Rate-dependent fracture behavior of gelatin-based hydrogels

Hydrogels exhibit rate-dependent fracture behavior, due to solvent diffusion, rearrangement of the polymer network, and other mechanisms. To explore rate-dependent fracture behavior, a series of creep fracture experiments were performed on gelatin-based hydrogels under different controlled humidity, and load conditions. The crack tip boundary condition was controlled to non-immersed and fully water-saturated conditions. Additionally, full-field measurements of the displacement field were performed with digital image correlation. From these experiments, we show that humidity influences the crack initiation time but not the growing crack speed, and that water on the crack tip will significantly influence the fracture properties of the failure zone. Schapery's viscoelastic J-like integral was adopted for analysis of the experimental measurement to distinguish bulk viscoelastic dissipation from the fracture process zone dissipation. We show that viscoelastic J-like integral is path-independent and can serve as a characterizing parameter for quasistatic crack growth, which provides a way to predict crack growth speed in the simulations.