Research On The Vibro-acoustic Modeling Theory And Characteristics Of Functionally Graded Nano-reinforced Plate Structure

Functionally graded nano-reinforced composite material is a kind of potential lightweight and high-strength materials,which has strong design ability and good environmental adaptability.It has broad application prospects in aerospace,high-speed train,automobile and other fields.With the development of engineering materials/structures in the direction of ultra-lightweight,functional specialization and performance integration,the demand for comprehensive performance such as vibration and sound characteristics is gradually increasing for new materials.It is very important to study the vibro-acoustic characteristics of functionally graded nano-reinforced materials/structures for their vibroacoustic theory development and engineering application.However,there are few reports on the vibro-acoustic characteristics of the materials/structures,especially under complex loads such as force,heat and sound.Therefore,based on theoretical analysis,numerical simulation and vibro-acoustic experiments,the present work researches the theoretical modeling,vibro-acoustic mechanism and parameter analysis of the functionally graded nano-reinforced plate.The main research contents are as follows:The multi-scale parameter equivalent modelling theory of nano-reinforced composites are studied.The Halpin Tsai generalized modified micromechanical model suitable for arbitrary shape,size and orientation of reinforcement is proposed.The layered gradient and continuous gradient models are established for different gradient distribution forms of nanoreinforcement.The mixed solution method is used to make samples of nano-reinforced composites and their mechanical properties are tested,and the microstructures are observed.The sound radiation modeling theory and method for functionally graded nanoreinforced thin plates under thermal-mechanical loads are studied.Based on the Halpin-Tsai modified model considering temperature,the high-order shear deformation plate theory and Hamilton principle,the plate vibration control equation under thermal environment is derived.The theoretical model of sound radiation for the plates are established by Rayleigh integral and element radiation method.The modeling theory and calculation method in this thesis are verified by comparing with the open literature.Moreover,the effects of nanoreinforcement weight fraction,distribution,temperature and other parameters on the vibration and acoustic radiation characteristics of functionally graded nano-reinforced plates are analyzed.A simple quasi-3D plate theory is proposed for the vibro-acoustic modeling theory of functionally graded nano-reinforced porous thick plates.The simple quasi-3D high-order shear plate theory considers the effects of transverse bending,transverse shear and thickness extension,then combining with the Halpin-Tsai modified model and Hamilton principle,the vibration control equation of the functionally graded nano-reinforced porous plate is established.The vibration and sound radiation characteristics of functionally gradient nanoreinforced porous plates are analyzed using Navier and Rayleigh methods.Finally,the effects of nano-reinforcement and pore distribution,porosity,weight fraction of nanoreinforcement,damping and other parameters on the vibro-acoustic characteristics of the functionally graded nano-reinforced porous plate are discussed.Based on the state space method and three-dimensional elastic wave theory,the sound insulation modeling theory of the finite functionally gradient nano-reinforced porous plate under oblique wave incidence is established,and the concept of stiffness sound insulation is proposed.Based on modal analysis method,the sound insulation theoretical model of the functionally graded nano-reinforced porous plate is constructed.The acoustic load is converted into the equivalent force load.The element radiation method is used to calculate the radiated sound power.Combining the incident sound power,the sound transmission loss of the functionally graded nano-reinforced porous plate is calculated and the effects of the nano-reinforcement and pore parameters,damping and sound wave incidence angle on sound insulation characteristics of the plate are analyzed.The vibration and acoustic characteristics experiment of a graded metal laminated plate and graded porous laminated plate are carried out.The natural vibration test,sound radiation test under force load,and sound insulation test under sound load for the above plates are carried out.Compared the experimental results with theoretical prediction results of this thesis,it shows that the experimental results are in good agreement with the theoretical prediction,which verified the theoretical modeling and calculation method in this thesis.