Decohesion of a rigid punch from an elastic layer: Transition from “flaw sensitive” to “flaw insensitive” regime

A cohesive zone model is used to study the pull‐off of a rigid flat cylindrical punch of radius c from an elastic layer of thickness h. The adhesion between the punch and the elastic layer is assumed to be sufficiently weak so that pull‐off occurs by the growth of a crack from the edge of contact. Our result shows that the pull‐off stress, when normalized by the interfacial strength σo, depends on a single dimensionless parameter χf = σ c(1−v2) g(ξ)/2πEWad, where E and v are the Young's modulus and Poisson's ratio of the elastic layer, respectively, Wad is the work of adhesion, and g(ξ) is a known dimensionless function of ξ ≡ c/h. χf can be viewed as a generalized Tabor parameter. It characterizes the transition from a “brittle” or flaw sensitive failure regime to a “ductile” or flaw insensitive regime. The result in this work is used to generalize Maugis' theory of adhesive contact to the case where the elastic substrate is of finite thickness.