Study On The Vibration Characteristic Of Fiber Reinforced Composite Plate

The fiber-reinforced composite has excellent mechanical properties,the good thermal stability and capability on weight reduction,which is widely used in the aeronautics,astronautics,automotive,naval vessel and weapon industry.Currently,there are a large number of such composite thin plate structures,such as solar panels,aircraft engine fan blades,large wind turbine blades and etc.As often working on the harsh environments,the vibration problems of such composite blades and plates have become increasingly acute,such as an excessive vibration,wear and tear and fatigue failure.Besides,the fiber-reinforced composite material is obviously different from traditional isotropic material,whose macro plate structure will show nonlinear stiffness and damping properties.These nonlinear characteristics have brought a great deal of difficulties and challenges to the traditional analysis methods,which are mainly on the basic of linear equivalence principle.Therefore,it is of great scientific significance to study its vibration characteristic and the corresponding theoretical analysis methods.To solve the above problems,the carbon/epoxy composite thin plate is taken as research object,and its vibration characteristic is studied.The details are as follows:(1)The fiber reinforced composite thin plate under cantilever boundary condition is taken as research object,and based on the classical lamination theory,the natural characteristic is obtained by orthogonal polynomial method and beam function method.In addition,the natural characteristic calculation process of two theorical methods is proposed.Meanwhile,the natural characteristic test system is established and the natural frequencies and mode shapes of TC300 carbon/epoxy composite plate are measured.At last,the natural characteristic results obtained by two theorical methods are compared,and the correctness is verified by comparison with the experimental results.(2)The frequency-domain response characteristic of composite thin plate under base excitation and the time-domain response characteristic under pulse excitation are investigated.And the fiber reinforced composite thin plate under cantilever boundary condition is taken as research object,the frequency domain vibration response under base excitation is obtained based on multilevel iterative correction technique,meanwhile,the time domain vibration response under pulse excitation is obtained by assuming the hammering signal as a harmonic half wave signal.In addition,vibration response prediction processes are proposed,and the vibration response test system of FRCP is established.Finally,TC300 carbon/epoxy composite plate is taken as research object,and the vibration response under base excitation and pulse excitation are measured.Further,the prediction results and experimental results are compared.(3)Based on the frequency-response function(FRF)of composite plate obtained by experimental test and theoretical analysis,the frequency response function approximation method(FRFAM)to identify mechanical parameters of fiber-reinforced composite is proposed.Since the pulse excitation is assuming as short period harmonic half wave signal,the time domain vibration response of composite thin plate can be obtained by using mode superposition method.Then the MATLAB software is used to obtained the FRF of composite thin plate under pulse excitation based on FFT technology.Further,the identification principle based on FRFAM is illustrated and its correctness is validated by comparing with other published literature.At last,FRFAM is applied in a study case,where the elastic moduli,Poisson’s ratios and loss factors of the TC300 carbon/epoxy composite thin plate are identified.(4)A strain energy density function method is proposed to investigate the nonlinear vibration characteristic of fiber-reinforced composite thin plate.First of all,according to Jones-Nelson nonlinear material model,the elastic moduli of the fiber composite are expressed as the function of the strain energy density,and the nonlinear vibration model of composite plate is established by combining the classical laminates theory with Ritz method.Then,the nonlinear natural frequencies and vibration responses can be solved by iterative algorithm,and the specific analysis procedure of the nonlinear natural frequency and vibration response of such composite plate are proposed.At last,TC300 carbon/epoxy composite plate is taken as a research object,and its nonlinear natural frequencies and vibration responses under different excitation levels are obtained both by theoretical calculation and experimental test.By comparing the results,the correctness of the proposed method is verified.In this paper,the vibration characteristic of fiber reinforced composite thin plate is further revealed which have the important predictive effect on the vibration failure and fatigue damage of composite plate.In addition,this research has important engineering and academic significance for many aspects such as structural design,response prediction and dynamic performance optimization of composite structures.Moreover,the relevant research achievements can provide significant technical support for the application of composite plate in engineering practice.