(to be submitted for journal publication)
H.M. Yin, G.H. Paulino and W.G. Buttlar
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Newmark Laboratory, 205 North Mathews Avenue, IL 61801, USA
Abstract
Abstract: Elastic fields of a brittle film bonded to a ductile substrate subjected to a tensile stress are studied. A two-dimensional explicit elastic solution is derived for one section between two discontinuities of the film with a frictional interface or a fully bonded interface. This solution is applied to calculate the energy release rate of three-dimensional channeling cracks. The fracture toughness and the nominal tensile strength of the film are obtained through the measurement of the relation between the crack spacing and the tensile strain in the substrate. Comparisons of this solution with finite element method simulations show that the proposed model provides a very accurate solution for the film/substrate system with a frictional interface; whereas for a fully bonded interface it produces a good prediction only when the substrate is not overly compliant or when the crack spacing is large compared with the thickness of the film. If the section is infinitely long, this solution in terms of the energy release rate is reduced into Beuth’s exact solution for a fully cracked film bonded to a semi-infinite substrate. Interfacial shear stress and the edge effect on the energy release rate of an asymmetric crack are analyzed. Fracture toughness and crack spacing are calculated and are in good agreement with the available experiments.
KEY WORDS: A. Fracture Toughness; A. Energy Release Rate; B. Elastic Materials; C. Analytic function; Thin Film