Cohesive failure of multilayer composite films

A theoretical model is proposed for the cohesive failure of multilayer composite systems. A general formula is derived which relates values of structural and geometrical parameters at which crack generation is energetically favorable in such composite systems. For one-layer film/substrate systems, the critical thickness is found above which the cohesive fracture of films is energetically favorable. Nucleation of an intermediate layer due to diffusion across a film/substrate interphase boundary is considered. It is shown that the generation and the growth of the diffusion layer may result in the spontaneous cracking of the film.