Estimation of limit strains in disk-type flywheels made of a compliant elastomeric matrix composite undergoing radial creep

Fibre reinforced elastomeric matrix composites (EMCs) offer potential advan tages of construction of rotors for flywheel energy storage systems. One po tential advantage, for safety considerations, is the existence of maximum s tresses near the outside radius of thick circumferentially wound EMC disks, which could lead to a desirable self-arresting failure mode at ultimate sp eeds. certain undirectionally reinforced EMCs, however, have been noted to sreep readily under the influence of stress transverse to the fibres. In th is paper, stress redistribution in a spinning thick disk made of a circumfe rentially filament wound EMC material on a small rigid hub has been analyze d with the assumption of total radial stress relaxation due to radial creep . It is shown that, following complete relaxation, the circumferential stra ins and stresses are maximized at the outside radius of the disk. Important ly, the radial tensile strains are three times greater than the circumferen tial strains at any given radius. Therefore, a unidirectional EMC material system that can safely endure transverse tensile creep strains of at least three times the elastic longitudinal strain capacity of the same material i s likely to maintain the theoretically safe failure mode despite complete r adial stress relaxation.