Effect of patterned nanoscale interfacial roughness on interfacial toughness: A finite element analysis

A finite element analysis was used to determine how patterned, nanoscale interfacial roughness could potentially increase the apparent interfacial toughness of brittle, thin-film material systems. The pattern analyzed was composed of parallel channels with either a rectangular-toothed or a rippled cross-section. Results are presented for a thin, linear elastic, bimaterial strip loaded by displacing the top edge relative to the bottom edge. The finite element calculations indicate that the interface does not unzip in a steady, continuous manner. Instead, the crack tip stalls as it tries to kink in a direction that is offset from its original path. The apparent interfacial toughness is found to depend on the intrinsic interfacial toughness, the ratio of real-to-nominal interfacial area, the extent of ligament, tooth-tip damage that occurs before crack propagation, strain energy locked in by persistent contact, and the level of energy dissipation associated with dynamic fracture.