A COUPLED ELASTIC-PLASTIC DAMAGE MODEL FOR RUBBER-MODIFIED EPOXY ADHESIVES

A continuum damage model for rubber-modified epoxy adhesives is presented. The macro- and micromechanical observations are translated into a constitutive theory based on thermodynamics with internal state variables. An extension of the principle of strain equivalence, which makes a phenomenological derivation more systematic, is proposed. Important features of the material model are: (1) An isotropic damage measure is used. (2) The irreversible strain consists of a deviatoric part due to plastic flow and damage, and a dilatoric part due to damage. (3) The criteria for plastic flow and for damage growth are dependent on the hydrostatic stress. The model response in tension, compression and shear is studied. The model is likely to be valid for a wider class of polymeric materials.