DYNAMIC-MECHANICAL PROPERTIES OF MULTIFUNCTIONAL EPOXY-RESIN CURED WITH DIAMINE AND FILLED WITH PITCH-BASED CARBON SHORT FIBERS TREATED WITH COUPLING AGENTS

We have been conducting research on the development of heat-resistant composite materials filled with functional short fibers in multi-funct ional epoxy resin. As part of such effort, the filling effects of pitc h-based carbon short fibers were investigated. In addition, the effect s of treatment of coupling agents were studied by filling treated fibe rs into matrices cured with acid anhydride taking the large surface ac tivity of fibers into account. In this report, matrices cured with dia mine were investigated and were compared with those cured with acid an hydride. Pitch-based carbon short fibers treated with five types of co upling agents were filled in three types of multi-functional epoxy res in cured with two types of diamine for 22.2 wt%. The dynamic mechanica l properties were measured for these materials in the temperature rang e of -150 degrees C to 300 degrees C. The glass transition temperature s (T-g) for all the tested materials became higher than those filled w ith short fibers not treated with coupling agents. The dynamic storage moduli, E', also increased in the glassy state region of low temperat ure (-140 degrees C) and room temperature (25 degrees C) as well as at high temperature of 200 degrees C. However, the rise of T-g and incre ase of E' differed depending on the combination of epoxy resin and har deners. All the values of E' at room temperature (25 degrees C) were l arger than the predicted value from the rule of mixtures for all the s amples. Although the modified Halpin-Tsai equation by Nielsen yielded better prediction for some of the materials, E' for most of the materi als were larger than the predicted values thus demonstrating the filli ng effect by short fibers treated with coupling agents in multi-functi onal epoxy resin cured with diamine hardeners. For flexural strength o f the tested specimens, while the effect of treating with coupling age nts on short fibers was small, the filling effect was evident for the materials whose matrices were brittle. It was found, as a result, that the materials made of multi-functional epoxy resin cured with diamine filled with pitch-based carbon short fibers treated with coupling age nts were more heat-resistant with higher stiffness than those cured wi th three types of acid anhydride.