This paper provides an efficient method for performing global layup optimization of composite laminates with buckling and manufacturing constraints. The optimization problem is divided into two stages and is based on the use of lamination parameters. During the first stage, exact finite strip analysis and continuous optimum design are employed for buckling optimization of the lamination parameters and laminate thickness. In the second stage, a logic-based procedure combining the branch and bound method with a global layerwise technique is employed to find the optimal stacking sequences to match the optimized lamination parameters obtained in the first stage. In order to ensure the optimized layup can be used in practice, four manufacturing constraints are added into the logical search process, and the feasible region for the lamination parameters with a manufacturing constraint which requires at least 10% of each of four possible ply orientations is studied. By comparing the logic-based method with the use of a genetic algorithm for searching stacking sequences under different requirements, the high efficiency and ability to achieve a global optimal result of the logic-based method are demonstrated.

In this paper, a new lamination parameter based method is proposed for the layup optimization of builtup composite laminates with ply drop-offs. The optimization process is divided into two stages. In the first stage, the multilevel optimization feature of the exact strip software VICONOPT MLO is extended to use the lamination parameters and laminate thicknesses of each component panel as design variables to minimize the weight of the whole structure subject to buckling and lamination parameter constraints. For the second stage, instead of using the common heuristic optimization methods, a novel dummy layerwise branch and bound (DLBB) method is proposed to search the manufacturable stacking sequences to find those needed to achieve a blended structure based on the use of 0°, 90°, +45° and -45° plies and having lamination parameters equivalent to those determined in the first stage. The DLBB method carries out a logical search to circumvent the stochastic search feature of heuristic methods for the determination of stacking sequences. This two-stage method is an extension of a previous highly efficient two-stage method for a single laminate [1]. The effectiveness of the presented method is demonstrated through the optimization of a benchmark wing box.

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