Experimental study of the fiber orientations in single and multi-ply continuous filament yarns

Abstract

A detailed identification, using X-ray microtomography, of the filament trajectories within twisted single and multi-ply continuous filament yarns is presented in this article, to accurately determine the distributions of orientations of filaments which govern the mechanical behavior of those yarns and the mechanisms of failure. The resolution of the images obtained by means of the X-ray microtomography experimental setup associated to the capabilities of an in-house developed image processing software allowed the reconstruction of the trajectories of almost all filaments within different yarn specimens. Various structural information are derived from these trajectories, dealing in particular with the orientation of individual segments of filaments with respect either to the ply trajectory or to the yarn axis. Compared to orientation distributions provided by different analytical models available in the literature, those resulting from reconstructed trajectories show similar global trends, while providing more details in peripheral regions and regions close to contact zones between plies. Maps of radial and spatial distributions of orientations provide a comprehensive representation of how filaments are oriented within the plies, which gives valuable insight into the inner structural arrangement of fibers which is one of the sources of nonlinearities in the mechanical behavior of filament yarns.