Design And Experimental Study Of Intelligent Structure Based On Macro Fiber Composites

With the rapid development of aviation industry,both civil and military fields have put forward higher requirements for aircrafts.Moreover,under the continuous improvement of aircraft flying speed,it is particularly important to improve aeroelasticity of aircraft.Therefore,the variant aircraft came into being,and its aerodynamic shape can adaptively change with flight conditions.Most of the traditional morphing wings use hinges,servo motors and other mechanical structures and actuation modes,and it is difficult to be used in the field of Unmanned Aerial Vehicle(UAV)due to the large size and high weight.With the continuous development of intelligent materials,more and more scholars begin to pay attention to the use of intelligent materials in the morphing structure of UAV.Among them,MFC has become a research hotspot at home and abroad due to its large torque,light weight,easy control and fast response.Based on the research background of small and medium-sized morphing wing UAVs and MFC actuators,this paper proposes two intelligent structures: piezoelectric cantilever plates model(a simplified model of high-aspect ratio wings)and trailing edge variable camber wings.The dynamic characteristics of the two structures under a variety of complex excitations are studied by a combination of experiments and finite element analysis.The main content of this dissertation can be summarized as following sections.(1)A simplified finite element model of MFC is proposed and its performance is simulated.Then a static experimental platform is set up to measure the MFC itself and the electrified deformation attached to the substrate,and the experimental results are compared with the finite element calculation results.(2)A finite element model for the dynamic analysis of piezoelectric cantilever plates is established,in which the influence of orthogonal anisotropic materials on the calculation accuracy is considered in the modeling of the substrate.The dynamic characteristics of the piezoelectric cantilever plate in a single physical field and high-low frequency coupling fields are calculated respectively.Subsequently,a dynamic test platform is set up,and the dynamic characteristics of the piezoelectric cantilever plate are analyzed experimentally.The first two natural frequencies of the piezoelectric cantilever plate are measured by the frequency sweep experiment,and then the influences of amplitudes of the transverse displacement excitation and frequencies of the alternating current excitation on the vibration response of the piezoelectric cantilever plate under different physical fields(force field and electric field)are studied.Secondly,the influence of high-low frequency coupling excitation on the dynamic characteristics of piezoelectric cantilever plate is discussed.Finally,the finite element calculation results are compared with the experimental results to verify the correctness of the finite element modeling.(3)An intelligent wing which can achieve continuous smooth deformation of the trailing edge of the wing is proposed.The MFC is used as the actuator,and the carbon fiber reinforced composite is used as the load-bearing member.The airfoil with variable curvature at the rear edge is taken as the research object.Based on the CFD module in COMSOL Multiphysics,SST turbulence model is used for aerodynamic numerical simulation.The influence of parameters such as trailing edge deflection Angle,Angle of attack and inlet velocity on aerodynamic characteristics of deformed wing is studied from the aspects of flow field structure,pressure distribution and lift-drag characteristics.(4)Based on the above aerodynamic analysis results,an experimental model is made,and the static deformation of the wing’s trailing edge deformation ability is studied by DC experiments.Then,for the working conditions that the trailing edge can deflect when the trailing edge actively deflects,a dynamics experimental platform is set up to study the dynamic stability of MFC variable camber wing structures under multi-frequencies and externally coupled excitations of different amplitudes.