X Li, X Yu, W Zhai*, Less is more: Hollow truss microlattice metamaterials with dual sound dissipation mechanisms and enhanced broadband sound absorption, Small. 2022 Sep 22:2204145, link In this work, we presented a class of hollow-truss metamaterial (HTM) that is capable of harnessing dual concurrent dissipation mechanisms from its complex truss interconnectivity and its hollow interior. Experimental sound absorption measurements reveal superior and/or customizable absorption properties in the HTMs as compared to their constitutive solid-trusses. An optimal HTM displays a high average broadband coefficient of 0.72 at a low thickness of 24 mm. Numerically derived, a dissipation theorem based on the superimposed acoustic impedance of the critically coupled resistance and reactance of the outer-solid and inner-hollow phases, across different frequency bands, is proposed in the HTM. Complementary mechanical property studies also reveal improved compressive toughness in the HTMs. |
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X Li, X Yu, J W Chua, and W Zhai*, Harnessing cavity dissipation for enhanced sound absorption in Helmholtz resonance metamaterials, Materials horizons, 2023, open access link Helmholtz resonance, based on resonance through a narrow pore and cavity, constitutes the underlying functioning principle of the majority of acoustic metamaterials. Current methods to improve the sound absorption performance of such metamaterials generally include the introduction |
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Z Li, X Li, Z Wang*, W Zhai*, Multifunctional sound-absorbing and mechanical metamaterials via a decoupled mechanism design approach, Materials Horizons, 2023, link In this work, we report a new paradigm in the design of acousto-mechanical metamaterials via decoupling the underlying mechanisms for each function. In particular, we leverage the absorption mechanism of the Helmholtz resonance, which enables independence in the design of structural elements from the sound-absorbing elements. For the sound absorption design, we adopt a coherent coupling design to achieve a favorable localized resonance, while for the mechanical response, we adopt customizable strut features. The metamaterials are 3D printed as a proof of concept. As experimentally demonstrated, the metamaterial is capable of excellent broadband low-frequency (o1.0 kHz) sound absorption, shows high deformation recoverability (up to 98%), and has a physically-tolerable strength for human use (o1 MPa), is pseudoreusable, and impact resistant. Both the absorption and mechanical responses are fully customizable depending on the requirements. |
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X Li, X Yu, M Zhao, Z Li, Z Wang, W Zhai*, Multi-level bioinspired microlattice with broadband sound-absorption capabilities and deformation tolerant compressive response, Advanced Functional Materials. 2023, link Herein, leveraging the inherent mechanical robustness of the biological cuttlebone, by introducing dissipative pores, a high-strength microlattice is presented which is also sound-absorbing. Its absorption bandwidth and deformation tolerance are further enhanced by introducing another level of bioinspiration, based on geometrical heterogeneities amongst the building cells. Across a broad range of frequencies from 1000 to 6300 Hz, at a low thickness of 21 mm, the optimized microlattice displays a high experimentally measured average absorption coefficient of 0.735 with 68% of the points higher than 0.7. The absorption mechanism attributes to the resonating air frictional loss whilst its broadband characteristics attribute to the multiple resonance modes working in tandem. The heterogeneous architecture also enables the microlattice to deform with a deformation-tolerant plateau behavior not observed in its uniform counterpart, which thereby leads to a 30% improvement in the specific energy absorption. |
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X Li, X Yu, W Zhai*, Additively manufactured deformation-recoverable and broadband sound-absorbing microlattice inspired by the concept of traditional perforated panels, Advanced Materials. 2021 Nov; 33(44):2104552, link Herein, we revisit the traditional concepts of perforated panels and incorporate it with additive manufacturing for the development of a novel microlattice-based sound absorber with additional impact resistance multifunctionality. The structurally optimized microlattice presents excellent broadband absorption with an averaged experimental absorption coefficient of 0.77 across a broad frequency range from 1000–6300 Hz. High deformation recovery up to 30% strain is also possible from the strut-based design and viscoelasticity of the base material. Overall, the excellent properties of the microlattice overcome tradeoffs commonly found in conventional absorbers. Additionally, this work aims to present a new paradigm: revisiting old concepts for the development of novel materials using contemporary methods. |
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X Li, X Yu, JW Chua, HP Lee, J Ding, W Zhai*, Microlattice metamaterials with simultaneous superior acoustic and mechanical energy absorption, Small. 2021 Jun; 17(24):2100336, link In this work, we present four types of FCC-based plate and truss microlattices as novel metamaterials with simultaneous excellent sound and mechanical energy absorption performance. High sound absorption coefficients nearing 1 and high specific energy absorption of 50.3 J g-1 have been measured. Sound absorption mechanisms of microlattices are proposed to be based on a “cascading resonant cells theory”, an extension of the Helmholtz resonance principle, which we have conceptualized herein. Characteristics of absorption coefficients are found to be essentially geometry limited by the pore and cavity morphologies. The excellent mechanical properties in turn derive from both the approximate membrane stress state of the plate architecture and the excellent ductility and strength of the base material. Overall, this work presents a new concept on the specific structural design and materials selection for architectured metamaterials with dual sound and mechanical energy absorption capabilities. |
