单向纤维复合材料声学超表面

An acoustic metasurface composed by unidirectional fiber composite materials

声学超表面是一种能够调节声波反射、透射和吸收特性的超薄人工结构,对于空间受限的应用领域具有重要价值,目前声学超表面主要借助超构材料来实现。提出一种非超构材料的新型声学超表面,采用单向纤维周期复合材料对声波进行调制,实现了声波的定向反射调控。借助复合材料细观力学方法,采用均匀化理论和优化方法设计周期复合材料单胞的组分,使单胞具有特定的等效力学性能与声学性能,并满足特性阻抗匹配,从而形成超表面所需的声速梯度分布。通过能带分析获得了单胞纵波波速与频率的关系,显示出复合材料超表面的宽频特性。定向反射仿真展示了复合材料超表面操控声波的有效性,并验证了对于垂直入射声波纵波是影响波控性能的主要因素。研究工作为声学超表面及其他声学波控装置的设计提供了一种新途径。

Acoustic metasurfaces are artificial materials of subwavelength thickness capable of manipulating reflection, transmission and absorption of acoustic waves. Acoustic metasurfaces have important values for space limited application fields. At present, the strategy for the design of acoustic metasurfaces depends on the metamaterials. Therefore, we proposed a scheme by designing a kind of non-metamaterials acoustic metasurface to manipulate the wavefont in fluids. Based on this idea, a new type of reflection acoustic metasurface composed by the unidirectional fiber composites with periodicity was studied. Through homogenization theory and optimization method of micromechanics the fractions of composites unit cells were designed in order to obtain the effective mechanical and acoustics prosperities of unit cells to satisfy the densities and longitudinal velocities of discrete metasurfaces needed, as well as the impedance matching condition. Finally, the gradient longitudinal velocity of the acoustic metasurfaces needed was achieved. Using Bloch-Floquet analysis, the relationship between longitudinal velocity and frequency was studied. The band diagrams exhibit the broadband characteristics of the designed metasurfaces. Simulations of reflection control were studied for the designed metasurfaces with normally incident plan wave. Excellent wavefont manipulation effects were observed in broadband frequencies. Accordingly, it is verified that longitudinal modes are the most important factors for wave manipulation under normally incident waves. The research work provides a novel idea and potential method for the design and physical implementation of the acoustic metasurfaces as well as the other acoustic wave manipulation devices.