Hygrothermal Aging Effects on Moisture Absorption Behavior and Dielectric Degradation of Glass Fiber/Epoxy Composites

Glass Fiber/Epoxy Composites (GF/EP) are widely used in high-performance industries due to their excellent mechanical and insulating properties. However, their performance degradation under hygrothermal environments, particularly in marine and high-voltage applications, remains a critical challenge. This study investigates the moisture absorption behavior and dielectric performance of GF/EP composites subjected to deionized water immersion at room temperature (RT) and 80 °C. Experimental results reveal distinct moisture absorption kinetics. Under RT conditions, GF/EP exhibits three-stage absorption: initial slow diffusion (0–3 days), accelerated interfacial channel formation (5–7 days), and equilibrium stabilization (9 days). Elevated temperature (80 °C) doubles the absorption rate by promoting interfacial hydrolysis and microcrack expansion. Dielectric testing indicates that hygrothermal aging significantly reduces breakdown strength. After 1-day immersion in 80 °C deionized water, breakdown voltage drops by 9.67% compared to pristine samples, attributable to interfacial delamination and conductive pathway formation. The findings provide critical insights for predicting long-term material reliability and designing multifunctional composites for harsh environments. The methodology integrates experimental and analytical approaches, offering a foundation for developing multiscale failure models under coupled hygrothermal-mechanical-electrical fields.