Computational efficiency and accuracy of multi-step design optimization method for variable stiffness composite structures

A multi-step metamodel based optimization method is presented for the buckling design of a variable stiffness composite cylinder. Followed by sampling, metamodeling and optimization at the first step, the design domain is shrunk by narrowing down the side constraints of the design variables around the optimum points resulted from the previous steps. This procedure is repeated until a convergence is reached for both the design variables and the objective function. The structural response of the optimum variable stiffness composite cylinder resulting from this method is shown to significantly improved compared with its constant stiffness counterpart. The computational efficiency along with the accuracy of this method is also assessed by analyzing the metamodeling and evaluation errors in different optimization steps and different sample sizes. The results show that the multi-step method is considerably more efficient than a single-step optimization method.