Crack spacing in brittle films on dissimilar planar and axisymmetric elastic substrates

The phenomenon of multiple cracking in brittle films on dissimilar elastic substrates is analyzed using a fracture mechanics approach. Film cracking is based on an energy release rate criterion. Energy release rates are calculated using finite elements and the domain integral method. Both planar and axisymmetric configurations are considered. Crack spacing curves are obtained as a function of applied load for a range of materials and geometric parameters. These curves may be used to determine the film fracture toughness if either the crack initiation stress or crack spacing is measured experimentally. The results obtained are applicable to the cases of mechanical or residual stress induced cracking in thin films and to the tensile test of a thin coated fiber.