An acoustic characterization of polymethyl methacrylate and three epoxy formulations

Abstract

This paper presents the results of an experimental study conducted to obtain an acoustic characterization of polymethyl methacrylate (PMMA) and three Epon 828 formulations in their glassy state. By using a pulse‐transmission technique, ultrasonic dispersion data were obtained for these polymericmaterials as a function of frequency and temperature, and then the principle of time‐temperature superposition was used to transform the dispersion data for each material into a linear‐viscoelastic ``master‐curve'' representation. The master curve for each material contains sufficient information to determine the propagation characteristics of a low‐amplitude wave as a function of its frequency (or frequency spectrum) and the temperature of the polymer. This representation is equivalent to the more common stress‐relaxation‐modulus and complex‐moduli representations of linear‐viscoelastic behavior and is valid over an extensive frequency range.