In a fiber spinning process molten polymer is
extruded into a fiber. The resulting fiber known
as as-spun fiber is relatively weak and shows 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
ratio. 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.
| Identifer | oai:union.ndltd.org:GATECH/oai:smartech.gatech.edu:1853/11475 |
| Date | 18 May 2006 |
| Creators | Vohra, Sanjay |
| Publisher | Georgia Institute of Technology |
| Source Sets | Georgia Tech Electronic Thesis and Dissertation Archive |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
| Format | 4929903 bytes, application/pdf |
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