Low-Frequency Broadband Absorption in a Hexagonal Coral-Inspired Metamaterial Panel

To address the limitations of conventional sound-absorbing materials—namely poor low-frequency performance, heavy weight, and single functionality—this study proposes a hexagonal coral-inspired panel structure. Drawing inspiration from coral morphology, a periodic sound-absorbing unit with a hexagonal configuration is designed, incorporating a synergistic mechanism of cavity resonance and viscous dissipation to achieve low-frequency broadband absorption. A thermo-viscous acoustic finite element analysis is conducted to investigate the effects of structural parameters such as aperture size and porosity on acoustic performance, thereby elucidating the boundary-layer dissipation mechanism. Based on these findings, physical prototypes are fabricated via 3D printing, and the sound absorption characteristics are tested using an impedance tube. Experimental results demonstrate that the hexagonal coral-inspired panel exhibits excellent absorption performance in the 280–620 Hz range, with an average absorption coefficient of 0.8. Furthermore, the energy dissipation characteristics under quasi-static uniaxial compression are examined, revealing outstanding mechanical multifunctionality.