Experimental study on curing strain of epoxy-alumina composite applied to UHV GIS spacer

Curing induced residual stress of epoxy-alumina composites influences properties of large scale epoxy casting products like Ultra High Voltage(UHV) GIS spacer. It will result in defects like cracks and voids which will worsen electric field distribution and degrade insulation characteristics of spacers, then endanger the safety and stability of power system during long-time operation. According to the technological process of UHV basin insulator, mixture of epoxy and micron alumina was prepared. Fiber Bragg Grating (FBG) was positioned into mixture, using a simple guiding system. The FBG was applied to monitor residual strain of the whole system during cure, post-cure and subsequent cooling down to room temperature. Residual strain characteristics of system with alumina content 300% is first tested and analyzed. Samples with and without demold were tested to study the influence of demold. Effect of alumina content from 0% to 300% on residual strain was also investigated. The test results showed that residual strain came from two parts in the whole technological process, curing reaction and cooling treatment. Increase of residual strain was still monitored in post-cure and tended to be zero at the end of post-cure. It was concluded that demold could effectively relieve the cure-induced residual strain. Residual strain decreased with alumina content increasing, but presenting a saturation trend.