Experimental Study of Quasistatic Brittle Crack Propagation

This Letter presents an experimental study of controlled brittle crack propagation in thin glass strips, using a thermally induced stress field. For straight and oscillating crack propagation, three regimes are observed, controlled by a set of characteristic lengths. Direct measurements of the thermal field allows meaningful comparison with a model for straight symmetric crack based on two-dimensional elasticity. This strongly supports a velocity-independent fracture energy. For the oscillating onset, it is shown that the Cotterell-Rice criterion is not valid here.