Pre-buckling and buckling of unsymmetrically-laminated stiffened composite panels with stringer terminations under in-plane loads

A meshless approach is developed and used to predict buckling loads of discretely assembled composite panels made from skin and stiffeners. Particular emphasis is given to stringer run-outs within a stiffened panel, where abrupt eccentricity can trigger very large transverse displacements of the skin in front of the run-out tip and perturb the internal in-plane loads distribution. The effect of load eccentricity is included in the formulation. The final set of non-linear equations is obtained by combining von Karman's formulation for moderately large deflections in plates with an extended Timoshenko approach for small initial perturbations. Solutions are calculated by means of a Rayleigh-Ritz method in conjunction with a Galerkin technique. Orthogonal eigenfunctions are employed to expand the variables of interest in generalized Fourier series. An iterative algorithm is proposed to calculate buckling loads. Limits of applicability, convergence of results and further potential exploitations are discussed. Numerical results are compared with those from finite element analysis and other numerical approaches.