The Study Of Laminate Acoustic Metamaterials Based On CFRP For Vibration Reduction

Acoustic metamaterials are engineered materials that were extensively investigated over the last few years.This new type of periodic structure exhibit unusual properties that do not exist in nature under certain conditions-negative equivalent mass density and negative equivalent bulk modulus.Consequently,they open the door for improved or completely new applications,such as acoustic super-lens,acoustic cloak,artificial acoustics black hole,acoustic negative refraction,subwavelength imaging,etc.On the basis of this,scientists have introduced the study of band structure,and the concept of local resonant bandgap was proposed,which can successfully suppress the propagation of large wavelength(low frequency)acoustic waves by small size structure.In this paper,the technical problems of lightweight and wide low-frequency stopband faced with local resonant acoustic metamaterials are studied,the laminate acoustic metamaterials are proposed,which consists of two parallel orthotropic laminates and a periodic array of mass-spring-damper subsystems integrated between the two laminates.The simulation has verified that the laminate acoustic metamaterials with the superior strength to weight ratio of CFRP are very effective to suppress the low-frequency vibration,the main research work is given as follows:(1)For the first time,a new laminate acoustic metamaterials based on CFRP is proposed.It is designed by integrating two parallel orthotropic laminates,which is composed of carbon-fiber-reinforced polymer(CFRP),with a periodic array of mass-spring-damper subsystems.And the bandgap characteristics of the structure are studied.(2)The calculation methods of band gap of anisotropic local resonant metamaterials are improved.The band gap of laminate acoustic metamaterials has been derived by dispersion analysis in this work,then a wide stopband is observed.(3)The finite modeling and frequency response analysis are performed to confirm its stopband behavior for a finite laminate acoustic metamaterial,which validate the theoretical analysis.In addition,the effects of the relevant parameters on the stopband of laminate acoustic metamaterial are discussed in this work,and the stopband's width is determined by vibration-absorber-mass/unit-laminate-mass ratio.Damping in vibration absorbers can efficiently lower the response in low-frequency areas and broaden the stop band at the same time.(4)The excellent performance of laminate acoustic metamaterials has been applied to design the vehicle door,and the vibration of the vehicle door is suppressed significantly,Finally,the guidelines for designing a vehicle door composed of low-frequency acoustic metamaterial laminate are proposed.