In this work, three optimization algorithms-Levenberg-Marquardt, simulated annealing and a newly developed and proposed hybrid differential evolution particle swarm optimization are considered in the shape optimizations of cross-sections of integrally stiffened panels (ISP) for aeronautical applications, when subjected to buckling deformation modes within the elasto-plastic range. The proposed algorithm is shown to be robust and more effective, in the tested examples, than conventional optimization algorithms, leading to optimum designs of ISP cross-sections for a pre-defined buckling load-carrying capacity, combined with elasto-plastic nonlinear behaviors. (C) 2011 Elsevier Ltd. All rights reserved.