A Mechanics Framework for Modeling Fiber Deformation on Draw Rollers and Freespans
In a fiber spinning process molten polymer is extruded into a fiber. The resulting fiber known as as-spun fiber is relatively weak and ahows a large plastic central zone in its constitutive behavior. As a result the fiber deforms substantially without a significant change in load thus making it unsuitable for stress bearing applications. The range of plastic deformation is related to the natural draw ration. In order to improve the mechanical properties of as spun fibers, fiber spinning is followed by a fiber draw process. With multi stage draw the as-spun fiber is drawn beyond the plastic region in various drawing zones which produces greater orientation of the polymer chains in the axial direction of the fiber thus enhancing mechanical strength characteristics of the fiber. The multistage draw process consists of several rollers each rotating at a speed greater than the one prior to it.
The objective of this work is to develop a first approximation to model fiber draw in the multistage drawing process, with and without a draw pin. As the first step the slippage of fibers on rollers was analysed by including centrifugal acceleration and acceleration due to stretching. The draw in a free span is also modelled. Several representative draw processes were examined. It was found draw pin localizes the draw significantly although the resulting mechanical unloading complicates the analysis. Draw in the free span is impossible for isothermal draw processes, and anisothermal draw induces thermal unloading in the system. A comprehensive analysis of various draw processes will be examined.
Advisor:Karl I. Jacob; Youjiang Wang; Mary Lynn Realff; Arun Gokhale; Rami Haj-Ali
School:Georgia Institute of Technology
School Location:USA - Georgia
Source Type:Master's Thesis
Keywords:polymer textile fiber engineering
Date of Publication:05/18/2006