Evaluation of Fiber Orientation by X-Ray Diffraction on Carbon Fiber Reinforced Polyamide 6

: Fiber orientation is important for the development of carbon fiber reinforced thermoplastics (CFRTPs). The purpose of this work is the development of an easy and effective technique to analyze carbon fiber (CF) orientation in CFRTPs in a short time. For this purpose, we investigated the CF orientations in CFRTPs reinforced with polyamide 6 (PA6) as observed by X-ray diffraction (XRD), and discuss the suitability of XRD for the measurement of the CF orientation in CFRTPs. The 200, 002, and 202 reflections of PA6; and the 002 reflection of graphite were observed in the XRD pattern of the CFRTPs. The XRD pattern of uni-directional CFRTP (UD-CFRTP) in the diffraction angle ( 2 θ ) range from 25̊ to 33̊ was almost entirely dominated by contributions from CF. The dependence of the 002 XRD intensity in the 2 θ range from 25̊ to 33̊ on the azimuth ( I(φ) ) of UD-CFRTP and cloth CFRTP (c-CFRTP) showed the CF orientations in those. The direction and distribution of the CF orientations in the discontinuous CF reinforced thermoplastics (D-CFRTP) could be estimated based on the I(φ) obtained by the XRD. Each test piece showed a variable direction and distribution of CF orientation. Fiber orientation order parameters of D-CFRTPs were estimated by I(φ) obtained from the XRD of D-CFRTP and that of UD-CFRTP. The CFs in the D-CFRTP were almost oriented along the molding direction. The tensile modulus was correlated with the orientation order parameters estimated from the XRD patterns of the D-CFRTP. We could obtain these results from studying a UD-CFRTP, a c-CFRTP and a D-CFRTP with performing easy measurements using a general XRD system for 10min. Therefore, XRD may be the one of the most effective methods for the estimation of CF orientations in CFRTPs reinforced with PA6.