Characterization of the Structure of Carbon Fibers by Wide-Angle and Small-Angle X-ray Scatterings

Abstract

Listen

Translate article

A characteristic feature of carbon fiber structure is that the fibers comprise the preferentially oriented carbon-layer stacks and the needle-like microvoids oriented nearly parallel to the fiber axis. In order to study the anisotropic nature of the carbon fiber structure by the X-ray measurement, it is necessary to carry out the measurement on a unidirectionally aligned fiber bundle. For this purpose, it is inappropriate to apply the Bragg, Scherrer, and Warren equations for wide-angle X-ray diffraction and the currently used theories for the small-angle X-ray scattering of isotropic bodies. The present authors have developed previously the methods enabling one to analyse the wide- and small-angle X-ray scatterings from a carbon fiber bundle. In this paper, these methods, together with a convenient method determining the primary beam power by using air scattering, are concisely summerized to facilitate their practical application, and are discussed in relation to the Bragg, Scherrer, and Warren equations. By the proposed methods, the structural parameters characterizing the stacks of carbon layers, such as lattice constants, stacking regularity, sizes, orientation and volume fraction are evaluated from the wide-angle X-ray diffraction intensity distribution, and the characteristic parameters of microvoids, such as cross-sectional sizes, volume fraction, number per unit cross-sectional area of the fiber, inter-void spacing, variation in electron density, crosssectional size distribution and cross-sectional shape are evaluated from the small-angle X-ray scattering intensity distribution.