Laminates Vibration Andacoustics Characteristicsanalysis And PVDF Modal Sensor Design

Composite laminated plate structures with high strength, high modulus, goodfatigue resistance performance, strong design and low noise characteristics, are widelyused in aerospace engineering. Aerospace laminates often vibrate at low frequencies,therefore, the study of vibration and acoustic characteristics of composite laminatedplate structures at low frequency is of great significance and practical value.Free vibration of laminated composite plates is studied. For composite laminatedplate structure vibration problems, this article proposes a numerical analysis formlayer-wise theory expressed by a Navier double trigonometric functions, calculating thenatural frequencies of non-damped laminates and natural frequencies and loss factors ofvisco-elastic damping laminates. In the numerical analysis section, influencing factors,such as laying angle, thickness ratio, and the elastic modulus, on natural frequencies andloss factors are analyzed and discussed. Results show that the layer-wise theorycalculation method can accurately calculate the natural frequencies of compositelaminated plates and the loss factors of visco-elastic damping laminates. Meanwhile,different material parameters have certain effects on calculation results.FEM software ABAQUS is used to model the laminates, analyzing their vibrationcharacteristics and obtaining natural frequencies and modal shapes, while laminatesvibration modal experiment study was conducted, and compared with ABAQUSanalysis results. Results indicates that, the laminated plate model established by FEMsoftware ABAQUS is reliable; in engineering early, ABAQUS can precisely forecastnatural frequencies and modal shapes of laminated plates; due to the laminated plates’complexity, such as damping mechanism complexity, boundary conditions objectivefactors and other reasons, modal experiment can more objectively react vibrationcharacteristics of laminates.Acoustic radiation modal amplitudes of laminated plates under forced vibration arestudied. First-order shear deformation theory combined with the finite element method,gets strain energy and kinetic energy expression. Through the principle of virtualdisplacements, a laminated plate vibration equation is established. For solving dynamicresponse of laminated plate under external excitation, modal superposition method isused to acquire dynamic response, that is, normal velocity. Through combining normal velocity and acoustic radiation modal theory, acoustic radiation modal amplitudes aregained. In the numerical analysis section, acoustic radiation modal amplitudes andsound power are calculated. Through numerical analysis, results show that the algorithmcan efficiently calculate the vibration and acoustic characteristics, such as naturalfrequencies, dynamic response, and acoustic radiation modal amplitudes of laminatedplates with different material parameters.A set of PVDF array modal sensor is designed to measure acoustic radiation modalamplitudes of laminates. At low frequencies, controlling acoustic radiation modalamplitudes can be effective control total acoustic power, so acquiring acoustic radiationmodal amplitudes is the key link of reducing structural noise. In this paper, a set of samerectangle shape PVDF films is pasted onto the plate surface to form array modal sensor.The appropriate weighting factors are designed for each PVDF block, to enable theweighted fitting output charge signals be the corresponding acoustic radiation modalamplitudes. Results show that the design method can obtain acoustic radiation modalamplitudes of composite laminated plates.