2021 年 47 巻 2 号 p. 43-50
Continuous carbon fiber-reinforced Tg-less epoxy resin was produced and evaluated to create a creep-less composite material usable in continuously loaded structural parts. The Tg-less epoxy resin was obtained through the anionic curing of ordinary epoxy resin with an alkaline salt of carboxylic acid. In the viscoelastic behavior of the cured Tg-less epoxy resin, the storage modulus did not drop and the resin remained in a glassy state even at elevated temperatures, such as 300ºC. Additionally, the loss tangent was low at all testing temperature ranges. This indicates that stress relaxation hardly occurred; thus this resin may enable the creation of a creep-less composite material. The brittleness of the cured Tg-less epoxy resin was successfully overcome through modification with nano-rubber particles. Finally, creep tests were conducted using a three-point bending mode for carbon fiber-reinforced composite materials using modified and unmodified Tg-less epoxy resins as the matrices. As a result, in the case of Tg-less epoxy resin containing 16 wt% of nano-rubber particles, the creep strain rate became almost zero after a testing time of over 50 h.