Chemo-mechanical coupling in curing and material-interphase evolution in multi-constituent materials

Chemical reactions at bimaterial interfaces during manufacturing of fiber–matrix systems result in an interphase that plays a dominant role in the response of the composite when subjected to mechanical loads. An accurate modeling of the degree of cure in the interfacial region, because of its effect on the evolving properties of the interphase material, is critical to determining the coupled chemo-mechanical interphase stresses that influence the structural integrity of the composite and its fatigue life. A mixture model for curing and interphase evolution is presented that is based on a consistent thermodynamic theory for multi-constituent materials. The mixture model is cast in a stabilized finite element method that is developed employing variational multi-scale ideas for edge-based stabilization and consistent tying of the constituents at the domain boundaries. The ensuing computational method accounts for curing and interphase chemical reactions for the evolution of the density and material modulus of the constituents that have a direct effect on the interfacial stiffness and strength. Several test cases are presented to show the range of applicability of the model and the method.