Dynamic mechanical properties of multi-functional epoxy resin filled with pitch-based carbon short fibers

Abstract

Three types of multi-functional epoxy resins cured with six types of hardeners were filled with pitch-based carbon and graphite short fibers for 22.2 wt%. It was found by SEM observation that the distribution of short fibers in the resin was random. Dynamic mechanical properties were measured for short fiber filled composites in the temperature range of -150 to 300° C. The glass transition temperature (Tg) for the composites became higher than that for the matrices, and the dynamic storage moduli, E', were also increased. The values of E' for the graphite filled composites in the glassy region at low temperature (-140° C) and room temperature (25° C) were larger than those for the carbon filled composites but at high temperature (200° C), E' for the carbon filled composites became larger as the surface activation of carbon was higher than that of graphite. The value of E' for the composites at 25° C was larger than the estimated values from the rule of mixture for both types of composites, thus demonstrating the filling effect. The experimental values were in good agreement with the Halpin-Tsai equation modified by Nielsen. However, some variations on the increase of Tg and E' were seen depending on the combination of epoxy resin and hardener as well as the difference between carbon and graphite as the pitch-based carbon fibers. The filling effect on flexural strength was evident in the composites whose matrices were brittle. It was found that heat resistant and high modulus composites can be developed by using multi-functional epoxy resin as the matrix filled with functional short fibers.