Engineering Commons^™

Thermal And Mechanical Numerical Modeling Of Extrusion-Based 3d Printed Reinforced Polymers For Selecting Manufacturing Process Parameters, Sunil Bhandari

Electronic Theses and Dissertations

Extrusion-based 3D printing of thermoplastic polymer composites manufactures parts that have nonhomogenous, orthotropic, and process-dependent macro-scale material properties. As a part of the dissertation, research works were carried out to: • improve the interlayer mechanical properties and reduce the orthotropy, • use experimentally homogenized orthotropic material properties to numerically model the mechanical behavior of the non-homogenous orthotropic 3D printed parts, • create an efficient numerical thermal model to predict the process-dependent thermal history of the 3D printed part, and • aid the manufacturing process by selecting a suitable set of processing parameters based on a simplified sequentially coupled thermomechanical model. …

An Investigation Into Energy-Material Properties Interaction In Additive Manufacturing Of Polymers., Pu Han

Electronic Theses and Dissertations

Additive manufacturing (AM), known as three-dimensional (3D) printing, is a fabrication process to build 3D objects layer by layer based on computer aided design (CAD) model or digital 3D model. Fused filament fabrication (FFF) has become a preferred method for additive manufacturing due to its cost-effectiveness and flexibility. However, the parts built using FFF process suffer from lower mechanical strength compared to that fabricated using traditional method and rough surface finish. With this motivation, this dissertation aims to develop and implement a novel in-process laser assisted technique on FFF to heal the microstructure of FFF built objects by enhancing reptation …

Synthesis, Crystal Structure And Ionic Conductivity Of Ruddlesden-Popper Oxide Materials: Effects Of Ionic Radii And Defects On Lithium-Ionic Conductivity., Selorm Joy Fanah

Electronic Theses and Dissertations

Layered perovskite oxides of the Ruddlesden-Popper (RP) type structure can be good lithium-ion conductors for solid electrolyte applications in all-solid-state batteries, due to the large gap separating octahedral layers which can be useful pathways for Li-ion conduction. However, little work has been done on their lithium-ion transport properties in these materials despite their interesting structural properties. This work highlights the synthesis and study of the ionic conductivities in a series of n = 2 and 3 Ruddlesden-Popper oxides, as part of an ongoing investigation in search of alternative solid electrolyte materials. Several different strategies were employed for the enhancement of …

Finite Element Analysis Of Surface Hardening Treatments Of Steels For Automotive Powertrain Applications, Filippo Jones

Electronic Theses and Dissertations

Surface hardening is a procedure that is usually performed on steel components, in order to impart in these the strength and surface hardness that are necessary for their correct operation, whilst maintaining a reasonable value of ductility in the overall component.

The latter is usually composed of a sequence of heat treatments: carburizing, quenching and tempering. Each of these have different effects that, if correctly combined, can lead to the desired final mechanical properties in the component.

Carburizing is a process that increases the amount of carbon concentration at the component surface. Quenching is a quick decrease in temperature that …

Optimization Of Chemistry And Process Parameters For Control Of Intermetallic Formation In Mg Sludges, Yintian Fu

Electronic Theses and Dissertations

Intermetallic formation in sludge during magnesium (Mg) melting, holding and high pressure die casting practices is a very important issue. But, very often it is overlooked by academia, original equipment manufacturers (OEM), metal ingot producers and even die casters. The aim of this study was to minimize the intermetallic formation in Mg sludge via the optimization of the chemistry and process parameters. Through the analyses of the commercial sludges, it was found that AZ91D recycling ingot sludge, and AZ91D, AM60B and AE44 die casting sludge contained intermetallic of 2.77wt.%, 10.33wt.%, 34.07wt.% and 44.81 wt.%, respectively. The Al8Mn5 intermetallic particles were …

Optimization Of Chemical Compositions Of Al-Si-Cu-Ni-Sr Alloys With High Strengths And Electrical Conductivities, Yuxian Li

Electronic Theses and Dissertations

Mechanical strengths and electrical conductivity are the very important engineering properties of lightweight metallic materials used in the automotive industry, especially for battery-powered electric vehicles (BEV). However, the main issue is that high strength and high electrical conductivity are mutually exclusive due to physical nature of these properties. The aim of this study is to develop new cast aluminum alloys for the production of rotor bar in the rotor with high as-cast strength and electrical conductivity. A design of experiment (DOE) technique, Taguchi method, was used to develop high as-cast strength and electrical conductivity alloys with various element addition of …

Correlation Between Microstructure And Mechanical Properties Of Press-Hardenable Steels For Various Quenching Rates, Radha Thakkar

Electronic Theses and Dissertations

Manufacturing structural automotive components by hot stamping advanced high strength steel sheets with tailored mechanical properties helps to reduce vehicle weight and improve crashworthiness. The purpose of this research work is to establish a relationship between the die temperature in hot stamping, the corresponding as-quenched microstructural features and mechanical properties. A series of experiments were carried out in which 1.4 mm 22MnB5 and 1.4 mm 37MnB4 steel sheet specimens were austenitized to 930°C and quenched between dies preheated to different temperatures. The mechanical properties were determined from tensile tests and hardness measurements and the corresponding microstructures were analyzed. It was …

Rapid Annealing Of Perovskite Solar Cell Thin Film Materials Through Intense Pulse Light., Amir Hossein Ghahremani

Electronic Theses and Dissertations

Perovskite solar cells (PSCs) have garnered a great attention due to their rapid efficiency improvement using cheap and solution processable materials that can be adapted for scalable high-speed automated manufacturing. Thin film perovskite photovoltaics (PVs) are typically fabricated in an inert environment, such as nitrogen glovebox, through a set of deposition and annealing steps, each playing a significant role on the power conversion efficiency (PCE), reproducibility, and stability of devices. However, atmospheric processing of PSCs would achieve lucrative commercialization. Therefore, it is necessary to utilize materials and methods that enable successful fabrication of efficient PSCs in the ambient environment. The …

Mixed Metal Oxide Nanowires Via Solid State Alloying., Veerendra Atla

Electronic Theses and Dissertations

Mixed metal oxide materials with composition control find applications in energy conversion and storage processes such as heterogenous catalysis, photoelectrochemical catalysis, electrocatalysis, thermal catalysis, and lithium-ion batteries. Mixed metal oxides and/or complex oxides with composition control and in one-dimensional form as nanowires could be interesting to various catalysis applications due to control on single crystal surfaces, active sites, acidity versus basicity site density, and oxygen vacancies. The major challenge is to synthesize mixed metal oxide nanowires beyond binary oxides with composition control. In this dissertation, solid state alloying of binary oxide nanowires with solid and liquid precursors is studied to …

Interfacial Heat Transfer In Squeeze Casting Of Cast Al Alloy A380 And Mg Alloy Az91 And Wrought Alloy Az31, Luyang Ren

Electronic Theses and Dissertations

The weight reduction of vehicles and airplanes in the automotive and aerospace industries is urgently needed due to the government regulation and market demand. To satisfy engineering performance of lightweight auto and aero components, high strength light alloys such as aluminum (Al) or magnesium (Mg) alloys are usually adopted. This study was intended to explore a solution for casting high strength cast and wrought Al and Mg alloys. Before light alloys can be utilized for mass production, critical processing parameters need to be accurately determined. The interfacial heat transfer coefficient is one of the most important factors in casting processes. …

Nanostructured Self-Assembled Thin Films Of Cationic Bottlebrush Block Copolymers, Hathaithep Senkum

Electronic Theses and Dissertations

Biofouling which is an accumulation of small species on submerged surfaces that causes detrimental impacts on economic and environmental factors for aquaculture activities and human health. To suppress the fouling, polymeric coatings from amphiphilic block copolymers provide nanostructured surfaces and carry multiple functional groups in a molecular chain. Polymers with quaternary ammonium functional groups enable material coatings to inhibit microbial adhesion by killing bacteria, consequently prolonging the material efficiency of, for example, medical implanted devices. Herein, well-defined architectures with full-arm density of quaternary ammonium bottlebrush polymers were generated from grafting-through ring opening metathesis polymerization (ROMP). Factors such as the halide …

Development Of Hybrid Ultra-High Performance Concrete Thermoplastic Composite Panels For Blast And Ballistic Protection, Alyssa M. Libby

Electronic Theses and Dissertations

In recent years, ultra-high performance concrete (UHPC) has become a material of interest for structures needing resistance to impact and blast loadings. These types of loadings have induced brittle flexural failure in UHPC due to punching shear from the impactor. One way to improve the impact resistance, energy absorption, and ductility of UHPC is by adding fiber-reinforced polymer (FRP) skins to the front and rear faces of the concrete, resulting in a sandwich configuration. In this study, E-glass fiber-reinforced thermoplastic laminates were bonded to UHPC panels using a heated consolidation process known as stamp thermoforming. The bond between the UHPC …

Handling And Manipulation Of Water- And Air- Borne Biological Samples Using Liquid-Infused Surfaces, Daniel P. Regan

Electronic Theses and Dissertations

Research on novel materials to handling water- and airborne samples for biological threats analysis is in great demand due to the COVID-19 pandemic. Work conducted on a new field of material science, called liquid-infused surfaces, demonstrate strong potential for the handling and manipulation of biological samples. As a result of the field’s infancy, only a limited number of studies have explored how liquid-infused surfaces can apply droplet manipulation strategies to address real-world problems. Presented in this dissertation are two platforms that leverage liquid-infused surfaces to address the challenges associated with handling water- and airborne biological samples. When dealing with waterborne …

Monitoring Of Overhead Polymer Core Composite Conductors Under Excessive Mechanical Loads Using Fiber Bragg Grating Sensors, Daniel H. Waters

Electronic Theses and Dissertations

This combined experimental and numerical study addresses mechanical effects associated with static and dynamic loading of novel High Temperature Low Sag (HTLS) transmission line polymer core composite conductors. The developed methodology was successfully applied to ACCC® to explain the complex failure mechanisms associated with combined bending and tension loading. Furthermore, the use of Fiber Bragg Grating (FBG) sensors was investigated for the first time to monitor the ACCC® design during installation and in-service.

Transverse low-velocity impacts to the ACCC® conductor having either free or constrained end conditions and large axial tensile loads were performed. It was identified that the most …

Quality Assurance Of Lightweight Structures Via Phase-Based Motion Estimation, Ikenna E. Ifekaonwu

Electronic Theses and Dissertations

In recent years, lightweight structures have become mature and adopted in various applications. The importance of quality assurance cannot be overemphasized hence extensive research has been conducted to assess the quality of lightweight structures. This study investigates a novel process that exploits motion magnification to investigate the damage characteristics of lightweight mission-critical parts. The goal is to assure the structural integrity of 3D printed structures and composite structures by determining the inherent defects present in the part by exploiting their vibration characteristics. The minuscule vibration of the structure was recorded with the aid of a high-speed digital camera, and the …

Reclamation Of Fused Silica From Investment Shells Used For Casting Steel, Samuel L. Holt

Electronic Theses and Dissertations

Fused silica is widely used for investment casting shell molds. Fused silica shells are discarded after being used for casting one time. This is due to the transformation of fused silica to beta cristobalite above 1652℉ (900℃). To reduce cost and waste of investment casting foundries, this study is exploring a method to inhibit transformation of fused silica and reclaim it from high temperature investment casting shells. This research has employed firing to minimalize fused silica transformation to cristobalite. The phase transformation is minimalized due to sintering and coarsening of the particles during firing. Coarsening reduces surface area to volume …

Mechanical Properties Of Nanomodified Hybrid Gfrp Composite Materials, Micah Rop Kimutai

Electronic Theses and Dissertations

The mechanical behavior of the nanomodified hybrid epoxy matrix was investigated in glass fiber reinforced plastics (GFRP). In this study, five nanocomposites enriched with as received halloysite, nanomer I.28E, HNT-APTES, and the hybrid combinations of the two HNTs with the nanomer I.28E were successfully fabricated. To evaluate the effects and morphological characteristics of the individual fillers and the hybrid configurations on the epoxy resin matrix, TGA, DSC, and DMA were analyzed. To understand the effect of the five configurations on the neat GFRP laminate, mode I interlaminar fracture toughness, tensile, and vibration properties were investigated. Electron microscopy testing techniques were …

Biomechanical Investigation Of Plant Vascular Tissue For Bio-Inspired Design And Flexible Composites, Mukesh Roy

Electronic Theses and Dissertations

No abstract provided.

Development Of A High Strength Composite Material Using Large Scale 3d Printing Applications Using Waste Plastic And Steel, Naga Sri Madhavareddy

Electronic Theses and Dissertations

This project focuses on developing a high strength composite material for largescale 3D printing applications using recycled materials like High-Density Polyethylene (HDPE) and Steel 430. This material has applications for in-space manufacturing (the Moon or Mars) as well as large-scale manufacturing on earth. In addition to creating a strong useful material, materials that are easily recycled, but are often not recycled, are used. Recycling plastic and metal reduces pollution, saves resources, reduces waste going to landfills, and prevents the destruction of habitats from the polymerization of new plastic and similarly mining new ore. The percentage of HDPE generated from recycled …

Observation Of New Particle Formation In The Northern Hemisphere At Altitude From 4 To 20 Km, Mohamed Saad

Electronic Theses and Dissertations

New particle formation (NPF) is investigated using measurements of aerosol size distributions and meteorological variables made in two continents, including USA and Europe. Despite the considerably different aerosol particle abundances among the sites, a common relationship was found between the characteristics of NPF events and the air mass convective and/or advective transport. CO and O3 act as tracers of tropospheric and stratospheric air, respectively, their statistical relationship can be used to quantify air mass characteristics and origins. The mixing ratio values of CO increased within the upper troposphere layer before/during NPF events, which may serve as an indicator of occurring …

Recycling Of Fiber Polymer Matrix Composites In Cementitious Materials, Edward Patton Clark

Electronic Theses and Dissertations

Recycling options for fiber polymer matrix composite waste materials are limited because they typically cannot be reused, reprocessed for down-cycling, and are generally environmentally unfriendly. The utility industry, specifically electrical distribution, has been increasingly using hybrid carbon, glass fiber, and epoxy resin composite rods for high-voltage (HV) conductor transmission lines. The high-voltage conductor core (HVCC) used in the transmission line can have an optimal in-service-life of roughly several decades, in which the material is then retired to a waste landfill. Currently, there is limited research and recycling methodology for these hybrid composite rods. In this research, powder carbon fiber, glass …

The Development Of A Holistic Quality Score Using In-Situ Monitoring Of Laser Powder Bed Fusion, Ryan Daigneault

Electronic Theses and Dissertations

Additive manufacturing processes allow for a great degree of flexibility in terms of part production. The process is autonomous once the part has started printing in that the operator generally does not need to intervene until the part is finished. One issue that this introduces, however, is an inability to determine part quality during the printing process. Once a part has started printing, the operator must either wait until the part is finished or regularly check on the part during the print to determine the part quality. Using data gathered from multiple sensors, a quality score can be used to …

Effect Of Composition And Print Orientation On Thermal Conductivity Of 3d Printed Composites, Cory Jacques

Electronic Theses and Dissertations

Additive manufacturing (AM) technologies have become widely used for rapid prototyping and are beginning to be used for end-use applications. Fused Deposition Modeling (FDM) is a type of 3D printing where molten thermoplastic is extruded layer by layer to create parts. There is an increasing need for improvement and diversification of material properties to further extend the use of AM parts. AM parts have not been commonly used in heat transfer applications due to the limited availability of information on thermal conductivity of materials and the effects of printing orientation. A special apparatus was designed and built to experimentally test …

Material Analysis Of 3d Welded 5356 Aluminum Alloy, Ryan Fouts

Electronic Theses and Dissertations

Metal 3D printing has been reserved for aerospace and high-end automotive industries because of its cost. A gas metal arc welder (GMAW) on a rugged 3D printer frame could make metal additive manufacturing an option for more industries and consumers. 3D welded aluminum has not been examined in depth as an option for additive manufacturing (AM). Extensive tests are necessary to determine the correct settings to use a metal inert gas (MIG) welder for AM. Porosity within the welded material must be evaluated to better understand the additive process. The material properties of 3D welded aluminum will be tested and …