Multi-Level Bioinspired Microlattice with Broadband Sound-Absorption Capabilities and Deformation-Tolerant Compressive Response

Owing to the omnipresent noise and crash hazards, multifunctional sound-absorbing, and deformation-tolerant materials are highly sought-after for practical engineering design. However, challenges lie with designing such a material. 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. A high-fidelity microstructure-based model is developed to predict and optimize properties. 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. Overall, this work presents an effective approach to the design of sound and energy-absorbing materials by modifying state-of-the-art bioinspired structures.