ABSTRACT
Quasi-static and fatigue tests were carried out to determine the effects of manufacturing route, fiber type, and vacuum environment on the tensile behavior of candidate composite materials for flywheel energy storage applications. The slight misalignment of fibers in flat carbon/epoxy coupons made by “hoop” filament winding on a flat mandrel let to significantly less ultimate strain than that observed in similar material systems with truly 0-deg. fibers manufactured by either filament winding or prepreg lay-up. This loss of capacity was attributed to detrimental edge effects in the slightly angle-plied materials. Glass and carbon composites conditioned and fatigue tested in vacuum lost about 10% of remaining strength per decade of logarithmic lifetime over the range of lifetimes investigated. The ZenTron™ glass/epoxy composite was noted to have more overall fatigue sensitivity than either E-glass or T700S carbon due to a steeper slope of the S-N curve at very low cyclic lifetimes.
