Strain gradient fracture of a mode III crack in an elastic layer on a substrate

This paper studies the problem of a mode III crack in an elastic layer on a substrate under the framework of strain gradient elasticity theory. The effects of volumetric and surface strain gradient parameters on the crack tip asymptotic stress and crack shape are investigated. Due to strain gradient effect, the crack opening, the magnitude of the stress ahead of the crack tip, and the stress intensity factor are significantly higher than those in classical linear elastic fracture mechanics. More significantly, the direction of the stress ahead of the crack tip with strain gradient is opposite to that in the classical linear elastic fracture mechanics. The conventional linear elastic fracture mechanics results are recovered when the gradient parameter reduces to zero. The influence of the substrate on the fracture mechanics parameters is very significant when the strain gradient effect of the materials is considered.