Composites with Tg-less Epoxy Resin Matrix for Creep-Free Materials

Abstract

In order to suppress the creep of continuous carbon fiber reinforced plastics (CFRP), the use of a Tg-less epoxy resin as a matrix was investigated. This Tg-less epoxy resin can be easily obtained by curing a standard liquid epoxy resin with an alkali metal salt of a carboxylic acid. After curing, this resin maintains a glassy state with little decrease in storage modulus even at temperatures up to 300°C. At the same time, its loss tangent is low at all test temperatures, suggesting that the-stress relaxation hardly occurs. In this study, we attempted to elucidate the curing and Tg-less mechanisms of this resin system, and also fabricated CFRP and evaluated its creep properties. Meanwhile, the brittleness of the cured Tg-less epoxy resin was overcome by modifying it with nano-rubber particles. Creep tests using a three-point bending mode showed that the creep strain rate of the Tg-less epoxy resin containing 16 wt% nano-rubber particles reached almost zero after 50 hours of testing.