A calibrated fracture process zone model for thin film blistering

The purpose of this work was to examine the feasibility of using fracture p rocess zone models for extracting the adhesive fracture energy of thin film s on a thick substrate from circular blister experiments that involve a sub stantial amount of inelastic deformation in the thin film. The interface pr oduced by vapor depositing polyimide on aluminum formed the basis of the ex periments that were conducted. The experiments were conducted in volume con trol while the pressure history and the corresponding three dimensional bli ster shape were measured. The analysis accounted for the nonlinear kinemati cs and material behavior of the polyimide film and included a traction-sepa ration law for the interface. The traction-separation law for the interface was calibrated in an iterative manner by comparing measured pressure-volum e responses and crack opening displacements. The adhesive fracture energy o btained from the selected traction-separation law was reasonable considerin g that fracture occurred in an interphase region. It was bounded by values that were obtained from elastic analyses (with updated kinematics) of the t ype performed by Gent and Lewandowski (1987) and Chu et al. (1992 a, b).