THE CHARACTERIZATION OF THE ENERGY OF FRACTURE AT OR NEAR INTERFACES BETWEEN VISCOELASTIC SOLIDS

The problem of separating two viscoelastic solids of different properties in a time dependent manner is considered. This work is part of a wider study concerned with the time dependent failure of viscoelastic adhesive bonds at and/or near the interface, including propagation of a crack away from the interface. Inasmuch as such a study requires sufficient bond strength to control the orientation of crack propagation, this paper deals with the characterization of interface strength. Following earlier analysis of crack propagation in homogeneous and bimaterial viscoelastic solids, experimental studies concerned with rate dependent fracture at the interface are evaluated in terms of the viscoelastic functions associated with homogeneous fracture of the adherends and a separate interface-intrinsic strength which is determined by the chemistry at the interface. This interface strength multiplies a viscoelastic function, which, for the interface problem, is a combination of the properties of the homogeneous solids. Interface strength on the same order as those of the adherends is achieved.