PATTERN-FORMATION IN THIN-FILM FAILURE

While thin films bonded to solid substrates are integral to most moder n technologies, their failure mechanisms are not well understood. It h as long been observed,. however, that the mechanical failure of thin f ilms under large stresses produces a,rich phenomenology of pattern for mation. In this paper, we describe the results of computer simulations of stress relief in thin films under either tensile or compressive st ress applied by their substrates. For films which contain quenched dis order, tensile stress relief results in the fragmentation of the film layer into a patchwork of undamaged firm surrounded by cracks. When th e applied stress is moderate, the dynamics of the cracks are sufficien tly simple that a mean-field theory can be constructed to describe the crack-length statistics in the final fragmented state. For firms unde r large compressive stresses, the simulations reproduce a very peculia r delamination pattern which has been experimentally observed for seve ral decades; the buckled regions of film have a sinusoidal shape behin d a propagating tip. These strikingly regular sinusoidal blisters prop agate over large distances in the film with constant lateral widths an d constant wavelengths.