Enhanced dielectric performance of AFRP via bidirectional modification: a fluorinated SiO ₂ honeycomb-like architecture on fiber surfaces and Al ₂ O ₃ nanoparticle doping in a resin matrix

As the core component of gas-insulated switchgear (GIS) and ultra-high voltage transmission systems, the reliability of high-performance insulating rods is crucial for system stability. Aramid fiber-reinforced epoxy resin composites (AFRP) have become ideal materials for high-performance insulating rods due to their lightweight properties and high strength. However, the interfacial weakening effect in AFRP, caused by the low surface energy and chemical inertness of aramid fibers (AF), remains a critical technical bottleneck limiting their engineering applications. This study constructs a honeycomb-like surface structure on AF through the synergistic interaction of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FDTS) and SiO₂ nanoparticles. By incorporating Al₂O₃ nanoparticles into the epoxy matrix, the interfacial bonding strength and insulation properties of AFRP are synergistically enhanced. The interfacial shear strength and tensile strength of AFRP increased by 123.02% and 129.13%, respectively, while the breakdown field strength improved by 64.45%. Analysis of micro-nano structural characterization reveals that the interfacial enhancement originates from the combined effects of AF surface modification and Al₂O₃ doping, which optimize interfacial insulation properties through non-bonding interactions introduced by FDTS, SiO₂, and Al₂O₃.