Buckling-induced delamination: Connection between mode-mixity and Dundurs parameters

Abstract

Modern electronics, micromechanical devices and applications demanding high reliability to weight or cost ratio consist of various combinations of multilayered thin films on rigid and compliant substrates, whereas the used materials can differ in their mechanical properties. In recent years, differences in the elastic moduli and Poisson’s ratios of such structures are becoming more pronounced. Therefore, a strong push to investigate interface stability with a more in-depth view on the elastic material properties mismatch influence is needed. Measurements of the adhesion of thin films on different substrate materials can be easily performed by the spontaneous buckling method described by Hutchinson and Suo. However, the original approach assumes several simplifications. One is to omit the changes of the influence of the elastic mismatch between the thin film and substrate on the basis of small variations in then-used materials, which is not true for modern materials combinations with vastly different elastic properties. The elastic mismatch on the interface between two different materials can be described by the Dundurs parameters. In this work, finite element modelling is combined with analytical solutions according to general description of the original model to extend the usability of the Hutchinson and Suo method for use with more different materials with higher accuracy. Obtained results point out the fact that disregarding the Dundurs parameters introduces significant errors in evaluating adhesion energy in relation to loading mode, proving the necessity to properly include elastic mismatch.Modern electronics, micromechanical devices and applications demanding high reliability to weight or cost ratio consist of various combinations of multilayered thin films on rigid and compliant substrates, whereas the used materials can differ in their mechanical properties. In recent years, differences in the elastic moduli and Poisson’s ratios of such structures are becoming more pronounced. Therefore, a strong push to investigate interface stability with a more in-depth view on the elastic material properties mismatch influence is needed. Measurements of the adhesion of thin films on different substrate materials can be easily performed by the spontaneous buckling method described by Hutchinson and Suo. However, the original approach assumes several simplifications. One is to omit the changes of the influence of the elastic mismatch between the thin film and substrate on the basis of small variations in then-used materials, which is not true for modern materials combinations with vastly different elastic properties. The elastic mismatch on the interface between two different materials can be described by the Dundurs parameters. In this work, finite element modelling is combined with analytical solutions according to general description of the original model to extend the usability of the Hutchinson and Suo method for use with more different materials with higher accuracy. Obtained results point out the fact that disregarding the Dundurs parameters introduces significant errors in evaluating adhesion energy in relation to loading mode, proving the necessity to properly include elastic mismatch.