This study compares the mechanical, tribological, and dielectric properties of glass fiber-reinforced epoxy (GFRE), presenting various fiber/matrix adhesions. Three GFRE composites were studied. The only difference between them is in the initial preparation of fibers which is intentionally simplified compared to the complex sizings used in industry. Thus, fibers treated with aminosilane or silicone coupling agents were compared with fibers simply washed with deionized water. The dielectric measurements show the leading role of interfacial bonding in the trapping or diffusion of electric charges. To obtain high mechanical properties, a fiber treatment that contributes to the diffusion of electric charges along the fiber/matrix interface is preferred. In addition, after friction, a modification of the dielectric properties in all materials is observed, and the trapping or the diffusion of the charges along the interfaces can make it possible to lower the friction coefficient, or the wear.
