Low-velocity impact response of friction riveted joints for aircraft application

In this paper, the sensitivity of carbon fiber reinforced polyether-ether-ketone (CF-PEEK) friction riveted joints to impact damage was assessed as well as the damage propagation during fatigue and quasi-static mechanical testing. The joints were impacted with energies between 5 J and 30 J at room temperature and the impact damage was evaluated through microscopy and ultrasonic C-scan. Two damage types were identified: barely-visible impact damage with mainly shear-driven damage in the first plies of the composite and visible impact damage with delamination and premature failure of the rivet-composite interface owing to peel stresses upon the impact event. The joint strength and fatigue life were not compromised by the barely-visible impact damage, while a 40% decrease of quasi-static strength and lower fatigue resistance were achieved for visible impact damage. Despite altered fatigue behavior of impacted joints, damage accumulated towards fatigue was not critical to the joint mechanical integrity, confirmed by the residual strength of up to 96% after 106 cycles for 20 J impacts.