Fatigue Failure Mechanism of Low‐Frequency Vibration‐Assisted Self‐Piercing Riveted CFRP/Aluminum Structures

ABSTRACT Traditional self‐piercing riveting (T‐SPR) of CFRP/aluminum assemblies often produces insufficient rivet and sheet deformation, resulting in a limited mechanical interlock and reduced fatigue performance. Leveraging the vibration‐induced softening effect, this study developed low‐frequency vibration‐assisted self‐piercing riveting (LV‐SPR) to enhance plastic deformation and joint durability. Under a maximum cyclic load of 65% F m , LV‐SPR joints exhibited a 177.8% longer fatigue life than T‐SPR joints. Fatigue cracks initiated in the aluminum sheet near the interlock and propagated across its width until fracture. The promotion of joint longevity stems from the fact that the vibration energy input refines the grains in the aluminum plate by 9.7% while elevating dislocation density by 14.9%, raising resistance to microcrack initiation. During cyclic loading, fine equiaxed recrystallized grains formed along crack‐propagation path and impeded crack growth. These results demonstrate that LV‐SPR improves the fatigue performance of CFRP/aluminum joints through enhanced plastic deformation and favorable microstructural evolution.