The effect of interface strength on crack interactions in thin film coated substrates

Abstract

Crack interactions and propagation paths for thin film and substrate systemsare studied by using finite element method. 2D edge crack analysis are performed tovalidate robustness of the method used; results are compared to analytical results available in literature. A script is developed for 2D crack propagation which is embeddedinto finite element program. 3D edge cracks in thin films are studied; calculated valuesof stress intensity factors are compared to analytical results from literature and 2Dresults. Thin film on an elastic substrate with an edge crack is investigated. During the study, stress intensity factors, crack initiation angles and energy release rates arecalculated for each case. Crack front profile determination and its effects on crack prop-agation paths in thin film-substrate systems are studied. Effect of elastic mismatchis examined by performing analysis using several different material properties for thin film and substrate. Interface effect is studied by crack propagation path comparison ofparallel edge cracks and an edge crack on a square plate with a corner cut. Interfacestrength is modeled by elastic perfectly plastic and cohesive zone material models.