Fabrication of Continuous Fiber-reinforced Thermoplastic Composites with Structural Gradient from Sheath-core Type Bicomponent Fibers

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Sheath-core type bicomponent fibers consisting of polypropylene (PP) or polycarbonate (PC) as a sheath component and thermoplastic liquid crystalline polymer (TLCP) as a core component were prepared by the high-speed melt spinning process. The attainable highest take-up velocity of TLCP was improved by co-processing with PP or PC. Tensile modulus and strength of the TLCP component in the PP/TLCP and PC/TLCP bicomponent fibers increased with an increase in the take-up velocity. Continuous fiber reinforced thermoplastic composites, in which TLCP act as a reinforcing fiber and PP or PC as a matrix polymer, were fabricated by the compression molding of uni-axially aligned bicomponent fibers. Comparison of the wide-angle X-ray diffraction patterns of the starting fibers and fabricated composites indicated that the noticeable orientation relaxation of TLCP did not occur in the compression molding process. Accordingly, the tensile modulus and strength of the PP/TLCP and PC/TLCP composites wer … More e similar to those of the respective bicomponent fibers. Various types of composites were also fabricated from bicomponent fibers. Composites having structural gradient was fabricated by compression molding of bicomponent fibers accumulated on a bobbin by changing the sheath/core composition in the high-speed melt spinning process. Composites reinforced with ultra-fine TLCP fibers were fabricated through the preparation of bicomponent fibers in which 261 micro-fibers were embedded in a single bicomponent fiber. Bi-directional and tri-directional multi-layered composites were also prepared using the filament-winding method. As predicted by the lamination theory, composites with tri-directional reinforcement exhibited isotropic tensile modulus in the layered plane. The textile fabrics were woven from the bicomponent fibers and tri-directionally reinforced composites were fabricated by the compression molding of these fabrics. In this manner, it was proved that flexibility in the designing of continuous fiber reinforced thermoplastic composites can be improved by utilizing the high-speed spun bicomponent fibers as a starting material. Less