The evaluation of advanced composite material. Performance in high speed pulsed power rotor applications

The successful and optimal utilization of advanced composite materials in pulsed power rotating machinery depends on the availability of well-defined and characterized material properties and failure modes. A key application of these materials is bands for supporting rotor conductor coils and for increasing stored energy. This paper reports on the results of a comprehensive series of experiments that utilize a unique, low cost spin-burst technique that allows the determination of delivered material strength and failure modes in filament wound rotors, under realistic dynamic loads. The measured in-situ failure strength of a series of carbon fiber materials (T650-42, IM7, M40J, M46J, and M60J) is reported. Apparent fiber strengths in as-fabricated rotors are compared to vendor-supplied raw fiber properties. The results indicate that the fiber damage and apparent delivered fiber strength reduction tends to increase with raw fiber modulus. In the series of burst experiments, carbon band failure modes were also observed and characterized using high-speed laser photography, and indicate a general tendency for sudden inelastic failure resulting in multi-segmented burst events generating a cloud of small fragments. The degradation of fiber strength in filament wound carbon bands is corroborated by tensile tests on fiber tows prepared before and after the winding operation.