Multilevel Optimization of Composite Structures

Abstract

A multilevel optimization scheme for large laminated composite structures, which allows the use of ply thickness and orientation as variables, is described. The lower level of optimization uses a multi-criteria objective function which combines a weight function and a strain energy change function into a utility function which is minimized and in which the relative importance of each part is reflected by weighting coefficients. Minimizing the change in strain energy ensures load path continuity in the overall structures when switching between upper and lower levels of optimization, and so decouples the problems at the two levels. This system has been used to optimize various aircraft-type structures using strain, buckling, displacement and gauge constraints, and an example is given to illustrate the effectiveness of the multilevel optimization scheme.