Engineering the Interphase in Reinforced Plastics

Abstract

Careful investigation of the mechanics of the interphase between fibres such as Kevlar, carbon and glass, and thermosetting polymers, strongly suggests that the interphase fails by brittle fracture rather than yielding. Works of fracture can be as low as 10 Jm⁻², so interphase toughening should improve the properties of fibre composites very significantly. To this end, glass fibre reinforced epoxies have been made with rubber interphases. Both reactive and non-reactive liquid and solid rubbers were investigated, and the viscoelastic properties of the rubbers were modified using fine solid particles. The results indicate that the work of fracture of the composites can be increased significantly, without any great loss in other mechanical properties. Neat rubbers were better overall than filled rubbers, and the best results were obtained when there was a chemical interaction between the rubber and the silane sizing on the fibres.