Influence of Infusion Vacuum on the Electrical Insulation of Epoxy/Polyester Fiber Composites

ABSTRACT The vacuum infusion process is a critical factor determining the curing quality and final electrical performance of epoxy composites. This study employs molecular dynamics simulations to investigate the differences in molecular chain motion between polyester fiber (PET) and its epoxy‐based composite (EP/PET), and systematically explores the influence mechanism of infusion vacuum on the microstructure, dielectric properties, and charge trap behavior of the EP/PET composite. The results indicate that the epoxy cross‐linked network effectively suppresses the motion of molecular chain segments and polar groups in the polyester fiber. Reducing the infusion absolute pressure significantly decreases internal defects in the material, improves its dielectric properties (breakdown voltage increases, while dielectric constant and loss decrease), and promotes a shift in trap distribution from shallow to deep energy levels, thereby enhancing charge trapping capability. When the infusion absolute pressure is reduced to approximately 40 kPa or lower, the influence of further increasing the vacuum level on the interfacial microstructure and electrical properties has only a limited influence.