Multiscale Modeling of Fracture and Plasticity in Layered Structures

Plasticity in the geometrical confinement of a multilayered composite material is studied with a dislocation-based model, where the mutual interaction of dislocations in the elastically inhomogeneous layered structure is defined within the theory of elasticity on the continuum level. The interface between two different layers is described as a cohesive zone, which allows crack initiation and delamination to be studied on a rather fundamental level, taking into account information on atomic binding energies across the interface. With this combined dislocation dynamics-cohesive zone model we investigate whether a pre-existing crack in a ductile layer of the composite structure will blunt or rather propagate in a brittle fashion. It is seen that the length scale defined by the geometrical confinement of the plastic zone in the layered structure plays a critical role in determining the behaviour of the entire structure.