Simulation and Experimental Measurement of Liquid Crystal Polymer Directionality During Melt Processing
Sullivan, Anthony.
2019
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Liquid crystal
polymers (LCPs) comprise a class of high-performance, melt-processable materials that
have historically fallen short of widespread adoption in industry due to their
anisotropic bulk behavior. The anisotropy is a direct result of the unique polymer
microstructure, and the ability to predict the polymer morphology generated during
manufacturing is essential to isotropic material ... read moreprocess design. This dissertation
presents the implementation of a practical modeling tool to simulate the evolution of
LCP directionality during melt processing. The hybrid methodology leverages commercial
CFD software to first simulate the polymer flow through full-scale processing
geometries, followed by post-processing calculations to predict the orientation state of
the director field. Parallel investigations of LCP directionality during injection
molding and cast film extrusion are presented to demonstrate the robustness of the
modeling tool across two common melt processing methods. Wide-angle x-ray scattering
(WAXS) is used to experimentally validate the orientation states predicted by the model,
and mechanical, thermal and dielectric material testing confirm the strong dependence of
macroscopic behavior on the polymer microstructure. Comparison of simulations and WAXS
verify the ability to not only predict bulk orientation, but also the intricacies of the
hierarchal structure, specifically the skin and core morphologies, and their relative
amounts. Furthermore, the full suite of simulations, WAXS, and material testing
elucidate the LCP structure-property-processing relationships that are critical to
driving isotropic material process design.
Thesis (Ph.D.)--Tufts University, 2019.
Submitted to the Dept. of Mechanical Engineering.
Advisors: Michael Zimmerman, and Anil Saigal.
Committee: Ayse Asatekin, and Jay Whitacre.
Keywords: Mechanical engineering, and Materials Science.read less - ID:
- xp68kv59t
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