The evaluation and testing of graphite fiber composite materials for high speed rotors

High speed rotating machine designs may depend on high strength, filament wound carbon fiber composite bands to contain discrete metal conductors in the spinning rotor. Both the failure strength and stiffness of these composite bands play a major role in determining the limiting speed and stored energy in the rotor. This paper describes the results of an investigation to evaluate the mechanical properties of several candidate advanced carbon fiber materials for composite rotors. An experimental technique utilizing a mass-loaded spinning composite ring (rotor) has been developed to provide a viable and cost-effective way to characterize, under relevant dynamic loading conditions, the delivered strength of candidate graphite fibers in filament wound constructions. The test concept and development are described, and the measured in-situ strengths of several representative candidate fibers (T650-42, IM7, M46J composite rotors) are compared to available data. Up to 40 percent reduction of delivered fiber strength in the filament wound rotors compared to vendor-supplied fiber tow strengths were observed.