Failure modes of Al-Li alloy friction stir welded stiffened panels subjected to shear load

•The static and fatigue failure modes of 1.2 mm and 1.5 mm Al-Li alloy FSW stiffened panels subjected to shear load were investigated.•The static failure modes of panels are weld cracking and skin cracking. The fatigue failure mode of panels is skin cracking.•The residual stress profiles of 1.2 mm panel were measured by X-ray method and calculated by thermo-mechanical coupling method.•The fatigue damage evolution model was built to calculate the fatigue life and the crack initiation position of the panels.•Residual stress has great influence on fatigue life, while it has less effect on buckling/post-buckling mode of stiffened panel under shear loading.