Fatigue Behavior of Woven Glass Fiber-Reinforced Epoxy Laminated Insulation (IEC 60893 EPGC 203) for High-Voltage Applications

This study investigates the mechanical performance and fatigue behavior of a woven glass fiber-reinforced epoxy laminated composite classified as IEC 60893 EPGC 203, widely used in structural insulating components for high-voltage (HV) equipment. With evolving energy infrastructures introducing dynamic and cyclic loading conditions, understanding the long-term mechanical reliability of such materials has become increasingly important. A comprehensive experimental program was conducted, including flexural, compressive, tensile, Charpy impact, and fatigue tests. Mechanical properties were evaluated according to relevant ISO standards at room temperature and 120 °C to assess temperature-dependent performance. Fatigue tests were performed under fully reversed loading conditions (R=−1), and stress–life (S-N) curves were established. The results revealed notable reductions in strength and stiffness at elevated temperature, together with progressive damage accumulation under cyclic loading. Failure features observed after fatigue testing were correlated with static mechanical properties to improve understanding of degradation behavior. The study is limited to the mechanical and fatigue characterization of EPGC 203 and does not include dielectric evaluation. Therefore, its relevance to HV applications is considered from the standpoint of the mechanical reliability of structural insulating components. The findings provide essential insights into the durability and reliability of EPGC 203 composites under realistic service conditions.