Development and Validation of a General Theory for the Onset of Cavitation

Abstract

The overarching goal of this dissertation is to develop and validate a general theory of the onset of cavitation in any nonlinear elastic isotropic material under any arbitrary stress state. Our theory is an extension and generalization of an earlier closed-form criterion for the onset of cavitation in neo-Hookean solids developed by Lopez-Pamies et al. The validation assessment of our general theory is conducted through comparisons with finite element simulations and experiments on an ultra-soft triblock copolymer (PMMA-PnBA-PMMA). A commercial finite element software is utilized to study cavitation of a few classes of hyperelastic constitutive models under various macroscopic hydrostatic and deviatoric loadings. Additionally, we developed a new experimental technique, superimposed shear cavitation, to measure the cavitation response of soft matter under complex stress states. Our experimental apparatus combines elements from the Taylor-Couette flow apparatus and the needle-induced cavitation technique developed by Crosby et al. In our superimposed shear experiments, the macroscopic deviatoric stress state can be independently controlled via the rotation of the inner cylinder in a coaxial-cylinder system. With our general theory and associated experimental observations, the effect of strain stiffening and/or softening, surface tension, and size of defect on cavitation is now better understood. Although not the focus of this work, our general criterion for the onset of cavitation may prove useful in understanding, modeling, and mitigating traumatic brain injuries.