Scholarly Works, Materials Science and Engineering (MSE)

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Research articles, presentations, and other scholarship

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Browsing Scholarly Works, Materials Science and Engineering (MSE) by Department "Mathematics"

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    First-principles study of several hypothetical silica framework structures
    Teter, D. M.; Gibbs, Gerald V.; Boisen, Monte B. Jr.; Allan, D. C.; Teter, M. P. (American Physical Society, 1995-09-15)
    Several hypothetical silica structures have been generated using a simulated-annealing strategy with an ab initio based covalent-bonding potential. First-principles total-energy pseudopotential methods have been used to examine several. promising hypothetical structures and to compare their structural parameters, cohesive energies, and bulk moduli with those of low quartz;, low cristobalite, silica sodalite, and stishovite. The cohesive energies of these hypothetical structure types are found to be equivalent to those of low quartz, low cristobalite, and silica sodalite, and significantly lower than that of stishovite.
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    Using startup of steady shear flow in a sliding plate rheometer to determine material parameters for the purpose of predicting long fiber orientation
    Ortman, Kevin; Baird, Donald G.; Wapperom, Peter; Whittington, Abby R. (AIP Publishing, 2012-07-01)
    The properties of long glass fiber reinforced parts, such as those manufactured by means of injection molding and compression molding, are highly dependent on the fiber orientation generated during processing. A sliding plate rheometer was used to understand the transient stress and orientation development of concentrated long glass fibers during the startup of steady shear flow. An orientation model and stress tensor combination, based on semiflexible fibers, was assessed in its ability to predict fiber orientation when using model parameters obtained from the fits of the stress responses. Specifically, samples of different initial fiber orientations was subjected to the startup of steady shear flow, and an orientation model based on bead and rod theory was coupled with a derived stress tensor that accounts for the semiflexibility of the fibers to obtain the corresponding model parameters. The results showed the semiflexible orientation model and stress tensor combination, overall, provided improved rheological results as compared to the Folgar-Tucker model when coupled with the stress tensor of Lipscomb et al. [J. Non-Newtonian Fluid Mech. 26, 297-325 (1988)]. Furthermore, it was found that both stress tensors required empirical modification to accurately fit the measured data. Finally, orientation models provided encouraging results when predicting the transient fiber orientation for all initial fiber orientations explored. (C) 2012 The Society of Rheology. [http://dx.doi.org/10.1122/1.4717496]