DYNAMIC-MECHANICAL PROPERTIES OF MULTIFUNCTIONAL EPOXY-RESIN FILLED WITH PITCH-BASED CARBON SHORT FIBERS

Three types of multi-functional epoxy resins cured with six types of h ardeners were filled with pitch-based carbon and graphite short fibers for 22.2 wt%. It was found by SEM observation that the distribution o f short fibers in the resin was random. Dynamic mechanical properties were measured for short fiber filled composites in the temperature ran ge of -150 to 300 degrees C. The glass transition temperature (T-g) fo r the composites became higher than that for the matrices, and the dyn amic storage moduli, E', were also increased. The values of E' for the graphite filled composites in the glassy region at low temperature (- 140 degrees C) and room temperature (25 degrees C) were larger than th ose for the carbon filled composites but at high temperature (200 degr ees C), E' for the carbon filled composites became larger as the surfa ce activation of carbon was higher than that of graphite. The value of E' for the composites at 25 degrees C was larger than the estimated v alues from the rule of mixture for both types of composites, thus demo nstrating the ailing effect. The experimental values were in good agre ement with the Halpin-Tsai equation modified by Nielsen. However, some variations on the increase of T-g and E' were seen depending on the c ombination of epoxy resin and hardener as well as the difference betwe en carbon and graphite as the pitch-based carbon fibers. The filling e ffect on flexural strength was evident in the composites whose matrice s were brittle. It was found that heat resistant and high modulus comp osites can be developed by using multifunctional epoxy resin as the ma trix filled with functional short fibers.