Vibration of metallic and composite shells in geometrical nonlinear equilibrium states

By making use of high order shell models, the present work discusses frequency and mode change of thin structures subjected to large displacements and rotations. The models are implemented in the domain of the well established Carrera Unified Formulation (CUF) and employ the full Green-Lagrange strain tensor, in a total Lagrangian scenario. In this manner, finite elements to be applied indistinctively to metallic and laminated composite shells, having refined layerwise kinematics, and providing accurate nonlinear equilibrium states as well as vibration analysis in both moderate and large displacement fields are provided. Several numerical examples are discussed for shell problems dominated by flexure and compression. The validity of the proposed formulation is demonstrated and modal aberrations as a consequence of the loading, the nonlinear equilibrium state, and the material anisotropy is discussed.