Dielectric and friction behaviour of unidirectional glass fibre reinforced epoxy (GFRE)

The aim of this paper is to confirm the role of the electric charges on the friction behaviour of non-conductive materials. This correlation is proven using tribo-tests and SEMME (Scanning Electron Microscope Mirror Effect) measurements carried out on the neat epoxy matrix and on two GFRE composites, which only differ by the sizing of the fibres. For the matrix, the influence of friction is only obvious inside the friction track but, for the composites, a modification of the properties of the whole composite (inside and outside the friction track) is observed after friction. Consequently, the glass fibre/matrix interfaces play the role of diffusion path and, then, allow the trapping of electric charges, inducing the formation of defects, as proved by the dielectric modification of material, outside the friction track. In addition, it will be noted that a diffusion of electric charges through the fibre-matrix interfaces permits a stabilization of the friction coefficient and a limitation of the wear, whereas a localised trapping of charges on the interfaces is a source of damage and wear. In this way, the choice of the sizing process permits to control the motion of the electric charges and, consequently, to optimize the mechanical and tribological properties of the composites. (C) 2008 Elsevier B.V. All rights reserved.