Flywheel energy storage systems employing high speed composite flywheels and advanced electric motor/generators are being evaluated by the Department of Defense (DoD), NASA [1], and firms [2,3] to replace electrochemical battery banks in satellites and manned space applications. Flywheel energy storage systems can provide extended operating life and significant reduction in weight and volume compared to conventional electrochemical systems. In addition, flywheels can provide momentum or reaction wheel functions for attitude control. This paper describes the design, fabrication, and spin testing of two 10 MJ composite flywheel energy storage rotors. To achieve the demonstrated energy density of greater than 310 kJ/kg in a volume of less than 0.05 m 3 , the rotors utilize flexible composite arbors to connect a composite rim to a metallic shaft, resulting in compact, lightweight, high energy density structures.The paper also describes the finite element stress and rotordynamics analyses, along with a description of the fabrication and assembly techniques used in the construction of the rotor. A description of the experimental setup and a discussion of spin testing of the rotors up to 45,000 rpm (965 m/s tip speed) are also presented. Accurate measurements of rotor centrifugal growth made with laser triangulation sensors confirmed predicted strains of greater than 1.2% in the composite rim.Due to the weight penalty associated with flywheel designs requiring containment structures, there is a strong need to develop flywheel systems which operate safely in space, preferably without dedicated containment structures. A future paper will describe results of a 28,600 rpm composite rotor burst test performed in a containment structure as a step towards understanding composite rotor failure modes.

A model has been developed to compute the effective properties for an arbitrarily shaped element with multiple anisotropic material regions. The analysis utilizes a finite element technique to resolve the complexity of three-dimensional layer geometry, anisotropy, ply orientations, and multi-material regions within an element. Accordingly, the model accounts for complex geometries requiring changes in mesh density and/or arbitrarily shaped elements that cannot be readily aligned with the layers of the laminate. Discontinuity due to ply drop-off or layer terminations within an element is also considered. The computed elastic constants are accurate, especially for the transverse shear properties. The analysis is particularly suitable for finite element applications of near-net shaped thick-section structures. A preprocessor was developed incorporating the effective property model to allow for generation of finite element representations for computer codes such as DYNA3D and ABAQUS.

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-In this paper, detailed three-dimensional (3D) transient electromagnetic (EM) analyses with temperature-dependent material properties were performed using a state-of-the-art analysis tool to calculate current densities, body force densities, and temperature distribution in launch package and rail conductors. The body force densities, temperature distribution, and package accelerations generated by the EM model were then provided to a 3D multiple-step nonlinear static structural model for detailed mechanical analyses. The combined 3D EM and structural analyses can be used to accurately predict the EM launching performance and launch package structural integrity. Furthermore, armature optimization and package survivability enhancement can also be achieved with the help of these analyses.

Electromagnetic (EM) Rail Guns offer the potential of launching kinetic energy projectiles at higher energies and/or velocities than conventional powder guns. Recent firings of air-defense projectiles of tactical configuration out of a 90 mm electromagnetic rail gun at the DNA-Maxwell Green Farm Facility are beginning to demonstrate some of this potential. A Rodman Cone launch package, for example, achieved a record 6.35 MJ muzzle energy for plasma armatures at a velocity of 2.18 k d s with a launch mass of 2.67 kg. After sabot separation, the projectile perforated cleanly a four inch thick steel target at negligible angle of attack.Results of several recent firings are presented. The launch packages were accelerated by base-pushed, plasma armatures with composite-supported steel penetrators. These are the first projectiles of tactical configuration to achieve these muzzle energies and velocities from an electromagnetic rail gun. Key to the success of these firings was the design, fabrication, integration, and testing approach implemented along with addressing critical issues unique to launching tactical projectiles from EM Rail Guns.

-As the power density requirement for new compulsator (CPA) designs increases, designers are driven to use more composites to reduce mass, spin the rotors faster to store more energy, and operate the machine at higher voltages to increase machine power output. In any particular compulsator design, the rotor windings are subjected to high strain levels as the rotor is spun and experiences radial growth. A critical component in the rotor winding design is the high voltage insulation. As the rotor is spun, the induced strains are applied to the insulation system on the coil conductors. This implies that over the operating life of a compulsator, the coil structure and the high voltage insulation must remain structurally intact, while undergoing repeated cyclic loading. This paper presents the design and testing of a compulsator rotor winding that has been recently fabricated at the Center for Electromechanics at The University of Texas at Austin. The paper focuses on the testing done both at room and elevated temperature to evaluate the winding structure and high voltage insulation system under both tensile and transverse strain conditions. Data presented suggests a factor of safety of at least five for strain to failure values and high voltage insulation good for at least twice line voltage after testing to strain failure.

Composites with hard undeformable particles are better suited for creep resistant applications. Al m -TiB 2 particulate composite is one such composite. Its flow properties and formability are investigated and presented in the paper. A suitable temperature range for working this particulate composite is ascertained by using uniaxial axysymmetric compression tests and ring compression tests. Warm working is found to be suitable for this composite in the temperature window of 473-523 K.

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