Study on the ultra-wide band gap characteristics of novel star-shaped chiral metamaterials

The suppression of vibration and noise has always been an important issue in engineering，and metamaterials have shown significant application value in vibration and noise reduction. In this paper，a novel hollow starshaped chiral metamaterial is designed by incorporating chiral structural characteristics into traditional hollow starshaped metamaterials and further evolves it into a solid star-shaped chiral metamaterial. The bandgap formation mechanism is analyzed through vibration mode analysis，and the effects of different structural parameters on the bandgap are studied. The propagation characteristics of elastic waves in the structure are investigated through dispersion surfaces，wave propagation direction，group velocity，and phase velocity. Finally，the transmission characteristics of finite periodic structures are studied. The results show that the solid star-shaped chiral metamaterial can generate an ultra-wide bandgap with a width of 5 116 Hz. The bandgap formation is mainly due to the rotational vibrations of the concave stars and ligaments dissipating the energy of elastic waves. Additionally，a decrease in the inner concave angle <i>α</i> and an increase in the angle <i>θ</i> between the ligaments and the horizontal direction result in a wider largest bandgap. The finite periodic structure can generate significant displacement amplitude attenuation within the bandgap range. This novel metamaterial has excellent vibration isolation performance.