Fundamental physical principles and cohesive zone models at finite displacements – Limitations and possibilities

Cohesive zone modeling at finite displacements and crack openings are discussed and evaluated in relation to the fundamental principles provided by thermodynamic consistency, balance of angular momentum and material frame indifference. It is shown that among the existing prototype cohesive zone models within the classical cohesive zone framework, only fully isotropic elastic models or fully isotropic elastic models combined with isotropic damage theory fulfill all of the aforementioned fundamental principles whereas present elasto-plastic models do not. For this reason, and still within the classical cohesive zone framework, a novel elasto-plastic model is proposed which fulfills all requirements. Subsequently, the classical cohesive zone framework is generalized and within this new framework a consistent elasto-plastic model is proposed.