Design Optimization Procedure for Monocoque Composite Cylinder Structures Using Response Surface Techniques
An optimization strategy for the design of composite shells is investigated. This study differs from previous work in that an advanced analysis package is utilized to provide buckling information on potential designs. The Structural Analysis of General Shells (STAGS) finite element code is used to provide linear buckling calculations for a minimum buckling load constraint. A response surface, spanning the design space, is generated from a set of design points and corresponding buckling load data. This response surface is incorporated into a genetic algorithm for optimization of composite cylinders. Laminate designs are limited to those that are balanced and symmetric. Three load cases and four different variable formulations are examined. In the first approach, designs are limited to those whose normalized in-plane and out-of-plane stiffness parameters would be feasible with laminates consisting of two independent fiber orientation angles. The second approach increases the design space to include those that are bordered by those in the first approach. The third and fourth approaches utilize stacking sequence designs for optimization, with continuous and discrete fiber orientation angle variation, respectively. For each load case and different variable formulation, additional runs are made to account for inaccuracies inherent in the response surface model. This study concluded that this strategy was effective at reducing the computational cost of optimizing the composite cylinders.