Energy release rate for cracks on a non-planar interface

In this work, a systematic study is conducted for the purpose of establishing a framework to characterize the effect of interface non-planarity on interface fracture toughness. Simple models for non-planar (deterministic) and rough (random) interfaces are developed. Based on these models, crack-tip singular fields are solved. These solutions lead to the quantification of the shielding/intensifying effects on the crack-tip fields due to the interface non-planarity and/or roughness. The results enable us to estimate the apparent toughness variation caused by interface non-planarity or roughness. It is found that (i) non-planarity/roughness, in most realistic cases, reduces the stress concentration near the crack tip (shielding). Consequently, it increasing the apparent toughness, (ii) in some special cases non-planarity/roughness may actually intensify the crack tip stress concentration, and therefore reduce the apparent interface toughness, (iii) the shielding/intensifying effects can be quantified in terms of the interface morphological parameters, and (iv) the shielding/intensifying effects due to inclination angle are more pronounced for mode II loading.