Effect of Carbon Fiber Surface Roughness on Interfacial Adhesion Strength between Carbon Fiber and Epoxy Resin

The influence of the surface roughness of carbon fiber derived from the precursor, on the interfacial adhesion strength between the carbon fiber and the epoxy matrix resin waz investigated. The interfacial adhesion strength was evaluated in terms of interfacial shear strength (τ), interlaminar shear strength (ILSS) and transverse flexural strength (FS 90°). τ, ILSS and FS 90° increased with the increase in surface oxygen content and surface roughness of carbon fiber. τ and ILSS which are related to longitudinal shear strength, had a good first-order correlation. However, FS 90° which is related to transverse adhesion strength, did not correlated with τ . The shear strength may depend on the friction coefficient. The surface roughness of the carbon fiber was considered to increase the roughness component of the friction coefficient. FS 90° relied on the process of destruction. It was considered that crack propagation was stopped by the surface roughness and the rise in the resistance of crack propagation resulted in the high values of FS 90°.