Deflections and stress resultants of laminated composite stiffened elliptic paraboloids on skewed platform - a geometrically nonlinear approach

Abstract

The research studies on nonlinear bending characteristics of skewed elliptical paraboloids with composite stiffeners and non-uniform boundary conditions arc missing. This paper aims to work on this area. An isoperimetric finite element code with c0 continuity is formulated using eight noded elements for panels and three noded elements for stiffeners. The governing equation is derived using geometrically nonlinear strains and first order shear deformation theory. Newton-Raphson iterations are adopted for the solution of non linear equations. Correctness of the proposed formulation IS con finned by comparing present outputs with closed Conn and experimental results available In literature. The deflections, force and moment resultants are critically studied for varying non-uniform support conditions, skew angles, laminations of graphite/epoxy and glass/epoxy composites, ratios of radii of curvatures and side to thickness ratios. The number, eccentricities and depth of stiffeners are also varied. Parametric invest igations indicate that the performances of elliptical paraboloids are the best for graphite/epoxy composites. The deflections are governed by boundary conditions, laminations and skew angles. The performance generally improves by in creasing the number of stiffeners, but the optimum stiffener arrangement depends on boundary conditions of the pane l. The study of force and moment resultants confirmed that the deflections should not act as the only benchmark to predict the overall bending performance as the stress resultants play an equally important role to determine the best panel option for industrial applications.