Controlled crack arrest in brittle thin films: The effect of embedded voids

Controlled crack arrest is useful for controlling self-assembled crack paths in micro-fabrication, as well as limiting crack length in toughening composites. Compliant inclusions and voids can effectively attract and arrest cracks, thereby controlling the crack pattern. Analytical stress solution indicates that when the inclusion is about 10 times more compliant than its matrix, it may be effectively modeled as a void. The crack arrest capability is expressed in terms of the critical angle of the initial crack path, as the inclusion size, shape, crack origin and film properties are varied. Simple criteria are established to maximize the crack arrest ability and to determine the critical crack angle. The effectiveness of using different void patterns to arrest cracks is also explored. The results are useful for both controlling and restricting cracks in brittle thin films, through the utilization of compliant or void-like inclusions as crack arrestors.