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.