SIF-based fracture criterion for interface cracks

The complex stress intensity factor K governing the stress field of an interface crack tip may be split into two parts, i.e., \(\hat{K}\) and \(s^{-\mathrm{i}\varepsilon }\), so that \(K=\hat{K}s^{-\mathrm{i}\varepsilon }, s\) is a characteristic length and \(\varepsilon \) is the oscillatory index. \(\hat{K}\) has the same dimension as the classical stress intensity factor and characterizes the interface crack tip field. That means a criterion for interface cracks may be formulated directly with \(\hat{K}\), as Irwin (ASME J. Appl. Mech. 24:361–364, 1957) did in 1957 for the classical fracture mechanics. Then, for an interface crack, it is demonstrated that the quasi Mode I and Mode II tip fields can be defined and distinguished from the coupled mode tip fields. Built upon SIF-based fracture criteria for quasi Mode I and Mode II, the stress intensity factor (SIF)-based fracture criterion for mixed mode interface cracks is proposed and validated against existing experimental results.