Composite Energy Storage Flywheel Design for Fatigue Crack Resistance

Abstract

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 pre-compression in the radial direction that improves mechanical strength by preventing radial separation of rotors. This design and fabrication process however leaves the radial and axial directions of rotor vulnerable to propagation of fatigue crack growth in the rotor. A semi-empirical approach is proposed to enhance the "crack growth" 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.

A case study investigation into the risk of fatigue in synchronous flywheel energy stores and ramifications for the design of inertia replacement systems

“…Composite material flywheels have been a particular focus of structural analysis, having grown in popularity since the 1970s [9]. Tzeng and Moy considered the prevention of fatigue cracking in composite flywheel designs [25], suggesting (through the development of analytical expressions for stress fields in composite material flywheels) that axial reinforced and press fit shaft interfacing can significantly enhance the crack resistance properties of composite material flywheels. It should be noted however that, due to their comparatively high unit cost, composite materials are most suitable for flywheel design when rotational speeds are high.…”

Structure Design Method of Multi-Ring Carbon Fiber Composite Flywheel

“…The technology of flywheel energy storage has the characteristics of high energy density and specific power, fast charging and discharging, long product life, non-pollution, standing out from the numerous energy storage technologies. The flywheel energy storage technology is widely applied in many fields, such as aerospace, automotive industry, power system, etc [1][2][3][4]. Compared with metal materials, carbon fiber composite material is the optimum material of making flywheel with the characteristics of low density, high strength.…”