Enhancing Toughness of Thin Films and Coatings through Embedded Nanoinclusions

Buckling of thin films and coatings due to thermal residual stresses has been thoroughly investigated. The subsequent fracture at the film-to-substrate interface triggered by buckling may result in a complete delamination of the film, effectively making the structure useless. The approach to the prevention or alleviation of delamination and spalling of the compressed film suggested in the paper is based on embedding random stiff nanoinclusions in the pristine film material. This results in an increase of both the stiffness of the film and the buckling stresses. If the enhanced stiffness is not sufficient to prevent buckling, the strain energy release rate is decreased as a result of embedded nanoinclusions as demonstrated in the paper. This reduction is particularly significant in films whose stiffness is increased by a large factor as compared to that of the pristine material. The effectiveness of the method is particularly evident if the compressive stress exceeds the critical stress of the nanoreinforced film by a relatively small factor. At very high compressive stresses the method of improving toughness considered in the paper is still valid but its relative effectiveness diminishes