Isotactic inertial amplification metamaterials with superior low-frequency bandgap

The integration of inertial amplification with metamaterials has facilitated the manipulation of low-frequency elastic waves in lightweight structures. However, conventional symmetric linkage inertial amplification structures are constrained by the connecting rod angle, limiting the amplification factor to <10 times and often encountering the dead point at small angles. To overcome these limitations, this study introduces isotactic linkage inertial amplification metamaterials by breaking symmetry, which achieve an ultra-high amplification factor exceeding 20 times, thereby enabling a lower frequency bandgap without increasing the additional mass. A generalized theoretical framework for asymmetric configurations is developed by extending the traditional inertial amplification formula, and the superiority of isotactic metamaterials in low-frequency bandgap attenuation has been rigorously analyzed by the complex band. Experimental results demonstrate that the start frequency of bandgap in the continuous assembly isotactic configuration can be reduced to 37.53 Hz, representing a 42.8 % decrease compared to the traditional symmetric configuration. Moreover, a spaced assembly structure, utilizing only half the additional mass of the continuous assembly structure mentioned above, achieves comparable low-frequency performance, offering significant advantages for lightweight design. Additionally, the dead-point problem in link mechanisms is effectively resolved through the isotactic configuration. Isotactic inertial amplification metamaterials exhibit potential for applications in vibration isolation, elastic wave manipulation and energy harvesting, particularly in low-frequency scenarios.