Abstract: A flywheel system includes an annular rim mounted for high speed rotation on a flywheel hub. The hub has a radially splined exterior surface facing radially outwards. The rim includes an annular rim liner having an axis of rotation coinciding with the axis of rotation of the hub, and having an inner surface facing radially inward. The inner surface of the rim liner has integral splines projecting radially inward and extending axially. The rim liner splines mate with the hub splines. The flywheel rim liner has a modulus of elasticity el, and a density ?l, and a liner ratio Rl equal to El/?l. The flywheel rim has a modulus of elasticity er in the hoop direction and a density ?r; and a rim ratio Rr equal to Er/?r. The materials and configuration of the rim and rim liner are designed so that Rl is less than or equal to Rr, so said flywheel rim liner grows radially with the rim.

Abstract: An epoxy resin composition for a cured material, comprising (A) an epoxy resin comprising an epoxy compound X, the epoxy compound X has an epoxy equivalent weight of at least 400, (B) a curing agent, and (C) a liquid rubber that is liquid at room temperature and comprises a reactive group; wherein the epoxy compound X has a solubility parameter value of SpX, the liquid rubber has a solubility parameter value of SpY and the ratio of SpY/SpX could be in the range of 0.7 to 1.3; and wherein the liquid rubber could form no visible domains by optical microscopy or has a maximum domain size of at most 3 microns in the cured material is described. The epoxy resin composition provides a fiber-reinforced material with higher compressive modulus and strength, toughness and better handling ability over standard epoxy resin systems. This invention is excellent for small thin walled tube structures like fishing rods or applications that require good compressive strength.

Abstract: A composite flywheel rim has multiple fiber layers in each of a plurality of radially contiguous zones. The layers in the intermediate zones each have a mixture of carbon fiber tows and glass fiber tows. The ratio of carbon fiber tows to glass fiber tows in each layer of any single zone is constant and the ratio incrementally increases zone-by-zone radially toward the outside of the rim, and the distribution of carbon fiber tows is macroscopically uniform in each zone. The flywheel rim is made by winding a band of fiber tows, impregnated with wet resin, onto a mandrel. The macroscopically uniform distribution can be achieved by controlling the correlation between lead rate of the fiber band as it is wound onto the mandrel per mandrel revolution and the winding length.

Abstract: An epoxy composition includes an epoxy resin, a latent curing agent, and a catalyst. The composition includes two epoxide groups per molecule, and the latent curing agent is preferably a dicyanopolyamide, and most preferably dicyandiamide. The catalyst includes 2,4-toluene bis dimethyl urea, preferably in a concentration exceeding 70% by weight. The composition can be used in prepregs. The relative concentrations of the epoxy resin, curing agent, and catalyst are selected to achieve desired properties, including specific curing times and temperatures, and glass transition temperatures that enable a cured resin composition to be removed from a mold after being heated to its curing temperature, without being cooled. Exemplary formulations have reduced cure times, at both high and low curing temperatures, as compared to prior art formulations.

Abstract: An epoxy resin composition for a cured material, comprising (A) an epoxy resin comprising an epoxy compound X, the epoxy compound X has an epoxy equivalent weight of at least 400, (B) a curing agent, and (C) a liquid rubber that is liquid at room temperature and comprises a reactive group; wherein the epoxy compound X has a solubility parameter value of SpX, the liquid rubber has a solubility parameter value of SpY and the ratio of SpY/SpX could be in the range of 0.7 to 1.3; and wherein the liquid rubber could form no visible domains by optical microscopy or has a maximum domain size of at most 3 microns in the cured material is described. The epoxy resin composition provides a fiber-reinforced material with higher compressive modulus and strength, toughness and better handling ability over standard epoxy resin systems. This invention is excellent for small thin walled tube structures like fishing rods or applications that require good compressive strength.

Abstract: A composite flywheel rotor includes an annular rim mounted on a hub for high speed rotation in an evacuated flywheel enclosure. A smooth epoxy layer is applied to the rim and is cleaned or maintained clean in preparation for a metal coating on the rim. The rim may be baked in a vacuum furnace to drive off the volitiles and water vapor, and a thin metal coating is applied over the entire rim to retard outgassing from the resin in the flywheel composite rim. The metal coating on flywheel rim is preferably aluminum because aluminum adheres well to epoxy and is economical. The metal coating is deposited on the flywheel rim by physical vapor deposition and may be built up after an initial PVD coating by electroplating. A tough protective polymer is applied over the metal coating to protect metal coating from mechanical damage during handling.

Abstract: An in-situ curing filament winding process for making high quality flywheel rims at low cost, and the rims made by the process, and also an apparatus for performing the process, continuously cures resin during the filament winding process. A lower winding process temperature is used along with a lower cure temperature and inherently higher toughness epoxy resin system allows for the rim to be wound continuously, using a conservative radial deposition rate of approximately ¼-½ inch per hour. Multiple types of fibers can be used in a rim where they best serve the strength and stiffness requirements of the structure. The winding temperature can be kept at approximately 55° C.-80° C., providing low thermal residual stresses. Aliphatic amine or ether amine curing agents with epoxy resin generally work well to reduce the winding temperature and allow low viscosity, but other resin systems that provide similar characteristics can be used.

Abstract: A composite flywheel rotor includes a flywheel hub having tapered outer surface and an axis of rotation and a flywheel rim having an axis of rotation coinciding with the hub axis of rotation. The flywheel rim has multiple rings axially press-fit together to precompress the rings to form a composite flywheel rim. Each ring is made of approximately equal radial thickness and the entire non-dimensionalized radial thickness ratio of the assembled rim should be between approximately 0.38 to 0.48. The rim is optimally made up of four or five individual rings, each of which rings has tapered inner and outer diameters, preferably tapered at small angles to produce large radial forces when the rings are pressed onto each other and the hub by pressing axially, resulting in a high radial compressive preload in the assembled rim. A taper angle of 1-5° is suitable.

Abstract: An epoxy composition including an epoxy resin, a latent amine curing agent, and a specific catalyst. Preferably, the epoxy resin includes two epoxide groups per molecule, and the latent amine curing agent is a dicyanopolyamide, most preferably, dicyandiamide. The specific catalyst is preferably 2,4-toluene bis dimethyl urea. A prepreg employing the epoxy composition of the present invention can achieve a 95% cure in about one half of the time required by a prepreg that differs only in the catalyst employed. Furthermore, prepregs employing the epoxy composition of the present invention have glass transition temperatures higher than the curing temperatures when cured at a temperature range from about 80° C. to about 150° C., enabling cured prepregs to be removed from molds without being cooled. Use of the prepregs of the present invention thus enables composite component manufacturers to substantially increase production rates without requiring the use of additional molds.

Abstract: A composite flywheel rotor includes a flywheel hub having tapered outer surface and an axis of rotation and a flywheel rim having an axis of rotation coinciding with the hub axis of rotation. The flywheel rim has multiple rings axially press-fit together to precompress the rings to form a composite flywheel rim. Each ring is made of approximately equal radial thickness and the entire non-dimensionalized radial thickness ratio of the assembled rim should be between approximately 0.38 to 0.48. The rim is optimally made up of four or five individual rings, each of which rings has tapered inner and outer diameters, preferably tapered at small angles to produce large radial forces when the rings are pressed onto each other and the hub by pressing axially, resulting in a high radial compressive preload in the assembled rim. A taper angle of 1-5° is suitable.