Effect of far-field compliance on local failure dynamics of soft solids

The resistive forces and failure of a soft gel upon large strain indentation with small, spherically-tipped indenters (or puncture mechanics) has been studied previously by Fakhouri et al., (2015). The above work is extended to include the effect of far-field compliance on the critical crack initiation event via puncture in soft acrylic triblock copolymer gels. It is found that critical puncture force, Pc, reduces with increasing far-field compliance, Cs, due to the change in local probe velocity, vg. A power-law relation between Pc and Cs is established and is shown to be valid across a range of global probe velocity, vc, varied over three orders of magnitude. Small-strain mechanical response of the gels characterized via oscillatory shear rheology and large strain response measured from puncture mechanics show rate-independent behavior. Our experiments and analysis provide insight into local rate-dependent failure processes in elastic triblock copolymer gels.