Fiber and interface failure characterization of glass fiber reinforced polymer for composite insulators after liquid permeation

Composite insulators are of great significance in power systems due to their excellent electrical and mechanical properties. The mechanical load of insulator is borne by the rod made of glass fiber reinforced polymer (GFRP). Despite the considerable load margin, abnormal fractures have been reported continuously during actual operation. Among them, the evolution of decay-like fracture has still not been illustrated, which is why no effective preventive measures can be proposed. Liquid permeation, especially nitric acid, is supposed to play a vital role in the fracture. Thus, in this paper, the characteristics of glass fiber, fiber-epoxy interface, and GFRP-sheath interface immersed in different liquids are investigated. Based on the results, the significant role of boron element in the stress corrosion of glass fiber is illustrated. Therefore, the application of glass fiber without B is rather necessary. Also, the failure of fiber-epoxy interface by acid is identified by broadband dielectric response, which forms the channels of current concentration. It is key for the development of decay-fracture. Moreover, the degradation of GFRP-sheath interface after immersion is recognized by the measurement of interfacial resistivity. Consequently, coupling agents with good resistance to acid should be adopted, in order to avoid further liquid permeation into the GFRP rod.