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Processing Of Preceramic Polymers For Direct-Ink Writing, James W. Kemp
Processing Of Preceramic Polymers For Direct-Ink Writing, James W. Kemp
Doctoral Dissertations
Preceramic polymers are organosilicon polymers that, when pyrolyzed to above 1000°C, convert from a polymer to an amorphous ceramic. These polymers have been used for fiber spinning, polymer infiltration, and casting of materials but have recently gained interest for use as the feedstock material for additive manufacturing techniques. This work explores preceramic polymers being used for direct-ink writing (an additive manufacturing method) and many of the issues that occur with the polymers during curing and pyrolysis.
The first chapter of this dissertation provides a review of preceramic polymers, while the second and third chapters focus on the development of inks …
A Multi-Scale Homogenization Scheme For Modeling Anisotropic Material’S Elastic And Failure Response, Justin Matthew Garrard
A Multi-Scale Homogenization Scheme For Modeling Anisotropic Material’S Elastic And Failure Response, Justin Matthew Garrard
Doctoral Dissertations
The effect of small-scale random defects such as microcracks or inclusions are critical to the prediction of material failure, yet including these in a fracture simulation can be difficult to perform efficiently. Typically, work has focused on implementing these through a statistical characterization of the micro- or meso-scales. This characterization has traditionally focused on the spatial distribution of faults, assuming the material is purely isotropic. At the macro-scale, many materials can be assumed to be fully isotropic and homogeneous, but at the small scale may show significant anisotropy or heterogeneity. Other materials may be effectively anisotropic in bulk, such as …
Interfacial Bonding Between Thermoset And Thermoplastic Polyurethane Reinforced Textile Grade Carbon Fiber: Structure Property Relationships, Surbhi Subhash Kore
Interfacial Bonding Between Thermoset And Thermoplastic Polyurethane Reinforced Textile Grade Carbon Fiber: Structure Property Relationships, Surbhi Subhash Kore
Doctoral Dissertations
The research work focused on examining the interfacial adhesion of unsized, epoxy, and urethane-sized textile grade carbon fiber (TCF) reinforced in different classes of polyurethane (PU) thermoplastic (TPU) and thermoset (TSU) polyurethane (PU) through the structure-property relationship. The Carbon Fiber Technology Facility (CFTF) at Oak Ridge National Laboratory (ORNL) has produced TCF to reduce the cost of commercial-grade carbon fiber. The first part of the research examined the fundamental relationships between (a) soft segment thermoplastic polyurethane (S-TPU), (b) hard segment thermoplastic polyurethane (H-TPU), (c) thermoset polyurethane (TSU) and TCF reinforcement’s molecular behavior at the interface using the surface and thermal …
Innovations In Aligned And Overmolded Long Fiber Thermoplastic Composites, Shailesh P. Alwekar
Innovations In Aligned And Overmolded Long Fiber Thermoplastic Composites, Shailesh P. Alwekar
Doctoral Dissertations
Long fiber thermoplastic (LFT) composite materials are increasingly used in high performance lightweight automotive, sporting, and industrial applications. LFT composites are processed with extrusion-compression molding (ECM) and/or injection molding (IM). Melt extrusion offers unique opportunities to align long fibers in a thermoplastic polymer melt. The properties of LFT materials are highly influenced by processing techniques which leads to different porosity content, fiber length distribution, and fiber orientation distribution. Hence, it is important to understand the various LFT processing techniques and their effect on mechanical, thermal, and microscopic properties.
The fundamental process-property relationships in LFT composites are investigated in this dissertation. …
Structural Stability Of Thermosets During Material Extrusion Additive Manufacturing, Stian K. Romberg
Structural Stability Of Thermosets During Material Extrusion Additive Manufacturing, Stian K. Romberg
Doctoral Dissertations
Over the past decade, the scale of polymer additive manufacturing has been revolutionized with machines that print massive thermoplastic parts with greater geometric complexity than can be achieved by traditional manufacturing methods. However, the heat required to print thermoplastics consumes energy and induces thermal gradients that can reduce manufacturing flexibility and final mechanical properties. With the ability to be extruded at room temperature and excellent compatibility with fibers and fillers, thermoset resins show promise to decrease the energy consumption, expand the manufacturing flexibility, and broaden the material palette offered by large-scale polymer additive manufacturing. However, structural instability in the uncured …
Assessing Mechanical Performance Of Dissimilar Steel Systems Made Via Wire-Arc Additive Manufacturing, Obed Daniel Acevedo
Assessing Mechanical Performance Of Dissimilar Steel Systems Made Via Wire-Arc Additive Manufacturing, Obed Daniel Acevedo
Masters Theses
Hot stamping is part of a specific type of metalworking procedure widely used in the automotive industry. This research seeks to help make hot stamp tooling component production more cost-effective by using large-scale additive manufacturing. Additive manufacturing can produce dissimilar steel components that can be more cost-effective and time-efficient and allow for complex geometries to be made. A dissimilar steel system consisting of 410 martensitic stainless steel and AWS ER70S-6 mild steel is proposed to make hot stamps, making them more cost-efficient. However, the material interface's mechanical behavior in 410SS-mild steel additively manufactured material systems is not well understood. This …
Experimental And Computational Study Of Determining Mass Transport Parameters In Vanadium Redox Flow Batteries, Tugrul Y. Ertugrul
Experimental And Computational Study Of Determining Mass Transport Parameters In Vanadium Redox Flow Batteries, Tugrul Y. Ertugrul
Doctoral Dissertations
Vanadium redox flow batteries are a promising large-scale energy storage technology, but a number of challenges must be overcome for commercial implementation. At the cell level, mass transport contributes significantly to performance losses, limiting VRFB performance. Therefore, understanding mass transport mechanisms in the electrode is a critical step to mitigating such losses and optimizing VRFBs.
In this study, mass transport mechanisms (e.g. convection, diffusion) are investigated in a VRFB test bed using a strip cell architecture, having 1 cm2 active area. It is found that diffusion-dominated cells have large current gradients; convection-dominated cells have relatively uniform current distribution from …
Digital Cutting Force Modeling For Milling Operations, Timothy T. No
Digital Cutting Force Modeling For Milling Operations, Timothy T. No
Doctoral Dissertations
Process improvement in milling through improved understanding of machining dynamics is an on-going research endeavor. The objective of this project is to advance digital modeling of the milling process by incorporating tool-specific geometry in the machining analysis. Structured light scanning will be used to perform tool geometry measurements and produce a 3D model. The 3D model data will include the spatial location of the cutting edges, as well as the rake and relief profiles from the tool cross section. The rake and relief profiles will be imported, together with the work material flow stress model, into a finite element analysis …
Transients In Plastic Instabilities During Thermo-Mechanical Reversals In An Additively Manufactured Ti6al4v, Sabina C. Kumar
Transients In Plastic Instabilities During Thermo-Mechanical Reversals In An Additively Manufactured Ti6al4v, Sabina C. Kumar
Doctoral Dissertations
A complex interaction of process variables in an evolving geometry during Additive Manufacturing (AM), can bring about spatial and temporal transients of temperature and stress within each layer in a part. Although AM shares commonalities with conventional processing techniques such as casting, welding, and thermo-mechanical process, published literature has shown that the steady-state conditions are not strictly valid during AM process. Macro-scale fluctuations of thermal gradients (dT/dx: 103 to 107 K/m) combined with local changes in thermal expansion coefficients, crystallographic strains and localized stress-strain constitutive properties in conjunction with thermal cycles, can bring about a plastic strain gradient …
Effects Of Pillar And Sealing Design On Thermal And Mechanical Performance Of Vacuum Insulated Glazing, Wenyuan Zhu
Effects Of Pillar And Sealing Design On Thermal And Mechanical Performance Of Vacuum Insulated Glazing, Wenyuan Zhu
Masters Theses
Vacuum insulated glazing with a low-emittance coating has a great market potential as an effective transparent insulator. The thermal insulating performance of VIG is determined by its design, including material selection and configuration of different components. Thermal conductance of the vacuum gap, as a transport bottleneck, is one of the primary factors controlling the thermal transport across VIG. In particular, since support pillars and sealings provide the main thermal transport channels across the vacuum gap, increasing the pillar and sealing thermal resistance is a key strategy for effective thermal insulation, while maintaining the vacuum space and mechanical strength of VIG. …
Design And Simulation Of A Supervisory Control System For Hybrid Manufacturing, Michael Buckley
Design And Simulation Of A Supervisory Control System For Hybrid Manufacturing, Michael Buckley
Masters Theses
The research teams of Dr. Bill Hamel, Dr. Bradley Jared and Dr. Tony Schmitz were tasked by the Office of Naval Research to create a hybrid manufacturing process for a reduced scale model of a naval ship propeller. The base structure of the propeller is created using Wire Arc Additive Manufacturing (WAAM), which is then scanned to compare created geometry to desired geometry. The propeller is then machined down to match the desired geometry. This process is iterated upon until the final product meets design tolerances. Due to the complex nature and numerous industrial machines used in the process, it …
Development Of A Temperature Measurement Camera Using Cost Effective Hardware, Benjamin F. Thieme, Jesse Wilson
Development Of A Temperature Measurement Camera Using Cost Effective Hardware, Benjamin F. Thieme, Jesse Wilson
Haslam Scholars Projects
The recent outbreak of the COVID-19 pandemic has caused lock downs around the globe, forcing many schools and businesses to temporarily close. For them to reopen safely, it is imperative to identify cases quickly so that individuals can be quarantined before the virus spreads to more people. An alternative to testing is to screen individuals for high temperatures that would indicate fevers. With the risk of contagion that occurs during close contact between humans, traditional thermometers may be unsuitable. Thus, the purpose of this design project is to design, construct, and test a temperature measurement system using a thermal camera …
3d Printing Of Hybrid Architectures Via Core-Shell Material Extrusion Additive Manufacturing, Robert Cody Pack
3d Printing Of Hybrid Architectures Via Core-Shell Material Extrusion Additive Manufacturing, Robert Cody Pack
Doctoral Dissertations
Biological materials often employ hybrid architectures, such as the core-shell motif present in porcupine quills and plant stems, to achieve unique properties and performance. Drawing inspiration from these natural materials, a new method to fabricate lightweight and stiff core-shell architected filaments is reported. Specifically, a core-shell printhead conducive to printing highly loaded fiber-filled inks, as well as a new low-density syntactic foam ink, are utilized to 3D-print core-shell architectures consisting of a syntactic epoxy foam core surrounded by a stiff carbon fiber-reinforced epoxy composite shell. Effective printing of test specimens and structures with controlled geometry, composition, and architecture is demonstrated …
Motor Control-Based Assessment Of Therapy Effects In Individuals Post-Stroke: Implications For Prediction Of Response And Subject-Specific Modifications, Ashley Rice
Doctoral Dissertations
Producing a coordinated motion such as walking is, at its root, the result of healthy communication pathways between the central nervous system and the musculoskeletal system. The central nervous system produces an electrical signal responsible for the excitation of a muscle, and the musculoskeletal system contains the necessary equipment for producing a movement-driving force to achieve a desired motion. Motor control refers to the ability an individual has to produce a desired motion, and the complexity of motor control is a mathematical concept stemming from how the electrical signals from the central nervous system translate to muscle activations. Exercising a …
Process-Structure-Property Relationships In 3d-Printed Epoxy Composites Produced Via Material Extrusion Additive Manufacturing, Nadim S. Hmeidat
Process-Structure-Property Relationships In 3d-Printed Epoxy Composites Produced Via Material Extrusion Additive Manufacturing, Nadim S. Hmeidat
Doctoral Dissertations
Extrusion-based additive manufacturing (AM) technologies, such as direct ink writing (DIW), offer unique opportunities to create composite materials and novel multi-material architectures that are not feasible using other AM technologies. DIW is a novel 3D-printing approach in which viscoelastic inks, with favorable rheological properties, are extruded through fine nozzles and patterned in a filament form at room temperature.
Recent developments in DIW of polymer composites have led to expanding the range of materials used for printing, as well as introducing novel deposition strategies to control filler orientation and create improved functional/structural composite materials. Despite these substantial advancements, the successful and …
Utility Scale Building Energy Modeling And Climate Impacts, Brett C. Bass
Utility Scale Building Energy Modeling And Climate Impacts, Brett C. Bass
Doctoral Dissertations
Energy consumption is steadily increasing year over year in the United States (US). Climate change and anthropogenically forced shifts in weather have a significant impact on energy use as well as the resilience of the built environment and the electric grid. With buildings accounting for about 40% of total energy use in the US, building energy modeling (BEM) at a large scale is critical. This work advances that effort in a number of ways. First, current BEM approaches, their ability to scale to large geographical areas, and global climate models are reviewed. Next, a methodology for large-scale BEM is illustrated, …
Displacement-Based Dynamometer For Milling Force Measurement, Michael F. Gomez
Displacement-Based Dynamometer For Milling Force Measurement, Michael F. Gomez
Doctoral Dissertations
This project will study the design and testing of a low-cost dynamometer for milling dynamic force measurement. The monolithic design is based on constrained-motion/flexure-based kinematics, where force is inferred from displacement measured using a low-cost optical interrupter (i.e., a knife edge that partially interrupts the light beam in an emitter-detector pair). The time-dependent displacement of the dynamometer’s moving platform caused by the milling force is converted to the frequency domain, multiplied by the inverse of the dynamometer’s ideally single degree of freedom (SDOF) frequency response function (FRF), and converted back into the time-domain to obtain the time-dependent cutting force. The …
Characterization Of Near Isothermal Compression And Expansion For Energy Storage, Saiid Kassaee
Characterization Of Near Isothermal Compression And Expansion For Energy Storage, Saiid Kassaee
Doctoral Dissertations
As the global share of electricity generation from intermittent renewable energy sources increases, developing efficient and scalable electricity storage technologies becomes critical to modernizing the grid, matching the supply and demand, and raising the capacity factor of renewable generation. The Ground-Level Integrated Diverse Energy Storage (GLIDES) is an efficient energy storage technology invented at Oak Ridge National Laboratory (ORNL). GLIDES stores energy by compressing gas using a liquid piston in pressure vessels benefiting from employing hydraulic turbomachinery which are more efficient than gas turbomachinery. Therefore, GLIDES has higher round-trip efficiency (RTE) than Compressed Air Energy Storage (CAES). Since GLIDES employs …
Optimization Of Dynamic Simulations To Identify Movement Patterns That Simultaneously Reduce The Risk Of Injury And Enhance Human Performance, Dhruv Gupta
Doctoral Dissertations
Every movement, whether routine or sporting, achieves certain goals. Routine movements like walking takes us from one place to the other and sporting movements like hitting a volleyball help win the game. But each motion puts strain on certain joints of the body putting them at risk of injury. Walking can lead to chronic disorders like knee osteoarthritis over the years. Hitting a volleyball can put the shoulder at risk of a rotator cuff injury. The purpose of this work is to find optimal movement patterns that enhance human ability to achieve the goals of the movement, but at the …
Development Of Data Science Tools For Part Qualification In Additive Manufacturing, Sujana Chandrasekar
Development Of Data Science Tools For Part Qualification In Additive Manufacturing, Sujana Chandrasekar
Doctoral Dissertations
In recent years, metal additive manufacturing processes have become popular choices for part production especially for low volume, high complexity parts. To enable widespread adoption of these methods, it is essential to understand the link between process parameters and part properties. This is particularly because additive manufacturing processes cause inherently complex thermo-mechanical cycles and drastically different local process conditions within a part, compared to conventional manufacturing processes like casting and forging. Additionally, properties of feedstock material like metal powder impact final part properties. The focus of this dissertation is on development of data-driven methods using in situ monitoring, as a …
Correlating Fracture Toughness And Surface Roughness For A Ductile Epoxy Adhered To Aluminum Substrates, Kurt Ryan Smith
Correlating Fracture Toughness And Surface Roughness For A Ductile Epoxy Adhered To Aluminum Substrates, Kurt Ryan Smith
Masters Theses
Adhesively bonded joints are used across multiple disciplines as an efficient and cost effective method for reinforcing, repairing, or creating new structures. Sufficient understanding of the bond line characteristics of the adhesive is necessary to properly design a reliable bonded joint and ensure a long service life. It is well understood that surface preparation has a significant impact on these interface characteristics as a given level of surface roughness achieves mechanical interlocking between the resin and metal and is important to prevent premature interfacial failure [1]. The goal of this study is to characterize the fracture toughness values for an …
Experimental Investigation Of Spray Cooling/Heating Of A Near-Isothermal Hydro-Pneumatic Energy Storage System, Saiid Kassaee
Experimental Investigation Of Spray Cooling/Heating Of A Near-Isothermal Hydro-Pneumatic Energy Storage System, Saiid Kassaee
Masters Theses
Proposing experimental investigation of spray cooling/heating of a near-isothermal, scalable, efficient, high density, hydro-pneumatic integrated energy storage system; capable of spray cooling/heating during gas compression/expansion and capable of excess heat integration. The invented Ground-Level Integrated Diverse Energy Storage (GLIDES) is an energy storage technology capable of storing energy in high-pressure vessel using hydro-pneumatic concept. Indicated roundtrip efficiencies of 98% can be reached using the proposed technology marking an isothermal compression/expansion energy storage.
Design And Fabrication Of Invar Layup Tool Molds Using Additive And Subtractive Manufacturing, Matthew Lamsey
Design And Fabrication Of Invar Layup Tool Molds Using Additive And Subtractive Manufacturing, Matthew Lamsey
Masters Theses
The development of novel additive manufacturing technologies, such as Wire Arc Additive Manufacturing (WAAM), has opened the door for the fabrication of complex part geometries that could not be achieved with traditional manufacturing methods. Best practices for designing parts for fabrication with WAAM are still in their infancy. This thesis presents a novel design and fabrication framework for parts created using WAAM, which was realized through the fabrication of two demonstration composite layup tool molds. The framework includes design principles for WAAM, finite element simulation of part performance, metrological analysis of printed preforms, and considerations for closely integrating the WAAM …
Design Of A Cable-Driven Manipulator For Large-Scale Additive Manufacturing, Phillip Chesser
Design Of A Cable-Driven Manipulator For Large-Scale Additive Manufacturing, Phillip Chesser
Masters Theses
Additive manufacturing of concrete is a growing field of research, yet current motion platforms do not offer viable routes towards large scale deployable systems. This thesis presents the design and analysis of a novel cable-driven robot for use in large scale additive manufacturing. The system developed, termed SkyBAAM, is designed to be easily deployable to a construction site for on-site additive manufacturing of buildings and other large structures. The design philosophy behind this system is presented. Analysis of this system first explores the kinematics, and stiffness as a function of cable tension. Analysis of the workspace and singularities is also …