On the mechanics of delamination and spalling in compressed films

The mechanics of the delamination and spelling of compressed films or coatings has been analyzed using a combination of fracture mechanics and post-buckling theory. It is demonstrated that the delamination of pre-compressed films only occurs if the film buckles, whereupon a stress intensification develops at the buckle perimeter. The associated stress intensity depends on the magnitude of the prestress and the film thickness. Conversely, the delamination of indented coatings occurs without buckling and the stress intensity in this instance depends on the indentation volume, the film thickness and the radius of the delamination. Preliminary attempts have also been made to predict critical spall conditions, following the incidence of buckling.