Impact of Defect Structures on Interfacial and Insulation Properties in Epoxy-Impregnated Aramid Paper

This study investigates the impact of interface defects on the electrical performance of epoxy-impregnated aramid papers (EAPs). Various composites with different degrees of defects were prepared and analyzed for their structural, mechanical, partial discharge, and insulation performance. The results demonstrate the widespread presence of void defects in the composites, negatively affecting paper compactness, mechanical properties, initial discharge voltage, and leading to significant gas gap discharge phenomena. In terms of insulation performance, composites with severe defects exhibit a 40-fold increase in low-frequency dielectric loss, a 16-fold increase in electrical conductivity, and up to a 64% reduction in breakdown field strength, along with noticeable shallowing of charge traps. Phase field modeling of electro-thermal breakdown reveals that void-type defects guide discharge trajectories, causing lateral damage diffusion, localized overheating, and severe electric field distortion, ultimately endangering the voltage resistance. This study provides the research support for the application of aramid paper as a matrix for a novel epoxy-impregnated insulating paper.