An experimental investigation of fracture at a bimaterial interface

by Bowen, John Murray

Abstract (Summary)
The growth of a crack located at the interface between two linearly (visco)elastic solids is investigated experimentally. It is found that the crack may advance by kinking into either of the adherends or by propagating along the interface itself, depending on the applied loading. For the separation problem, in which crack advance occurs along the bimaterial interface, it is demonstrated that the time-dependent unbonding of the two joined viscoelastic solids follows a rate-dependent fracture process that can be described to a large extent by the viscoelastic properties of the two adherends. Moreover, the strength of the interfacial bond can be characterized in terms of an equilibrium interface-intrinsic fracture energy, the magnitude of which represents the bond strength quantitatively. In particular, interface strength on the same order as those of the adherends is achieved. In contrast to the time-dependent approach developed for the separation problem, the propensity of the interface crack to kink out of the interface upon loading is evaluated in the context of (time-independent) linearly elastic fracture mechanics. It is demonstrated that crack propagation along the interface occurs for a finite range of load mixity, a phenomenon predicted by linear analysis of the bimaterial joint but absent from the corresponding homogeneous development. Agreement between observed kinking behavior and analytical results is seen to improve by suitable manipulation of a presumably material characteristic length, the origin of which is rooted in the linearized analysis. The influence of material rate effects on the crack kinking behavior is also investigated.
Bibliographical Information:

Advisor:Wolfgang Gustav Knauss

School:California Institute of Technology

School Location:USA - California

Source Type:Master's Thesis



Date of Publication:05/06/1992

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