EXPERIMENTAL-STUDY OF QUASI-STATIC BRITTLE CRACK-PROPAGATION

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