Design, fabrication and testing of advanced composite energy storage flywheels

In recent years there has been a resurgence in the interest of developing an environmentally clean and efficient, practical energy storage battery for both vehicular and stationary applications. Flywheels are one potentially promising solution to this problem. When constructed of composite materials, they can offer very high specific energy and specific power capabilities. Problems inhibiting the commercial viability of flywheel batteries are poor design, high material and manufacturing costs, and also safety concerns regarding flywheel containment if a catastrophic rotor failure occurs. The objective of the work presented here is to develop new technology to increase the performance and practicality of composite energy storage flywheels.; Advances made include a flywheel design method using superposed anisotropic elasticity solutions for fast and accurate design of multiple ring composite flywheels. Loading conditions include internal and external pressures from press-fits, rotational loading, temperature change and also residual stresses from manufacturing of the composite rings.; An in-situ curing filament winding method was developed allowing very high speed manufacturing of high quality epoxy matrix composite rings. Radial deposition rates of composite material at 20.3 cm/hr (8 in/hr) are believed to be by far the fastest ever reported. A simple method of predicting the residual stresses in in-situ cured rings was also developed.; A new in-situ curing method for filament winding of urethane matrix composites was developed using solvent dilution of the resin to dodge the problems of high room temperature viscosities and short elevated temperature pot lives. Again, very high quality composites were shown to be easily achieved. The use of these composites was shown from design analysis to yield a predicted benign failure mode.; Work was done to develop methods for assembly of multiple ring flywheels using both press-fits for radial precompression and cured elastomeric interlayers for radial stress isolation between adjacent rings. Press-fits were assembled with pressures as high as 100 MPa (14.5 ksi) without adverse effect.; Spin testing was conducted on several rotors containing elastomeric components. Elastomeric component rotors offer great potential for simplifying rotor design and manufacturing but have typically been avoided due to fear of nonsynchronous rotor whirl. The use of a sufficiently low stiffness bearing system is however believed to avert this problem. Spin testing of both a multiple elastomeric interlayer rotor and an elastomeric matrix rotor on a flexible quill shaft to 1101 m/sec and 532 m/sec, respectively, showed no existence of nonsynchronous rotor whirl.