Modelling of fiber metal laminates thermoforming using superimposed membrane-shell elements

This study presents an advanced numerical modelling framework for simulating the thermoforming of fiber metal laminates (FMLs) composed of AZ31B magnesium alloy sheets and thermoplastic polymer-based prepregs. The core innovation lies in the implementation of superimposed membrane-shell elements that simultaneously account for the out-of-plane compressive and in-plane tensile behaviors of the prepreg, as well as the inter-ply friction between the metallic and composite layers. This integrated model enables a more accurate prediction of forming loads and thickness evolution across a range of process parameters. To calibrate the model, uniaxial tensile and through-thickness compaction tests were performed on the prepreg to characterize its mechanical response at forming temperatures. Additional tensile tests were conducted on AZ31B sheets to capture their temperature-dependent thermomechanical behavior. The model was validated through thermoforming experiments on hat-shaped FML parts manufactured under varying blank-holder forces. The numerical predictions showed strong agreement with experimental data, with a maximum deviation of 8.9 % in forming force and 4.0 % in thickness distribution. These results confirm the robustness and predictive accuracy of the proposed modelling approach, offering a reliable tool for the virtual design and optimization of thermoformed hybrid laminates.