Formation of Epoxy Composites from Single Short Fibers

Starting with very low concentrations Vf greater than 0.01, single short fibers can be unidirectionally oriented, statistically overlapped and effectively packed into highly filled, shaped granules or impregnated tapes with concentrations as high as Vf 0.6. This packaging of fibers is demonstrated using E-glass, graphite and boron fibers and a binder of epoxy resin. The mechanical properties of the composites formed by molding the granules and tapes of fibers are superior to those reported previously. In particular, the strength utilization factor for E-glass fibers and epoxy resin composites is increased from the normal level 0.25 to 0.55 to a higher level 0.55 to 0.88. The main reason for this increase is the statistical distribution of single fibers in the composites which requires a much higher percentage of fiber breakage when the composite fails under stress. Fiber orientation, damage, wetting, void content and the adhesion with resin are also the limiting factors on the strength utilization factor.