Geometrically nonlinear analysis of laminated composite stiffened shells

Investigation of the geometric nonlinear analysis of eccentrically stiffened composite shells has been carried out for the first time using total Lagrangian coordinate system. The paper uses conventional nine-noded Lagrangian curved element stiffened with laminated stiffeners for studying composite stiffened shells. An improved version of the stiffener modelling has been adopted in which stiffeners can be placed anywhere inside the shell element providing much flexibility in mesh division. Though the papers dealing with the large deflection analysis of bare isotropic and composite shells are numerous, the research on the nonlinear analysis of stiffened composite shells are absolutely scanty and they only deal with concentric stiffeners. For the first time in the literature, eccentric stiffeners have been considered for the geometric nonlinear analysis of composite stiffened shells. Neither the problem nor this type of modeling of stiffeners are available in any commercial finite element packages. Standard iterative solution procedure, like the Newton-Raphson method in conjunction with the modified Rik's method which accommodates fully automatic variable load increment procedure is used to trace the nonlinear equilibrium path of laminated stiffened shells beyond the critical point. As the application area is new, a large variety of numerical examples are presented for the geometric nonlinear analysis of both concentrically and eccentrically laminated stiffened shells which includes the effects of laminae orientation, eccentricity and other parameters.