Prediction Of Effective Properties And Design Of Microstructures Of Composite Materials For Vibration And Noise Reduction

Control of vibration and noise of structures plays an important role in both defense industry and people's lives.Therefore,the use of viscoelastic damping materials of structures and the use of elastic wave bandgap materials are two effective methods for vibration and noise reduction.In order to improve the performance of both viscoelastic damping materials and elastic wave bandgap materials,it is necessary to design the microstructures of the materials to increase the damping and adjust the frequency band of bandgap to realize the effective partitioning of the vibration.The establishment of the relationship between the macroscopic properties and the microstructures is the basis of designing the microstructures of the material.Therefore,it is necessary to construct a method for rapid prediction of the equivalent performance of materials with periodic microstructures.It is found that some materials with a negative Poisson's ratio(NPR)(such as chiral and concave hexagonal truss materials,etc.)have good bandgap characteristics,thus we can design the materials with bandgap properties by designing the microstructures of materials with NPR.This paper studies the design of microstructure and the equivalent performance prediction method for vibration and noise reduction of composites.The homogenization method of the equivalent performance prediction of viscoelastic composites is studied.Then the method is applied realize the fast relationship between the damping performance and the microstructure of the material.The design of microstructures of the NPR material is studied and its negative Poisson's ratio and bandgap performance.The main contents are as follows:(1)A novel implementation of AH method for predicting effective complex modulus of viscoelastic materials.This paper presents a novel implementation of AH method to predict effective complex modulus of periodic viscoelastic materials(NIAH-VE).The effective complex modulus of particle reinforced composites and fiber reinforced composites are predicted by using NIAH-VE.The damping ratio of the viscoelastic composites can be calculated by the loss and storage modulus.It is proved that the new implementation method is effective for prediction of effective properties of 2D and 3D viscoelastic composites by comparison with cases in literature.Besides,it is assumed that the fiber reinforced composite satisfies the standard solid model,and the effective complex modulus in frequency domain is fitted by the least square method to obtain the relaxation modulus in time domain.(2)Analysis of viscoelastic properties and geometric parameters of particle reinforced composites.Composites consisted of various kinds of singe materials often have better mechanical properties than a single one.Based on the combination of elastic materials and viscoelastic materials,the embedding and outsourcing particle reinforced composites under steady-state excitation are studied by using NIAH in frequency domain.The influence of geometrical parameters(volume fraction,shape and arrangement form)of particle phase on the stiffness and viscoelastic properties are studied.It is found that the volume fraction of the particle has the greatest influence on damping ratio,followed by the shape and arrangement form.Besides,the effective complex modulus and the damping ratio of the composite material is not linear with the volume fraction of the particle phase.Furthermore,we study the relationship between the damping ratios of the particle reinforced composites and the base materials.We find that if the damping ratios of the two base materials are the same at some frequency,the composites consisted of the base ones have the same damping ratios with the base materials,which is nothing to do with their topology.(3)A novel implementation of AH method for predicting effective complex modulus of periodic viscoelastic plate structures.Viscoelastic plate structures often have better control of vibration and noise.The rapid prediction of the damping performance helps compare different plates and select the optimal one.In this paper,a NIAH for predicting effective complex modulus of periodic viscoelastic plate structures is proposed(NIAH-VEP).The effective viscoelastic properties of homogeneous isotropic plates and truss sandwich panels are calculated by NIAH.For a plate structure with complicated microstructures,many element types can be used simultaneously,such as beam,plate,solid elements and so on.(4)Design of microstructures of a novel material with negative Poisson's ratio(NPR)and analysis of bandgap property.Chiral and concave hexagonal materials are found to have good bandgap characteristics.In this paper,we present a novel type of planar auxetic material with low porosity.The effective Poisson's ratios of three typical low porosity materials are calculated by using NIAH for predicting elastic properties,which are compared with results of finite element analysis of low porosity structures with finite size.We find the NPR property of the novel type of auxetic materials is tunable.Besides,the auxetic performance of the auxetic structures are observed by experiments.The bandgap property of the novel NPR material is analyzed.It is found that when the Poisson's ratio is negative and the absolute value is larger,the bandgap width will be larger and the center frequency of the bandgap will be lower.Thus,the novel NPR material has a tunable bandgap property.