Application of a cohesive-zone zig-zag theory to the modeling of mode II dominant delaminations in laminated composites

Delamination fracture of layered beams is studied using a homogenized structural model. The model applies local enrichments to the displacement field of a classical equivalent single layer theory in order to (i) better describe the effects of the layered structure on global and local fields and (ii) account for the presence of delaminations, while avoiding the through the thickness discretization of the problem. A homogenization technique is applied and equilibrium equations are derived which depend on only three global displacement variables for any numbers of layers and delaminations. Single and multiple delamination fracture in bend beams is studied using only in-plane discretization. The results are compared with accurate 2D solutions and experiments showing the capability of the homogenized model to predict energy release rate in layered systems, follow unstable crack growth and capture the effects of the interaction of multiple delaminations.