A Dugdale model based geometrical amplifier enables the measurement of separation-to-failure for a cohesive interface

Regardless of all kinds of different formulae used for the traction-separation relationship in cohesive zone modeling, the peak traction σ_m and the separation-to-failure δ₀ (or equivalently the work-to-separation Γ) are the primary parameters which control the interfacial fracture behaviors. Experimentally, it is hard to determine those quantities, especially for δ₀, which occurs in a very localized region with possibly complicated geometries by material failure. Based on the Dugdale model, we show that the separation-to-failure of an interface could be amplified by a factor of L/r_p in a typical peeling test, where L is the beam length and r_p is the cohesive zone size. Such an amplifier makes δ₀ feasible to be probed quantitatively from a simple peeling test. The method proposed here may be of importance to understanding interfacial fractures of layered structures, or in some nanoscale mechanical phenomena such as delamination of thin films and coatings.