Crack propagation in swelling gels

Hydrogels are crosslinked polymer networks that can absorb and retain large amounts of water. Under certain conditions, swelling can lead to the formation of cracks, which is undesirable in applications. This phenomenon of swelling-induced rupture is challenging to study with the standard theories of fracture mechanics due to the coupling between fluid diffusion and large deformations. Using theory and simulation, we consider a simple geometry in which a pre-cracked hydrogel is partially submerged in fluid. As the fluid is drawn into the hydrogel, the non-uniform expansion produces residual stresses, driving crack growth. We develop a phase field model capable of simulating large deformation quasi-static swelling-induced fracture and study where cracks originate and what paths they take for a range of hydrogel geometries.