Effect of moisture sorption on ac properties of glass–epoxy composites



Alternating current responses of fiberglass-reinforced epoxy composites have been studied as a function of frequency (10 Hz to 100 kHz) and temperature (−30 to 100°C). At higher water content, permanent defects are created presumably at the fiber—matrix interfaces as the temperature goes down to 0°C. These defects increase significantly the dielectric losses. A recovery of the initial state is possible under thermal annealing above the glass transition temperature of the epoxy resin.