Vibration Fatigue Analysis Of Thermal Protection Structure Of High-Speed Aircraft

High-speed aircraft is an extremely important development direction in the field of aerospace in the world.Its flying speed is very fast,which makes the load environment be very complex and harsh.Most of the outer surfaces of high-speed aircraft are subjected to strong aerodynamic heating and noise.The function of thermal protection system(TPS)is to avoid overheating or burning down of aircraft.Composite sandwich panels are usually used as thermal protection structures of high-speed aircraft.Their panels and core layers have good thermal insulation function,and also play a bearing role.But if the strength of thermal protection structure is not enough,it will affect the normal flight of aircraft and lead to serious consequences.Therefore,the dynamic response and strength of thermal protection structures of highspeed aircraft are studied in this paper.In this paper,a rectangular TPS sandwich plate is studied by modal test combined with finite element simulation.By comparing the modal results of three different modeling methods,a reasonable modeling method of TPS sandwich plate is selected.Based on the analysis method of structural random vibration response and vibration fatigue,the finite element modeling and random vibration fatigue of TPS components and TPS plates on aircraft surface were studied respectively.Vibration fatigue life prediction of TPS-based external panel is carried out by time domain method and frequency domain method respectively.The results show that the life obtained by the two methods is similar.The life prediction results obtained by different parameters in frequency domain mathod are compared,and the influence of thermal stress caused by temperature on life is considered in time domain life prediction.The finite element model of TPS plates pasted on the whole and surface of the aircraft is established,and the model is revised based on the existing experimental data.The elastic modulus of stiffness weakening elements at the joints of each compartment is selected as the design variable.The relative error between the revised modal calculation results and the test results is within a reasonable range.The transient responses of the aircraft in cruise and boost states are analyzed by direct method and modal superposition method respectively.The stress response of TPS panel pasted on the front of the aircraft is obtained.The results obtained by the two methods are compared,and the results are very close.Vibration fatigue analysis was carried out based on the transient response results.The results show that no vibration fatigue damage occurred in the outer panel of TPS plate under both working conditions.The process of finite element modeling,dynamic response calculation and vibration fatigue life prediction for practical engineering problems is summarized.