Materials Science and Engineering Commons^™

Finite Element Model Of A Tennis Racket, Sayali Shashikant Kapatkar

Mechanical & Aerospace Engineering Theses & Dissertations

An explicit finite-element (FE) model of a tennis racket and string was produced in NASTRAN/PATRAN. MSC/NASTRAN is a general-purpose FEA program capable of solving a wide variety of engineering problems such as linear static analysis, static analysis with geometric and material with nonlinearities, transient analysis with geometric and material nonlinearities. A finite element racket model was used to study the engineering characteristics that affect the "sweet spot" of a te1mis racket. A similar model was simulated by creating a tennis racket, a tennis ball and a string-bed, and it was validated against MADYMO (Mathematical Dynamic Model) data.

The MADYMO validation …

Multiscale Modeling Of Impact On Heterogeneous Viscoelastic Solids With Evolving Microcracks, Flavio V. Souza

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Multiscale computational techniques play a major role in solving problems related to viscoelastic composite materials due to the complexities inherent to these materials. In the present work, a numerical procedure for multiscale modeling of impact on heterogeneous viscoelastic solids containing evolving microcracks is proposed in which the (global scale) homogenized viscoelastic incremental constitutive equations have the same form as the local scale viscoelastic incremental constitutive equations, but the homogenized tangent constitutive tensor and the homogenized incremental history dependent stress tensor depend on the amount of damage accumulated at the local scale. Furthermore, the developed technique allows the computation of the …

Carbon Nanotube Membranes For Use In The Transdermal Treatment Of Nicotine Addiction And Opioid Withdrawal Symptoms, Caroline L. Strasinger, Nicole N. Scheff, Ji Wu, Bruce J. Hinds, Audra L. Stinchcomb

Pharmaceutical Sciences Faculty Publications

Transdermal systems are attractive methods of drug administration specifically when treating patients for drug addiction. Current systems however are deficient in therapies that allow variable flux values of drug, such as nicotine for smoking cessation or complex dosing regimens using clonidine when treating opioid withdrawal symptoms. Through the use of functionalized carbon nanotube (CNT) membranes, drug delivery to the skin can be controlled by applying a small electrical bias to create a programmable drug delivery system. Clearly, a transdermal patch system that can be tailored to an individual's needs will increase patient compliance as well as provide much more efficient …

Synthesis Of Magnetic Porous Hollow Silica Nanotubes For Drug Delivery, H. Ma, J. Tarr, M. A. Decoster, J. Mcnamara, D. Caruntu, J. F. Chen, Charles J. O'Connor, Weilie Zhou

Chemistry Faculty Publications

In this paper, we report a synthesis of magnetic porous hollow silica nanotubes (MPHSNTs) using sol-gel method. The MPHSNTs were fabricated by coating Fe(3)O(4) nanoparticles and silica on surfactant hexadecyltrimethylammonium bromide (CTAB) modified CaCO(3) nanoneedles surface under alkaline condition. CaCO(3) nanoneedles and surfactant CTAB are introduced as nanotemplates to form the hollow and porous structures, respectively. After removing CTAB by calcination and etching CaCO(3) nanoneedles away in diluted acetic acid, magnetic porous hollow silica nanotubes with Fe(3)O(4) nanoparticles embedded in the silica shell were achieved. The products were characterized by scanning electron microscopy, transmission electron microscopy, and N(2) adsorption-desorption isotherms. …

Investigation Of Electrical And Optical Properties Of Bulk Iii-V Ternary Semiconductors, Travis C. Gomez

Theses and Dissertations

Bulk grown III-V ternary semiconductors of In_0.08Ga_0.92Sb and In_0.15Ga_0.85As were investigated through Hall-effect and photoluminescence measurements to determine carrier concentration, mobility, sheet resistivity, and luminescence spectrum. In the past, epitaxial layers of ternary compounds have been grown on binary compound substrates, and thus very limited lattice matched ternary alloys were available. Recently, bulk grown ternary substrates have been developed, and it has presented a renewed interest in using these substrates to grow high quality ternary compounds for use in many next generation optoelectronic devices. The results of photoluminescence (PL) study for the …

Non-Destructive Evaluation Of Aerospace Composites, Jeremy D. Johnson

Theses and Dissertations

Five methods of non-destructive material evaluation (NDE) were used to inspect various forms of damage commonly found in aerospace fiberglass composites: voids, edge and sub-surface delaminations, surface burning, and cracking. The images produced by X-ray, X-ray Computed Tomography, terahertz (THz) imaging, ultrasound, and flash IR thermography were analyzed for the detection of defects. Test results and analysis of each NDE method's capabilities provide a comparison study of conventional techniques versus the emerging technology of THz imaging for the non-destructive evaluation of aerospace composite materials. A comparison guide to the five methods' damage detection effectiveness for fiberglass composites is provided by …

Effects Of Environment On Creep Behavior Of Nextel720/Alumina-Mullite Ceramic Composite With ±45º Fiber Orientation At 1200ºc, Muzaffer Ozer

Theses and Dissertations

The present effort will investigate the off-axis creep behavior of the Nexte720/Alumina-Mullite CMC, a material system which relies on a porous alumina/mullite matrix for damage tolerance as compared to the pure alumina matrix in earlier studies. This research evaluated the creep behavior of N720/AM with a ± 45° fiber orientation at 1200°C in: laboratory air, steam, and argon environments. Creep-rupture tests at the creep stress levels of: 32, 30, 26, and 20 MPa were conducted in each environment. Additionally 35 MPa stress level examined in air and 13 MPa stress level examined both in air and steam. The N720/AM with …

Creep And Fatigue Interaction Characteristics Of Pwa1484, Christian J. Pierce

Theses and Dissertations

One of the main methods for predicting the service life of jet engine turbine blades is through creep analysis. A sample of the turbine blade material will be mechanically tested to characterize its creep performance. This characterization will be used to determine safe operating conditions for the material. While methods for modeling creep behavior are generally well developed, this constant load creep testing does not fully represent the loading conditions present in a jet engine due to cyclic loading caused by the mission profile and throttle movements. As the industry seeks to become more accurate in physics based modeling of …

Analysis And Application Of The Bi-Directional Scatter Distribution Function Of Photonic Crystals, Robert B. Lamott

Theses and Dissertations

Photonic crystals (PCs) are periodic structures built from materials with different refractive indices repeated at sub-wavelength intervals, which results in unusual optical characteristics, including narrowband laser protection, and zero reflectance and high absorption anomalies. Most of the research into the optical properties of PCs has concentrated only on the small range of wavelengths and angles where these effects occur. To better understand where all light leaving a PC is scattered, a Complete Angle Scatter Instrument was used to analyze the scatter from three Guided Mode Resonance Filters designed for laser protection. In the plane of incidence, measurements of the scatter …

Effects Of Contact Load On The Fretting Fatigue Behavior Of In-100 At Elevated Temperature, Alfred G. Traylor Ii

Theses and Dissertations

This thesis studied the effects of contact load of 8006 N on the fretting fatigue behavior of IN-100 at an elevated temperature of 600°C. First, S-N curves were created for a range of applied axial stresses at an identical stress ratio of 0.03 at 8006 N. A condition of partial slip condition necessary to fretting fatigue was verified by generating hysteresis loops, plotting shear force against axial stress. The half-contact width and the crack initiation location were determined for all of the fretting specimens using optical and scanning electron microscopes. The contact widths were consistent with expected analytical values and …

Ceramic Matrix Composite Characterization Under A Combustion And Loading Environment, Andrew R. Nye

Theses and Dissertations

Lightweight materials that can withstand high temperatures and corrosive environments are constantly sought after in the aerospace industry, typically for Gas Turbine Engine (GTE) application. These materials need to retain their strength throughout the long service period they would see in the combustor and turbine components of a GTE. One material that is ideal for these types of applications is an oxide/oxide Ceramic Matrix Composite (CMC). The fatigue behavior of the oxide/oxide CMC Nextel^TM 720/Alumina (N720/A) was investigated in a unique high temperature environment. N720/A consisted of an 8-harness satin weave of Nextel^TM aluminum oxide/silicon oxide fibers bound …

Production And Characterization Of High Repetition Rate Terahertz Radiation In Femtosecond-Laser-Induced Air Plasma, Michael L. Dexter

Theses and Dissertations

The purpose of this research was to produce and characterize high repetition rate terahertz radiation in ionized air plasma. An 800 nanometer, 50 femtosecond, 0.35 Watt, 40 KHz, pulsed Ti:Sapphire laser system was used as the source infrared beam. This beam was focused onto a second harmonic generation crystal to produce a collinear, perpendicularly polarized secondary beam at 400 nm. After realigning the polarization of the fundamental to the second harmonic and compensating for group velocity dispersion introduced by the optics, both beams were recombined and focused by a 3.75 cm focal length mirror to form an air plasma. An …

A Comparative Study Of The Bidirectional Reflectance Distribution Function Of Several Surfaces As A Mid-Wave Infrared Diffuse Reflectance Standard, Bradley Balling

Theses and Dissertations

The Bi-Directional Reflectance Distribution Function (BRDF) has a well defined diffuse measurement standard in the ultraviolet, visible, and near infrared (NIR), Spectralon(trade name). It is predictable, stable, repeatable, and has low surface variation because it is a bulk scatterer. In the mid-wave IR (MWIR) and long-wave IR (LWIR), there is not such a well-defined standard. There are well-defined directional hemispherical reflectance (DHR) standards, but the process of integrating BRDF measurements into DHR for the purpose of calibration is problematic, at best. Direct BRDF measurement standards are needed. This study use current calibration techniques to ensure valid measurements and then systematically …

Wave Optics Simulation Of Optically Augmented Retroreflections For Monostatic/Bistatic Detection, John J. Tatar Iii

Theses and Dissertations

Optical devices interrogated with a laser in the appropriate band can exhibit strong, deterministic reflections of the incident beam. This characteristic could be exploited for optical target detection and identification. The distribution of reflected power is strongly dependent on the geometry of the interrogation scenario, atmospheric conditions, and the cross section of the target optical device. Previous work on laser interrogation systems in this area has focused on analytic models or testing. To the best of my knowledge, I am presenting for the first time an approach to predict reflected power for a variety of interrogation configurations, targets, and propagation …

Interfacial Energy Between Carbon Nanotubes And Polymers Measured From Nanoscale Peel Tests In The Atomic Force Microscope, Mark C. Strus, Camilo I. Cano, R. Byron Pipes, Cattien V. Nguyen, Arvind Raman

Other Nanotechnology Publications

The future development of polymer composite materials with nanotubes or nanoscale fibers requires the ability to understand and improve the interfacial bonding at the nanotube-polymer matrix interface. In recent work [Strus MC, Zalamea L, Raman A, Pipes RB, Nguyen CV, Stach EA. Peeling force spectroscopy: exposing the adhesive nanomechanics of one-dimensional nanostructures. Nano Lett 2008;8(2):544–50], it has been shown that a new mode in the Atomic Force Microscope (AFM), peeling force spectroscopy, can be used to understand the adhesive mechanics of carbon nanotubes peeled from a surface. In the present work, we demonstrate how AFM peeling force spectroscopy can be …

Potential Migration Of Ε-Caprolactam To Water And Wine As Affected By Transportation And Storage, Joseph C. Ianneo

Master's Theses

Abstract: Under normal sealing and storage conditions, Nylon-6, poly-caprolactam-based plastic laminates may release impurities to packaged foods and liquids and the application of heat for cooking often increases the rate of migration. Epsilon-caprolactam is one of the main contaminates found to migrate from a Nylon-6 poly-caprolactam plastic film. The objectives of this study were to determine the effects of solvent, transportation and storage time on the migration of ε-caprolactam from a Nylon-6-based lidding material into water or a white wine substitute (12% ethanol). Polypropylene plastic cups were filled, sealed, packaged, stacked and exposed to a simulated 3-day cross-country shipment. Cups …

Optimization Of Gan Laser Diodes Using 1d And 2d Optical Simulations, Sean Richard Keali'i Jobe

Master's Theses

This paper studies the optical properties of a GaN Laser Diode (LD). Through simulation, the GaN LD is optimized for the best optical confinement factor. It is found that there are optimal thicknesses of each layer in the diode that yield the highest optical confinement factor. There is a strong relationship between the optical confinement factor and lasing threshold—a higher optical confinement factor results in a lower lasing threshold. Increasing optical confinement improves lasing efficiency. Blue LDs are important to the future of lighting sources as they represent the final color in the RGB spectrum that does not have a …

Development Of Microbial And Enzymatic Fuel Cells For Bio-Inspired Power Sources, Fatih Dogan, Shelley Minteer

Materials Science and Engineering Faculty Research & Creative Works

This report is based on some of the revolutionary concepts described in the Road Map on Bioinspired Power Systems within the AFRLRW Campus Challenge II. Development of biofuel cell concepts integrated with fuel regeneration and energy storage capabilities are proposed to create a compact and self-sustaining power system. The first part of this work identified a sediment based microbial fuel cell that could power small electronics and maintain electrical activity over long periods of time. AFRLRW does not feel that this work adequately addresses the original scope nor does it provide a basis on which to continue work. The second …

Competing Magnetic Interactions In The Intermetallic Compound Ho₂Mn₃Si₅, R. Nirmala, A. V. Morozkin, Jagat Lamsal, Zili Chu, V. Sankaranarayanan, K. Sethupathi, Y. Yamamoto, H. Hori, William B. Yelon, Satish K. Malik

Physics Faculty Research & Creative Works

The compound Ho2Mn3Si5 exhibits multiple magnetic transitions: (i) an ordering at ~78 K, (ii) a second magnetic transition at ~16 K, and (iii) an anomaly at ~4 K. Its paramagnetic Curie temperature is found to be small but positive. Assuming a free ion effective paramagnetic moment of 10.6µB for Ho3+ ion, the effective paramagnetic moment per Mn in this compound is calculated to be 1.73µB, which indicates the itinerant nature of Mn d electrons. The various transitions in magnetization data are perhaps due to the ordering of rare earth and Mn moments. The magnetization at 2 K in applied fields …

Electrical Properties Of Phosphate Glasses, Andrea Mogus-Milankovic, Ana Santic, Signo Tadeu Dos Reis, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

Investigation of the electrical properties of phosphate glasses where transition metal oxide such as iron oxide is the network former and network modifier is presented. Phosphate glasses containing iron are electronically conducting glasses where the polaronic conduction is due to the electron hopping from low to high iron valence state. The identification of structural defects caused by ion/polaron migration, the analysis of dipolar states and electrical conductivity in iron phosphate glasses containing various alkali and mixed alkali ions was performed on the basis of the impedance spectroscopy (IS). The changes in electrical conductivity from as-quenched phosphate glass to fully crystallized …

Materials And Coatings Derived From The Polymerizable Ionic Liquid Surfactants 1-(2-Acryloyloxyundecyl)-3-Methylimidazolium Tetrafluoroborate And 1-(2-Acryloyloxyundecyl)-3-Methylimidazolium 2-Acrylamido-2-Methyl-Propylsulfonate, Hong Gu

Master's Theses and Doctoral Dissertations

Polymerizable ionic liquid surfactants were synthesized and polymerized, yielding engineered advanced polymers that can be tailored for diverse applications. First, 1-(2-acryloyloxyundecyl)-3-methylimidazolium tetrafluoroborate (IL-BF₄) was synthesized and was copolymerized with methyl methacrylate (MMA) via microemulsion polymerization. The resulting polymer gels can be transformed into porous materials by anion exchange, and the porosity of the material can be tuned through the solvent shifting. Second, an ionic liquid composed of a 1-(2-acryloyloxyundecyl)-3- methylimidazolium (IL) cation and 2-acryloamido-2-methyl-propylsulfonate (AMPS) anion was synthesized and polymerized by UV irradiation, and introductory data are illustrated for humidity sensitive preparations suitable for chemFETs, for proton conducting …

The Effect Of Silicon Content On Impact Toughness Of T91 Grade Steels, Ajit K. Roy, Pankaj Kumar, Debajyoti Maitra

Mechanical Engineering Faculty Research

The impact resistance of silicon (Si)-containing modified 9Cr-1Mo steels has been investigated within a temperature regime of -40 to 440°C using the Charpy method. The results indicate that the energies absorbed in fracturing the tested specimens were substantially lower at temperatures of -40, 25, and 75°C compared to those at elevated temperatures. Lower impact energies and higher ductile-to-brittle-transition-temperatures (DBTTs) were observed with the steels containing 1.5 and 1.9 wt.% Si. The steels containing higher Si levels exhibited both ductile and brittle failures at elevated temperatures. However, at lower temperatures, brittle failures characterized by cleavage and intergranular cracking were observed for …

Preparation And Performance Of Co And La Co-Doped Li-Rich Lithium Manganate, Da-Qiao Zhou

Journal of Electrochemistry

The cathode material of Li_1.1Co_0.02La_0.01Mn₂O₄ was successfully synthesized by the method of co-precipitation followed by a solid state reaction.In the sintering temperature range of 700～850 ℃,X-ray diffraction(XRD) results showed a single phase of each material and the increase of crystallization degree,and scanning electron microscopic(SEM) images indicated that the particle size increased and the specific surface area decreased,respectively,with increasing the sintering temperature.Due to its lower polarization resistance,the Co and La co-doped lithium-rich lithium manganate(sintered at 800 ℃) positive electrodes showed the most promising electrochemical performance.The capacity retention after 50 cycles reached 98.5%.

Electrochemical Properties Of Functionalized Carbon Nanotubes And Their Applications In Analysis Of 6-Mercaptopurine, Bao-Yi Lu, Yan-Yan Lai, Hong Li

Journal of Electrochemistry

The electrochemical behaviors and adsorption properties of single-walled carbon nanotubes such as SWNT,SWNT-COOH,and SWNT-OH and multi-walled carbon nanotubes including MWNT,MWNT-COOH,and MWNT-OH modified at a graphite electrode have been investigated by using [Fe(CN)₆]^3-anion and [Co(phen)₃]³⁺ cation.It was shown that shows good redox reversibility of [Fe(CN)₆]^3-/4-reactions on the existed carbon nanotubes(CNT) modified electrode.Based on the strong adsorptive property of [Co(phen)₃]³⁺ on the CNT surface,the [Co(phen)₃]³⁺/CNT modified graphite electrode can be obtained by progressive potential sweeping and developed to monitor quantitatively 6-mercaptopurine(6-MP).The adsorption capacity of …

High Utilization Aupt Nanoparticles Supported On Mwcnts For Methanol Electro-Oxidation In Alkaline Medium, Xun Guo, Dao-Jun Guo, Xin-Ping Qiu, Li-Quan Chen, Wen-Tao Zhu

Journal of Electrochemistry

We synthesized gold-platinum electrocatalysts supported on multi-walled carbon nanotubes(MWCNTs) with high utilization by a simple one-step method.A high Pt loading series of bimetallic AuPt/MWCNTs catalysts were prepared by the improved ethylene glycol reduction method,and then were compared in terms of the electrocatalytic activity for methanol electro-oxidation using cyclic voltammetry(CV) and chronoamperometry in alkaline solutions.The structure of AuPt/MWCNTs was characterized by the transmission electron microscopy(TEM),X-ray diffraction(XRD) and energy-dispersive X-ray spectroscopy(EDS).The results showed that the AuPt/MWCNTs catalysts had high Pt utilization,uniform AuPt nanoparticles size and good electrocatalytic activity for methanol electro-oxidation.The effect of Au/Pt mass ratio on electrocatalytic activity was also investigated.The …

Preparation And Electrochemical Performance Of Li3V2(Po4)3, Hou-Gang Fan, Tao Jiang, Chun-Zhong Wang, Gang Chen, Ying-Jin Wei

Journal of Electrochemistry

The carbon coating Li₃V₂(PO₄)₃ powder samples were synthesized by carbon incorporation solid state reaction.The structure,morphology and electrochemical properties have been studied by X-ray powder diffraction,scanning electron microscopy and automatic battery tester system,respectively.Carbon coating on Li₃V₂(PO₄)₃ would prevent the particles from agglomerating,reduce the particle size,raise the conductivity and improve the samples′ electrochemical performance.

Silicon Nanowires As Anode Materials For Lithium Ion Batteries, Yan-Peng Fu, Hui-Xin Chen, Yong Yang

Journal of Electrochemistry

The SiNWs electrodes were fabricated by coating and direct growth methods,respectively.The structure,morphology and electrochemical performance of such materials were characterized by XRD,SEM and charge-discharge tests.The results show that the electrodes prepared by direct growth method had higher capacity,better battery life and also displayed and excellent cyclability at higher currents.During the process of lithiation,the initial crystalline Si transformed to amorphous LixSi,and the average diameter of the SiNWs increased.Despite the large volume changed,the SiNWs remained intact and did not break into smaller particles.

Electrocatalytic Reduction Of Oxygen On Tungsten Carbide Electrode, Chun-An Ma, Yun Huang, Ying-Hong Zhu, Zhao-Yang Chen

Journal of Electrochemistry

Tungsten carbide(WC) catalysts were prepared by gas-solid reaction using ammonium metatungstate as precursors which were pretreated with spray drying sphere miniaturation,carbon monoxide as carrier gas and hydrogen as deoxidizing gas.The WC electrode was fabricated using WC catalyst powders and PTFE as binding agent,and characterized by XRD and SEM.Electrocatalyst behavior of WC for oxygen reduction reaction in the sulphuric acid solution was studied by steady-state voltammetry and cyclic voltammetry.The results show that the WC powders obtained were in spheric particles and the prepared WC electrode had a good electrocatalyst activity to the oxygen reduction reaction.The electrode reaction was controlled by adsorption.The …

Nano-Sn/Hard Carbon Composite As Anode Material For Lithium Ion Batteries, Bing-Kun Guo, Jie Shu, Kun Tang, Ying Bai, Zhao-Xiang Wang, Li-Quan Chen

Journal of Electrochemistry

The tin(Sn) nano particles were embedded into the mesopores of hard carbon spherules(HCS) to form a composite anode material for lithium ion batteries.The structure of the obtained composite was characterized by X-ray diffraction(XRD) while its electrochemical performances were evaluated with galvanostatic cycling.It is found that the embedding Sn nanoparticles into porous HCS not only result in a composite material with high lithium storage capacity and capacity retention,but also increase the initial coulombic efficiency of the composite.Based on the infrared spectroscopic analysis,the enhanced initial coulombic efficiency is attributed to the inductive decomposition of the ROCO₂Li species in the solid …

19th International Symposium Of Fine Chemistry And Functional Polymers (Fcfp-Xix) & Iupac 5th Internaitonal Symoposium On Novel Materials And Synthesis (Nms-V), Editorial Office Of J.Electrochem.

Journal of Electrochemistry

No abstract provided.