Strength and Reliability of Unidirectional CFRPs with Different Fiber Surface Properties

Abstract

Chemically different fiber surface properties were created by electrolytic oxidation on continuous carbon fibers with uneven and smooth surfaces, in order to clarify the effect of bond strength between the fiber and matrix on the mechanical properties of unidirectional carbon fiber reinforced plastics (CFRP). It was proven from a fiber fragmentation test, using single fiber composites embedded in epoxy, that interfacial shear strength (IFSS) increases with an increase in ratio of oxygen to carbon (O/C) on the fiber surface. The result of the tensile tests of CFRP specimens with the different fiber surface properties showed that an appropriate IFSS not only increases tensile strength, but decreases coefficient of variation in tensile strength. It was discussed based on the previously reported simulation results that such an optimal IFSS should be given by the only value. Furthemore, using the same CFRP specimens, relation between IFSS and fatigue life was experimentally investigated.