Influence of Thermal Aging on SiC/Epoxy Resin Micro-composites

The effects of thermal aging on nonlinear conductivity and dielectric properties of functionally gradient materials are studied. The 30 wt% silicon carbide (SiC)/epoxy resin (EP) micro-composites are prepared. The composites are subjected to thermal aging for 1080 h at 180 °C. The nonlinear conductivity, dielectric properties, and DC breakdown strength of the composite are measured, respectively. The experimental results show that when the aging temperature is 180 °C, the current density of SiC/epoxy micro-composites decreases first and then increases with the increasing aging time at 5kV/mm. When the aging time reaches 720 h, the nonlinear coefficient of the composites increases obviously, but the switching electric field decrease distinctly. With the increasing aging time, the relative permittivity and loss tangent of composites increase gradually, and the DC breakdown strength decreases gradually. DRIFT analysis shows that the degradation of the composites is mainly caused by the fracture of ether bond and the formation of carbonyl group in epoxy matrix.