The results of the thermodynamic approach to fracture for the cases of a sharp crack without and with a cohesive zone are reviewed and discussed in detail. Particular care is devoted to the crack tip singularity analysis and to the issue of energy dissipation due to crack propagation. The case of a crack with a cohesive zone removing all thermomechanical singularities is then further developed, focussing the attention on the question of thermodynamic admissibility of subcritical crack growth, and on the hypotheses that lead to the derivation of crack growth laws. A two-phase cohesive zone model for discontinuous crack propagation is presented and its thermodynamics briefly analyzed, followed by an example of its possible application. The generality of the model presented herein is further examined in the context of a thermodynamically based discussion of some relevant cohesive zone models available from the literature.
