Active tuning of vibration and noise by the optimal design of acoustic metamaterial structures

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Smart or intelligent materials are widely used in the structural active vibration control because they have the sensitivity to external mechanical environment changes and the ability to actively respond. Therefore, these kinds of intelligent materials have a great potential to actively tune the band-gap properties of the acoustic metamaterials. Based on this fact, if the intelligent materials can be embedded into the acoustic metamaterial structures by using the active structural optimization design, the passive acoustic insulation ability of the acoustic metamaterials can be effectively combined with the active control performance of the intelligent materials. The proposed novel active metamaterial structures will possess the following two functions: (i) the stiffness and the mass of the unit-cell of the metamaterial structures can be actively tuned by the design of the control algorithm to actively control the widths and locations of the frequency band-gaps, and (ii) the vibration and noise in the frequency band-gaps can be suppressed by using the band-gap property of the acoustic metamaterials, while for the vibration and noise in the frequency pass-bands, they can be suppressed by the active control ability of the intelligent materials. Thus, the vibration and the noise can be reduced in the full frequency range via this proposed novel strategy. In this project, novel acoustic metamaterial structures with active control functions will be proposed and designed. In the novel systems, the piezoelectric macro-fiber composites (MFC) will be adopted as an active controller. Taking into account the effects of the material anisotropy and the electromechanical coupling properties of the MFC, theoretical, numerical and experimental investigations on the vibration band-gap property, the noise isolation ability and the active control optimization design will be systematically conducted. In the investigations, the passive control performance of the acoustic metamaterials and the active control ability of the piezoelectric materials will be effectively combined to suppress the vibration and the noise levels in the desired frequency range, which will provide a novel idea and a new approach for the structural vibration control, the elastic wave tuning and the development of novel noise reduction materials and structures. Thus, the project has a great importance and significance in innovative engineering applications of the acoustic metamaterials and structures for the vibration and noise reduction. This proposed project is a cooperation project by the German and the Chinese applicants. Both teams have a close cooperation since several years. Through this joint project, their previous cooperation should be pursued and strengthened. Both teams will work together on the proposed project, combine their individual research strengths and promote participating young German and Chinese scientists.