Wide-Angle X-ray Diffraction Investigations of Orientation of Chopped Fibers in Fabricated Thermoplastic Parts

摘要

A method of determining fiber orientation in composites using wide-angle X-ray diffraction (WAXD) is described. This approach is based upon examining the alignment of the highly oriented crystalline fibers. X-ray studies were carried out using Kevlar (poly(p-phenylene terephthalamide) (PPTA)) fibers suspended at a 0.31 volume fraction loading in a polycarbonate matrix. A pole figure device was used to determine the orientation distribution and average orientation factor of the PPTA crystallographic chain axes relative to reference axes located in the test specimen. We prepared ideally oriented uniaxial and biaxial composites as reference specimens using a compression molding machine. The fiber orientations in capillary extrudates, slit die extrudates, cold rolled sheets, and injection-molded specimens were examined by WAXD. The capillary extrudates showed uniaxial orientation but the slit die extrudates and cold rolled sheets exhibited biaxial orientation. Injection-molded specimens contained complex states of fiber orientation. Keywords: Kevlar; Fiber reinforced composites; Thermoplastic parts; Wide angle; X ray diffraction; Orientation; Reprints. (jhd)