Engineering Commons^™

Size Scaling Of Strength And Toughness For 3d Printed Polymer Specimens, Darren Thomas Bell

Open Access Theses

To find material systems that offer low density and high strength, stiffness or toughness, hierarchically designed material systems have provided a promising research area. This thesis lays the groundwork for designing efficient micro-architectured material systems by characterizing size effects for 3d printed polymer parts. Two methods were used to analyze data from 3-point bend tests for specimens of varying size: the load-separation method was used for finding the point of crack growth initiation and Bazant’s method was used to find shape independent strength at failure. The strength values were used as inputs for finding size independent material constants within a …

Design Of Nitroxide-Based Radical Polymer Materials For Electronic Applications, Martha E. Hay

Open Access Theses

Radical polymers represent a new class of organic electronic materials that rely on an oxidation-reduction (redox) reaction to transport charge. That is, stable radical sites pendant to the polymer backbone communicate electronically through a rapid oxidation-reduction reaction. This redox mechanism has previously been established as effective for charge-storage applications (e.g., secondary batteries). When applied in the solid state, radical polymers demonstrate electrical conductivity on par with that of first-generation conjugated polymer electronic materials. This initial success has prompted interest in developing design rules for radical polymers. Specifically, this thesis explores the impact of radical density in a polymer …

Degradation Of High Performance Polymeric Fibers: Effects Of Sonication, Humidity And Temperature On Poly (P-Phenylene Terephthalamide) Fibers, Nelyan Lopez-Perez

Open Access Theses

High performance fibers are characterized by properties such as high strength and resistance to chemicals and heat. Due to their outstanding properties, they are used on applications under harsh environments that can degrade and decrease their performance. Fiber degradation due to different chemical and mechanical factors, is a process that begins at a microstructural level. Changes in the polymer’s chemical or physical structure can alter their mechanical properties. Knowledge of the structure-properties relationship and the effects of environmental chemical and physical factors over time, is crucial for the improvement and development of high performance fibers.

In this study ballistic fibers …

Linking Nanoscale Mechanical Behavior To Bulk Physical Properties And Phenomena Of Energetic Materials, Matthew R. Taw

Open Access Theses

The hardness and reduced modulus of aspirin, RDX, HMX, TATB, FOX-7, ADAAF, and TNT/CL-20 were experimentally measured with nanoindentation. These values are reported for the first time using as-received micron sized crystals of energetic materials with no additional mechanical processing. The results for TATB, ADAAF, and TNT/CL-20 are the first of their kind, while comparisons to previous nanoindentation studies on large, carefully grown single crystals of the other energetic materials show that mechanical properties of the larger crystals are comparable to crystals in the condition they are practically used. Measurements on aspirin demonstrate the variation that can occur between nanoindentation …

The Influence Of Alkalinity Of Portland Cement On The Absorption Characteristics Of Superabsorbent Polymers (Sap) For Use In Internally Cured Concrete, Juan D. Tabares Tamayo

Open Access Theses

The concrete industry increasingly emphasizes advances in novel materials that promote construction of more resilient infrastructure. Due to its potential to improve concrete durability, internal curing (IC) of concrete by means of superabsorbent polymers (SAP) has been identified as one of the most promising technologies of the 21st century. The addition of superabsorbent polymers into a cementitious system promotes further hydration of cement by providing internal moisture during the hardening and strength development periods, and thus limits self-desiccation, shrinkage, and cracking.

This thesis presents the work performed on the series of cement pastes with varying alkalinity of their pore solutions …

Mechanism Of Shot Peening Enhancement For The Fatigue Performance Of Aa7050-T7451, Daniel James Chadwick

Open Access Theses

Shot peening is a dynamic cold working process involving the impingement of peening media onto a substrate surface. Shot peening is commonly employed as a surface treatment technique within the aerospace industry during manufacturing, in order to improve fatigue performance of structural components. The compressive residual stress induced during shot peening is understood to result in fatigue crack growth retardation, improving the performance of shot peened components. However, shot peening is a compromise between the benefit of inducing a compressive residual stress and causing detrimental surface damage. Due to the relatively soft nature of AA7050-T7451, shot peening can result in …

Passive Thermal Management Using Phase Change Materials, Yash Yogesh Ganatra

Open Access Theses

The trend of enhanced functionality and reducing thickness of mobile devices has led to a rapid increase in power density and a potential thermal bottleneck since thermal limits of components remain unchanged. Active cooling mechanisms are not feasible due to size, weight and cost constraints. This work explores the feasibility of a passive cooling system based on Phase Change Materials (PCMs) for thermal management of mobile devices. PCMs stabilize temperatures due to the latent heat of phase change thus increasing the operating time of the device before threshold temperatures are exceeded. The primary contribution of this work is the identification …

Additive Manufacturing Of Carbon Fiber-Reinforced Thermoplastic Composites, Nicholas M. Denardo

Open Access Theses

Additive manufacturing, or 3D printing, encompasses manufacturing processes that construct a geometry by depositing or solidifying material only where it is needed in the absence of a mold. The ability to manufacture complex geometries on demand directly from a digital file, as well as the decreasing equipment costs due to increased competition in the market, have resulted in the AM industry experiencing rapid growth in the past decade. Many companies have emerged with novel technologies well suited to improve products and/or save costs in various industries.

Until recently, the applications of polymer additive manufacturing have been mainly limited to prototyping. …

Solution Based Processing Of Garnet Type Oxides For Optimized Lithium-Ion Transport, Derek K. W. Schwanz

Open Access Theses

Current lithium based portable electrochemical storage devices are limited by the inherent instability and volatility of conventional electrolytes materials. Ceramic materials show much promise for use in advanced lithium based battery systems due to their inhibition of dendritic growth and high thermal and chemical stability. The main drawback of solid materials is their low ionic conductivity, relying on lattice hopping to transport ions between electrodes during cycling. Garnet type oxides, specifically of the base compositions Li7La3Zr2O12 and Li5L a3Bi2O12 have been synthesized through Pechini method solution based processing by the dissolution of reagent salts into nitric acid and creation of …

Development Of A Novel Polymer-Garnet Solid State Composite Electrolyte Incorporating Li-La-Zr-Bi-O And Polyethylene Oxide, Muhammed Ramazan Oduncu

Open Access Theses

Current lithium ion batteries are comprised of organic liquid electrolytes - a mixture of lithium salts and binary solvents such as ethylene carbonate (EC) and dimethyl carbonate (DMC). The main drawbacks of this liquid mixture related to safety are flammability of the organic solvents and chemical instability with the electrode materials. To date, various ceramic and polymer materials have been considered which overcome safety issues. However, a common problem of these solid state materials is that they are not able to provide high ionic conductivity at ambient temperatures. Garnet-type cubic Li7La 3Zr2O12 ceramic material has attracted much interest because of …

Polymerizable Lipids For Controlled Functionalization Of Layered Materials, Kortney Kaye Rupp

Open Access Theses

Self-assembled monolayers (SAM’s) offer a straightforward approach to tailoring the interfacial properties of metals, metal oxides and semiconductors. Noncovalent functionalization of single-layer graphene offers the possibility to finely tune surface chemistry for future applications in electronics. Polymerization of photochemically reactive molecules in a lying-down phase has been used to increase the strength of intermolecular interactions between long alkanes and HOPG substrates. Long-chain fatty acid derivatives with internal diyne groups yield a conjugated ene-yne polymer upon UV irradiation. Diyne lipids with phosphocholine (diyne PC) and phosphoethanolamine (diyne PE) groups offer a charged form of the head group that is robust towards …

Fabrication And Drying Of Cnc-Based Microcapsules With Pdms/Antimicrobial Oil Cores Via The Microcapillary Device, Yunze Dai

Open Access Theses

Cellulose nanocrystals (CNC) which are the crystalline regions of elementary microfibrils found in cellulose are becoming a promising biocompatible nanoscale building block. We report on the generation, evolution, and drying of CNC capsules with oil cores, obtained from double emulsion drops. Microcapillary devices were used to generate the double emulsion drops with outer diameters ranging from 75 to 225 µm, and shell thicknesses ranging from 5 to 60 µm. 10 wt% aqueous CNC suspensions without and with the addition of PEGDA, a UV-crosslinkable binder, were used as the shell material while 10 cSt PDMS oil was used in the core. …

Nanoscale Phonon Thermal Conductivity Via Molecular Dynamics, Jonathan M. Dunn

Open Access Theses

Molecular dynamics (MD) simulations provide a useful and simple means of calculating the nanoscale thermal properties of materials, which requires special analysis since the thermal properties of materials change when their dimensions reach the nanoscale. In this research, MD is used to investigate the nanoscale phonon thermal transport of materials that are attracting much interest in the areas of materials science and nuclear physics. In order to evaluate two distinct methods of calculating the thermal conductivity of materials using MD, the simulation methods are first applied to Si. Once an understanding of each simulation method is established, they are then …

Assessing The Performance Of A Soy Methyl Ester -Polystyrene Topical Treatment To Extend The Service Life Of Concrete Structures, D'Shawn G. Thomas

Open Access Theses

Experimental results show that soy methyl ester (SME), a derivative of soy bean oil, along with the incorporation of polystyrene (PS) is a non-toxic, biodegradable and renewable material that can be used effectively as a topical concrete surface treatment. While, concrete sealants and topical surface treatments can be used to extend to durability of concrete structures, it is difficult to predict the durability of concrete structures sealed with a sealant or topical surface treatment. This is due to a lack of necessary model inputs that can be used to address the durability of concrete structures treated with these materials. In …

Techniques And Technologies For Decontaminating Chemically Contaminated Premise Plumbing Infrastructure, Karen S. Casteloes

Open Access Theses

Recent large-scale drinking water chemical contamination incidents in Canada and the U.S. have affected more than 1,000,000 people. In all cases premise plumbing has become contaminated and disparate plumbing decontamination approaches have been applied. Premise plumbing components include the service line and piping within the building as well as various appurtenances (i.e., tanks, valves, fixtures). The overall research goal was to identify techniques and technologies that can be used for premise plumbing decontamination. To achieve this goal two separate studies were conducted and are presented as two independent thesis chapters.

The study described in Chapter 1 was designed to understand …

Effect Of Humidity On The Creep Response Of Cellulose Nanocrystals Films, Marianne C. Valone

Open Access Theses

Cellulose nanocrystals (CNCs) are a derivative of cellulose, the Earth’s most abundant source of a sustainable polymer. There are many applications for CNCs such as batteries, antimicrobial films, flexible displays and drug delivery. This research is focused on CNCs films and the mechanical properties once humidity was introduced.

The creation of self-aligned CNCs films was utilized to perform dynamic mechanical analysis (DMA) testing. The Forest Products Lab (FPL) in Madison, Wisconsin provided the CNCs used. Both 3.5 wt.% and 9.1 wt.% films were made and tested. A DMA method was created to test the creep response of the CNCs films …