Quantification of the compressibility of elastomers using DIC

Abstract

Both filled and unfilled elastomers are generally modeled as incompressible solids. However studies on the compressibility of elastomers have indicated that volume expansion is observed at large stretches coinciding with the onset of cavitation. Varying methods such as dilatometry and hydrostatic weighting have been used to calculate volume changes that elastomers undergo during stretching. However, these techniques cannot map volume variations for a heterogeneous state of stress, motivating the present work. In this study, carbon black filled elastomer samples were subjected to a uniaxial stretch and the deformation was recorded using two back-to-back stereo-correlation systems. The back-to-back stereo-correlation systems allow the in-plane strains on the front and back face of the specimen to be calculated along with the normal strain through the thickness. Using the assumption of plane stress, the volume variation of the elastomer as a function of the applied longitudinal strain was determined.