Nonlinear Aeroelastic Modeling and Analysis of Fully Flexible Aircraft

This paper introduces an approach to effectively model the nonlinear aeroelastic behavior of fully flexible aircraft. The study is conducted based on a nonlinear strainedbased finite element framework in which the developed low-order formulation captures the nonlinear (large) deflection behavior of the wings, and the unsteady subsonic aerodynamic forces acting on them. Instead of merely considering the nonlinearity of the wings, the paper will allow all members of the vehicle to be flexible. Due to their characteristics of being long and slender structures, the wings, tail, and fuselage of highly flexible aircraft can be modeled as beams undergoing three dimensional displacements and rotations. The cross-sectional stiffness and inertia properties of the beams are calculated along the span, and then incorporated into the 1-D nonlinear beam model. Finite-state unsteady subsonic aerodynamic loads are incorporated to be coupled with all lifting surfaces, so as to complete the state space aeroelastic model. Different Sensorcraft concepts are modeled and studied, including conventional single-wing and joined-wing aircraft configurations with flexible fuselage and tail. Based on the proposed models, roll responses and stabilities are studied and compared with linearized and rigidized models. At last, effects of the flexibility of the fuselage and tail on the roll maneuver and stability of the aircraft are presented.