A bio-inspired interface modification strategy for suppressing insulation degradation of aramid fiber/epoxy composites

Abstract

Designing effective interfaces for aramid fiber/epoxy (AF/EP) composites in electrical insulation applications is particularly challenging, given that interfacial failure is prone to occur at the AF/EP interface due to charge accumulation and inherent modulus mismatch. Inspired by mussel byssus and nacre, a bionic interface modification strategy is developed in this study, which integrates polydopamine coating and nanosilica (SiO₂) onto the fiber surface through a hierarchical assembly approach. The results show that the interfacial shear strength and interlaminar shear strength of the composites are improved by 126.46% and 47.86% respectively, due to the synergistic effects of enhanced interface bonding strength, mechanical interlocking and successful construction of gradient modulus transition layer. Furthermore, more charge traps and energy scattering centers are introduced by SiO₂. Consequently, interfacial insulation degradation process under high voltage is significantly suppressed in the channel length, cumulative damage area, and breakdown time. Compared to the unmodified AF/EP composites, the modified composites demonstrate exceptional dielectric properties with DC conductivity decreased by 83.38%, dielectric loss reduced by 10.36% and breakdown strength enhanced by 29.43%. This interface functionalization strategy provides novel insights into the performance improvement of AF/EP composites for high-end power equipment subjected to combined electrical and mechanical stresses.