Characterizing the off-axis dependence of failure mechanism in notched fiber metal laminates

Fiber metal laminates (FMLs) are usually more complicated in the failure aspect as compared to their constituents, especially when complex load is applied. In this paper, notched FMLs and the constituents, i.e., the aluminum and glass fiber reinforced plastic (GFRP) were subjected to off-axis tensile loading to evaluate the failure mechanism. Initial attention was paid on the off-axis dependence of mechanical responses, especially on its relation to the notch size. As expected, off-axis dependence of notched strength and notch sensitivity were closely related to the notch size, but different for GFRP laminates and FMLs due to their different damage behavior. Finite element model was employed to predict accurately the mechanical responses of FMLs, particularly for elucidating the damage mechanism. Failure of notched FMLs under off-axis loading was a combined transverse fracture and shear-off, while it was shear-dominated in notched GFRP laminates. Transverse fracture in aluminum appeared first, followed by the fiber breakage, which was postponed by the extensive subcritical damage. Thereafter, shear-failure in fiber and aluminum layers were encountered instantaneously at the descending part. Thus, the critical failure of off-axis notched FMLs was still tension-dominated as that in the on-axis case, but aluminum played the critical role.