Electrothermal effect of carbon fiber and graphite reinforced metakaolin-based geopolymer

This paper investigates the influence of carbon fiber and graphite on the cyclic electrothermal performance of geopolymers (inorganic polymers). It was observed that carbon fibers, graphite, and the carbon fiber/graphite composite could form a stable conductive network at low voltage (3 V). However, under high voltages (9 and 12 V), the current of the geopolymer exhibited a peak shape in the first cycle, with higher voltages resulting in larger peak values and decreased conductivity in subsequent cycles. While graphite improved electrical and thermal conductivity, it weakened the microstructure, leading to an increase in microcracks and voids, and a reduction in the strength of geopolymers. The cumulative energy during the electrothermal process was calculated. The failure mechanism of the conductive network in the geopolymer during cyclic electrical heating was explained, highlighting the disruptive effect of gel shrinkage due to water loss on conductive networks.