Customized quasi-zero-stiffness metamaterials for ultra-low frequency broadband vibration isolation

Quasi-zero-stiffness (QZS) metamaterials play an important role in ultra-low frequency vibration mitigation. In this study, a customized QZS metamaterial is proposed to isolate ultra-low frequency broadband vibration and its isolation performance is verified. A representative unit cell (RUC) that satisfies both optimal QZS performance and minimum size is designed for the metamaterial and optimized by matching the parameters of positive stiffness heart-shaped beam with the properties of negative stiffness cosine beam. Then, a new composite structure with multiple RUCs is designed by matching the optimal mass block for each RUC to meet the vibration isolation requirements of ultra-low frequency and broadband. The transmissibility test is performed, and the isolator made of the metamaterial is then integrated into an underwater glider to test the vibration isolation performance. The results show that the proposed QZS metamaterial can isolate broadband vibrations of 3.2 to 60 Hz and the isolator can attenuate the vibration signals of gliders to the background noise in air and water. Therefore, the customized metamaterial can be used in the engineering case of ultra-low frequency broadband vibration isolation and the design method of the metamaterial can be used for reference by other equipment.