Effect of Centrifugal Stiffening on the Natural Frequencies of Aircraft Wings During Rapid Roll Maneuvers

The rolling of an aircraft about its fuselage produces centrifugal forces which affect the stiffness of the wings. A number of previous studies explain the effect of centrifugal stiffening in rotating beams and consequently on the frequencies of the beam. Multiple cases of the rotating beam are explored in this thesis to investigate effects of mass distribution and boundary conditions on the frequencies of centrifugally stiffened beams. It is found that for a uniform beam with all degrees of freedom free on both ends, the rigid modes of the beam are affected and are no longer zero when it is stiffened from centrifugal forces. This thesis aims to set up a model to investigate the stiffening effects using the mAEWing2 aircraft. A preliminary analysis is done for the mAEWing2 aircraft and the roll rate, control surface deflection and angle of attack are identified as the parameters to be studied. For a given angle of attack and control surface deflection, the centrifugal forces in the aircraft in steady roll are determined using trim analysis. These are used to pre-stress the model for modal analysis. It is found that in mAEWing2 aircraft in steady roll maneuvers, the centrifugal stiffening effect on the natural frequencies is not significant. It emphasizes the need to conduct a sensitivity analysis to include centrifugal stiffening in the dynamic analysis while designing an aircraft. This, along with some de-stiffening due to gravity loads might be important for the future N+3 aircraft with their high aspect ratio large wingspans. MS