Design and Manufacturing for a Composite Multi-Ring Flywheel

This paper outlines a manufacturing analysis of a composite flywheel that can then be manufactured, assembled, balanced, and integrated with a magnetically suspended system test apparatus, for use in an inertial energy storage system. The preferred flywheel geometry was found to be a constant thickness disk with a hole in the center, having an inside to outside diameter ratio of 0.45. On the basis of the detailed stress analysis performed, the usable stored energy density of the interference assembled flywheel is 65 Watt - hour/kg, when operating over a speed range of 37.5% to 75% of maximum speed. The preferred flywheel fabrication method is wet filament winding, with high strength carbon fibers, in an epoxy matrix. These fibers are arranged in the hoop direction. A composite material test program was designed to validate the required performance of the, composite material. The methodology used to assemble the flywheel was developed to insure that the proper amounts of interference are achieved. Composite machining methods were defined which will insure that the dimensional accuracy required by the interference assembly method are achieved.