Dynamics Analysis Of Composite Structures In Ultra-high Velocity Airflow

Ultra-high-speed aircraft is an important direction for the development of aircraft today and in the future.Advanced aircraft can often defeat the enemy first and rapidly expand their strategic advantages.Since composite materials have been used in various weapons and advanced equipment,they have shown excellent performance and become one of the most commonly used materials in various fields,especially in the aerospace industry.Due to its light weight,high strength,and strong designability,composite materials will also become one of the main structures of ultra-high-speed aircraft.Because such aircraft are often used in complex high-speed and high-temperature environments,the vibration of the structure is affected by multiple factors,and the abnormal vibration often results in a decrease in the stability of the structure and even structural damage.Therefore,it is necessary to analyze the vibration characteristics of composite structures in ultra-high-speed airflow under the condition of multi-field coupling.This paper models the most common composite laminate structure in an aircraft,and studies the vibration characteristics of the structure in the case of multi-field coupling.The specific content is as follows:1)The displacement field of the composite laminate is obtained based on the shear deformation theory,and the relationship between the mid-plane strain and the non-mid-plane curvature and the displacement are obtained by combining the small deformation assumption;Based on the classic laminated plate theory,the constitutive and equilibrium equations of the composite structure are derived;the kinetic and strain energy of the structure are deduced and deformed respectively,and the dynamic equation of the composite laminate under axial motion is obtained by combining the Hamilton principle.2)Combined with the piston theory,the first-order aerodynamics is used to describe the aerodynamic load of the composite laminate under high-speed motion,and the dynamic equation of gas-solid coupling of the composite laminate is derived;The Galerkin method is used to discretize the dynamic equations of four-sided simply supported composite laminates,and the discrete equations are solved in conjunction with MATLAB programming;The vibration characteristics of the plate under subsonic and supersonic motion conditions are studied separately;The effects of multiple factors such as speed,plate thickness,aerodynamic force,axial force,and lay angle on the vibration stability of composite laminates are discussed through the changes of complex eigenvalues.3)Considering that the structure and air are heated by friction under high-speed motion,and that the composite laminate has thermal strain and thermal stress due to different thermal deformation of each layer,and combined with the given thermo-solid coupling constitutive relationship,the strain energy of the composite structure under temperature changes is deduced,and the thermo-solid coupling dynamic equation of the plate is obtained by combining the Hamilton principle;The MATLAB program was used to analyze the effects of temperature on the vibration stability of composite laminates with different thicknesses,different speeds,and different lamination methods;Based on the New Mark method,the response of the composite structure was analyzed through MATLAB programming.Through the study of the response of composite laminates with different thicknesses under simple harmonic excitation,the influencing factors of flutter and resonance were discussed.4)Based on the e-type piezoelectric constitutive equation,the deformation energy,coupling energy,pure electrical energy and electrical virtual work of the piezoelectric composite laminate are derived by considering the consideration of force-electric coupling.Combined with the Hamilton principle,the multi-field coupled dynamics equations of the piezoelectric composite layer structure considering the axial motion speed,aerodynamic force,temperature and other factors are obtained;The effects of speed and temperature on the vibration stability of the structure were studied separately;By studying the changes in the critical speed and temperature of piezoelectric composite laminates with different layup angles,the optimal layup angle range is discussed;The Newmark method is used to analyze the response of the plate under different forms of excitation,and the effect of the piezoelectric actuator voltage on the vibration response of the structure is also analyzed.