Materials Science and Engineering Commons^™

Computational Microstructure Modeling Of Asphalt Mixtures Subjected To Rate-Dependent Fracture, Francisco Aragao

Civil and Environmental Engineering Theses, Dissertations, and Student Research

Computational microstructure models have been actively pursued by the pavement mechanics community as a promising and advantageous alternative to limited analytical and semi-empirical modeling approaches. The primary goal of this research is to develop a computational microstructure modeling framework that will eventually allow researchers and practitioners of the pavement mechanics community to evaluate the effects of constituents and mix design characteristics (some of the key factors directly affecting the quality of the pavement structures) on the mechanical responses of asphalt mixtures. To that end, the mixtures are modeled as heterogeneous materials with inelastic mechanical behavior. To account for the complex …

Purely Electronic Switching With High Uniformity, Resistance Tunability, And Good Retention In Pt-Dispersed Sio2 Thin Films For Reram, Albert Chen

Albert B Chen

Resistance switching memory operating by a purely electronic switching mechanism, which was first realized in Pt-dispersed SiO2 thin films, satisfies criteria including high uniformity, fast switching speed, and long retention for non-volatile memory application. This resistive element obeys Ohm's law for the area dependence, but its resistance exponentially increases with the film thickness, which provides new freedom to tailor the device characteristics.

The Montana Mule: A Case Study In Interdisciplinary Capstone Design, Brock J. Lameres, Ahsan Mian, Hunter Lloyd, Robb Larson

Mechanical and Materials Engineering Faculty Publications

The Montana MULE: A Case Study in Interdisciplinary Capstone Design In May of 2010, NASA held the 1st annual Lunabotics Mining Competition at theKennedy Space Center in Florida. In this competition, 22 teams from across the nationbuilt remote-controlled, robotic excavators to mine lunar regolith simulant. The winnerof the competition was the team who could successfully deposit the most regolith into acollector in 15 minutes. The goal of this competition was to encourage multidisciplinarycapstone design projects. Of the 22 teams that participated in the competition, the“Montana MULE” from Montana State University (MSU) was the only robot tosuccessfully mine the qualifying weight …

Behavior Of Na+-Polystyrene Sulfonate At The Interface With Single-Walled Carbon Nanotubes (Swnts) And Its Implication To Swnt Suspension Stability, Tabbetha A. Dobbins, Richard Chevious, Yuri Lvov

Faculty Scholarship for the College of Science & Mathematics

The assembly of sodium polystyrene sulfonate (Na+-PSS) at the surface of single-walled carbon nanotubes (SWNTs) in pH 3 aqueous solution is described. Rather than forming linear or sheet-like chain morphologies over SWNT surfaces, Na+-PSS adopts a spherically collapsed conformation believed to be the result of cation (either Na+ or H+) condensation onto the ionized polymer chain. It is well reported that cations (and also anions) adsorb preferentially onto single-walled and multi-walled carbon nanotube surfaces leading to an increased ion concentration in the near surface regions relative to the bulk solution. This work provides experimental evidence for preferentially absorbed cation condensation …

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 …

In Situ Nanomechanical Testing In Focused Ion Beam And Scanning Electron Microscopes, Daniel S. Gianola, Andreas Sedlmayr, Reiner Mönig, Cynthia A. Volkert, Ryan C. Major, Edward Cyrankowski, S.A. Syed Asif, Oden L. Warren, Oliver Kraft

Departmental Papers (MSE)

The recent interest in size-dependent deformation of micro- and nanoscale materials has paralleled both technological miniaturization and advancements in imaging and small-scale mechanical testing methods. Here we describe a quantitative in situ nanomechanical testing approach adapted to a dualbeam focused ion beam and scanning electron microscope. A transducer based on a three-plate capacitor system is used for high-fidelity force and displacement measurements. Specimen manipulation, transfer, and alignment are performed using a manipulator, independently controlled positioners, and the focused ion beam. Gripping of specimens is achieved using electron-beam assisted Pt-organic deposition. Local strain measurements are obtained using digital image correlation of …

The Effects Of Humidity On The Dielectric Response In Ferroelectric Polymer Films Made By Langmuir-Blodgett Deposition, Kristin Kraemer, Alexander Sorokin, Christina Othon, Stephen Ducharme, Vladimir Fridkin

Christina M Othon

No abstract provided.

Electron Irradiation Effects On Ferroelectric Copolymer Langmuir-Blodgett Films, Christina M. Othon, Stephen Ducharme

Christina M Othon

The effect of irradiation on the ferroelectric properties of Langmuir-Blodgett films of the copolymer poly(vinylidene fluoride-trifluorethelene) is investigating using 1.26 MeV electrons with dosages from 16 to 110 Mrad. Irradiation causes a systematic decrease in the phase transition temperature, coercive field and polarization of these thin films.

Characterization Of A Pdms Microfluidic Reactor For Synthesizing Quantum Dots, Brian Harley

Materials Engineering

A PDMS microfluidic reactor was made in Cal Poly’s class 1000 clean room for the purpose of synthesizing quantum dots. The device master mold was made from a silicon substrate and SU-8 features 50μm tall. The PDMS reactor was cast from that mold. The flow rates of fluid through the channels, heating of the reactor and pressure in the reactor were measured in order to characterize the potential for synthesizing quantum dots. Flow rates of 20 mL/hr through 4 mL/hr were tested to characterize the consistency of amount of time the fluid remains in the reactor at a constant flow …

Understanding The Effects Of Temperature Extremes On The Tensile And Short Beam Shear Strength Of Epoxy-Based, Glass-Fiber Reinforced Composites, Jonathan Blake Patterson

Materials Engineering

Aptera (Oceanside, CA) has developed two epoxy-based, silica fiber-reinforced composites to be used on their three-wheeled all-electric vehicle called the 2e. Aptera’s composites were studied at temperature extremes using a dynamic mechanical analysis (DMA) system and by tensile and short beam shear (SBS) testing using an Instron testing system. These tests were conducted to simulate the loading of the composite in the 2e vehicle. Tensile and short beam shear samples were machined to 150 mm x 25 mm x 2 mm and 40 mm x 13 mm x 6 mm, respectively. DMA samples were machined to 30 mm x 5 …

Characterization Of The Relationship Between The Microstructure And Tensile Strength Of Annealed Ti-6al-4v, Aldo Corona

Materials Engineering

Tensile coupons of Ti-6Al-4V were heat treated at varying annealing temperatures from 1200°F (648°C) to 1450°F (787°C) at 50°F (23°C) increments for 1 hour. The samples were air cooled to room temperature or furnace cooled to 800°F (426°C) followed by air cooling to room temperature. Four tensile coupons were treated at each annealing temperature and cooling rate. Alpha case was observed to form on the surface of the samples post heat treatment with a maximum depth of 25 µm (.001 in). Samples were tensile tested for their ultimate tensile strength, yield strength, and percent elongation. Samples across all annealing temperatures …

Determining A Method For Rendering Low Cost Cdse(Zns) Core(Shell) Quantum Dots Aqueous Soluble Via Amphiphilic Polymer Wrapping, Patrick Mcbride

Materials Engineering

Herein is described the procedure of two amphiphilic polymer wrapping techniques that may be employed for obtaining aqueous soluble quantum dots (QDs) for use in biological fluorescent imaging applications. The advent of QDs has led to new nanoscale fluorescent materials that exhibit unparalleled quantum yields (QYs), high resistance to photobleaching, tunable emissions, and
absorption over a large optical range. However, the QD synthesis employed here at Cal Poly to obtain bright, photostable CdSe(ZnS) core(shell) QDs involves the use of organic solvents and surfactants, leading to hydrophobic QDs. Since all of biology relies on aqueous solubility, this hydrophobicity creates a major …

Design And Characterization Of A Process For Bulk Synthesis Of Cadmium Selenide Quantum Dots, Susan Harada

Materials Engineering

The objective of the process is to synthesize quantum dots that will fluoresce over the visible spectrum of 450 to 650nm; then to mix the quantum dots together in a polymer matrix so that when illuminated with a blue LED the mixture yields “white” light. The current quantum dot synthesis is a chemical process that involves adding a room temperature Se-TOP precursor to a 225°C Cd precursor solution to cause nucleation and growth of nanoparticles. This method, however, only yields quantum dots that fluoresce in the 520 to 600nm range. In order to create the “white” light phosphor replacement, red …

The Effects Of Colorant Oxides And Firing Rate On The Nucleation And Growth Of Zinc Silicate Crystals In Crystalline Glazes, Nicolas Coffey

Materials Engineering

This study looked at the effects of colorant oxides and firing rate on the nucleation and growth of crystals in zinc-based crystalline glazes. One weight percent of iron and copper oxide powders were mixed separately with a zinc-based crystalline glaze. The uncolored glaze along with both colored glazes were applied to test tiles and fired. Two different firing schedules were used with different ramp up firing rates of 165°C/hr (slow) and 205°C/hr (fast). X-ray diffraction (XRD) analysis found both zinc oxide and silica oxide in the raw glaze, which are the main components in the formation of zinc silicate. XRD …

Processing Pdms Gecko Tape Using Isopore Filters And Silicon Wafer Templates, Boris Luu

Materials Engineering

Gecko tape was processed through nanomolding involving two types of templates. One template was a Millapore Isopore polycarbonate membrane filter and the other template was an n-type silicon wafer processed to include four different pore diameters. These pore diameters were 20, 40, 80, and 160 microns. AutoCAD was used to design to a mask to be used later during photolithography. Two n-type wafers were sputtered with aluminum, underwent photolithography, and then etched using reactive ion etching. A template was placed into a Petri dish and Sylgard 184 polydimethylsiloxane (PDMS) was poured on the template. Once the PDMS cured, the 1 …

Investigating The Mechanical Properties Of Compression Molded Carbon Fiber Reinforced Sheet Molding Compound, Bradley A. Jones

Materials Engineering

Callaway Golf receives a proprietary blend of prepreg material from Quantum Composites. Callaway processes the prepreg in-house and supplied 254mm x 254mm x 1.3mm panels of carbon fiber sheet molding compound (CFSMC) for characterizing. Tensile strength was analyzed by conducting tensile tests per ASTM D3039. Tensile coupons were cut to 254mm long by 25.4mm wide. Tabs were constructed from 1.6mm thick GFRP printed circuit board material. A commercial grade two part epoxy was used to bond the tabs to the CFSMC. Tensile results were inconclusive due to consistent fractures occurring outside the gauge lengths of the specimens.

Flexure strength was …

Characterization Of The Oxidation Kinetics Of Fecral Ferritic Stainless Steels At 900°C For Catalytic Converter Applications, Stacy Stamm

Materials Engineering

This study characterized the oxidation kinetics of two types of ferritic stainless steel foils used as substrates for catalytic converters. Catalytic converters rely on an alumina layer on the surface of the foils, which allows the catalyst to attach to the substrate. Because the alumina layer is so important, this study characterized the weight gain, thickness, and composition of the alumina as it grew at 900°C for up to 400 hours. The two foils characterized were an MK foil, used for gasoline engines, and an EMS foil, used for diesel engines. The MK foil showed a percent weight gain of …

Dissimilar Metal Weld Variability Due To Lot Differences In Nitinol/ Stainless Steel Interface, Matthew R. Rudow

Materials Engineering

Abstract

An experiment was conducted to determine and reduce the causes of variation between a 304 Stainless Steel and super elastic Nickel Titanium dissimilar metal weld. Six factors were established to understand the cause of variation: perpendicularity, final grind, surface finish, weld force, weld pulse duration, and alignment. Using a rotational test with an air piston break pressures were established and charted in Minitab to identify trends. It was shown that weld force and weld pulse duration were the two factors that had the most influence on break strength. This data also showed that higher strength groups had less variability. …

Artificial Muscle Project: Process Development Of Polydimethyl Siloxane Thin Films For Use In Dielectric Electroactive Polymer Artificial Muscle Actuators, Vincent J. Gayotin, Richard W. Morrison, Paul A. Preisser

Materials Engineering

An artificial muscle design was created founded on the principles of a dielectric electroactive polymer (DEAP), which is fundamentally similar to a capacitor. A polydimethyl siloxane (PDMS)-based elastomer, Sylgard 184 from Dow Corning, was chosen for the design and spun coat onto polystyrene (PS) Petri dishes at varying speeds to create a thin film, using speeds of 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, and 6000 rpm. The film thicknesses were measured optically through use of a microscope with coupled computer imaging software to generate a characteristic curve of film thickness to spin speed, achieving a minimum film thickness …

The Design And Manufacture Of A Microfluidic Reactor For Synthesis Of Cadmium Selenide Quantum Dots Using Silicon And Glass Substrates, Peter Gonsalves

Materials Engineering

A microfluidic reactor for synthesizing cadmium selenide (CdSe) quantum dots (QDs) was synthesized out of silicon and Pyrex glass. Microfabrication techniques were used to etch the channels into the silicon wafer. Holes were wet-drilled into Pyrex glass using a diamond-tip drill bit. The Pyrex wafer was aligned to the etched silicon wafer and both were anodically bonded to complete the microfluidic reactor. Conditions for anodic bonding were created by exposing the stacked substrates to 300V at ~350^oC under 5.46N of force. Bulk CdSe solution was mixed at room temperature and treated as a single injection. The syringe containing …