Browsing by Author "Dr. Eunkyoung Shim, Committee Member"

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    The Influence of Staple Fiber Preparatory Equipment on Web Quality
    (2008-06-28) Moore, Emily Alexandra; Dr. William Oxenham, Committee Chair; Dr. Eunkyoung Shim, Committee Member; Dr. Donald Shiffler, Committee Member
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    An Investigation on Fluid Flow in Fibrous Materials via Image-Based Fluid Dynamics Simulations
    (2009-11-03) Jaganathan, Sudhakar; Dr. Joel Pawlak, Committee Member; Dr. Behnam Pourdeyhimi, Committee Co-Chair; Dr. Eunkyoung Shim, Committee Member; Dr. William Oxenham, Committee Member; Dr. David Dickey, Committee Member; Dr. Hooman Vahedi Tafreshi, Committee Co-Chair
    While there are a large number of analytical studies dedicated to developing permeability equations for a 2-D and 3-D models of fibrous disordered structures, there are only few numerical work that compares these models with real counterparts. For the first time, we present a series of numerical simulations performed on real fibrous media obtained via Digital Volumetric Imaging technique. An efficient procedure is presented for reconstructing 3-D images from the 2-D images of real fibrous media and processing them (meshing them) for performing fluid flow simulations. Permeability values obtained from these simulations are compared with those obtained from analytical equations given in the literature. We also present two scale modeling technique to predict macro scale permeability of fibrous structures. Second part of this thesis deals with unsaturated flow through the fibrous media. We start our study by computing the pore size distribution of typical hydroentangled nonwoven materials and present a theoretical model for their geometric pore size distributions based on Poisson line network model of the fibrous media. We also study connectivity of the pore space in fibrous media by computing and comparing the accessible and allowed pore volumes in the form of access function graphs. We also present a novel image-based technique to study the changes in the pore size distribution of a fibrous material exposed to compressive load. A combined micro- and macroscale modeling is presented to simulate the fluid infiltration in fibrous media. The Richards’ equation of two-phase flow in porous media is used here to model the fluid absorption in un-saturated fibrous thin sheets. The required consecutive equations, relative permeability and capillary pressure as functions of medium’s saturation, are obtained via microscale modeling and long column experiment, respectively. The Richards’ equation together with the above consecutive correlations is simultaneously solved for fibrous media inclined with different angles. To validate our simulations, we compared our numerical results with those of our long column experiment and observed good agreement.
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    Mechanisms in Bicomponent Fiber Spinning During Melt Blown Process
    (2009-02-23) Zapletalova, Terezie; Dr. Saad Khan, Committee Member; Dr. Stephen Michielsen, Committee Member; Dr. Eunkyoung Shim, Committee Member; Dr. Jan Genzer, Committee Co-Chair; Dr. Behnam Pourdeyhimi, Committee Chair
    ZAPLETALOVA, TEREZIE. Mechanisms in Bicomponent Fiber Spinning During Melt Blown Process (Under the direction of Dr. Behnam Pourdeyhimi and Dr. Jan Genzer) A series of melt blown bicomponent webs made with various grades of polypropylene and polyethylene were evaluated in terms of influence of process and polymer properties on fiber morphology and web mechanical properties. This study utilized full quadratic model with continuous factors of temperature and component ratio. We were able to obtain the effects these parameters on fiber and substrate properties with high statistical significance. Overall fiber crystallinity content as well as crystallinity content of each separate component can be well explained linked with a high degree of confidence to the processing temperature, component ratio, and several polymer component properties, including, enthalpy of melting, zero shear viscosity, activation energy of flow, and highest crystallization rate temperature. Fabric mechanical properties can also be correlated with the same structural parameters. Bicomponent fiber diameter could not be satisfactorily explained in terms of the same parameters, which indicates that there is another mechanism not described by the studied process and polymer data that largely influences substrate fiber diameter.