高温下における炭素繊維強化ポリアミド樹脂の繊維樹脂界面せん断強度に及ぼす樹脂へのシリカ添加の影響

抄録

It has been reported that the tensile strength of CFRTP becomes lower at high temperatures due to the decrease in the fiber matrix interfacial strength at high temperatures. This is due to the relaxation of the fiber-tightening pressure of the resin due to the thermal expansion of the resin at high temperatures. Therefore, it is important to suppress the thermal expansion of the resin. In this study, we focused on the addition of SiO₂ particles to the matrix resin as a means of suppressing the decrease in the fiber matrix interfacial strength at high temperatures, and conducted single-fiber pull-out tests at room temperature and 80 °C using carbon fibers and PA6 resin with different amounts and surface treatments of SiO₂. Up to 5.0 wt%, the higher the amount of SiO₂ added to PA6, the lower the coefficient of thermal expansion, but when 10 wt% was added, the coefficient of thermal expansion became higher due to agglomeration of SiO₂. The frictional force at the fiber matrix interface determined from the microdroplet test, which is considered to be the fiber-tightening pressure of the resin, corresponds to the fiber matrix interfacial strength determined from the single-fiber pull-out test at room temperature and 80 °C. The higher the fiber-tightening pressure of the resin, the higher the fiber matrix interfacial strength. The decline rate in strength from room temperature to 80 °C is lower for resins with a lower coefficient of thermal expansion. The addition of water-treated SiO₂ shows the lowest coefficient of thermal expansion and the lowest decrease in the fiber matrix interfacial strength from room temperature to 80 °C.