Characterizing and predicting the tensile mechanical behavior and failure mechanisms of notched FMLs—Combined with DIC and numerical techniques

Abstract This paper mainly extensively investigates the effects of layer direction, notch shape and notch size on the tensile mechanical behavior and failure mechanisms of notched fiber metal laminates (FMLs) by numerical and experimental methods. In virtue of Digital image correlation (DIC) technique, tensile tests are implemented to measure tensile stress-strain responses, displacement distributions and localized strain fields of different notched FMLs. Subsequently, the progressive damage analysis considering thermal residual stress is conducted to characterize failure modes and progressive damage evolution of notched FMLs, which contains the intra-laminar damage in composite laminates and the interfacial delamination between aluminum sheets/composite laminates simultaneously. Results demonstrate that the ultimate notch strength is more sensitive to layer direction and notch size in comparison with notch shape. FMLs with smaller notches exhibit more prominent directional dependence than those with larger notches. Additionally, regarding to fracture morphologies, notched FMLs present typical brittle fracture for on-axis case, while they manifest as initial transverse fracture following tilted cracking along fiber directions for off-axis case. Consequently, with the increase of layer direction, the final failure mode of notched FMLs results from fiber-driven to aluminum-driven, and the critical damage mechanism gradually transfers from tension dominated to tension-shear dominated.