The residual stress characteristics and mechanical behavior of shot peened fiber metal laminates based on the aluminium-lithium alloy

The effect of shot peen forming on the mechanical behavior of fiber metal laminates (FMLs) based on aluminium-lithium alloy was investigated to reveal the strengthening mechanism and to dispel the suspicion that shot peen forming may result in the performance deterioration of FMLs. The interlaminar, static strength and fatigue properties of shot peened FMLs were investigated. The residual stress characteristics of the shot peened FMLs was also involved with finite element analysis to help understanding the unique mechanical behavior. The results indicated that shot peening caused non-negligible work hardening in external metal layers, which increased the tensile strength of the laminates. But the work hardening did not deteriorate the elongations of FMLs since the failure still dominated by the limitation of fiber failure strain. Moreover, two yield stages were observed in the tensile tests of shot peened FMLs owing to the great difference in stress states between external and internal metal layers. The compressive stress introduced by shot peening effectively improved the FCG properties of FMLs. All metal layers possessed similar crack propagation rates despite that the stress difference was up to 300 MPa, which indicated that the fiber bridging effect still dominated the FCG of FMLs.