Mechanics of Periodic Film Cracking in Bilayer Structures Under Stretching

In a bilayer structure consisting of a stiff film bonded to a soft substrate, the stress in the film is much larger when the rigidity of the film is much higher than that of the substrate so that film cracking is a common phenomenon in bilayer structures such as flexible electronics and biological tissues. In this paper, a theoretical model is developed to analyze the normal stress distribution in the structure to explain the mechanism of the formation of periodic crack patterns. The effects of geometrical and material parameters are systematically discussed. The analytical result agrees well with finite element analysis, and the prediction of spacing between cracks agrees with experiments from the literature.