The mechanics of interface fracture in layered composite materials: (5) thin film spallation driven by pockets of energy concentration – microscopic interface fracture

A hypothesis is made that delamination can be driven by pockets of energy concentration (PECs) in the form of pockets of tensile stress and shear stress on and around the interface between a thin film and a thick substrate, where PECs can be caused by thermal, electrochemical or other processes. Based on this hypothesis, three analytical mechanical models are developed to predict several aspects of thinfilm spallation failure including nucleation, stable and unstable growth, size of spallation and final kinking off. The predictions from the developed models are compared against experimental results and excellent agreement is observed.