Study on the Effects of Thermal Vibration Aging and Water Penetration on the Insulation Performance of Epoxy/Glass Fiber

Epoxy/glass fiber (EP/GF) composite insulating materials are widely used in electrical equipment operating in various complex environments due to their excellent insulating and mechanical properties. However, they are vulnerable to thermal stress, mechanical vibration, and the intrusion of external moisture, which can lead to insulation degradation. Many studies have explored the thermal-oxidative aging behavior of EP/GF composites. However, the research on the influence mechanism of thermal-vibration coupling condition aging and moisture intrusion aging on the insulation performance of the specimens remains unclear. This work conducted moisture intrusion tests on EP/GF composites treated with thermal vibration aging at different times. The Hygroscopicity, microstructure morphology, functional groups, and dielectric loss of EP/GF composites with different aging degrees were characterized by water absorption rate, scanning electron microscopy, infrared spectroscopy, and dielectric spectroscopy tests. Studies show that as EP/GF composites' aging time increases, microcracks's size and scale keep growing, and their water absorption rate increases in two stages. In the early stage of aging (3 days), it rapidly increases from 0.07% to 0.18%, and in the later stage of aging (15 days), it slowly rises to 0.25%. The dielectric loss of EP/GF materials increases due to the generation of many polar groups during aging. Moisture, as a strongly polar substance, will cause a significant increase in the dielectric loss of the treated EP/GF materials after moisture invasion. This work provides theoretical support for the subsequent research on reducing dielectric loss and anti-aging of EP/GF composites.