Analysis Of Flutter Characteristics Of Composite Wing With Uncertain Parameters

Flutter is an important aeroelastic problem affecting aircraft safety,CCAR 25.629 specifies relevant airworthiness requirements for the aeroelastic stability of transport aircraft.The flutter characteristics are verified in a defined configuration during the validation and verification of the aircraft,but for composite wings,due to the differences in materials and manufacturing technology,the performance of the wing structure will be dispersed.The dispersion may cause the actual structure to deviate from the certification configuration,thereby affecting the flutter characteristics of the composite wing structure and may even affect the safety level required by the airworthiness regulations.For the reason,this paper comprehensively considers the common uncertain parameters in the process of composite wing flutter analysis,studies the influence of uncertainty parameters on the flutter characteristics,and identifies the key parameters that have a great influence on the flutter analysis results.Firstly,the two-dimensional airfoil was used to study.By establishing the aeroelastic motion equation,the flutter speed under the certainty parameters are calculated.Then the flutter speed was calculated by defining the uncertainty distribution characteristics of these parameters,the variation trend of the flutter speed was studied,and the main parameters that affecting the flutter speed was identified.The results of the flutter analysis were consistent with the results of the FAA-related studies,indicating the effectiveness of the analytical models and methods.It was found that when there is uncertainty in the parameters,the flutter speed will exhibit obvious dispersion,and the pitch stiffness parameter has the greatest influence on the flutter speed.Secondly,the 2D 3DOF airfoil/aileron system is established to calculate the limit cycle oscillation amplitude with certainty parameters.The effects of stiffness for pitch,plunge and torsion stiffness parameters to the LCO amplitude was studied,and the dispersion of the freeplay was also considered.In this study,the influence of different parameters on the amplitude of the LCO of the structure was also analyzed.The results showed that the LCO occurs due to the existence of the freeplay,so it becomes the main factor that affecting the amplitude.Finally,a composite wing flutter model was established,and the natural frequency and mode shape of the structure were obtained by modal analysis.Based on this results,the composite wing's flutter analysis was carried out.By defining the uncertainty distribution characteristics of the material parameters,the flutter speed's variation trend was analyzed,and the influence of each parameter on the flutter speed was also studied.The results showed that when considering the uncertainty of the parameters,the flutter speed distribution is normal distribution,and the elastic modulus of the main beam has a greater influence on the flutter speed.The research in this paper can provide some reference for the flutter analysis and airworthiness verification of composite wing.