Mechanics of Materials Commons^™

Thermal Barrier Coatings (Tbc's) For High Heat Flux Thrust Chambers, Christopher Michael Bradley

Open Access Theses & Dissertations

The last 30 years materials engineers have been under continual pressure to develop materials with a greater temperature potential or to produce configurations that can be effectively cooled or otherwise protected at elevated temperature conditions. Turbines and thrust chambers produce some of the harshest service conditions for materials which lead to the challenges engineers face in order to increase the efficiencies of current technologies due to the energy crisis that the world is facing. The key tasks for the future of gas turbines are to increase overall efficiencies to meet energy demands of a growing world population and reduce the …

Microstructure And Properties For Titanium Aluminide Superalloy Prototypes Fabricated By Electron Beam Melting And Thermally Processed, Jennifer Hernandez

Open Access Theses & Dissertations

Gamma TiAl has been considered to be an ideal replacement for Ni-base superalloy aerospace applications, particularly in weight-critical applications. While bulk, fully dense gamma-TiAl is 50% less dense than Ni-base superalloys, it also has excellent mechanical properties at high temperature (up to ~800°C). Pre alloyed (Ti-48Al-2Cr-2Nb) powder was used to fabricate solid, fully dense (3.85 g/cm3) components and foam components with densities ranging from 0.33 g/cm³ to 0.46 g/cm³ by electron beam melting (EBM). A 10:1 blend of 2-phase TiAl (Ti-48Al-2Cr-2Nb in ^a/_o) : Inconel 625 (Ni-22Cr-6Mo-2Nb in ^a/_o) pre-alloyed powders produced …

New Topics On Nanoindentation Of Polymers And Composite Materials, Ricardo Martinez-Hernandez

Open Access Theses & Dissertations

In this study, nanoindentation was used to determine Young's modulus of homogeneous plastic materials as well as inhomogeneous epoxy woven fabric composites using various indenters. In the first part, homogeneous PMMA and polycarbonate were characterized using conical and spherical indenters. The conventional approach of the inverse analysis was modified in order to account for effects obtained during spherical nanoindentation. The experimental results were verified using FEA analysis in ABAQUS. It was found that viscous effects were present in conical nanoindentations which led to an overestimation of contact stiffness. The second part, the response of carbon and glass fiber woven fabric …

Rbd2po4: Room Temprature Synthesis, Chemical And Structural Stablity Upon Heating, Masoud Mollaee

Open Access Theses & Dissertations

Monoclinic RbD2PO4 polycrystals were synthesized via the room temperature crystallization of RbH2PO4 dissolved in D2O. Powder x-ray diffraction (XRD) data collected at T=25 ºC indicate that this deuterated compound crystallizes in space group P21/m with unit cell parameters a=7.688í?, b=6.192í?, c=4.781í? and β=109.02°, and is isomorphic with the intermediate-temperature phase of its hydrogenated counterpart rubidium dihydrogen phosphate (RDP). We found no evidence of previously reported [Phase Transitions 80, 17 (2007)] polymorphic phase transition in rubidium dideuterium phosphate (DRDP) upon heating from room temperature to 210 ºC. All lattice parameters vary smoothly within this temperature range, demonstrating that the P21/m phase …

Biaxial Bending And Lateral-Torsional Instability Of Imperfect Frp I-Beams Including Effects Of Retrofitting, Jodi Marie Knorowski

Civil & Environmental Engineering Theses & Dissertations

This thesis presents the outcome of a theoretical and experimental study of the behavior of Fiber Reinforced Polymer (FRP) I-beams susceptible to lateral-torsional instability or when subjected to biaxial bending. Laboratory experiments involved application of vertical and horizontal static loads to a 4 x 4 x ¼ in. I-beam with various lengths, and the resulting displacement, twist, and strain were recorded. In the vertical direction, the beam was loaded from different reference load heights with respect to the shear center of the beam. The governing biaxial flexure and torsion differential equations were modified to account for the presence of initial …

A Resistance Based Structural Health Monitoring System For Composite Structure Applications, Dennis N. Boettcher

Master's Theses

This research effort explored the possibility of using interwoven conductive and nonconductive fibers in a composite laminate for structural health monitoring (SHM). Traditional SHM systems utilize fiber optics, piezoelectrics, or detect defects by nondestructive test methods by use of sonar graphs or x-rays. However, these approaches are often expensive, time consuming and complicated.

The primary objective of this research was to apply a resistance based method of structural health monitoring to a composite structure to determine structural integrity and presence of defects.

The conductive properties of fiber such as carbon, copper, or constantan - a copper-nickel alloy - can be …

Cellular Automaton For Simulation Of Oxide Layer Growth Influenced By Chromium Concentration Of Structure Material, Kuan-Che Lan, Yitung Chen, Ge-Ping Yu, Tzu-Chen Hung

College of Engineering: Graduate Celebration Programs

Chromium, an important alloying element, has been added in ferrous and nickel based alloy such as stainless steels and Inconel alloy to improve the corrosion resistance. High corrosion resistance of structural materials in extremely high working temperature is one crucial R&D objective of Gen IV nuclear power plants which propose to raise the thermal efficiency via high working temperature. A cellular automaton (CA) model based on the stochastic approach was proposed to simulate the process of oxidation and corrosion of structural material in flowing fluid. The relation of chromium concentration against oxide layer thickness during a specific period was found. …

Peridynamic Model For Dynamic Fracture In Unidirectional Fiber-Reinforced Composites, Wenke Hu, Youn Doh Ha, Florin Bobaru

Department of Mechanical and Materials Engineering: Faculty Publications

We propose a computational method for a homogenized peridynamics description of fiber-reinforced composites and we use it to simulate dynamic brittle fracture and damage in these materials. With this model we analyze the dynamic effects induced by different types of dynamic loading on the fracture and damage behavior of unidirectional fiber-reinforced composites. In contrast to the results expected from quasi-static loading, the simulations show that dynamic conditions can lead to co-existence of and transitions between fracture modes; matrix shattering can happen before a splitting crack propagates. We observe matrix–fiber splitting fracture, matrix cracking, and crack migration in the matrix, including …

Thin Film Growths Of Znte And Cdte On Various Substrates Using A Novel Close Space Sublimation Reactor Css4, Damian Marrufo

Open Access Theses & Dissertations

Thin films of CdTe have been grown on CdS in a variety of methods for use in thin film photovoltaic systems. Limits to the efficiency of CdTe/CdS solar cells have been attributed to defects in the lattice that occur between the interface of CdS and CdTe due to a lattice mismatch. A close space sublimation (CSS) reactor known as the CSS4 was designed and fabricated in UTEP to deposit complex layers of CdTe and ZnTe on top of a CdS film that is grown via chemical bath deposition in order to obtain a CdTe photovoltaic. Unfortunately, the original design and …

A Novel Method For The Curing Of Metal Particle Loaded Conductive Inks And Pastes, David Adrian Roberson

Open Access Theses & Dissertations

The emerging technology of printed microelectronics involving the use of conductive inks in conjunction with standard printing techniques offers a fast and low waste method for creating microelectronics compared with standard manufacturing processes. A clear path to the creation of flexible electronics is present due to the ease of printing on flexible substrates. Moreover, creation of novel 3D structural electronics is possible via the integration of printing technologies and additive manufacturing (AM) techniques.

A key obstacle to the manufacturing of flexible and structural electronics comes from the temperature restrictions imposed by the substrates, which are typically polymeric. This hindrance has …

Structure Morphology And Optical Properties Of Nanocrystalline Ga2o3 Thin Films, Sampath Kumar Samala

Open Access Theses & Dissertations

Gallium Oxide thin films were produced by sputter deposition by varying the substrate temperature (T_s) in a wide range (T_s=25-800 oC) and under variable deposition time. The structural characteristics and optical properties of Ga₂O₃ films were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Rutherford backscattering spectrometry (RBS) and spectrophotometric measurements. The effect of growth temperature is significant on the chemistry, crystal structure and morphology of Ga₂O₃ films. XRD and SEM analyses indicate that the Ga₂O₃ films grown at lower temperatures were …

The Effect Of Al, Mo, And B On The Oxidation Behavior Of Three Nb-Based Alloys, Victoria Rae Rangel

Open Access Theses & Dissertations

Extensive work has been undertaken to develop niobium based structural alloys for high temperature applications. These developments have led to the increase in engine operating temperatures and better performance efficiency. New materials including alloys based on metals with higher melting points such as molybdenum and niobium with silicon are now being examined as a better alternative to nickel base superalloys. Materials with a niobium silicide based composites have the potential for higher temperature capabilities. The oxidation behavior of Nb-20Cr-10Si and Nb-20Cr-10Si-5Al has been studied in a range of temperature from 700 to 1400°C in static air. Isothermal oxidation experiments indicate …

The Effects Of Uncommon Silicides On The Oxidation Of Alloys From The Nb-Cr-Si System, Daniel Brendan Voglewede

Open Access Theses & Dissertations

Niobium based alloys are being tapped as potential successors to current nickel base superalloys in high temperature applications. In the aerospace industry, high temperature materials are constantly being pushed to higher temperature regimes in order to improve engine efficiency however current superalloys cannot be pushed further due to melting temperature limitations. Niobium, being a refractory metal, can withstand much higher temperatures than nickel however its oxidation properties are woefully inadequate.

The purpose of this study is to ascertain whether increased silicon additions can improve niobium oxidation properties by: forming ternary silicides with better oxidation properties and by preventing the formation …

High Pressure Synchrotron X-Ray Diffraction Studies Of Superprotonic Transitions In Phosphate Based Solid Acids, Juan Daniel Hermosillo

Open Access Theses & Dissertations

Certain phosphate based solid acids, such as CsH2PO4 and RbH2PO4, have been shown to exhibit an abrupt, several-order-of-magnitude increase in their proton conductivity when heated above a temperature threshold. This so called superprotonic behavior allows the above-mentioned materials to function as fuel cell electrolytes at temperatures between 150C and 300C, a remarkable application that attracted significant interest especially from the automobile industry. Yet, the microscopic structures and dynamic mechanisms responsible for this behavior are not fully understood. In fact, until very recently, the very nature of the superprotonic behavior has been debate, with some groups attributing the steep proton enhancement …

Development Of Advanced Polymer Nanocomposite Capacitors, Miguel Mendoza

Open Access Theses & Dissertations

The current development of modern electronics has driven the need for new series of energy storage devices with higher energy density and faster charge/discharge rate. Batteries and capacitors are two of the most widely used energy storage devices. Compared with batteries, capacitors have higher power density and significant higher charge/discharge rate. Therefore, high energy density capacitors play a significant role in modern electronic devices, power applications, space flight technologies, hybrid electric vehicles, portable defibrillators, and pulse power applications. Dielectric film capacitors represent an exceptional alternative for developing high energy density capacitors due to their high dielectric constants, outstanding breakdown voltages, …

Hafnia-Based Nanostructured Thermal Barrier Coatings For Next Generation Gas Turbine Technology, Mohammed Noor-A-Alam

Open Access Theses & Dissertations

Extensive efforts have been directed in the last several decades towards improving thermodynamic efficiency of industrial gas turbines for power generation plants. The central theme of the efforts is to increase the turbine operating temperature and, thus, allowing higher efficiency. Thermal barrier coatings (TBC) constitute an advanced technology to protect the metallic surface from high temperature exposure for long time operation. The TBCs protect the gas turbine components from high temperature and allows further increase in engine operating temperature which subsequently increases the efficiency of the gas turbine power plant. However, the current TBC materials are capable of allowing the …

Applications Of Density Functional Theory In Materials Science And Engineering, Manuel Alvarado

Open Access Theses & Dissertations

Density Functional Theory (DFT) is a powerful tool that can be used to model various systems in materials science. Our research applies DFT to two problems of interest. First, an organic/inorganic complex dye system known as a Mayan pigment is modeled to determine chemical binding sites, verifying each model with physical data such as UV/Vis spectra. Preliminary studies on palygorskite-based mayan pigments (mayacrom blue, mayacrom purple) show excellent agreement with experimental studies when using a dimer dye geometry binding with tetrahedrally-coordinated aluminum impurity sites in palygorksite. This approach is applied to a sepiolite-based organic/inorganic dye system using thioindigo attached to …

Raman And Infrared Study Of Electrospun Plla/Pcl Nanofiber Blends For Use In Tissue Engineering, Jose Luis Enriquez Carrejo

Open Access Theses & Dissertations

Recently, the biomedical engineering field has developed at a very fast pace as improved techniques and materials become available to promote its growth. Consequently, the research in polymeric biomaterials has been highly stimulated by this trend. The goal of the current research is to demonstrate the usefulness of the Raman scattering, Raman mapping, and infrared absorption spectroscopies to tissue engineering, by spectroscopically characterizing blends of PLLA and PCL polymers, which were prepared by electrospinning with and without cell addition. The proposed use of these blends is as primary biomaterials in biodegradable scaffolds used in tissue engineering. Both Raman and infrared …

Development Of A Multi-Material, Multi-Technology Fdm System For Process Improvement Experimentation, David Espalin

Open Access Theses & Dissertations

Over the last three decades, developments within the area of Additive Manufacturing (AM) have resulted in novel technologies capable of producing highly customized, complex part geometries in a fraction of the lead time required by traditional manufacturing methods (e.g., injection molding, metal casting). In particular, fused deposition modeling (FDM), a material extrusion AM process, can produce parts using production-grade thermoplastics like acrylonitrile butadiene styrene, polycarbonate, and polyetherimide. Additionally, non-commercial materials (e.g., polycaprolactone, ceramic loaded polymers, carbon nanotube loaded polymers) have been processed using FDM in part to demonstrate the potential diversity in material selection.

Recently, a myriad of personal 3D …

The Effect Of Al And B Additions On The Oxidation Behavior Of Alloys From The Nb-Cr-Si System, Nydia Judit Esparza

Open Access Theses & Dissertations

Nickel based superalloys have been developed to perform substantially in industry however as technology develops, the need and desire to increase service temperatures to improve efficiency and performance is pushing the capabilities of these alloys. These aspired requirements entail the research and development of new structural materials that surpass the abilities of nickel alloys. Research in Nb-based alloys is underway as Nb alloys have shown to be a promising alternative with similar density but higher melting temperatures than the Ni alloys. However, because Nb has poor oxidation properties extensive studies are necessary to develop an alloy that can perform as …

A Study Of Wo3 And W0.95ti0.05o3 Thin Films Using Comparative Spectroscopy, James Heyward Howard

Open Access Theses & Dissertations

Tungsten oxide (WO3) is important and well-studied in materials science, particularly for sensor applications. In this research work, we consider the innovation of adding Ti to thin films of this material. Since the characteristics of any such material are strongly dependent on the conditions and methods used in its deposition, the main objective of this project is to provide a detailed spectroscopic characterization by Raman scattering, infrared absorption, and X-ray photoelectron spectroscopy (XPS) of WO3 and of W0.95Ti0.05O3. This characterization will be based on comparison of the morphology and composition of WO3-based thin films, grown by radio frequency magnetron reactive …

Development Of Nanocomposites For Energy Storage Devices, Md Ashiqur Rahaman Khan

Open Access Theses & Dissertations

With the ever-increasing need in improving the performance and operation life of future mobile devices, developing higher power density energy storage devices has been receiving more attention. Lithium ion battery (LIB) and capacitor are two of the most widely used energy storage devices and have attracted increasing interest from both industrial and academic fields. Batteries have higher power density than capacitor but significantly longer charge/discharge rates. In order to further improve the performance of these energy storage devices, one of the approaches is to use high specific surface area nano-materials. Among all the nano-materials developed so far, one-dimensional nanowires are …

Nanoprobe I-V Characterization Of Cdte/Cds Micro And Nano-Patterned Solar Cells, Heber Prieto

Open Access Theses & Dissertations

This thesis presents a novel way to characterize micro and nano patterned cadmium telluride thin film solar cells via a nano-probe system. A historical review of CdTe-based solar cells is presented first followed by review of the technology developed to produce the patterned CdTe cells. A detailed presentation is then provided on the use of a Zyvex nanoprobing system to characterize the patterned solar cells. The I-V response of micro- and nano-patterned solar cells stimulated under different e-beam conditions is presented and analyzed. Suggestions of how to improve the technique are provided. This work documents, for the first time, the …

The Influence Of Build Parameters On The Microstructure During Electron Beam Melting Of Ti6al4v, Karina Puebla

Open Access Theses & Dissertations

With the demand of devices to replace or improve areas, such as: electronic, biomedical and aerospace industries. Improvements in these areas of engineering have been in need due to the customer’s needs for product properties requirements. The design of components must exhibit better material properties (mechanical or biocompatible) close to those of any given product. Rapid prototyping (RP) technologies that were originally designed to build prototypes may now be required to build functional end-use products. To carry out the transition, from RP to rapid manufacturing (RM), the available materials utilized in RP must provide the performance required for RM. The …

Oxidation Of Borides And Carbides With Y2o3 And Ta Additions, Salvador Manuel Rodriguez

Open Access Theses & Dissertations

The study presented here describes an investigation of an oxidation scale of a fully-sintered Y2O3-ZrB2-TiC composite exposed in air at 1173K. Upon oxidation of the boride/carbide, a ZrO2-TiO2 was expected to form similar to the ZrO2-SiO2 dual scale of an oxidized ZrB2-SiC. The 47wt% Y2O3-38wt%ZrB2-16wt%TiC composite formed a dual scale consisting primarily of an Y2O3-ZrO2-TiC inner scale with an outer scale of ZrO2-TiO2-Y2O3.

The samples oxidized with a parabolic layer growth allowing the calculation of the effective diffusion coefficient indicating that the oxidation was controlled by oxygen ingress through primarily the ZrO2-Y2O3 phase. The oxygen potential between the inner layer …

Finite Element Analysis Of The Contact Deformation Of Piezoelectric Materials, Ming Liu

Theses and Dissertations--Chemical and Materials Engineering

Piezoelectric materials in the forms of both bulk and thin-film have been widely used as actuators and sensors due to their electromechanical coupling. The characterization of piezoelectric materials plays an important role in determining device performance and reliability. Instrumented indentation is a promising method for probing mechanical as well as electrical properties of piezoelectric materials.

The use of instrumented indentation to characterize the properties of piezoelectric materials requires analytical relations. Finite element methods are used to analyze the indentation of piezoelectric materials under different mechanical and electrical boundary conditions.

For indentation of a piezoelectric half space, a three-dimensional finite element …

The Effects Of Damage Arrestment Devices In Composite Plate Sandwiches With Fastener Holes, Mark Anderson, Nancy Hung Choy, Lacey Jones, Rita Kourskaya

Aerospace Engineering

Composite materials such as a carbon fiber are used in a variety of new technologies including aircraft, spacecraft, and motor vehicles. Carbon fiber has a high strength to weight ratio, a key advantage over other material options. This report discusses the use of composite damage arrestment devices (DADs) in composite sandwich panels with a foam core. There are three different curing cycles tested for the DADs: pressure only, vacuum only, and vacuum with 1000 lbs of pressure. Using a Tetrahedron Heat Press to cure the composite specimen and an Instron Machine to perform tensile testing, data was collected for each …

Preparation And Characterization Of Iron Oxide And Hydroxide Based Nanomaterials, Guillermo Carbajal Franco

Open Access Theses & Dissertations

Iron (Fe) oxides and hydroxides are common and abundant materials. They exhibit diverse crystal structures, properties and phenomena by virtue of which they find a wide range of scientific and technological applications. Controlled growth and manipulation of the specific structure and electronic behavior to meet the requirements of a given application is a challenging problem in view of many possible phases and composition of the resulting materials. The preparation method and experimental conditions will, therefore, significantly affect the properties and performance of Fe oxides and hydroxides. The goal of the project is to obtain Fe-based oxide/hydroxide catalytic materials and to …

Fundamental Studies Of Co-Base Superalloy Biomedical Prototypes Fabricated By Electron Beam Melting: Microstructures And Microstructural Architecture, Sara M. Gaytan

Open Access Theses & Dissertations

Rapid prototyping, especially electron beam melting (EBM) technology by ARCAM have proven to provide outstanding microstructural and mechanical properties on different alloys fabricated by this technology. Being a computer designed driven technology, complex components, that are hard or even impossible to fabricate by traditional manufacturing techniques, can be fabricated by layer-by-layer EBM technology.

Microstructural and mechanical properties are compared for an EBM femoral knee component prototype with a traditionally-fabricated and body-removed femoral knee implant. Block and cylindrical shape components fabricated by EBM were also analyzed for this project. The alloy utilized for these components is Co-26Cr-6Mo-0.2C characterized by the standards …

Ballistic Projectile Metallurgical Issues And Fundamentals: Aerosol Production In Rod Penetration Erosion And Erosion Phenomena Associated With Railgun Development, Brenda Ivette Machado

Open Access Theses & Dissertations

The issue is derived from ballistic erosion as it relates to nanoparticle production and respiration of these particles as a health concern ballistic erosion and ballistic erosion as it relates to railgun performance. A common thread between these two issues is dynamic recrystallization (DRX). DRX has been demonstrated to be the dominant mechanism for solid-state flow associated with ballistic projectile/target penetration and interaction, friction-stir welding phenomena, and other high-strain rate deformation phenomena.

Aerosol particulates collected on filters from ballistic penetration and erosion events for W-Ni-Co and W-Ni-Fe kinetic energy rod projectiles penetrating steel target plates were observed to be highly …