1. Inicio
  2. Atrás
Título: Theory and simulation of texture selection mechanisms in mesophase carbon fibers
Autores: Sharma, Dinesh, 1972-
Fecha: 2003
Publicador: McGill University - MCGILL
Fuente:
Tipo: Electronic Thesis or Dissertation
Tema: Engineering, Chemical.
Descripción: Carbon fiber precursors are spun from carbonaceous mesophases using standard melt spinning techniques. These melt spun carbon fibers exhibit a multitude of cross sectional fiber textures. The two widely reported textures in literature are planar radial (PR) and planar polar (PP). This thesis uses a mesoscopic model, based on the classical Landau de-Gennes theory of liquid crystals and adapted here to carbonaceous mesophases, to study the steady state and transient phenomena involved in the mesophase carbon fiber texture formation. The model is successfully able to capture the microstructure and the formation of the PR and PP textures. A phase diagram for classical PR and PP textures has been constructed cylindrical carbon fibers in terms of temperature and fiber radius, thus estabilishing the processing conditions and geometric factors that lead to the selection of these textures. The multi-path formation process of the planar polar texture through defect splitting, direct planar polar formation, and defect annihilation has been thoroughly characterized. A detailed analysis of defect core structure for defects of strengths s = +1 and s = +1/2 has be undertaken. The effect of various parameters namely temperature, elastic anisotropy, and fiber radii on the defect core structures of commonly observed fiber textures has been studied. The model is well suited for studying the defect core textures which are in the nano range and could be applied to the new emerging field of nano fibers. The results of this thesis provide us with knowledge for optimization and control of mesophase carbon fiber texture, and lay the ground work for the study of nano scale phenomena in nano fibers.
Idioma: en