Structural Stability of a Joined-Wing Sensorcraft

This thesis employed a multi-disciplinary design approach to determine the structural stability of the Boeing Joined-Wing SensorCraft. Specifically, this thesis sought to characterize the free vibration modes, ensure a buckling safe design and determine the influence of the geometric and aeroelastic nonlinearities associated with this joined-wing design. The clamped-free vibration modes were developed for a wind tunnel model and were compared to the free-free vibration modes, several differences were found. Linear static analyses were performed on numerous maneuver loads and gust conditions to determine the critical loading condition. The SensorCraft was then redesigned for the critical load case to be both panel and global buckling safe. The multi-disciplinary design process which incorporated both geometric nonlinearities and aeroelastic follower-force effects was then performed for the pre-gust trim and critical gust conditions. The resulting analysis showed that the deformations that resulted from the aerodynamic forces were not substantial enough to fully characterize the follower force effect. Furthermore this thesis demonstrates that the geometric and aeroelastic nonlinearities are not significant. However, for a fully optimized design incorporation of these coupled nonlinearities is critical.