An experimental investigation on dynamic analysis of high speed carbon–epoxy shaft in aerostatic conical journal bearings

Advanced composite materials are being increasingly used in aerospace and aircraft industry where high stiffness and strength to weight ratios are important. Most of the components usually designed are static components and often non-load bearing components. But focus by designers is now shifted to critically loaded structural components such as discs, blades, etc. In early stages composite shafts were operated in the sub critical region, therefore the research was directed towards the problem associated with their sub critical operation. However, the recent trend in design of high performance rotating machinery is towards higher operating speeds leading inevitably to supercritical operation of such shafts that gives rise to issues of vibration, stability and stress. As composite material like carbon–epoxy exhibits excellent properties for structures owing to high specific modulus, high damping and low thermal expansions and therefore composite shaft made of carbon–epoxy has been made for the high speed CNC grinding machines and the centrifuges. For the analysis purpose the one step composite shaft made of carbon–fibers in epoxy matrix has been manufactured with 16 layers having stacking angles [0°/90°/45°/−45°]2s using filament winding process. The experimental set up has been designed to investigate static and dynamic analysis and performance characteristics of the carbon–epoxy shaft in aerostatic conical journal bearing at high speeds in the range of 10,000–65,000 rpm. The vibration spectrum analysis has been observed and studied for the same. Comparison of amplitude of vibration decides the maximum operational speed of the shaft with low vibration in aerostatic conical bearings.