Mechanical performance assessment of rubber-interlayered aluminum/Polyurethane sandwich composites under quasi-static and dynamic loading

Rubber-interlayered sandwich composites offer a structural approach for tailoring stiffness, deformation tolerance, and energy dissipation in transportation-oriented panel systems. This study investigated the mechanical behavior of multilayer aluminum/polyurethane/rubber (Al/PU/R) sandwich composites experimentally and numerically under multiple loading conditions. The panels consisted of two aluminum face sheets, two polyurethane foam layers, four rubber layers, and Sikaflex-268 bonded interfaces. Six configurations (A1–A3 and B1–B3), combining two polyurethane foams with three rubber interlayers, were evaluated under compression, three-point bending, displacement-controlled cyclic bending, and low-velocity impact. A finite element model was also developed to support the bending analysis and examine stress localization. The results showed that mechanical performance depended strongly on loading mode and material combination. Under compression, B3 exhibited the most favorable response. In three-point bending, A3 showed the highest apparent flexural stiffness, reaching approximately 1.47 × 10 6 N·mm 2 . Under cyclic bending, peak reaction-force retention varied with frequency and configuration, with B3 showing the highest long-cycle retention at 1 Hz. Under low-velocity impact, A1 exhibited greater deformation tolerance, reaching nearly 19 mm displacement at 100 J while distributing the impact energy over a longer contact duration. The numerical model reproduced the general experimental apparent-flexural-stiffness trend with an average difference of 8.36%, although its results were interpreted as supportive rather than fully calibrated constituent-level predictions. Overall, the configurations exhibited distinct balances of stiffness, crushing resistance, cyclic load retention, and impact response, demonstrating the tailoring potential of PU/rubber combinations. However, mass-specific efficiency was not assessed because specimen mass and areal density were not measured. Moreover, without a rubber-free Al/PU/Al reference, the findings demonstrate comparative differences among the tested configurations rather than an inherent benefit of rubber incorporation.