Nonlinear equivalent plate modeling of wing-box structures

A geometrically nonlinear moderate-deformation equivalent plate modeling capability for wing structures is developed. It is a generalization of the simple-polynomial-based equivalent plate modeling techniques for linear wing structures. The formulation allows first-order shear deformation plate theory or classical plate theory to be used for modeling and solid thin plates as well as typical wing-box structures made of cover skins and an array of spars and ribs. Mass and stiffness matrix contributions of different wing-box elements are presented. Stiff springs are included to enforce a variety of boundary conditions. The resulting nonlinear equations can be solved for static and dynamic structural response. The new nonlinear equivalent plate modeling technique was validated by comparing its results with those of nonlinear finite element models and results of previous analyses. It is expected to lead to efficient nonlinear aeroelastic analysis of wings subject to in-plane compressive forces such as the rear wings in joined-wing airplane configurations.