Cyclic thermoresistivity of resin-based carbon fiber bars modified with mixed carbon powder and nano-silica

The addition of conductive fillers to the carbon fiber bar reduces its resistivity and improves electrical stability. Unstable conductivity and susceptibility to ambient temperature change impede the application of this technique in engineering, unless such influence can be eliminated by technical means or precisely predict. In this paper, modified epoxy Resin based carbon fiber bars with 4 sets of different mixed fillers have been designed to evaluate the temperature-resistance effect under different temperature cycles. Results show that the initial volume resistivity reduces due to the incorporation of carbon powder(CP) and nano-silica(NS), and meets the lowest when the CP and NS mass ratio is 1:0.6. The volume resistivity increases linearly with the temperature rising, and reaches the maximum temperature sensitivity coefficient of 78.8%. During the temperature cycle process, the volume resistivity of all specimens first decreases and then increases with the increasing temperature uniformly. The three groups (CP/NS ratio 1:0.2, 1:0.6, and 1:0) share the same PTC effect transition temperature range, from 30 to 60 °C. And for the 1:1 group, the transition temperature is about 0 °C, which is the lowest. Altogether, these enhancements provide avenues for future self-sensing carbon fiber composites in engineering structures.