Abstract
The main purpose of this work is to study the influence of high compressive stress on the deformation behaviour of a selection of commercially available silicone rubber (SiR) materials used in HV cable accessories. The SiR materials were subjected to compressive stresses from low to extreme size reductions i.e., 20, 40,70 and 80% to determine the threshold at which permanent deformation occurred. The effect of the strain rate on the deformation behaviour was also assessed. The strain rate was found to have minimal influence on the maximum compressive stress induced in hard SiR, whereas its effect on soft and semiconductive SiR was significant. Deformation profiles on the surfaces of SiR samples were analysed and quantitatively characterized with an optical profilometer. The study revealed that the deformation behaviour was highly dependent on both the grade of SiR and the level of compressive strain applied. A size reduction of 80% permanently deformed hard SiR samples, as the material failed to recover after 14 days of resting in ambient conditions, whereas soft SiR recovered completely, and semiconductive SiR exhibited intermediate recovery behaviour.