Modeling Kinetics Of Interfacial Debonding And Buckling In Multi-Cracked Films On Elastic Substrates

Nowadays,film-substrates systems are widely used in all fields.However,films are often under residual compression or tensile stress due to various mismatches between the film and the substrate.Channel crack is one of the most common failure modes of films under residual tensile stress,while compression stress usually leads to films wrinkle or buckle-delamination in films.In most cases,cracks may coexist with other failure modes,such as debonding or buckling.It is important to understand the mechanism of the coupling effect between crack and other failure modes.In this paper,we present a unified model to simulate the interfacial debonding or buckling behaviors in cracked films.The main work of this paper is as follows.We develop the theoretical model that integrates the equilibrium eigenstrain method for the elasticity of the cracked film,the Green function method for the substrate elasticity,the cohesive zone method for the interface.In the framework of total free energy minimization,the Ginsburg-Landau kinetic equations are derived to simulate the debonding in the cracked film.We reveal the influence of thickness and cracks distribution on the debonding process in the cracked film.Besides,we simulate the effect of anisotropic residual stress on the debonding process.Furthermore,we calculate the debonding process of island structure with different shape,and propose the mechanism of the shape influencing on the debonding behavior of islands.We further study the localized wrinkling pattern in the cracked film.Firstly,morphologies of brittle or ductile polymer films with mode I crack have been experimentally reported.The results show that localized buckling pattern only appears in the ductile polymer film.Then,we extend the previous model to account the crack propagation,plastic deformation,and out-of-plane deformation in the film.Our simulation results demonstrate that the plastic strain in the plastic zone near the crack tip leads to a compressive stress,which results in the localized buckling morphology.The inverse relation between the size of the plastic zone at the crack tip and the thickness of the film further explains why the width of the localized buckle is inversely proportional to the thickness of the film.