I. Introduction
Owing to its excellent electrical and mechanical properties, epoxy resin has been widely used as insulating material in electrical devices operating in aerospace [1]–[3]. It has been found that the material has to work in radiation environment, where high energy electron beam is often included [4]. The electron beam irradiation could introduce deep charging of the dielectrics that initiates electrical discharge, or change the chemical structure of the material which leads to the deterioration and thereby threatening its safe use. Accordingly, it is of great importance to investigate the effect of electron beam irradiation on the electrical performance of epoxy.