Tunable flexural properties of sandwich structures with Miura and creaseless herringbone buckling pattern cores via geometrical modifications

This study investigates the design tunability of sandwich structures incorporating a creaseless herringbone buckling pattern-inspired core and the Miura core. Three design strategies, namely gradation, hybridisation, and thickness optimisation, were applied to tune the mechanical properties of the sandwich structures. Core gradation adjusts cell widths within sandwich cores, where different widths yield varying bending performances. By incorporating cells with gradually increasing or decreasing widths, sandwich cores with tunable bending characteristics were produced. A hybrid core design, replacing mid-span cells with corrugation-like defects, alters bending stiffness—improving Miura core stiffness but reducing herringbone stiffness, with the Miura core failing by buckling and the herringbone by plastic hinge formation. Lastly, thickness optimisation improved both performance and structural efficiency compared to cores with uniform thickness. By adopting these geometrical modifications, bending stiffness was adjusted by up to 14%, and specific energy absorption was improved by up to 16% as compared to sandwich structures with uniform core. Experimental tests and numerical simulations provided key insights into the deformation mechanisms of each design. The sandwich structures demonstrate potential applications in industries requiring lightweight solutions, such as aerospace and automotive sectors.