Rifts in Rafts

Two-dimensional particle rafts are single-layers of aggregated sub-millimeter polydisperse particles floating at an air-fluid interface. The material failure of such rafts under an applied extensional load has a morphology that appears to be distinct from other known fracture modes. At low strain rates, the system fails like a ductile solid and it breaks at the point where a neck pinches off. However, at higher shear rates, numerous small-scale cracks are distributed diffusively throughout the entire system. We observe a dependence of the characteristics of this distributed failure on the surface tension and viscosity of the underlying fluid. These results indicate that the fluid plays an important role in controlling the velocity-dependent fracture.