A new construction technique offers the possibility of fail-safe or limited-failure composite flywheels, say researchers at Pennsylvania State University, University Park, Pa. One change consists of modifying the expected failure area to limit the amount of the rotor that will fly off at excessive speeds, say researchers Charles E. Bakis and Christopher W. Gabrys. Secondly, they would substitute a rubber-like elastomeric material for the rigid epoxy used in the conventional composite designs. The result, says Bakis, is a flywheel that would fail by having the outer-edge fibers peel from the wheel. The breakdown process would also be self-arresting since the inner material operates at lower stress levels due to the unique properties of the elastomeric matrix flywheels. The researchers say the added safety would encourage the consideration of flywheels as candidates for powering cars, stabilizing electrical current, and replacing batteries in spacecraft.