Research On Vibration Suppression Of Composite Structure With Variable Cross-section Based On Shape Memoryalloys

The blade is prone to large displacement and vibration deformation under the external loads with performances of geometric nonlinear deformation and fracture failure in severe cases.In this paper,the wind turbine blade is simplified into composite laminated structure with variable cross-section,pseudoelastic shape memory alloy(SMA)fibers are embedded in the top layer and the bottom layer of a variable cross-section composite structure to achieve passive control of blade vibration.Based on geometric nonlinear analysis,the static and dynamic responses of SMA hybrid composite laminated structure with variable cross-section are studied.The main work is as follows:(1)Firstly,taking into account the coupling between the phase transformation characteristics of SMA?material nonlinearity of SMA?structural geometric nonlinearity and so on,the nonlinear static equilibrium equation of composite laminated structures with embedded SMA fibers are established by the virtual work principle and the finite element method.The nonlinear statics response of the SMA hybrid composite structure with variable cross sections was simulated by MATLAB during the transverse and axial loading and unloading process and the results were compared with those from the geometric linear analysis.The simulation results show that the displacement-force curve of the SMA hybrid composite with variable cross-section during loading does not coincide with that during unloading,which form a closed hysteresis loop.And the area of the hysteresis loop obtained from the geometric nonlinear analysis is smaller than that obtained from the geometric linear analysis.Besides,the area of the stress-strain pseudoelastic hysteresis loop and the maximum martensite fraction of SMA got from the geometric nonlinear analysis are also smaller than those from the geometric linear analysis,where the former are about50%lower than the latter.(2)Secondly,the dynamic equilibrium equation of composite laminated structure with embedded SMA is established.The effect of the laying positions of SMA fiber,the volume contents of SMA fibers and the working temperatures on the dynamic response of composite beam with embedded pseudoelastic SMA fibers was simulated by MATLAB.At the same time,the effects of the deflection at the free end of composite laminated beams with variable cross-section embedded SMA fibers with considering SMA phase transformation and unconsidering SMA phase transformation are compared.The simulation results show that the farther the distance between SMA fiber and the middle of the laminated beam is,the stronger the pseudoelastic energy-consuming ability is;the higher the volume content of SMA fibers is,the smaller the deflection of laminated beam is,but the stiffness of laminated beam will be larger,which makes the energy dissipation capacity of SMA fibers per unit volume weaken;as the working temperature increases,the deflection of the laminated beam does not change much,but the elastic deformation stage of the SMA fibers becomes longer,the pseudoelastic hysteresis loop becomes higher and the hysteresis loop area becomes smaller.SMA fibers can withstand greater stress at high temperature than at low temperature.The deflection under considering SMA phase transformation is smaller than that under unconsidering SMA phase transformation.(3)Finally,under geometric nonlinear conditions,the effects of the different ply angles,ply sequences,volume contents of carbon fibers and loads on the dynamic effects of SMA hybrid composite laminated beams with variable cross-section were simulated by MATLAB.The simulation results show that,compared with the laying angle plan B1[0~0/-45~0]_s and B3[90~0/-45~0]_s,the deflection of the plan B2[45~0/-45~0]_s is the smallest,but the area of pseudoelastic hysteresis loop and martensite volume content of SMA are also the smallest,and the pseudoelastic energy dissipation capacity is the worst;compared with the asymmetric laying plan C2[45~0/-45~0/45~0/-45~0]and C3[45~0/45~0/-45~0/-45~0],the deflection of the symmetrical laying plan C1[45~0/-45~0]_s is the smallest,but the area of pseudoelastic hysteresis loop and martensite volume content of SMA are also the smallest,and the pseudoelastic energy dissipation capacity is the worst.The larger the volume content of carbon fibers is,the smaller the deflection at the free end of laminated beam is,but the smaller the pseudoelastic hysteresis loop area and the martensite volume content of SMA are.For laminated beams with 50%carbon fibers volume content,when harmonic uniform load amplitude pa=3500kN/m,there are not phase transformation of SMA at the top and bottom of the laminated beam;when pa=5000kN/m,there is not phase transformation of SMA at the top of the laminated beams,but SMA at the bottom of the laminated beam will be;when pa=6500kN/m,there are phase transformation of SMA at the top and bottom of the laminated beam.