The Variation with Temperature of the Dynamic Elastic Moduli of an Organic Glass at Two Frequencies

Measurements have been made of the dynamic shear modulus and velocity of longitudinal waves in an organic glass at frequencies of 4 Mc/s and 20 Mc/s. It has been found that there is a relaxation in the real part of the shear modulus which occurs at a higher temperature at 20 Mc/s than at 4 Mc/s; at each of these temperatures, the relaxation time is of the same order as the period of the applied stress. The real part of the bulk modulus calculated from the results appears to be independent of frequency but shows a transition in the form of its behaviour with temperature.