On the reference length and mode mixity for a bimaterial interface

We investigate properties that govern interfacial fracture within the framework of linear elastic fracture mechanics, including interfacial fracture toughness, mode mixity, and the associated reference length. The reference length describes the arbitrary location where the mode mixity is evaluated, ahead of the crack tip, in a bimaterial system. A method for establishing a reference length that is fixed for a given bimaterial system is proposed. This is referred to as the "characteristic reference length, " with the associated "characteristic mode mixity. " The proposed method is illustrated with an experimental investigation, utilizing a four-point bend test of a bimaterial system.