Application of folded plate formulation in analyzing stiffened laminated composite and sandwich folded plate vibration

A nine noded flat plate element, considering first order transverse shear deformation and rotary inertia with five degrees of freedom per node, is used to compute element stiffness and mass matrices for composite plates. Drilling degrees of freedom are introduced to account for three translations and three rotations per node, and transformed to obtain the global matrices for computing the dynamic response of stiffened laminated composite and sandwich folded plate structures. The stiffeners are visualized as parts of the folded plate. The formulation works well. New results for stiffened folded plates are reported with different arrangements of stiffeners to observe their effects.