Cavitation and Fracture of Soft Materials

Rapid expansion of soft solids subjected to a negative hydrostatic stress can occur through an elastic cavitation mechanism or an inelastic fracture mechanism. Balancing how these two mechanisms relate is important to applications in materials characterization, adhesive design, and tissue damage. Significant research effort has focused on understanding how these two mechanisms relate; however, the available experimental data in this area has been limited by both the techniques employed and materials considered. Experimental investigation into the transition between cavitation and fracture requires 1) knowledge of the initial cavity geometry and 2) a material system where both the elastic and fracture properties are independently characterized. In this work, recent improvements in needle-induced cavitation and independent characterization of elasticity and fracture in a set of model end-linked tetra-PEG gels are exploited to experimentally probe the relationship between the elasto-fracture length and cavitation and fracture. The results indicate that three distinct regimes exist where expansion occurs through either cavitation, cavitation-initiated fracture, or fracture.