Coupled cohesive zone models for mixed-mode fracture: A comparative study

• A consistency check for some mixed-mode cohesive zone models is performed.
• Significant stress and energy inconsistencies are found.
• Local model inconsistencies affect the global interface behavior.
• A thermodynamically consistent reformulation of an exponential model is presented.
• Loading, unloading, decohesion and contact are monolithically treated in the model.

This paper checks the consistency of some published exponential and bilinear mixed-mode cohesive zone models. The effect of coupling on traction-separation behavior and energy dissipation is investigated and the path-dependence of the debonding work of separation and failure domain is evaluated analytically and numerically. All selected models present several inconsistencies, except for the one by van den Bosch et al. (2006), which is, however, not currently formulated within a thermodynamical framework but postulated in an ad-hoc manner. We thus propose a thermodynamically consistent reformulation of this model within damage mechanics, which holds monolithically for loading, unloading, decohesion and contact.