Prediction of failure initiation of adhesively bonded joints using mixed-mode fracture data

An increased use of adhesively bonded joints in industrial applications has renewed the interest of mixed mode fracture research in adhesive joints. Most practical plane fracture problems are mixed mode, and most advanced materials and joints are shown to fail through mixed mode fracture. It is widely accepted that a useful method for characterizing the toughness of bonded joints is to measure the fracture toughness, GC; energy per unit area needed to produce failure. Mode mixity has a strong dependency toward fracture toughness, and fracture toughness is directly associated with load.; FRANC2D is used to model and analyze single-lap joint specimens to determine the mode mixity at failure initiation. Virtual loads are applied to the single-lap joint model to generate load vs. strain energy release rate curves. Failure loads obtained experimentally are then compared with predictions made by the mode-mixity fracture toughness curves for the two adhesive types considered.; It is concluded that failure loads predicted by mixed-mode fracture toughness curves are in good agreement with those obtained experimentally. Recommendations are made for future work in mixed-mode fracture toughness characterization, ranging from process stage to testing methods and analytical tools. (Abstract shortened by UMI.)...