Growth of damage in additively manufactured metal-composite joints

The mechanical behaviour of a novel metallic-composite joining technology (HYPER) is investigated. Joints are strengthened with an array of pins built using additive layer manufacture. A new approach to pulse-echo ultrasonic evaluation was developed for this application in order to allow damage within joints to be monitored. It was found that the orientation of the specimen is critical due to the potential for the pins to scatter the incident ultrasonic wave. Damage was progressively induced within a batch of single lap HYPER coupons through repeated tensile loadings. The inspection methodology was successful at capturing the propagation of damage. It was found that the interface between adherends achieved a complete disbond without observable laminate damage or pin fracture. All pins then failed in an catastrophic manner due to excessive shear stress at their bases. Limit load was 21% higher than the ultimate load of a comparable unpinned joint. The ultimate load of the HYPER coupons was 650% higher than the same unpinned benchmark joint.