinforced composite reduced from 48.54MPa to 40.75MPa which means the interface of the T700 carbon fiber reinforced composite had a good heat-aging resistance property.