Composite Energy Storage Flywheel Design for Fatigue Crack Resistance

Composite flywheels can be a high-density energy storage device because of the very high specific strength and strength per unit weight. The rotors are fiber reinforced in the circumferential direction to resist centripetal loads resulting from high-speed rotation. A press-fit process is also used to induce precompression in the radial direction that improves mechanical strength by preventing radial separation of rotors. However, this design and fabrication process leaves the radial and axial directions of rotor vulnerable to propagation of fatigue crack growth in the rotor. A semiempirical approach is proposed to enhance the ldquocrack growthrdquo resistance of the rotor. Axial glass plies are incorporated to confine the crack growth through the radius and along the circumferential direction of rotor. The fracture properties of specific hybrid laminates are then measured to provide information required for an optimal rotor design.