Finite element vibration analysis of composite box structures using the high order plate theory

This study deals with free vibration of folded structures and box beams made of composite materials using a four-noded Lagrangian and Hermite finite element that incorporates high order transverse shear deformation and rotary inertia. An 8×8 matrix is assembled to transform the system element matrices from the local to global co-ordinates, in which an eighth drilling degree of freedom (d.o.f.) per node is appended to the existing 7-d.o.f. system. The results obtained are in good agreement with the semi-analytical solutions and numerical results reported by other investigators. Sample studies are carried out for various layup configurations and boundary conditions. The significance of the high order plate theory in analyzing folded structures is enunciated in this paper.