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Title: Sustainable Material Solution for Flexible Pavements; Performance Evaluation and Impact Assessment of Utilizing Multiple Recycled Materials in HMA.
Creator: Golestani, Behnam, Nam, Boo Hyun, Chopra, Manoj, Tatari, Omer, Bai, Yuanli, University of Central Florida
Abstract / Description: The demand for pollution-free and recyclable engineering materials has been increased as the cost of energy and environmental concerns have risen. Green material design can lead to better environmental quality and sustainability of civil infrastructure. Road construction is one of the largest consumers of natural resources. Beneficial utilization of recycled materials can result in an important opportunity to save the mining and use of virgin materials, to preserve energy, and to save...
Show moreThe demand for pollution-free and recyclable engineering materials has been increased as the cost of energy and environmental concerns have risen. Green material design can lead to better environmental quality and sustainability of civil infrastructure. Road construction is one of the largest consumers of natural resources. Beneficial utilization of recycled materials can result in an important opportunity to save the mining and use of virgin materials, to preserve energy, and to save landfill space. Two main research questions addressed in this study are: (1) How much pollution, energy, natural resources, time and money can be salvaged by applying recycling materials to Hot-Mix Asphalt (HMA)?, (2) What are the optimum mix designs for those recycled materials in HMA?, and (3) Can multiple recycled materials be used at the same time to compensate each other's drawbacks? This study evaluates the structural performance and environmental-economical cost and benefit by substituting one or a combination of three recycled materials in HMA. The three recycled materials are Recycled Asphalt Shingle (RAS), Municipal Solid Waste Incineration (MSWI) Bottom Ash, and Recycled Concrete Aggregate (RCA). Performance evaluation of the HMA including those recycled materials has been performed by a series of laboratory experimental tests while the environmental impact was investigated by the Life Cycle Assessment (LCA). In addition, Life Cycle Cost Analysis (LCCA) method has been employed to evaluate the benefit of the aforementioned recycled materials.In 2008, the Florida Legislature established a new statewide recycling goal of 75% to be achieved by the year 2020. The impact of this research aligns with this policy as it introduces a sustainable HMA that reduces the necessity of virgin aggregate and asphalt binder to 50% and 20%, respectively. In terms of environmental and economic impacts, in comparison with the regular HMA, it generates 25% less greenhouse gas emission, and for a period of 20 years, the cost of construction and maintenance would be 65% less.
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Date Issued: 2015
Identifier: CFE0005798, ucf:50038
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005798

Title: Beneficial Utilization of Municipal Solid Waste Incineration Ashes as Sustainable Road Construction Materials.
Creator: Tasneem, Kazi, Nam, Boo Hyun, Chopra, Manoj, Reinhart, Debra, Sohn, Yongho, University of Central Florida
Abstract / Description: Incineration of municipal solid waste (MSW) is common for energy recovery, and management of municipal solid waste incineration (MSWI) ashes has received a growing attention around the world. In the U.S., generation of MSW has increased up to 65% since 1980, to the current level of 251 million tons per year with 53.8% landfilled, 34.5% recycled and composted, and 11.7% incinerated with energy recovery. In the process of incineration, MSWI ash is being produced as byproducts; about 80 to 90%...
Show moreIncineration of municipal solid waste (MSW) is common for energy recovery, and management of municipal solid waste incineration (MSWI) ashes has received a growing attention around the world. In the U.S., generation of MSW has increased up to 65% since 1980, to the current level of 251 million tons per year with 53.8% landfilled, 34.5% recycled and composted, and 11.7% incinerated with energy recovery. In the process of incineration, MSWI ash is being produced as byproducts; about 80 to 90% of the MSWI ash is bottom ash (BA) and 10 to 20% is fly ash (FA) by weight. The current practice of the U.S. is to combine both BA and FA to meet the criteria to qualify as non-hazardous, and all combined ashes are disposed in landfills.European countries have utilized MSWI BA as beneficial construction materials by separating it from FA. The FA is mostly limited to landfill disposal as hazardous material due to its high content of toxic elements and salts. BA has been actively recycled in the areas of roadbed, asphalt paving, and concrete products in many of European and Asian countries. In those countries, recycling programs (including required physical properties and environmental criteria) of ash residue management have been developed so as to encourage and enforce the reuse of MSWI ashes instead of landfill disposal. Moreover, many studies have demonstrated the beneficial use of MSWI ashes as engineering materials with minimum environmental impacts.On the other hand, the U.S. has shown a lack of consistent and effective management plans, as well as environmental regulations for the use of MSWI ashes., Due to persistent uncertainty of engineering properties and inconsistency in the Federal and State regulations in the U.S., however, the recycling of the MSWI ashes has been hindered and they are mostly disposed in landfills.In this research work, current management practice, existing regulations, and environmental consequences of MSWI ashes utilization are comprehensively reviewed worldwide and nationwide with an emphasis of the potential area of its utilization in asphalt paving and concrete product. This research also entails a detailed chemical and microstructural characterization of MSWI BA and FA produced from a Refuse Derived Fuel (RDF) facility in Florida so that the MSWI ash is well characterized for its beneficial uses as construction materials.The material characterization includes Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray Diffraction (XRD) techniques. In addition, leaching experiments have been conducted to investigate the environmental properties (e.g. leachate concentration) of BA and ash-mixed hot mix asphalt (HMA) and Portland cement concrete (PCC). Leaching results reveals the reduced leaching potential of toxic material from MSWI ashes while incorporated in HMA and PCC. Lastly, a preliminary experimental approach has been devised for the vitrification of FA which is a promising thermal process of transferring material into glassy state with higher physical and chemical integrity to reduce toxicity so that utilization of FA can be possible.
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Date Issued: 2014
Identifier: CFE0005425, ucf:50404
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005425

Title: Multimaterial Fibers and Tapers A Platform for Nonlinear Photonics and Nanotechnology.
Creator: Shabahang, Soroush, Abouraddy, Ayman, Vanstryland, Eric, Dogariu, Aristide, Belfield, Kevin, University of Central Florida
Abstract / Description: The development of optical sources and components suitable for the mid-infrared is crucial for applications in this spectral range to reach the maturity level of their counterparts in the visible and near-infrared spectral regimes. The recent commercialization of quantum cascade lasers is leading to further interest in this spectral range. Wideband mid-infrared coherent sources, such as supercontinuum generation, have yet to be fully developed. A mid-infrared supercontinuum source would allow...
Show moreThe development of optical sources and components suitable for the mid-infrared is crucial for applications in this spectral range to reach the maturity level of their counterparts in the visible and near-infrared spectral regimes. The recent commercialization of quantum cascade lasers is leading to further interest in this spectral range. Wideband mid-infrared coherent sources, such as supercontinuum generation, have yet to be fully developed. A mid-infrared supercontinuum source would allow for unique applications in spectroscopy and sensing.Over the last decade, it has been shown that high-index confinement in highly nonlinear fibers pumped with high-peak-power pulses is an excellent approach to supercontinuum generation in the visible and near-infrared. Nonlinear waveguides such as fibers offer an obvious advantage in increasing the nonlinear interaction length maintained with a small cross section. In addition, fiber systems do not require optical alignment and are mechanically stable and robust with respect to the environmental changes. These properties have made fiber systems unique in applications where they are implemented in a harsh and unstable environment.In extending this approach into the mid-infrared, I have used chalcogenide glass fibers. Chalcogenide glasses have several attractive features for this application: they have high refractive indices for high optical-confinement, have a wide transparency window in the mid-infrared, and have a few orders-of-magnitude higher nonlinearity than silica glass and other mid-IR glasses. Producing chalcogenide glass fiber tapers offer, furthermore, the possibility of dispersion control and stronger field confinement and hence higher nonlinearity, desired for supercontinuum generation.
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Date Issued: 2014
Identifier: CFE0005252, ucf:50594
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005252

Title: APPLICATION OF ABSORPTIVE TREATMENTS ON TRAFFIC NOISE BARRIERS IN FLORIDA.
Creator: Chua, Chin Boon, Wayson, Roger, University of Central Florida
Abstract / Description: In this thesis, the parallel barrier analysis feature in the Federal Highway Administration Traffic Noise Model (FHWA TNM), which is based on RAYVERB was used to explore the effects of multiple reflections due to single and parallel barriers and the use of absorptive treatment. Database was developed from the data collected from previous research efforts was used to generate a best fit equation model that can be used as a predetermining tool to determine the magnitude of parallel barrier...
Show moreIn this thesis, the parallel barrier analysis feature in the Federal Highway Administration Traffic Noise Model (FHWA TNM), which is based on RAYVERB was used to explore the effects of multiple reflections due to single and parallel barriers and the use of absorptive treatment. Database was developed from the data collected from previous research efforts was used to generate a best fit equation model that can be used as a predetermining tool to determine the magnitude of parallel barrier insertion loss. The best fit equation model was then used to test against measured/model result and TNM prediction results for its validity. Absorptive materials were also studied such that 3 top of them were selected and recommended for Florida highway barrier use. It was found that the top three absorptive treatments for use on Florida highway barriers have been determined to be cementitous material, metal wool and glass fiber. These materials can be used to reduce the sound reflections for single and parallel barriers. The developed best fit equation model from this research is Deg = -2.17NRC - CW0.42 + 1.97eln(BH) + RH0.29 + DBB0.27; the prediction results give moderately high R2 value of 0.55 if compared to the results from database. Prediction results from best fit equation model was also found to be consistent with the results from the measure/modeled results, providing further proof of the validity of the model. However, if compared results from equation model, TNM and measured/model (measured and model compared results using ANSI method), TNM was shown to provide higher insertion loss degradation. It was found that the most effective placement of absorptive material was the pattern which covers the barrier from the bottom up; it was also found that only about 60% from the bottom of the barrier area requires covering with high NRC absorptive treatment (NRC greater than 0.8) without sacrificing insertion loss. Also, if the barrier area near the top includes an easily obtainable NRC value of 0.4, only 40% to 50% of the bottom barrier needs absorptive treatment with a higher, more expensive NRC rating. These findings can substantially reduce the cost of conventional absorptive barrier which have full coverage of high NRC absorptive treatment. This research has begun important improvements in noise barrier design, additional work can be continued to further verify all the findings in this thesis such that easier and better equation model can be developed to calculate insertion loss degradation and cheaper absorptive barrier with less absorptive material usage can be built.
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Date Issued: 2004
Identifier: CFE0000008, ucf:46127
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000008

Title: TEMPORAL TRENDS IN GRAVE MARKER ATTRIBUTES: AN ANALYSIS OF HEADSTONES IN FLORIDA.
Creator: Reynolds, Patrisha, Schultz, Ph.D., John J., University of Central Florida
Abstract / Description: Grave markers reflect a wealth of information and collectively epitomize society's historic, social, and economic patterns over time. Despite an abundance of cemetery research in other parts of the country, little research has been undertaken to evaluate grave marker attributes in Florida. The purpose of this research was to determine how grave marker attributes have changed over time in north-central, central, and southeast Florida. Data were collected from ten cemeteries in five counties in...
Show moreGrave markers reflect a wealth of information and collectively epitomize society's historic, social, and economic patterns over time. Despite an abundance of cemetery research in other parts of the country, little research has been undertaken to evaluate grave marker attributes in Florida. The purpose of this research was to determine how grave marker attributes have changed over time in north-central, central, and southeast Florida. Data were collected from ten cemeteries in five counties in Florida, representing the grave markers of over 1,100 individuals. Data collection involved visiting each cemetery, photographing markers, and cataloging grave marker attributes. Attributes analyzed included marker type, marker material, epitaphs, iconographic images, memorial photographs, footstones, and kerbs. A number of important trends were noted. Marker material exhibited the clearest example of a temporal trend, shifting over time from 73% marble to 73% granite. Marker type varied greatly from upright and flat ground markers to a variety of customized markers and vaults. Cultural differences were also noted with in-ground vaults dominating traditionally black cemeteries. There were clear differences in marker style between affluent and less affluent cemeteries, with numerous hand-cast cement markers observed in less prosperous areas. Furthermore, beginning in the early 1980's there is an increase in customized laser engraved markers. Overall, Florida's cemeteries offer a rich history of the state's mortuary practices and further research should be conducted to preserve this history.
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Date Issued: 2012
Identifier: CFH0004240, ucf:44918
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004240

Title: PERCEPTIONS OF THE CONSUMPTION OF SEXUALLY-EXPLICIT MATERIAL AS AN ACT OF INFIDELITY IN THE CONTEXT OF COLLEGE ROMANTIC RELATIONSHIPS AND THEIR CONNECTION TO POPULATION VARIABLES.
Creator: Plaza, Diego, Negy, Charles, University of Central Florida
Abstract / Description: This study sought to examine whether individuals perceive the consumption (i.e., viewing) of sexually-explicit material (SEM) as an act of infidelity. The study also looked into whether ethnicity, sexual orientation, religiosity, self-esteem, and femininity/masculinity influence this opinion. As an extension of the study, the participants' susceptibility for jealousy, general attitudes toward infidelity, attitudes toward SEM, opinion toward sexuality, and fear of abandonment were also...
Show moreThis study sought to examine whether individuals perceive the consumption (i.e., viewing) of sexually-explicit material (SEM) as an act of infidelity. The study also looked into whether ethnicity, sexual orientation, religiosity, self-esteem, and femininity/masculinity influence this opinion. As an extension of the study, the participants' susceptibility for jealousy, general attitudes toward infidelity, attitudes toward SEM, opinion toward sexuality, and fear of abandonment were also analyzed. Social desirability was also used to find people's tendency to give socially desirable answers to questions related to sexuality. A statistical analysis of the study's results showed that religiosity significantly predicted opinions toward SEM as an act of infidelity. All other demographic values did not have significant predictability. An exploratory analysis showed that participants who think that viewing SEM is an acceptable behavior, are sexually liberal, use the internet for sexual purposes, and are less inclined to suffer jealousy in relationships were the most likely to believe that viewing SEM is not an act of infidelity.
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Date Issued: 2012
Identifier: CFH0004192, ucf:44846
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004192

Title: TERTIARY CREEP DAMAGE MODELING OF A TRANSVERSELY ISOTROPIC NI-BASED SUPERALLOY.
Creator: Stewart, Calvin, Gordon, Ali, University of Central Florida
Abstract / Description: Anisotropic tertiary creep damage formulations have become an increasingly important prediction technique for high temperature components due to drives in the gas turbine industry for increased combustion chamber exit pressures, temperature, and the use of anisotropic materials such as metal matrix composites and directionally-solidified (DS) Ni-base superalloys. Typically, isotropic creep damage formulations are implemented for simple cases involving a uniaxial state of stress; however,...
Show moreAnisotropic tertiary creep damage formulations have become an increasingly important prediction technique for high temperature components due to drives in the gas turbine industry for increased combustion chamber exit pressures, temperature, and the use of anisotropic materials such as metal matrix composites and directionally-solidified (DS) Ni-base superalloys. Typically, isotropic creep damage formulations are implemented for simple cases involving a uniaxial state of stress; however, these formulations can be further developed for multiaxial states of stress where materials are found to exhibit induced anisotropy. In addition, anisotropic materials necessitate a fully-developed creep strain tensor. This thesis describes the development of a new anisotropic tertiary creep damage formulation implemented in a general-purpose finite element analysis (FEA) software. Creep deformation and rupture tests are conducted on L, T, and 45°-oriented specimen of subject alloy DS GTD-111. Using the Kachanov-Rabotnov isotropic creep damage formulation and the optimization software uSHARP, the damage constants associated with the creep tests are determined. The damage constants, secondary creep, and derived Hill Constants are applied directly into the improved formulation. Comparison between the isotropic and improved anisotropic creep damage formulations demonstrates modeling accuracy. An examination of the off-axis creep strain terms using the improved formulation is conducted. Integration of the isotropic creep damage formulation provides time to failure predictions which are compared with rupture tests. Integration of the improved anisotropic creep damage produces time to failure predictions at intermediate orientations and any state of stress. A parametric study examining various states of stress, and materials orientations is performed to verify the flexibility of the improved formulation. A parametric exercise of the time to failure predictions for various levels of uniaxial stress is conducted.
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Date Issued: 2009
Identifier: CFE0002918, ucf:48012
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002918

Title: Touching the Unreal: The Definition, Narrative Strategies, and Aesthetics of 3D Cartoon Narratives.
Creator: Snow, Nathan, Mauer, Barry, Applen, JD, Grajeda, Anthony, Larsen, Darl, University of Central Florida
Abstract / Description: (")Touching the Unreal(") follows the structure set out by Scott McCloudin Understanding Comics to argue that understanding cartoons is serious business and requires that we define the art form, outline its basic tenets, and theorize how the mind understands it. The dissertation argues for a new definition of 3D computer generated cartoons, beginning with the most basic definition applicable to all forms of animation and taking into account new technological developments before arriving at...
Show more(")Touching the Unreal(") follows the structure set out by Scott McCloudin Understanding Comics to argue that understanding cartoons is serious business and requires that we define the art form, outline its basic tenets, and theorize how the mind understands it. The dissertation argues for a new definition of 3D computer generated cartoons, beginning with the most basic definition applicable to all forms of animation and taking into account new technological developments before arriving at the 3D cartoon narratives of today. The dissertation outlines the basic facets of 3D cartoon narratives in terms of narrative and aesthetics, arguing that, in spite of the technological changes required to produce the art form, narrative strategies have not changed significantly from 2D to 3D cartoon narratives. Rather, the 3D cartoon narrative aesthetic is focused primarily on synthetic, sculptural materiality to create a tactile, haptic viewing experience unavailable in any other form of animation. The dissertation advances theories of how the mind understands 3D cartoon narratives, starting with how these films guide the spectator to pre-determined conclusions based on character identification, flow theory, and mirror-neuron cognition. As a result of their narrative, aesthetics, and reception, these films constitute a new form of posthumanism and operate as a node in the modern viewer's web of distributed cognition, enchanting viewers through the ability to touch the unreal, synthetic images common to the modern world. (")Touching the Unreal(") contributes to the media field by providing a definition for 3D computer animation in all of its facets as genre, narrative, aesthetics, and ideology.
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Date Issued: 2018
Identifier: CFE0007101, ucf:51962
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007101

Title: Artificial Neuron using MoS2/Graphene Threshold Switching Memristor.
Creator: Kalita, Hirokjyoti, Roy, Tania, Sundaram, Kalpathy, Yuan, Jiann-Shiun, University of Central Florida
Abstract / Description: With the ever-increasing demand for low power electronics, neuromorphic computing has garnered huge interest in recent times. Implementing neuromorphic computing in hardware will be a severe boost for applications involving complex processes such as pattern recognition. Artificial neurons form a critical part in neuromorphic circuits, and have been realized with complex complementary metal(-)oxide(-)semiconductor (CMOS) circuitry in the past. Recently, insulator-to-metal-transition (IMT)...
Show moreWith the ever-increasing demand for low power electronics, neuromorphic computing has garnered huge interest in recent times. Implementing neuromorphic computing in hardware will be a severe boost for applications involving complex processes such as pattern recognition. Artificial neurons form a critical part in neuromorphic circuits, and have been realized with complex complementary metal(-)oxide(-)semiconductor (CMOS) circuitry in the past. Recently, insulator-to-metal-transition (IMT) materials have been used to realize artificial neurons. Although memristors have been implemented to realize synaptic behavior, not much work has been reported regarding the neuronal response achieved with these devices. In this work, we study the IMT in 1T-TaS2 and the volatile threshold switching behavior in vertical-MoS2 (v-MoS2) and graphene van der Waals heterojunction system. The v-MoS2/graphene threshold switching memristor (TSM) is used to produce the integrate-and-fire response of a neuron. We use large area chemical vapor deposited (CVD) graphene and MoS2, enabling large scale realization of these devices. These devices can emulate the most vital properties of a neuron, including the all or nothing spiking, the threshold driven spiking of the action potential, the post-firing refractory period of a neuron and strength modulated frequency response. These results show that the developed artificial neuron can play a crucial role in neuromorphic computing.
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Date Issued: 2018
Identifier: CFE0007203, ucf:52291
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007203

Title: Synthetic Design and Characterization of Polycyclic Aromatic Compounds in Molecular and Extended System.
Creator: Pour, Gavin, Belfield, Kevin, Frazer, Andrew, Elsheimer, Seth, University of Central Florida
Abstract / Description: The work presented herein focuses on the synthesis and characterization of polycyclic aromatic compounds for a wide variety of toxicological, analytical, and electronic applications. First, the modular synthesis of 12 dibenzo- and naphtho- fluoranthene polycyclic aromatic hydrocarbons (PAHs) via a Pd-catalyzed five-membered ring closing procedure is discussed. By understanding the various modes through which the Pd migrates during transformation, structural rearrangements were bypassed,...
Show moreThe work presented herein focuses on the synthesis and characterization of polycyclic aromatic compounds for a wide variety of toxicological, analytical, and electronic applications. First, the modular synthesis of 12 dibenzo- and naphtho- fluoranthene polycyclic aromatic hydrocarbons (PAHs) via a Pd-catalyzed five-membered ring closing procedure is discussed. By understanding the various modes through which the Pd migrates during transformation, structural rearrangements were bypassed, obtaining regioselectivity through various redesigns in the synthetic route. Each compound in the serious was rigorously characterized via 1D/2D NMR, absorption and emission spectroscopy as well as cyclic voltammetry, which shows vast differences due to small structural changes between these constitutional isomers. Next, a series of polyphenylated organic ligands for zirconium metal organic frameworks is presented as materials for post-synthetic Scholl cyclodehydrogenation. Lastly, a series of organic linkers featuring covalently anchored redox-active pendants is explored for tuneable redox activity in Zr-based metal-organic frameworks. Thin-films were grown onto fluorine-doped tin-oxide glass electrodes and analyzed by cyclic voltammetry. This is the first reported pre-synthetic incorporation of covalently-bound ferrocenyl pendants into such a system. By attenuating the proportions of redox active and inactive links the oxidative peak currents could be tuned. This body of work represents a contribution toward the practical design and synthesis of polycyclic aromatic for a wide variety of analytical and electrochemical applications.
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Date Issued: 2019
Identifier: CFE0007512, ucf:52647
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007512

Title: Investigation on electrical properties of RF sputtered deposited BCN thin films.
Creator: Prakash, Adithya, Sundaram, Kalpathy, Yuan, Jiann-Shiun, Lin, Mingjie, University of Central Florida
Abstract / Description: The ever increasing advancements in semiconductor technology and continuous scaling of CMOS devices mandate the need for new dielectric materials with low-k values. The interconnect delay can be reduced not only by the resistance of the conductor but also by decreasing the capacitance of dielectric layer. Also cross-talk is a major issue faced by semiconductor industry due to high value of k of the inter-dielectric layer (IDL) in a multilevel wiring scheme in Si ultra large scale integrated...
Show moreThe ever increasing advancements in semiconductor technology and continuous scaling of CMOS devices mandate the need for new dielectric materials with low-k values. The interconnect delay can be reduced not only by the resistance of the conductor but also by decreasing the capacitance of dielectric layer. Also cross-talk is a major issue faced by semiconductor industry due to high value of k of the inter-dielectric layer (IDL) in a multilevel wiring scheme in Si ultra large scale integrated circuit (ULSI) devices. In order to reduce the time delay, it is necessary to introduce a wiring metal with low resistivity and a high quality insulating film with a low dielectric constant which leads to a reduction of the wiring capacitance.Boron carbon nitride (BCN) films are prepared by reactive magnetron sputtering from a B(&)#172;4C target and deposited to make metal-insulator-metal (MIM) sandwich structures using aluminum as the top and bottom electrodes. BCN films are deposited at various N2/Ar gas flow ratios, substrate temperatures and process pressures. The electrical characterization of the MIM devices includes capacitance vs. voltage (C-V), current vs voltage, and breakdown voltage characteristics. The above characterizations are performed as a function of deposition parameters.
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Date Issued: 2013
Identifier: CFE0004912, ucf:49625
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004912

Title: Theoretical Studies of Nanostructure Formation and Transport on Surfaces.
Creator: Aminpour, Maral, Rahman, Talat, Stolbov, Sergey, Roldan Cuenya, Beatriz, Blair, Richard, University of Central Florida
Abstract / Description: This dissertation undertakes theoretical and computational research to characterize and understand in detail atomic configurations and electronic structural properties of surfaces and interfaces at the nano-scale, with particular emphasis on identifying the factors that control atomic-scale diffusion and transport properties. The overarching goal is to outline, with examples, a predictive modeling procedure of stable structures of novel materials that, on the one hand, facilitates a better...
Show moreThis dissertation undertakes theoretical and computational research to characterize and understand in detail atomic configurations and electronic structural properties of surfaces and interfaces at the nano-scale, with particular emphasis on identifying the factors that control atomic-scale diffusion and transport properties. The overarching goal is to outline, with examples, a predictive modeling procedure of stable structures of novel materials that, on the one hand, facilitates a better understanding of experimental results, and on the other hand, provide guidelines for future experimental work. The results of this dissertation are useful in future miniaturization of electronic devices, predicting and engineering functional novel nanostructures. A variety of theoretical and computational tools with different degrees of accuracy is used to study problems in different time and length scales. Interactions between the atoms are derived using both ab-initio methods based on Density Functional Theory (DFT), as well as semi-empirical approaches such as those embodied in the Embedded Atom Method (EAM), depending on the scale of the problem at hand. The energetics for a variety of surface phenomena (adsorption, desorption, diffusion, and reactions) are calculated using either DFT or EAM, as feasible. For simulating dynamic processes such as diffusion of ad-atoms on surfaces with dislocations the Molecular Dynamics (MD) method is applied. To calculate vibrational mode frequencies, the infinitesimal displacement method is employed. The combination of non-equilibrium Green's function (NEGF) and DFT is used to calculate electronic transport properties of molecular devices as well as interfaces and junctions.
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Date Issued: 2013
Identifier: CFE0005298, ucf:50504
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005298

Title: 1, 2, and 3 Dimension Carbon/Silicon Carbon Nitride Ceramic Composites.
Creator: Calderon Flores, Jean, Zhai, Lei, Campiglia, Andres, Yestrebsky, Cherie, Zou, Shengli, Khondaker, Saiful, University of Central Florida
Abstract / Description: Polymer-derived ceramics (PDCs) are exceptional ultra-high temperature and stable multifunctional class of materials that can be synthesized from a polymer precursor through thermal decomposition. The presented research focuses on 1-D nanofibers, 2-D films and 3-D bulk, carbon-rich silicon carbon nitride (SiCN) ceramics. 1-D nanofibers were prepared via electrospinning for light weight, flame retardant and conductive applications. The commercially available CerasetTM VL20, a liquid...
Show morePolymer-derived ceramics (PDCs) are exceptional ultra-high temperature and stable multifunctional class of materials that can be synthesized from a polymer precursor through thermal decomposition. The presented research focuses on 1-D nanofibers, 2-D films and 3-D bulk, carbon-rich silicon carbon nitride (SiCN) ceramics. 1-D nanofibers were prepared via electrospinning for light weight, flame retardant and conductive applications. The commercially available CerasetTM VL20, a liquid cyclosilazane pre-ceramic precursor, was mixed with polyacrylonitrile (PAN) in order to make the cyclosilazane electrospinnable. Carbon-rich PDC nano?bers were fabricated by electrospinning various ratios of PAN/cyclosilazane solutions followed by pyrolysis. Surface morphology of the electro spun nanofibers characterized by SEM show PDC nano?bers with diameters ranging from 100-300 nm. Also, thermal stability towards oxidation showed a 10% mass loss at 623oC. 2-D carbon/SiCN films were produced by drop-casting a mixture of PAN/cyclosilazane onto a glass slide followed by pyrolysis of the film. Samples ranging from 10:1 to 1:10 PAN:cyclosilazane were made by dissolving the solutes into DMF to produce solutions ranging from 1% to 12% by weight. Green, heat-stabilized, and pyrolyzed 8% films were examined with FTIR to monitor the change in chemical structure at each step of the ceramization. SEM shows that high PAN samples produced films with ceramic embedded spheroid components in a carbon matrix, while high cyclosilazane samples produced carbon embedded spheroid.Finally, this research focuses on the challenge of making fully dense, 3-D bulk PDCs materials. Here we present a composite of SiCN with reduced graphene oxide (rGO) aerogels as a route for fully dense bulk PDCs. Incorporation of the rGO aerogel matrix into the SiCN has its pros and cons. While it lowers the strength of the composite, it allows for fabrication of large bulk samples and an increase in the electrical conductivity of the PDC. The morphology, mechanical, electrical properties and thermal conductivity of graphene-SiCN composite with varying rGO aerogel loading (0.3-2.4%) is presented. The high temperature stability, high electrical conductivity and low thermal conductivity of these composites make them excellent candidates for thermoelectric applications. Generally, carbon-rich SiCN composites with improved thermal and electrical properties are of great importance to the aerospace and electronics industries due to their expected harsh operating environments.
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Date Issued: 2015
Identifier: CFE0005768, ucf:50095
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005768

Title: CHEMICAL BATH DEPOSITION OF GROUP II-VI SEMICONDUCTOR THIN FILMS FOR SOLAR CELLS APPLICATIONS.
Creator: KHALLAF, HANI, Chow, Lee, University of Central Florida
Abstract / Description: Chemical bath deposition (CBD) is the analog in liquid phase of the well-known chemical vapor deposition technique in the vapor phase. In CBD, deposition of thin films takes place from aqueous solutions at low temperatures by a chemical reaction between dissolved precursors, with the help of a complexing agent. Among all techniques used to grow Group II-VI semiconductors, CBD has the advantage of being a simple, low temperature, and inexpensive large-area deposition technique. So far, its...
Show moreChemical bath deposition (CBD) is the analog in liquid phase of the well-known chemical vapor deposition technique in the vapor phase. In CBD, deposition of thin films takes place from aqueous solutions at low temperatures by a chemical reaction between dissolved precursors, with the help of a complexing agent. Among all techniques used to grow Group II-VI semiconductors, CBD has the advantage of being a simple, low temperature, and inexpensive large-area deposition technique. So far, its contribution in thin film solar cells industry has been mainly limited to growing n-type CdS and/or ZnS window layers for CdTe-based and CIGS-based solar cells. In this work we first optimize the CBD process of CdS using nitrilotriacetic acid and hydrazine as complexing agents as an alternative to ammonia. We then study the effect of the cadmium precursor on the optical/electrical properties, as well as crystal structure, morphology, and composition of CBD-CdS films. A better understanding of the CBD process of CdS as a whole has been achieved and high quality CBD-CdS films have been obtained. Next, we investigate in-situ doping of CBD-CdS with group III elements, such as B, Al, In, and Ga. The objective is to show that CBD is capable of not only growing CdS but also of doping it to reduce its resistivity and, as a result, facilitate its use in solar cells as well as other optoelectronic device fabrication. A four orders of magnitude drop of film resistivity has been achieved without a significant change in film bandgap, structure, or morphology. Finally, we test the possibility of using CBD to grow transparent conducting oxide (TCO) films, such as Al-doped ZnO films and cadmium stannate films. First, we study CBD of ZnO and later in-situ doping of ZnO using Al. High quality ZnO thin films have been grown using CBD with the help of four different complexing agents. Post heat treatment in argon ambient helped reduce resistivity of CBD-ZnO undoped films to ~ 10-1 Ω-cm. In-situ doping of such films using Al shows promising results. Such films could be an alternative to indium tin oxide (ITO) layers that are commonly used as TCO layers for solar cells. Another approach is to use CBD to grow CdO and SnO2 thin films, with the goal of obtaining Cd2SnO4 by later annealing of these two layers. Cadmium stannate is another TCO candidate that could replace ITO in the near future. We have succeeded in growing CBD-CdO thin films using three different complexing agents. Undoped CBD-CdO films with a resistivity as low as 1.01 x10-2 -cm and a carrier density as high as 2.59 x 1020 cm-3 have been obtained. SnO2 films have been successfully grown using CBD. Fabrication of Cadmium stannate thin films using CBD is investigated. In summary, our objective to expand the use of CBD beyond just growing CdS and ZnS, and to test the possibility of using it for in-situ doping of group II-VI semiconductors as well as TCO layers fabrication proved to be successful. We believe that this may have a significant impact on solar cells as well as other optoelectronic devices fabrication industry, due to the simplicity and the cost-effectiveness of CBD.
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Date Issued: 2009
Identifier: CFE0002860, ucf:48071
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002860

Title: Optical Properties of Single Nanoparticles and Two-dimensional Arrays of Plasmonic Nanostructures.
Creator: Zhou, Yadong, Zou, Shengli, Harper, James, Zhai, Lei, Chen, Gang, Zheng, Qipeng, University of Central Florida
Abstract / Description: The tunability of plasmonic properties of nanomaterials makes them promising in many applications such as molecular detection, spectroscopy techniques, solar energy materials, etc. In the thesis, we mainly focus on the interaction between light with single nanoparticles and two-dimensional plasmonic nanostructures using electrodynamic methods. The fundamental equations of electromagnetic theory: Maxwell's equations are revisited to solve the problems of light-matter interaction, particularly...
Show moreThe tunability of plasmonic properties of nanomaterials makes them promising in many applications such as molecular detection, spectroscopy techniques, solar energy materials, etc. In the thesis, we mainly focus on the interaction between light with single nanoparticles and two-dimensional plasmonic nanostructures using electrodynamic methods. The fundamental equations of electromagnetic theory: Maxwell's equations are revisited to solve the problems of light-matter interaction, particularly the interaction of light and noble nanomaterials, such as gold and silver. In Chapter 1, Stokes parameters that describe the polarization states of electromagnetic wave are presented. The scattering and absorption of a particle with an arbitrary shape are discussed. In Chapter 2, several computational methods for solving the optical response of nanomaterials when they are illuminated by incident light are studied, which include the Discrete Dipole Approximation (DDA) method, the coupled dipole (CD) method, etc. In Chapter 3, the failure and reexamination of the relation between the Raman enhancement factor and local enhanced electric field intensity is investigated by placing a molecular dipole in the vicinity of a silver rod. Using a silver rod and a molecular dipole, we demonstrate that the relation generated using a spherical nanoparticle cannot simply be applied to systems with particles of different shapes. In Chapter 4, a silver film with switchable total transmission/reflection is discussed. The film is composed of two-dimensional rectangular prisms. The factors affecting the transmission (reflection) as well as the mechanisms leading to the phenomena are studied. Later, in Chapter 5 and 6, the sandwiched nano-film composed of two 2D rectangular prisms arrays and two glass substrates with a continuous film in between is examined to enhance the transmission of the continuous silver film.
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Date Issued: 2018
Identifier: CFE0007117, ucf:51943
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007117

Title: Chemical Vapor Deposition Growth of Large Area 2D MoS2 Layers: Layer Orientation Control, Heterostructure Integration, And Applications for Stretchable Sensors.
Creator: Islam, Md. Ashraful, Jung, YeonWoong, Sundaram, Kalpathy, Yuan, Jiann-Shiun, Roy, Tania, Cho, Hyoung Jin, University of Central Florida
Abstract / Description: Two-dimensional (2D)-layered MoS2 layers have exhibited a broad set of unusual and superior material properties unattainable in any traditional bulk materials, drawing significant research interests nowadays. For instance, they present excellent semiconducting properties accompanying high carrier mobility and large current ON/OFF ratio as well as extensive in-plane strain limit and thickness, projecting high suitably for emerging flexible and stretchable electronics. Such properties and...
Show moreTwo-dimensional (2D)-layered MoS2 layers have exhibited a broad set of unusual and superior material properties unattainable in any traditional bulk materials, drawing significant research interests nowadays. For instance, they present excellent semiconducting properties accompanying high carrier mobility and large current ON/OFF ratio as well as extensive in-plane strain limit and thickness, projecting high suitably for emerging flexible and stretchable electronics. Such properties and applications strongly depend on the physical orientation and chemical composition of constituent 2D layers. 2D MoS2 layers chemically grown in two distinct orientations, e.g., horizontal alignment for electronics and optoelectronics, and vertical alignment for electrochemical and sensing applications. Moreover, 2D heterostructure layers composed of vertically stacked dissimilar 2D TMDs held via weak van der Waals (vdW) attractions offer unique 2D/2D interfaces, envisioned to display exotic material properties, unattainable in their monocomponent counterparts. However, the underlying principle of their layer orientation-controlled growth and integrations are not well suited for scalable production, leaving their projected technological opportunities far from being realized for various novel applications. Herein, I study various aspects of 2D MoS2 layers that were studied from their large-area layer-orientation controlled growth and heterostructures integration to applications in stretchable electronic devices. I developed a chemical vapor deposition (CVD) synthesis, which can grow large-area ((>) cm2) 2D MoS2 layers in a layer-controlled manner and investigated their underlying growth mechanism. I then developed a viable transfer approach of the as-grown 2D layers and integrated them into secondary target substrates to realize a new type of 2D MoS2-layers based heterostructures. To further extend their layer-controlled CVD growth and integration approach, a high-performance stretchable 2D MoS2-based electrical sensors were demonstrated on the elastomeric substrates with unconventional structural layouts. This study paves the way to explore this emerging atomically-thin material in realizing a wide range of unusual device and technologies which have been foreseen to be impossible otherwise.
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Date Issued: 2019
Identifier: CFE0007820, ucf:52812
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007820

Title: Design, Synthesis, Stability, and Photocatalytic Studies of Sustainable Metal-Organic Frameworks.
Creator: Logan, Matthew, Uribe Romo, Fernando, Zhai, Lei, Yuan, Yu, Kuebler, Stephen, Rahman, Talat, University of Central Florida
Abstract / Description: The presented dissertation focuses on the design, synthesis, and characterization of metal-organic frameworks (MOFs) composed of earth-abundant elements the exhibit photoredox activity and studied their application as heterogeneous photocatalysts in organic synthesis and in solar-to-chemical energy conversion. In particular, the structure-property relationships of titanium-based MOFs relating the structure of the organic building unit and the photophysical and photochemical activity of the...
Show moreThe presented dissertation focuses on the design, synthesis, and characterization of metal-organic frameworks (MOFs) composed of earth-abundant elements the exhibit photoredox activity and studied their application as heterogeneous photocatalysts in organic synthesis and in solar-to-chemical energy conversion. In particular, the structure-property relationships of titanium-based MOFs relating the structure of the organic building unit and the photophysical and photochemical activity of the solid material is studied. The first novel family of seven MOFs isoreticular to MIL-125-NH2, includes functionalized with N-alkyl groups with increasing chain length (methyl to heptyl) and with varying connectivity (primary or secondary). The functionalized materials displayed reduced optical bandgaps correlated with the increased inductive donor ability of the alkyl substituents, enhanced excited-state lifetimes, mechanistic information towards visible light CO2 reduction, and improved water stability. The second family of titanium MOFs was prepared with a new secondary building unit and organic links of varying lengths, for which Their crystal structure was solved utilizing powder X-ray diffraction crystallography. This work provides guidelines for the next generation of photocatalyst for the conversion of solar-to-chemical energy and other organic transformations.
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Date Issued: 2018
Identifier: CFE0007219, ucf:52217
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007219

Title: Experimental study and modeling of mechanical micro-machining of particle reinforced heterogeneous materials.
Creator: Liu, Jian, Xu, Chengying, An, Linan, Gordon, Ali, Bai, Yuanli, Gong, Xun, University of Central Florida
Abstract / Description: This study focuses on developing explicit analytical and numerical process models for mechanical micro-machining of heterogeneous materials. These models are used to select suitable process parameters for preparing and micro-machining of these advanced materials. The material system studied in this research is Magnesium Metal Matrix Composites (Mg-MMCs) reinforced with nano-sized and micro-sized silicon carbide (SiC) particles.This research is motivated by increasing demands of miniaturized...
Show moreThis study focuses on developing explicit analytical and numerical process models for mechanical micro-machining of heterogeneous materials. These models are used to select suitable process parameters for preparing and micro-machining of these advanced materials. The material system studied in this research is Magnesium Metal Matrix Composites (Mg-MMCs) reinforced with nano-sized and micro-sized silicon carbide (SiC) particles.This research is motivated by increasing demands of miniaturized components with high mechanical performance in various industries. Mg-MMCs become one of the best candidates due to its light weight, high strength, and high creep/wear resistance. However, the improved strength and abrasive nature of the reinforcements bring great challenges for the subsequent micro-machining process.Systematic experimental investigations on the machinability of Mg-MMCs reinforced with SiC nano-particles have been conducted. The nanocomposites containing 5 Vol.%, 10 Vol.% and 15 Vol.% reinforcements, as well as pure magnesium, are studied by using the Design of Experiment (DOE) method. Cutting forces, surface morphology and surface roughness are characterized to understand the machinability of the four materials. Based on response surface methodology (RSM) design, experimental models and related contour plots have been developed to build a connection between different materials properties and cutting parameters. Those models can be used to predict the cutting force, the surface roughness, and then optimize the machining process.An analytical cutting force model has been developed to predict cutting forces of Mg-MMCs reinforced with nano-sized SiC particles in the micro-milling process. This model is different from previous ones by encompassing the behaviors of reinforcement nanoparticles in three cutting scenarios, i.e., shearing, ploughing and elastic recovery. By using the enhanced yield strength in the cutting force model, three major strengthening factors are incorporated, including load-bearing effect, enhanced dislocation density strengthening effect and Orowan strengthening effect. In this way, the particle size and volume fraction, as significant factors affecting the cutting forces, are explicitly considered. In order to validate the model, various cutting conditions using different size end mills (100 (&)#181;m and 1 mm dia.) have been conducted on Mg-MMCs with volume fraction from 0 (pure magnesium) to 15 Vol.%. The simulated cutting forces show a good agreement with the experimental data. The proposed model can predict the major force amplitude variations and force profile changes as functions of the nanoparticles' volume fraction. Next, a systematic evaluation of six ductile fracture models has been conducted to identify the most suitable fracture criterion for micro-scale cutting simulations. The evaluated fracture models include constant fracture strain, Johnson-Cook, Johnson-Cook coupling criterion, Wilkins, modified Cockcroft-Latham, and Bao-Wierzbicki fracture criterion. By means of a user material subroutine (VUMAT), these fracture models are implemented into a Finite Element (FE) orthogonal cutting model in ABAQUS/Explicit platform. The local parameters (stress, strain, fracture factor, velocity fields) and global variables (chip morphology, cutting forces, temperature, shear angle, and machined surface integrity) are evaluated. Results indicate that by coupling with the damage evolution, the capability of Johnson-Cook and Bao-Wierzbicki can be further extended to predict accurate chip morphology. Bao-Wierzbiki-based coupling model provides the best simulation results in this study. The micro-cutting performance of MMCs materials has also been studied by using FE modeling method. A 2-D FE micro-cutting model has been constructed. Firstly, homogenized material properties are employed to evaluate the effect of particles' volume fraction. Secondly, micro-structures of the two-phase material are modeled in FE cutting models. The effects of the existing micro-sized and nano-sized ceramic particles on micro-cutting performance are carefully evaluated in two case studies. Results show that by using the homogenized material properties based on Johnson-Cook plasticity and fracture model with damage evolution, the micro-cutting performance of nano-reinforced Mg-MMCs can be predicted. Crack generation for SiC particle reinforced MMCs is different from their homogeneous counterparts; the effect of micro-sized particles is different from the one of nano-sized particles.In summary, through this research, a better understanding of the unique cutting mechanism for particle reinforced heterogeneous materials has been obtained. The effect of reinforcements on micro-cutting performance is obtained, which will help material engineers tailor suitable material properties for special mechanical design, associated manufacturing method and application needs. Moreover, the proposed analytical and numerical models provide a guideline to optimize process parameters for preparing and micro-machining of heterogeneous MMCs materials. This will eventually facilitate the automation of MMCs' machining process and realize high-efficiency, high-quality, and low-cost manufacturing of composite materials.
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Date Issued: 2012
Identifier: CFE0004570, ucf:49196
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004570

Title: Nonlinear Optical Response of Simple Molecules and Two-Photon Semiconductor Lasers.
Creator: Reichert, Matthew, Vanstryland, Eric, Hagan, David, Likamwa, Patrick, Peale, Robert, University of Central Florida
Abstract / Description: This dissertation investigates two long standing issues in nonlinear optics: complete characterization of the ultrafast dynamics of simple molecules, and the potential of a two-photon laser using a bulk semiconductor gain medium. Within the Born-Oppenheimer approximation, nonlinear refraction in molecular liquids and gases can arise from both bound-electronic and nuclear origins. Knowledge of the magnitudes, temporal dynamics, polarization and spectral dependences of each of these mechanisms...
Show moreThis dissertation investigates two long standing issues in nonlinear optics: complete characterization of the ultrafast dynamics of simple molecules, and the potential of a two-photon laser using a bulk semiconductor gain medium. Within the Born-Oppenheimer approximation, nonlinear refraction in molecular liquids and gases can arise from both bound-electronic and nuclear origins. Knowledge of the magnitudes, temporal dynamics, polarization and spectral dependences of each of these mechanisms is important for many applications including filamentation, white-light continuum generation, all-optical switching, and nonlinear spectroscopy. In this work the nonlinear dynamics of molecules are investigated in both liquid and gas phase with the recently developed beam deflection technique which measures nonlinear refraction directly in the time domain. Thanks to the utility of the beam deflection technique we are able to completely determine the third-order response function of one of the most important molecular liquids in nonlinear optics, carbon disulfide. This allows the prediction of essentially any nonlinear refraction or two-photon absorption experiment on CS2. Measurements conducted on air (N2 and O2) and gaseous CS2 reveal coherent rotational revivals in the degree of alignment of the ensemble at a period that depends on its moment of inertia. This allows measurement of the rotational and centrifugal distortion constants of the isolated molecules. Additionally, the rotational contribution to the beam deflection measurement can be eliminated thanks to the particular polarization dependence of the mechanism. At a specific polarization, the dominant remaining contribution is due to the bound-electrons. Thus both the bound-electronic nonlinear refractive index of air, and second hyperpolarizability of isolated CS2 molecules, are measured directly. The later agrees well with liquid CS2 measurements, where local field effects are significant. The second major portion of this dissertation addresses the possibility of using bulk semiconductors as a two-photon gain medium. A two-photon laser has been a goal of nonlinear optics since shortly after the original laser's development. In this case, two-photons are emitted from a single electronic transition rather than only one. This processes is known as two-photon gain (2PG). Semiconductors have large two-photon absorption coefficients, which are enhanced by ~2 orders of magnitude when using photons of very different energies, e.g., ??_a?10??_b. This enhancement should translate into large 2PG coefficients as well, given the inverse relationship between absorption and gain. Here, we experimentally demonstrate both degenerate and nondegenerate 2PG in optically excited bulk GaAs via pump-probe experiments. This constitutes, to my knowledge, the first report of nondegenerate two-photon gain. Competition between 2PG and competing processes, namely intervalence band and nondegenerate three-photon absorption (ND-3PA), in both cases are theoretically analyzed. Experimental measurements of ND-3PA agree with this analysis and show that it is enhanced much more than ND-2PG. It is found for both degenerate and nondegenerate photon pairs that the losses dominate the two-photon gain, preventing the possibility of a two-photon semiconductor laser.
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Date Issued: 2015
Identifier: CFE0005874, ucf:50871
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005874

Title: Modeling Repair Patches of Ship Hull and Studying the Effect of Their Orientation on Stresses.
Creator: Enwegy, Halima, Moslehy, Faissal, Kassab, Alain, Bai, Yuanli, University of Central Florida
Abstract / Description: The hull is the most important structural part of any maritime vessel. It must be adequately designed to withstand the harsh sailing environmental conditions and associated forces. In the past, the basic material used to manufacture the ship hull was wood, where the hull was usually shaped as cylindrical wooden shanks. In the present, hull designs have developed to steel columns or stiffened panels that are made of different types of materials. Panels that are stiffened orthogonally in two or...
Show moreThe hull is the most important structural part of any maritime vessel. It must be adequately designed to withstand the harsh sailing environmental conditions and associated forces. In the past, the basic material used to manufacture the ship hull was wood, where the hull was usually shaped as cylindrical wooden shanks. In the present, hull designs have developed to steel columns or stiffened panels that are made of different types of materials. Panels that are stiffened orthogonally in two or more directions and have nine independent material constants are defined as orthotropic panels, and they achieve high specific strength.This thesis presents the effect of different patch orientations on the resulting strain and stress concentrations at the area of interaction between the panel and the patch. As it is known, the behavior of stiffened plates is affected by several important parameters, e.g., length to width ratio of the panel, stiffener geometry and spacing, aspect ratio for plates between stiffeners, plate slenderness, von Mises stresses, initial distortions, boundary conditions, and type of loading. A finite element model of the ship hull has been developed and run on ABAQUS (commercially available finite element software). The stiffened panel and patch are modeled as equivalent orthotropic plates made of steel. The panel edges are considered to be simply supported, and uniaxial tension was applied to the equivalent stiffened panel in addition to the lateral pressure (from water interaction). The developed model successfully predicted the optimal orientation of the panel for maximum stress concentration reduction. Moreover, in order to minimize the severe conditions caused by the mismatch that occurs if the material properties of the patch and the panel are the same during the patching process, it is necessary to stiffened the patch more than the panel. The developed model also suggested that an isotropic layer be added at the interaction to decrease the severity of arising stresses.
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Date Issued: 2014
Identifier: CFE0005162, ucf:50701
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005162

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