Hypersonic Velocities and Submicrocrack Formation in Ductile Polymers under Uniaxial Tensile Stress

Publisher Website
Google Scholar
Abstract
Longitudinal hypersonic sound velocities in two kinds of ductile polymer, polycarbonate (PC) and polyethylene terephthalate (PET), were examined by Brillouin scattering. These two materials exhibited a decrease in hypersonic sound velocity (the softening phenomenon) when stress was applied, but the amount of softening as well as its angular dependence with respect to the stress direction were much smaller than those for a typical brittle polymer, poly (methyl methacrylate) (PMMA). Furthermore, a correlation between these acoustic properties and the formation of submicrocracks was demonstrated by small-angle X-ray scattering (SAXS) measurements. The difference in the anisotropies in the softening of sound velocity between ductile and brittle polymers is discussed from the viewpoint of the shape and density of the submicrocracks