Nonlinear bending of laminated composite rhombic stiffened elliptical paraboloids

This study investigates bending performance of laminated composite rhombic stiffened elliptical paraboloids which is missing in the literature. The deflections, force, and moment resultants of uniformly loaded panels are solved using a C0 continuous finite element code that combines geometrically nonlinear strains, first-order shear deformation theory, and eight-noded elements. The governing equation is derived by minimizing the total potential energy and solved through the Newton-Raphson iterative approach. Experimental and closed-form results are used as the benchmarks to confirm correctness of the proposed model. The bending performance of panels with central and multiple stiffeners is studied for different boundary conditions, laminations of graphite and glass-epoxy composites, and side tilts of rhombic panels. The number, thickness, and locations of stiffeners are varied. Effects of varying shear correction factors are studied also. The bending actions are minimized when 0°/90°/0°/90° laminate and 7 × 7 stiffeners are adopted for CFCF panels. The 0°/90°/0° laminate and 7 × 0 stiffeners should be preferred for FCFC panels. The panels tilted to 30° perform the best, especially for eccentrically concave stiffeners having a depth 10 times that of the panel thickness.