Interface failure modes explain non-monotonic size-dependent mechanical properties in bioinspired nanolaminates

Bioinspired discontinuous nanolaminate design becomes an efficient way to mitigate the strength-ductility tradeoff in brittle materials via arresting the crack at the interface followed by controllable interface failure. The analytical solution and numerical simulation based on the nonlinear shear-lag model indicates that propagation of the interface failure can be unstable or stable when the interfacial shear stress between laminae is uniform or highly localized, respectively. A dimensionless key parameter defined by the ratio of two characteristic lengths governs the transition between the two interface-failure modes, which can explain the non-monotonic size-dependent mechanical properties observed in various laminate composites.