Topographic Study of Glass Fibers by Atomic Force Microscopy

Abstract

To better understand certain physical behaviors of glass fibers used to reinforce a polymer matrix (in composite materials), it is necessary to know their topography. In this paper, E glass fibers are studied using atomic force microscopy (AFM) and scanning electronic microscopy (SEM). To compare three different kinds of fibers (uncoated or virgin glass fibers and those coated either with an epoxy or aminosilane coupling agent only or with a complete sizing), their topography is analyzed using AFM and SEM, the former permitting the mean rugosity (R_a ) measurement of the fiber surface. Virgin (uncoated) glass fibers show a relatively smooth structure (R_a = 13 nm) with, here and there, bumps that look like craters. Fibers coated with a coupling agent alone have a non-uniform structure because areas all along the length of each fiber are torn off when it is separated from others in the glass roving. Grooves appear when the coupling agent is removed from the fiber's surface; otherwise, there are longitudinal bumps. Fibers coated with a complete sizing have no tom-off areas. The whole to pography is regular, bumps seldom protrude from the overall surface plane, and the roughness value is always lower than that of virgin fibers.