Dynamic mechanical properties of multi-functional epoxy resin cured with diamine and filled with pitch-based carbon short fibers treated with coupling agents

Author： Tanaka Katsutoshi Yamaguchi Muneaki

Publisher： Taylor & Francis Ltd

ISSN： 1568-5519

Source： Advanced Composite Materials, Vol.5, Iss.1, 1995-01, pp. : 45-62

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Abstract

We have been conducting research on the development of heat-resistant composite materials filled with functional short fibers in multi-functional epoxy resin. As part of such effort, the filling effects of pitch-based carbon short fibers were investigated. In addition, the effects of treatment of coupling agents were studied by filling treated fibers into matrices cured with acid anhydride taking the large surface activity of fibers into account. In this report, matrices cured with diamine were investigated and were compared with those cured with acid anhydride. Pitch-based carbon short fibers treated with five types of coupling agents were filled in three types of multi-functional epoxy resin cured with two types of diamine for 22.2 wt%. The dynamic mechanical properties were measured for these materials in the temperature range of -150° C to 300° C. The glass transition temperatures (T_g) for all the tested materials became higher than those filled with short fibers not treated with coupling agents. The dynamic storage moduli, E', also increased in the glassy state region of low temperature (-140°C) and room temperature (25° C) as well as at high temperature of 200° C. However, the rise of T_g and increase of E' differed depending on the combination of epoxy resin and hardeners. All the values of E' at room temperature (25° C) were larger than the predicted value from the rule of mixtures for all the samples. Although the modified Halpin-Tsai equation by Nielsen yielded better prediction for some of the materials, E' for most of the materials were larger than the predicted values thus demonstrating the filling effect by short fibers treated with coupling agents in multi-functional epoxy resin cured with diamine hardeners. For flexural strength of the tested specimens, while the effect of treating with coupling agents 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 agents were more heat-resistant with higher stiffness than those cured with three types of acid anhydride.