微穿孔蜂窝-波纹复合声学超材料吸声行为

民用及国防工业领域对工程材料结构提出了更高的应用需求.单一材料结构越来越难以满足实际应用需求，通过人工复合结构实现超常单一及多物理性能的超材料设计已经成为材料结构应用的重要发展方向.本文基于传统的蜂窝夹层结构，在其内部引入波纹结构，并在面板和波纹上分别进行微穿孔形成微穿孔蜂窝-波纹复合声学超材料，在其优异力学承载基础上，实现了低频段的宽频有效吸声降噪.应用微穿孔板吸声理论和声阻抗串并联理论，建立了微穿孔蜂窝-波纹复合声学超材料的吸声理论模型；发展了考虑黏热效应的声传播有限元模型，通过数值模拟验证了理论模型的准确性，并数值计算了声波在超材料微结构内的黏热能量耗散分布，发现超材料能量耗散主要集中于微穿孔处的黏性边界层；进一步开展了超材料吸声参数和尺度设计参数的分析讨论，阐明了不同尺度设计参数对超材料吸声性能的影响规律.本文工作对兼具力学承载与吸声降噪的新型材料结构设计有重要的理论指导价值.

Micro-perforated acoustic metamaterial with honeycomb-corrugation hybrid core for broadband low frequency sound absorption

A novel acoustic metamaterial is proposed by making micro-perforations on both the top facesheet and the corrugate plates of sandwich plate with honeycomb-corrugation hybrid core. The hybrid-cored metamaterial is ultra-lightweight, occupies a small volume, and exhibits excellent mechanical properties and good low-frequency sound absorption property. Based on the classical Maa theory of thin plates with micro-perforations, a theoretical model of sound absorption is established for the proposed metamaterial. The method of finite elements is subsequently used to validate the model, showing that their good agreement is achieved. Physical mechanism behind the energy dissipation in each sub-structure of the metamaterial is explored. It is found that the main route of energy dissipation is via viscous effect at the micro-perforation, and thermal dissipation is negligible. The influence of key geometrical parameters, such as upper facesheet thickness, perforation diameter and corrugated plate thickness, on sound absorption is systematically investigated. The present results are helpful for designing multifunctional lightweight materials/structures for simultaneous load-bearing, energy absorption and noise control.