Composite-flywheel burst-containment study

A key component impacting total flywheel energy storage system weight is the containment structure. This report addresses the factors that shape this structure and define its design criteria. In addition, containment weight estimates are made for the several composite flywheel designs of interest so that judgements can be made as to the relative weights of their containment structure. The requirements set down for this program were that all containment weight estimates be based on a 1 kWh burst. It should be noted that typical flywheel requirements for regenerative braking of small automobiles call for deliverable energies of 0.25 kWh. This leads to expected maximum burst energies of 0.5 kWh. The flywheels studied are those considered most likely to be carried further for operational design. These area: The pseudo isotropic disk flywheel, sometimes called the alpha ply; the SMC molded disk; either disk with a carbon ring; the subcircular rim with cruciform hub; and Avco's bi-directional circular weave disk. The flywheel materials for the disk are S-glass; the subcircular rim is Kevlar over S-glass. Test data on flywheel bursts and containment failures were analyzed. Recommendations are made for further testing.