Failure of aerospace composite scarf-joints subjected to uniaxial compression

The uniaxial compression behavior of adhesively bonded composite scarf-joints was studied and the role of scarf-angle on joint strength and failure mechanism was investigated. Adhesively bonded scarf-joints made of carbon-fibre reinforced polymer laminates and ‘AF-163-2’ structural film adhesive were compressed to final failure and the responses of the joints to the compressive loads were measured. The results showed that the compressive strength of the joints decreased monotonically as the scarf-angle (with respect to the loading axis) increased. The studies on post-fractured specimens revealed that the failure mechanism switched from predominantly fiber microbuckling for joints with scarf-angles below 3°, to cohesive shear deformation of the adhesive layer (with attendant fiber microbuckling), for joints with scarf-angles above 3°. These findings are useful for assessing the knockdown of compressive-joint strengths of adhesively bonded composite joints for less than ideal scarf-angles.