Optimum design of thin-walled composite beams for flexural–torsional buckling problem

The objective of this research is to present formulation and solution methodology for optimum design of thin-walled composite beams. The geometric parameters and the fiber orientation of beams are treated as design variables simultaneously. The objective function of optimization problem is to maximize the critical flexural–torsional buckling loads of axially loaded beams which are calculated by a displacement-based one-dimensional finite element model. The analysis of beam is based on the classical laminated beam theory and applied for arbitrary laminate stacking sequence configuration. A micro genetic algorithm (micro-GA) is employed as a tool for obtaining optimal solutions. It offers faster convergence to the optimal results with smaller number of populations than the conventional GA. Several types of lay-up schemes as well as different beam lengths and boundary conditions are investigated in optimization problems of I-section composite beams. Obtained numerical results show more sensitivity of geometric parameters on the critical flexural–torsional buckling loads than that of fiber angle.