On the interfacial strength of bonded scarf joints

•The effects of geometrical factors on interfacial strength are studied.•Interfacial strength does not vary significantly with interface dimensions.•The orders of stress singularity are obtained for 3-D scarf joints.•A new empirical equation to predict the interfacial strength is proposed. The interfacial strength of bi-material bonded scarf joints is evaluated by an integrated experimental and numerical investigation. The effects of the scarf angle, interface dimension and the stress singularity on the interfacial strength were examined using a series of aluminum/PMMA and aluminum/polycarbonate bi-material specimens under static bending moments. The experimental results showed that the maximum principal tensile stress at failure did not vary significantly with interface dimension. The measured maximum principal tensile stress of scarf joints at failure decreases as the scarf angle increases. We correlated fracture initiation with critical values of the stress intensities of the singular fields near the three-dimensional interface corner. The order of the singularity at three-dimensional interface corners and edges was obtained numerically using common finite element methods. Finally, an empirical equation based on interface fracture mechanics was determined by curve fitting of the experimental results to predict the interfacial strength of bonded scarf joints.