Structural heterogeneity and stress distribution in carbon fiber monofilament as revealed by synchrotron micro-beam X-ray scattering and micro-Raman spectral measurements

The Raman band shift has been measured under tension for carbon fiber (CF) monofilaments of different structural heterogeneity as characterized by a synchrotron micro-beam X-ray diffraction measurement. The apparent Raman band shift factor or the band shift caused by an application of bulk tensile stress 1 GPa was found to be larger for the CF fiber with the higher modulus or the sample with the harder skin part. In order to interpret the observed Raman shift data concretely, a complex mechanical model consisting of parallel array of skin and core parts has been proposed as a temporary model, which allows us to understand the structure–mechanical property relationship of the carbon fiber monofilament in a semi-quantitative manner.