TEMPERATURE AND STRAIN RATE DEPENDENCES OF INTERFACIAL YIELD SHEAR STRENGTH AND CRITICAL FIBER LENGTH FOR CARBON FIBER-EPOXY RESIN COMPOSITES

Abstract

In the short carbon fiber-thermosetting resin composites, the interfacial yield shear strength or critical fiber length is one of the dominating factors for the effect of reinforcement. In this paper, strain rate and temperature dependences of these factors were studied for carbon fiber-epoxy resin composites.
The interfacial yield shear strength decreases with the increase in temperature. This trend of decrease can be explained mainly by the decrease of shear strength of matrix with increase in temperature in case of treated carbon fiber, and by the relaxation of thermal stress and secondary bond at the fiber-matrix interface with increase in temperature in case of untreated carbon fiber. Also, the interfacial yield shear strength increases in proportion to the logarithm of strain rate and the slope is the same in all experimental temperature. The strain rate-temperature reduction holds for the interfacial yield shear strength and the mean critical fiber length.