Damage propagation in a model cohesive granular medium

Understanding how a crack propagates in a heterogeneous medium is essential in numerous fields, since this process can lead to catastrophic events. The opening of a crack can lead to the emission of an elastic wave, which can interfere with the rest of the material, and provide energy to open new cracks. In particular, in a brittle material, the critical stress leading to rupture is different from one experiment to another. This is usually imputed to the presence of defects, which are weaker points in the material, making crack propagation easier. The interaction of the elastic waves emitted by a crack opening, and existing defects is still not fully understood.
We study a model material made of a monolayer of glass grains attached by individual elastic bridges. Using a high-speed camera, we can follow the propagation of elastic waves in this material as well as the crack opening dynamics. We can in particular observe the interaction of existing cracks and defects.