Coupled multi-scale cohesive modeling of failure in heterogeneous adhesives

A multi-scale cohesive numerical framework is proposed to simulate the failure of heterogeneous adhesively bonded systems. This multi-scale scheme is based on Hill's variational principle of energy equivalence between the higher and lower level scales. It provides an easy way to obtain accurate homogenized macroscopic properties while capturing the physics of failure processes at the micro-scale in sufficient detail. We use an isotropic rate-dependent damage model to mimic the failure response of the constituents of heterogeneous adhesives. The finite element method is used to solve the equilibrium equation at each scale. A nested iterative scheme inspired by the return mapping algorithm used in computational inelasticity is implemented. We propose a computationally attractive technique to couple the macro- and micro-scales for rate-dependent constitutive laws. We introduce an adhesive patch test to study the numerical performance, including spatial and temporal convergence of the multi-scale scheme. We compare the solution of the multi-scale cohesive scheme with a direct numerical simulation. Finally, we solve mode I and mode II fracture problems to demonstrate failure at the macro-scale.