Mechanics of composite rotating machines for pulsed power applications

Composite rotating machines are currently used in pulsed power generators, which convert kinetic energy stored in the rotor into electrical current. The rotor could be constructed from a series of concentric press-fitted field coils and composite cylinders. Radial compressive stresses are "built-in" to compensate for the centripetal force resulting from high-speed rotation, and to enhance the shear and radial strength at the interfaces. This paper discusses mechanical concerns at the interfaces of the rotor including press-fit, rotor dynamics, preload relaxation, and a potential rotor failure mechanism. Models and analyzes were then developed for the rotor structural optimization based on these critical parameters, in particular, the concerns about prestress loss attributed to the creep and stress relaxation in the composite materials. Stresses induced by centripetal and magnetic forces might initiate delamination at the interfaces that could eventually propagate causing rotor failure.