Modeling nonlinear thermo-elastic response for glassy polycarbonate using ultrasonic results under compression in a confined cell

We develop a nonlinear thermo-elastic model for polycarbonate (PC) using ultrasonic longitudinal and shear waves applied on a sample under confined compression. The model is a thermodynamically consistent model developed based on data obtained from a modified pressure-volume-temperature measurement system that also provides the longitudinal and shear wave moduli (Masubuchi et al., 1998. Materials Science Research International 4(3), 223-226). The heat capacity data was obtained by using a differential scanning calorimeter. The resulting model reproduces the ultrasonic behavior of the PC over the temperature range of 35 °C to 150 °C and under pressures from 0 to 70 MPa. Since the response at constant pressure is close to linear below the glass transition temperature of 147 °C, one may extend the use of the model to temperatures below 35 °C, possibly covering most of the range of use for most applications.