Experimental and Computational Investigation of Fracture Patterns in Thin Films and Multilayers

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Experimental and Computational Investigation of Fracture Patterns in Thin Films and Multilayers.This project aims to investigate fracture patterns in thin films and multilayers in a combined experimental and computational effort. Thin films are normally pre-stressed, primarily due to the mismatch of the thermal expansion coefficients of the film and the substrate. The residual stress can be relieved in time by fracture. Failure occurs when the residual stress levels are high, and in addition an external mechanical and/or thermal stresses are applied. While these failures are very common, the fundamentals of fracture patterns formation are yet to be understood. This proposal considers fracture patterns formation in thin films both in tension and compression. It is proposed to study the origin of sinusoidal and spiral cracks in tension, as well as "telephone cord" delamination formation in compressed films. Fundamental understanding of the fracture patterns formation process will provide a framework of failure prevention in thin films and coatings, which reflects the intellectual merit of this proposal. We are surrounded by devices that have thin films in them. Protective coatings and thin films are widely used in many industries, from microelectronics, to automobile and aerospace. While they serve various purposes, depending on the application, the films should stay intact and attached to the substrate. Good thin film adhesion and fracture properties are required. The broader impact of the proposed research on the society is immediately evident from the applications of the knowledge gained in the proposed research, which will prevent thin films and coatings failures. Additional broader impacts will include research and development training of graduate and undergraduate students, course enrichment, and broad interdisciplinary publications.