Postbuckling analysis and optimization of composite laminated panels using a novel perturbation-based approximation FE method

When composite laminated panels under compression are allowed to continuously loaded into the moderately deep postbuckling regime, further weight savings can be achieved. For this purpose, this work presents an optimization scheme for the design of postbuckling behavior of composite laminates. An efficient tool, termed the Koiter perturbation-based approximation FE method, is developed to obtain the postbuckling behavior of composite laminated panel. The initial postbuckling response is represented by the nonlinear predictor solved by the reduced order model, while the deformations in the moderately deep postbuckling regime are obtained by applying the correction phase under the design load. Five different indices, including the critical buckling load, postbuckling stiffness, stiffness residual, and in-plane and out-of-plane deformations under the design load, are proposed to assess various postbuckling performances of the compressed panel. The postbuckling indices can be flexibly selected to be either the objective or the nonlinear constraints in the lamination optimization. A genetic algorithm is subsequently used to determine the optimal lamination configuration for the most favorable postbuckling performance. The optimizations of composite laminates under uniaxial and biaxial compression for different boundary conditions are carefully studied and discussed with the consideration of initial geometric imperfections.