Dynamic buckling delamination of a bonded thin film under residual compression

Summary

A thin solid film or coating bonded to a solid substrate may be in a state of residual stress due to mismatch in thermal expansion coefficient between the film and the substrate or other effects. If the residual stress is compressive, the tendency for film buckling is suppressed by the relatively high stiffness of the substrate. However, at a flaw in the interfacial bonding between the film and substrate, buckling of the film can and does occur. The focus here is on the process of delamination buckling under these circumstances, including dynamic effects. For an interfacial defect of a certain size, the compressive force in the film may exceed the buckling load, in which case the buckling process is inherently dynamic. Both cases of plane strain and axially symmetric deformation are considered, and propagation of the buckle is permitted provided that an energy balance separation condition is satisfied. Post-bifurcation response of the film is described by means of the von Karman plate theory. Hamilton’s principle is applied to obtain an approximate representation of the deformation in terms of two generalized coordinates, namely, the midpoint deflection of the buckled region and the size of the buckled region. Dynamic effects included are the transient deformation from the bifurcation state to the post-buckling configuration and the possibility of buckle nucleation due to waves impinging on the film from within the substrate. Histories of transient buckle deflection and buckle width are determined for representative material parameters.