Decoupled multifunctional metamaterials for ultra-broadband sound absorption in a two-port system and efficient mechanical properties

Abstract

Acoustic-mechanical multifunctional metamaterials extend beyond the conventional application scope of single-domain acoustic or mechanical metamaterials. Its significant potential in fields such as aerospace, marine engineering, and mechanical manufacturing underscores broad prospects for future development. A central challenge in such multifunctional design, particularly in two-port systems, lies in enhancing additional functionalities without compromising the original acoustic performance. In this paper, a novel multifunctional metamaterial that achieves high performance in both acoustic and mechanical domains was developed. Acoustic functionality was realized by exploiting the impedance manipulation characteristics of double resonant cavities in a two-port system. Connecting multiple such cavities with staggered resonant frequencies enabled ultra-broadband absorption, yielding an average absorption coefficient of 0.73 within 120–3350 Hz using an ultra-thin structure of only 46 mm. For mechanical performance, the integration of lattice and chiral structures yielded remarkable improvements. The lattice-based metamaterial exhibited an 80.4% increase in specific plateau stress, indicating superior load-bearing stability. The chiral-based metamaterial achieved a specific compressive strength of 8.87 ± 0.41 MPa·cm³/g and a specific energy absorption of 3.41 ± 0.27 kJ/kg at a low density of 0.34 g/cm³, demonstrating exceptional efficiency. Crucially, the acoustic and mechanical components are decoupled in design, allowing the mechanical core to be replaced to meet different application demands without affecting the acoustic performance in the two-port system. This decoupling metamaterial offers a new paradigm for designing versatile multifunctional metamaterials.