A Cohesive-Zone-Model Based Fracture Criterion for Silicon Microstructures with Sharp Notches

摘要

Anisotropically etched silicon microstructures may contain atomically sharp notches, which quite often become the origin of mechanical failure. For sharp notches a relation between the notch stress intensity factor and the microscopic surface separation energy similar to the one for classical crack problems, does not exist. A general fracture criterion independent of notch angle has been sought in the literature. In this study, by postulating the existence of a cohesive zone in front of the notch tip and using a simple Barenblatt cohesive zone model, a relation between the critical macroscopic notch stress intensity factor and material's microscopic separation energy is derived. Being different to the relation for classical crack problems, this general relation is also a function of material's cohesive strength. The criterion has been applied to silicon microstructures with sharp notches, where experimental results are available.