The effect of film thickness variations in periodic cracking: Analysis and experiments

► The effect of film thickness variation on periodic cracking experiments is analysed. ► The length scale of variation in relation to crack spacing is found to be important. ► Refinements to interfacial shear stress calculations are presented. ► A model AlxOy/Cu system is analysed in regard to film thickness variations. ► Analysis shows statistical distribution of film strength is due to thickness variation.