Crack kinking in brittle materials

Although they are rooted in the mechanics of solids and in its history, most crack propagation criteria reveal incorrect safe equilibrium domains. With the obvious exception of the maximum energy release rate, all of them show unacceptable energy dissipation in mixed mode crack growth. They convey important physical information and allow a degree of freedom in material modeling, in the same spirit as the elastic limit surfaces in the mechanics of materials. Maintaining such a degree of freedom in modeling brittle material behavior while preserving the mandatory requirements in terms of energy and of safe equilibrium domain is investigated in this paper, in the light of a recently proposed incremental description of (linear elastic) fracture mechanics.