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Hysteresis and Fracture in Soft Materials

Rong Long Department of Mechanical Engineering, University of Colorado Boulder

Soft materials have been utilized in a wide range of emerging applications such as soft robotics, stretchable electronics, and biomedical implants. Many of these applications require the underlying soft materials to be stretchable and yet fracture resistant. A key mechanism of toughness enhancement is to introduce energy dissipation and thus shield a crack from the external loading. However, fracture mechanics of such soft dissipative materials involves nonlinear deformation and complex material behaviors, and as a result quantitative prediction of the fracture toughness remains challenging. In this seminar, I will first present a theoretical framework that relates fracture toughness and bulk dissipation in soft dissipative materials. To predict fracture toughness based on this theoretical framework, quantitative results in two aspects are necessary : 1) an accurate constitutive model to capture hysteresis and dissipation ; 2) the nonlinear strain fields around the tip of a crack undergoing large deformation. I will present our efforts in evaluating the nonlinear crack tip fields in hyperelastic solids using a particle-tracking based experimental method. I will also discuss our ongoing efforts in in developing physics-based constitutive models for damage in soft polymers.