修正応答曲面を用いたフラクタル分枝限定法による積層構成最適化

Abstract

The fractal branch and bound method has been developed by the authors for optimization of stacking sequences to maximize buckling load of composite structures. The method demands approximation of a design space with a response surface comprising quadratic polynomials for pruning fractal branches of stacking sequences. The approximation of the design space with quadratic polynomials has been confirmed for the buckling load maximization and flutter speed limit maximization using lamination parameters as predictors. In the present study, flutter speed maximization for clamped panel flutter problem is employed as an example of stacking sequence optimization by means of the fractal branch and bound method for the flutter problem, which has complicated design space due to coupling of high-order vibration modes of flutter. The theoretical background of the Fractal branch and bound method, and the modified response surface method with newly proposed the adjusted coefficient of evaluation Eadj2 (E-square-adjusted) for complicated design-spaced problem is proposed; approximation using quadratic polynomials with lamination parameters as predictors. After that, the effectiveness of the method for the supersonic clamped panel flutters of composite laminates is investigated. As a result, the method is successfully applied, and the practical optimal stacking sequence is obtained using modified response surfaces.