In this paper, authors use a fi nite element model based on higher-order displacement plate theory for analysis of stiffened laminated composite plates. Transverse shear deformation is included in the formulation making the model applicable for both moderately t hick and t hin composite plates. | Vietnam Journal of Mechanics, VAST, Vol. 30, No. 2 (2008), pp. 112-121 ANALYSIS OF STIFFENED LAMINATED COMPOSITE PLATE S BY FINITE ELEMENT BASED ON HIGHER-ORD ER DISPLACEMENT THEORY Tran Ich T hinh Hanoi University of Technology Tran H uu Quoc Vietnam Academy of Science and Techno logy Abstract . In this paper, authors use a fi nite element model based on higher-order displacement plate theory for analysis of stiffened laminated composite plates. Transverse shear deformation is included in the formu lation making the model applicable for both moderately t hick and t hi n composite plates. The plate element used is a nine-noded isoparametr ic one with nine degrees of freedom at each node. The stiffness of stiffener is reflected at a ll nine nodes of plate element in which it is placed. Accord ingly, the stiffeners can be positioned anywhere within the place element. Free vibration and defl ection of stiffened laminated composite plates are carried out, and resu lts are compared with existing analytical and other solutions. 1. INTR ODUCTION Stiffened laminated composite plates are widely used in many industrial structures such as aerospace structures, road bridges, ship hull, etc. due to their high strength to weight ratios. In order to analyse stiffened laminated composite plates, some authors used finite difference method [1], Rayleigh-Ritz method and finite element method. In [2], Ahmadian M. T. and Zangeneh M. S. used the combination of plate super elements and beam super elements, the plate and beam elements having 55 and 18 degrees of freedom respectively. Olson and Hazell [3] have presented results from a theoretical and experimental comparison study on the vibration characteristics of all clamped and eccentrically stiffened isotropic plates. They used a triangular finite element in the calculations. Koli [4] developed a 9-noded rectangular plate element and 3-noded beam element; the beams are placed along the plate nodal lines. Biswal and Ghosh [5] used .
