Dynamic Analysis Of Moving Composite Cantilever Plate

Supersonic unmanned fixed wing aircraft is always affected by continuous variable force and temperature loads during flight.Airfoil is a critical part of unmanned fixed wing aircraft,which will be failure due to instability under loads.Airfoil made of fiber reinforced composites has the characteristics of light weight,high strength and designability.Airfoil is modeled as a moving composite cantilever plate structure.Stability of the moving cantilever plate is researched in the case of different kinds of loads.Effects of piezoelectric structure on the stability of moving cantilever plate is analyzed.The details are as follows:The geometric equation of composite cantilever plate is established based on large deformation theory and high-order shear theory.The stiffness matrix of asymmetric laminated composite plates is derived by using the constitutive relationship of anisotropic composites.The kinetic energy and deformation energy of composite cantilever plate under high-speed flight are calculated from the constitutive relationship and stiffness matrix.Based on the Hamiltonian principle,the dynamic equation of composite cantilever plate under high-speed flight is established.The stability of cantilever plate is studied based on state space method.The critical speeds of undamped systems and damped systems are studied.Simulation of aerodynamic forces in supersonic flight based on piston theory.The critical velocity of cantilever plates with different structures is analyzed.The energy in the cantilever plate can be dissipated by aerodynamic damping to increase the critical velocity.Decreasing aspect ratio,increasing thickness and ply angle will increase the critical velocity of cantilever plate.Study the influence of aerodynamic thermal load on stability during high-speed flight.The results show that the natural frequency and critical velocity of cantilever plate will gradually decrease with the increase of temperature.Increasing the ply angle will improve the stability of cantilever plate.The stability of antisymmetric ply is better than that of symmetric ply.Increasing the fiber volume fraction in the composite plate will increase the flutter temperature,but reduce the flutter velocity.Based on the constitutive relation of piezoelectric structure,the dynamic equation of piezoelectric composite cantilever plate is established.The influence of piezoelectric plate parameters on the vibration of composite cantilever plate is studied.The influence of geometric parameters of piezoelectric sheet on the vibration of composite cantilever plate is studied.The displacement response of cantilever plate subjected to excitation force is studied by Newmark method.Voltage is applied to the piezoelectric structure to control the cantilever plate.The Research results show that changing the thickness of piezoelectric sheet will affect the natural frequency and flutter velocity of cantilever plate.When the flight speed is less than the flutter speed,the response of the cantilever plate will gradually converge after being excited,and when it is greater than the flutter speed,the response will gradually increase,LQR control can effectively reduce the vibration displacement amplitude of cantilever plate and increase the critical speed of flight.