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.

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    DESIGN AND PERFORMANCE EXPLORATION OF A SCALED-UP MILLIGRAM-SCALE FLAME CALORIMETER
    (2024) Cromwell Reed, Kyra; Raffan-Montoya, Fernando; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Fire causes thousands of lost lives and injuries, as well as billions of dollars of property damage, each year. It is critical to understand the fire hazard associated with materials used in the built environment. One method to evaluate the flammability properties of a material is through bench- scale and milligram-scale testing with apparatus such as the Milligram-Scale Flame Calorimeter (MFC). The MFC has previously been used to test samples ranging from 30 mg – 50 mg in mass. The small samples were useful for testing materials under development or materials cost prohibitive to test at larger sizes, but presented some difficulties in testing, including in sample preparation and as inconsistency in the results of testing on inhomogeneous materials. Furthermore, the small size of the MFC caused difficulty in heater manufacturing, requiring laborious by-hand construction. The size of the MFC crucible and apparatus was increased in this work to allow testing on larger sample masses, ranging in size from 90 mg – 150 mg, and for the exploration of five alternate heater manufacturing techniques. The MFC was rebuilt with a larger heater and optimized to create the best possible test conditions for this work. Tests were conducted on five polymers: polymethyl methacrylate (PMMA), polyethylene (PE), polyvinyl chloride (PVC), and polyether ether ketone (PEEK), and on a wood-based material: oriented strand board (OSB). The tests showed general consistency when materials were tested at different sample masses and sample presentations. The results for the heat release rate and heat of combustion of the materials also aligned well with testing conducted using the previous version of the MFC apparatus. The updates to the MFC conducted in this work constitute an improvement to the versatility of the apparatus, allowing for testing on larger sample masses, but future work is needed to resolve flow and exhaust issues that caused some inconsistency in the test results and to further explore and develop alternate heater manufacturing techniques.
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    DEVELOPMENT OF A PYROLYSIS MODEL FOR ORIENTED STRAND BOARD
    (2021) Zhou, Hongen; Stoliarov, Stanislav I.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Oriented Strand Board (OSB) is a widely used construction material responsible for a substantial portion of the fire load of many buildings. To accurately model the response of OSB to fire, Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Microscale Combustion Calorimetry (MCC) tests were carried out to construct a thermal decomposition model using a numerical solver, ThermaKin2Ds, and a hill climbing (HC) optimization algorithm. The model was determined to consist of two distinct processes. The first process is a single step water vaporization. The second process is a chain of four consecutive reactions representing thermal decomposition of the organic constituents of OSB. The experiments and modeling revealed that the first two of the four reactions are endothermic, while the last two are exothermic, and that the net heat of decomposition is near zero. The heat capacities of condensed-phase species and heats of combustion of evolved gases were also determined from inverse modeling of the DSC and MCC tests, respectively. Controlled Atmosphere Pyrolysis Apparatus II (CAPA II) experiments were performed at 35 kW m-2 and 65 kW m-2 of the radiant heat flux. The sample bottom temperature data obtained at 65 kW m-2 were used to determine the thermal conductivities of condensed-phase species. The complete pyrolysis model of OSB was subsequently validated by comparing the experimental CAPA II mass loss rate profiles with the model predictions. The undecomposed OSB density was found to vary both along the sheet surface and through thickness. However, these density variations had only a minor impact on the key features of the mass loss rate profiles.