Damage tolerance investigation of high-performance scarf joints with bondline flaws under various environmental, geometrical and support conditions

The criticality of disbonds on the load-carrying capacity of scarf joints under different environmental conditions was experimentally investigated. Tests were conducted on scarf joints containing bondline flaws of varying lengths and locations under room-temperature (RT), cold-dry (CD) and hot-wet (HW) conditions. The results showed that the residual strength of scarf joints under RT and CD condition decreases exponentially with the size of the bondline flaw up to a threshold length and remains almost unchanged for larger bondline flaws. In contrast, those specimens under HW condition were less sensitive to the presence of disbonds. The effects of scarf angle, adherend composite layup and support condition on the load-carrying capacity of scarf joints with a bondline flaw were also investigated. For specimens where the eccentricity was counteracted by a sandwich support, the residual strength of the joint improved considerably. Fractographic analysis using Micro Computed Tomography and SEM were carried out to examine the effects of the environmental condition on the failure mechanisms of scarf joints.