TOPOLOGY OF 3-DIMENSIONALLY BRAIDED FABRICS USING PULTRUDED RODS AS AXIAL REINFORCEMENTS

This paper examines the topology of two-step braided fabrics incorpora ting rigid rods in the axial direction. Fabricated by pultrusion, the I-mm diameter rods are composed of unidirectional Kevlar fibers and vi nylester resin. A modified two-step braiding set-up designed to incorp orate the robs is developed. In comparison with conventional three-dim ensional fabric composites, using the rods can significantly reduce th e level of crimp in both axial and braiding yarns. Crimp-induced probl ems such as irregular fabric patterns can be effectively improved. The resulting composite geometry parameters are experimentally characteri zed. According to the micrographs, rods that are placed in an orderly way greatly improve yam compactness. The braiding yam paths are modele d by the minimum length criterion. Using this criterion, the braiding processes are simulated, taking into account yam jamming conditions. T he interlacing pattern and the length of the fabric convergence cone a re examined. The topology is described in terms of physically measurab le parameters, and the effects of yam size, rod spacing, and pitch len gth on the resulting fabric geometry are analyzed.