The influence of failure criteria on the design optimization of stacked-ply composite flywheels

This paper presents some approaches to the optimal design of stacked-ply composite flywheels. The laminations of the disk are constructed such that the principal fiber direction is either tangential or radial. In this study, optimization problems are formulated to maximize the energy density of the flywheel. This is accomplished by allowing arbitrary, continuous, variation of the orientation of the fibers in the radial plies. The paper compares designs based on minimizing cost functions related to the (1) the maximum stress, (2) the maximum strain, and (3) the Tsai-Wu failure criteria. It is shown that the optimized designs provide an improvement in the flywheel energy density when compared to a standard stacked-ply design. The results also show that, for a given disk design, the estimate of the energy density can vary greatly depending on the failure criteria employed.