Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

Browse

Filters

2014 - 20162

Settings

Author: search.filters.author.Nixon, Jason RobertSubject: search.filters.subject.Engineering

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Structure dependencies for multiscale polymer composites using extrusion processes
    (2016) Nixon, Jason Robert; Bigio, David I; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Multiscale reinforcement, using carbon microfibers and multi-walled carbon nanotubes, of polymer matrix composites manufactured by twin-screw extrusion is investigated for enhanced mechanical and thermal properties with an emphasis on the use of a diverging flow in the die for fluid mechanical fiber manipulation. Using fillers at different length scales (microscale and nanoscale), synergistic combinations have been identified to produce distinct mechanical and thermal behavior. Fiber manipulation has been demonstrated experimentally and computationally, and has been shown to enhance thermal conductivity significantly. Finally, a new physics driven predictive model for thermal conductivity has been developed based on fiber orientation during flow, which is shown to successfully capture composite thermal conductivity.
  • Thumbnail Image
    Item
    New Measures for the Study of Distributive Mixing in Continuous Creeping Flows
    (2014) Nixon, Jason Robert; Bigio, David I; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    New mathematical measures are developed for the investigation of fluid-fluid mixing in continuous laminar flows as a function of mechanisms of mixing, namely the eigenvectors of the rate of deformation tensor. Previous theoretical work in this field has shown that interfacial reorientation and chaotic advection produce improved mixing over deterministic mixing. However, these previous approaches have failed to explore the nature of the mechanisms of mixing present in the continuously spatially varying flow fields. Four new measures are presented to relate the deformation of an infinitesimal material element to the eigenvectors of the rate of deformation tensor. These expressions characterize material deformation as a function of the spatial relationship between material and the eigenvectors in a variety of general flows. The application of these measures is shown using CFD simulations for three steady flows, the Couette channel, the diverging channel, and the steady state lid driven cavity. These measures improve the understanding of mixing in the various flow field models and produce new insight into the nature of mixing in continuous flow fields.