Degradation characteristics of epoxy resin of GFRP rod in the decay-like fracture of composite insulator

The decay-like fracture is an emerging mode of abnormal mechanical failure of composite insulators the study of which is still in its infancy. The degradation of epoxy resin of glass fiber reinforced polymer (GFRP) rod caused by discharge and current distinguish the decay-like fracture from both normal mechanical fracture and brittle fracture. In the present work, the detailed degradation of epoxy resin of GFRP rod in the decay-like fracture of composite insulator were examined using scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The results show that the generation, expansion and release of pyrolysis gas is responsible for the formation of the bubbles and holes in the epoxy resin and the initial formation of holes in the silicone rubber housing during the degradation process. The erosion and pyrolyzation of epoxy resin results in mass loss of epoxy resin leading to degradation of the GFRP rod. High resolution XPS spectra of C1s and N 1s in GFRP rod reflects that oxidization process, exposure of glass fiber, and the introduction of nitrogen-containing compounds occurs during the degradation process. Microscopic photographs to explain the degradation of the epoxy resin and the initial formation of puncture holes in the silicone rubber housing are proposed based on the experimental results.