A graded quasi-zero-stiffness metastructure featuring tunable high-static-low-dynamic stiffness resonators for low-frequency broadband vibration suppression

Metastructures with high-static-low-dynamic stiffness (HSLDS) resonators are effective in generating low-frequency bandgaps but face limitations due to narrowing in widths of low-frequency bandgaps at lower frequencies. In this research, a one-dimensional graded quasi-zero-stiffness (QZS) metastructure with tunable HSLDS resonators is proposed to broaden the low-frequency bandgap. The tunable HSLDS resonator integrates a tunable negative stiffness element with a positive stiffness element in parallel, allowing for stiffness contraction and adjustments. A mathematical model is developed to predict the bandgap followed by a parametric study for optimization. Results show that the proposed graded QZS metastructure achieves a 81.4% increase in low-frequency bandgap width compared its uniform counterpart, highlighting its superior performance for low-frequency broadband vibration suppression.