PRESSURE-SENSITIVITY AND TENSILE STRENGTH OF AN ELASTOMER AT HIGH STRAIN RATES

Abstract

Pressure‐shear plate impact experiments have been conducted to study the mechanical response of an elastomer (polyurea) at very high strain rates: 105–106 s−1. Thin samples are cast between two hard steel plates. Longitudinal waves reverberating through the sample are used to determine the slope of the isentrope at compressive stresses greater than, say, 500 MPa—the initial pressure at impact. Shear waves measure the shearing resistance at the pressure attained after the “ring‐up” of the pressure in the sample is complete. In the current work, release wave experiments and plane wave simulations are used to extend the isentrope into the tensile regime—and ultimately to failure. The previous work is also extended to determine the pressure‐sensitivity of the material's shearing resistance at high shearing rates and low pressures. To achieve the latter, the impact configuration is designed so that an unloading longitudinal wave reflected from the rear surface of the target assembly arrives at the sample midway through its loading by the incident shear wave. As a result, the sample is sheared at high strain rates—at both high and low pressure—during a single experiment.