A continuum theory of cohesive zone models: deformation and constitutive equations

A general three-dimensional continuum constitutive theory of cohesive zone models is presented. This development is part of a larger theory in which f racture is studied using elements of continuum theories of interfacial evol ution. The main thrust of this work is the establishment of a systematic pr ocedure for deriving cohesive interphase constitutive equations, where crac k deformation is accounted for not only via the opening displacement, but a lso via crack surface strain tensors. The material frame indifference axiom is used to show that in traditional cohesive zone models, where the openin g displacement is the only crack deformation descriptor, cohesive forces mu st be pointwise parallel to the opening displacement itself. This result in dicates that the use of additional crack surface strain measures is require d for the description of realistic crack-tip microstructures with possible anisotropic behavior. (C) 1998 Elsevier Science Ltd. All rights reserved.