Research on the connection performance and failure mechanism of composite double-sided countersunk rivets based on stress regulation

Aiming at the problem of stress concentration around the hole and composite material damage caused by the coupling of upsetting head transition expansion and axial load in composite wing head riveting, a new rivet double-sided head riveting process method based on stress regulation is proposed in this paper. The simulation-experiment collaborative verification method of double-sided countersunk pressure riveting revealed the plastic flow and stress distribution of rivets. The pull-off, shear performance, and fatigue characteristics of riveted parts were studied, and the specimens' connection strength, failure mechanism, and fatigue life were analyzed. The research shows that the new rivet structure reduces the maximum circumferential stress in the countersink hole area by 18% on average through stress regulation. The pull-off and shear strength are increased by more than 30%, and the pull-off failure mode is improved from the plastic shrinkage of the countersunk head to the necking fracture of the rivet bar. The fatigue life is exponentially higher than that of ordinary rivets, and the axial dispersion evolution occurs in the fatigue risk area.