Monitoring electrically-active defects in silicafilled epoxy using light detection

Epoxy resins have been used for long as the insulation of electrical systems. It is generally formulated with a dispersion of micro-fillers to improve thermal and mechanical properties. However, there are concerns on the possible influence of these fillers on the electric behavior, especially on the long term ageing under functional stresses. Defects (decohesion between matrix and fillers, macro and micro-voids in the resin, etc.) can be detected using tomography but there is no indication of the harmfulness of these defects under electrical stress. The possibility of monitoring defects by electroluminescence is put forward in this work.