Investigation on bandgap modulation of locally resonant metamaterials with shape memory alloy resonators under temperature and multi-mode pre-deformation

Elastic and acoustic metamaterials with locally resonant (LR) arrays can generate bandgaps that attenuate or block elastic waves. Although extensive research has explored thermally induced tuning or single-mode mechanical pre-deformation, systematic comparative analyses of different pre-deformation strategies remain insufficient. To address this research gap, this study incorporates shape memory alloys (SMAs) into metamaterial architectures to realize tunable bandgaps via pre-tension, pre-bending, pre-twisting, and composite pre-deformations strategies, while also exploring the feasibility of achieving lower-frequency bandgaps. Experiments demonstrate that distinct pre-deformation modes induce differentiated shifts in the bandgap, and systematic trends throughout heating are presented. As temperature increases, these shifting effects progressively diminish due to the shape memory effect of the SMA, thereby establishing a temperature-dependent tuning range. To further elucidate the underlying tuning mechanism, numerical simulations investigate symmetric pre-bending and pre-twisting at various angles, revealing the quantitative relationship between pre-deformation magnitude, temperature, and bandgap tunability. The contributions of bending and twisting in hybrid configurations are also examined, providing insights into the optimal structural design of such systems. Finally, the study extends to two-dimensional metamaterial plate structures incorporating SMA resonators. Simulation show broader and more flexible bandgap tunability under thermal actuation, underscoring their potential for adaptive low-frequency vibration isolation and control.