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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. …

Design, Quantification, And Strengthening Of Interface Interaction Between Aramid Fibers And Polymer Matrix, Karrar Al-Quraishi

Electronic Theses and Dissertations

Composites reinforced by aramid fibers may suffer poor interface interactions during mechanical loading due to the smooth and chemically inert surface of the fibers. Three main strategies have been used to improve the interface shear strength (IFSS) including increasing surface roughness, enriching fiber surface with functional groups, and surface coating with ceramic particles. Plasma treatment is usually employed to functionalize and roughen surface of the fibers, leading to strengthening of the interface between the fibers and polymer matrix. A concern for fibers reinforced polymers is that the IFSS would significantly decrease once the composite is exposed to elevated temperatures. To …

Development Of A Novel Haptic Feedback System For Gait Training Applications, Mohsen Alizadeh Noghani

Electronic Theses and Dissertations

Until recently, study and correction of motor or gait functions required costly sensors and measurement setups (e.g., optical motion capture systems) which were only available in laboratories or clinical environments. However, due to (1) the growing availability and affordability of inertial measurement units (IMUs) with high accuracy, and (2) progress in wireless, high bandwidth, and energy-efficient networking technologies such as Bluetooth Low Energy (BLE), it is now possible to measure and provide feedback in real-time for biomechanical parameters outside of those specialized settings. To enable gait training without an expert who can provide verbal feedback, augmented feedback, which is divided …

The Effect Of Non-Local Electrical Conductivity On Near-Field Radiative Heat Transfer Between Graphene Sheets, Behrad Zeinali Tajani

Electronic Theses and Dissertations

Every object above zero kelvin emits electromagnetic radiation with the dominant wavelength determined using the Wien’s law (10 microns at room temperature). These waves can transfer energy and hence are the foundation of radiative heat transfer (RHT). RHT consists of two regimes: far-field and near-field. If the distance between the heat exchanging media is more than the dominant wavelength, the regime is far-field and is limited to the ideal Planck’s blackbody, and only propagating waves contribute to heat transfer. On the other hand, when the distance is less than the dominant wavelength, the regime is called the near-field. In near-field …

Optimization Of Thermoelectric Materials For Marine And Power Plant Application, Travis Thornton Wallace

Electronic Theses and Dissertations

Thermoelectric materials are an enabling technology that has the potential to increase overall plant efficiency and reduce greenhouse gas emissions for shoreside power plants and for the marine industry. These materials do this by directly converting waste heat energy into usable electricity that could be harnessed for use on any existing electrical grid. This dissertation describes work done to understand, model, and investigate improvements to bismuth telluride and bismuth telluride antimony thermoelectric materials to better match the materials to available heat flux from industrial plants. Presented within this work are models to investigate homogenous materials, functionally graded materials, and segmented …

Structural And Material Characterization Of Inflatable Drop-Stitch Panels Used In Bending Applications, Elisabeth M. Waugh

Electronic Theses and Dissertations

Inflatable beams, arches and panels have become increasingly popular for load-bearing applications and have a variety of military and civil applications. The popularity of these structures comes from being lightweight, easy to transport, and being able to regain shape after the structure has been overloaded and the load is removed. The majority of inflatable beams and arches – commonly termed “airbeams” – are cylindrical pressure vessels with a circular cross-section. In contrast, drop-stitch panels incorporate yarns that connect the top and bottom surfaces, giving a wide, shallow cross-section with parallel top and bottom surfaces. Unlike airbeams, drop-stich panels do not …

Characterization Of Coated Particles To Use In High-Temperature Solid Particle Receivers, Seyed Adib Taba

Electronic Theses and Dissertations

High-temperature solid particle receivers have been widely studied for use in concentrated solar power systems to absorb concentrated solar radiation. Many efforts have been made to select a particle that can increase the performance of these systems. In this experimental study, available coating technology for particles is used to examine whether it could enhance heat transfer. A packed bed setup is designed and validated to assess the heat transfer of these particles. The validated packed bed opens the scope in which a packed bed can be used as a primary experiment for the prediction of suitable alternative particles and reduce …

Active Blade Pitch And Hull-Based Structural Control Of Floating Offshore Wind Turbines, Eben Lenfest

Electronic Theses and Dissertations

Floating offshore wind turbines (FOWTs) have the potential to bring renewable energy to waters too deep for traditional offshore wind turbines while still being able to harness strong coastal winds in areas near population centers. However, these floating wind turbines come at a higher capital cost relative to fixed foundations and are more susceptible to vibrations induced by waves. Advances in control technologies offer the potential to reduce fatigue loads due to these vibrations, extending the life of the platform and thereby spreading the capital costs of the turbine over a longer period of time. One such advance is in …

Gait Rehabilitation Using Biomechanics And Exoskeletons, Jacob Bloom

Electronic Theses and Dissertations

A healthy gait is often taken for granted when walking. However, if a stroke, spinal cord injury (SCI), or traumatic event occurs the ability to walk may be lost. In order to relearn how to walk, gait rehabilitation is required. Including arm swing in gait rehabilitation has been shown to help in this process. This thesis presents two tasks to investigate the mechanics of arm swing and ways to provide assistance to induce arm swing in gait rehabilitation.

The firsts task completed was a study on the effects of forearm movement during gait. Twelve healthy subjects walked under three conditions …

High Fidelity Computational Modeling And Analysis Of Voice Production, Weili Jiang

Electronic Theses and Dissertations

This research aims to improve the fundamental understanding of the multiphysics nature of voice production, particularly, the dynamic couplings among glottal flow, vocal fold vibration and airway acoustics through high-fidelity computational modeling and simulations. Built upon in-house numerical solvers, including an immersed-boundary-method based incompressible flow solver, a finite element method based solid mechanics solver and a hydrodynamic/aerodynamic splitting method based acoustics solver, a fully coupled, continuum mechanics based fluid-structure-acoustics interaction model was developed to simulate the flow-induced vocal fold vibrations and sound production in birds and mammals. Extensive validations of the model were conducted by comparing to excised syringeal and …

Modeling Of Non-Newtonian Fluid Flow In A Porous Medium, Hamza Azzam

Electronic Theses and Dissertations

Flows of Newtonian and non-Newtonian fluids in porous media are of considerable interest in several diverse areas, including petroleum engineering, chemical engineering, and composite materials manufacturing. In the first part of this thesis, one-dimensional linear and radial isothermal infiltration models for a non-Newtonian fluid flow in a porous solid preform are presented. The objective is to investigate the effects of the flow behavior index, preform porosity and the inlet boundary condition (which is either a known applied pressure or a fluid flux factor) on the infiltration front, pore pressure distribution, and fluid content variation. In the second part of the …

Design And Fabrication Of A 3-Dimensional Capacitive-Based Force Sensor, Md Shafiqur Rahman

Electronic Theses and Dissertations

The detection of abnormal gait patterns is imperative for early diagnoses and treatment of serious health issues such as loss of mobility and balance, risk of falls, cardiovascular disease, etc. Human gait analysis is the tool used to detect abnormal gait patterns. Gait analysis also can help to understand the cause of gait abnormalities and to make a treatment plan for individual patients. Ground reaction forces (GRFs) at the foot during walking or running are essential for kinetic analysis of the human gait. However, there are no wearable systems that can directly measure three-directional (3D) forces during daily walking. Currently, …

Wave Attenuation Capacity Of Suspended Aquaculture Structures With Sugar Kelp And Mussels, Longhuan Zhu

Electronic Theses and Dissertations

Large aquaculture systems may have the potential to damp wave energy for coastal protection. The performance of these systems are influenced by the dynamics of components such as flexible kelp blades and mussel droppers. In this thesis, the dynamics of kelp blades and mussel droppers were investigated with a consistent-mass cable model with focus on understanding the asymmetric motion of kelp blades. The results showed the asymmetric blade motion in symmetric waves is caused by the spatial asymmetry of the encountered wave orbital velocities due to blade displacements and the asymmetric action on the blade by vertical wave orbital velocities. …

Investigation Of Infiltration Measurements Using Wind Induced Pressure Response On An Enclosure, Aaron R. French

Electronic Theses and Dissertations

Air infiltration into a building is unintentional air leakage, resulting in heat losses or gains and the consequent energy usage to recondition the building to comfortable levels. Methods of evaluating air infiltration provide accurate measures of air exchange rate but must be done per building and take significant experimentation and data collection. This warrants investigation into ways to decrease the time to evaluate building infiltration to decrease the associated costs. For this reason, interior pressure response is the subject of investigation in the present work. Interior pressure of a building responds to a pressure rise on the building face when …

Development And Test Of High Temperature Surface Acoustic Wave Gas Sensors, Armando E. Ayes Moncada

Electronic Theses and Dissertations

The demand for sensors in hostile environments, such as power plant environments, exhaust systems and high-temperature metallurgy environments, has risen over the past decades in a continuous attempt to increase process control, improve energy and process efficiency in production, reduce operational and maintenance costs, increase safety, and perform condition-based maintenance in equipment and structures operating in high-temperature, harsh-environment conditions. The increased reliability, improved performance, and development of new sensors and networks with a multitude of components, especially wireless networks, are the target for operation in harsh environments. Gas sensors, in particular hydrogen gas sensors, operating above 200°C are required in …

A Linear Actuator/Spring Steel-Driven Glove For Assisting Individuals With Activities Of Daily Living, Daniel Chizhik

Electronic Theses and Dissertations

Over three million people in the U.S. suffer from forearm and hand disabilities. This can result from aging, neurological disorders (e.g., stroke), chronic disease (e.g., arthritis), and injuries. Injuries to hands comprise one-third of all work-related injuries worldwide. This can lead to difficulties with activities of daily living (ADL), where one needs to grasp, lift, and release objects in the household. There is a rise in demand for assistive orthoses and gloves that can allow many people to regain their grasping/releasing ability and, thereby, their independence. The main contribution of this thesis is developing an assistive glove with the actuating …

Impact Resistance Of Fiber-Reinforced Composites Using Computational Simulations, Maitham Alabbad

Electronic Theses and Dissertations

Composite materials are widely used in aerospace, automotive and wind power industries due to their high strength-to-weight and stiffness-to-weight ratios and their improved mechanical properties compared to metals. The damage resistance of composite materials due to low velocity impact depends on fiber breakage, matrix cracking and delamination between the interfaces. In this research, a numerical investigation of low velocity impact response of a multidirectional symmetric carbon-epoxy composite laminate is carried out and presented. Two different finite element models are developed for composite laminates made of non-crimp fabric to investigate their behavior under different levels of impact energy. In the first …

Modeling, Simulation, And Validation Of Process-Structure-Property Relationships In Fused Filament Fabrication, Aaron Grant

Electronic Theses and Dissertations

As additive manufacturing (AM) grows in popularity, the need for better simulation tools to predict the process-structure-property relationships of AM parts becomes ever more necessary to employ the technology in design of functional parts with varying degrees of complexity and performance requirements. Many simulation tools and techniques have been developed that aim to achieve this goal, and the main purpose of this research is to explore how well different simulation tools and modeling approaches can capture various AM-specific features such as inter-raster and end-of raster voids, and residual stresses induced by dissimilar rates of thermal expansion. Process simulation of fused …

Damage Resistance And Tolerance Of 3d Woven Composites, Justin T. Mcdermott

Electronic Theses and Dissertations

Composite materials have been adopted into primary aircraft structures by virtue of their great strength-to-weight and stiffness-to-weight ratios, fatigue insensitivity, and corrosion resistance. These characteristics are leveraged by aircraft designers to deliver improved fuel effciency and reduced scheduled maintenance burdens for their customers. These benefits have been impressively realized in the Boeing 787 and Airbus A350 XWB, with airframes utilizing about 50% composites by weight. Tempering these successes, however, are the inherent vulnerabilities of carbon-fiber reinforced composites. When compared to conventional metallic structure, composite laminates are more sensitive to stress concentrations at mechanical fastenings and damage due to low-velocity impact. …

Design, Analysis, And Optimization Of Compactible Origami-Inspired Shelters, Anthony M. Verzoni

Electronic Theses and Dissertations

Origami-inspired design is a growing field with numerous engineering applications, including rapidly compactable and erectable shelters with nondeformed flat panels, which are considered in this research. Shelter geometry is controlled by the shape, size, and connectivity of individual panels that must fold and unfold in a kinematically compliant manner resulting in no panel intersection. Panel size and shape are altered to yield shelter designs with varying volumetric capacities. Thin panels are initially used to study the kinematics of shelter concepts as traditional origami. With increasing panel thickness, the location of fold or hinge lines exerts a large influence on the …

Global Performance Testing, Simulation, And Optimization Of A 6-Mw Annular Floating Offshore Wind Turbine Hull, Hannah L. Allen

Electronic Theses and Dissertations

Floating offshore wind turbine (FOWT) hull technologies are evolving rapidly with many technically viable designs. However, a commercially dominant architecture has yet to emerge. This thesis presents a methodology for evaluation of the hydrodynamic performance of an annular FOWT hull. This hull shows significant promise from a manufacturing and installation standpoint, but limited performance data exists. This thesis will provide ample documentation on scale model testing of an annular FOWT hull as well as the corresponding numerical validation approach and opportunities for design improvement.

The first portion of this work involves testing a 1/100th-scale model in the Harold Alfond Wind …

Metal Thin Film Stiffness Extraction Technique For Surface Acoustic Wave Filters, Travis R. Weismeyer

Electronic Theses and Dissertations

Accurate knowledge of the surface acoustic wave (SAW) properties propagating at the surface of a piezoelectric substrate with thin films, electrodes or temperature compensated films, is critical in SAW filter design to meet the target frequency response, power durability and performance prior to device fabrication. While reliable material constants exist for substrates such as LiNbO3 used in SAW filters, the absolute elastic constants associated with operational thin films used for electrodes or temperature compensation do not exist. Although the bulk values of the constituent materials are known, the composite film/substrate properties are difficult to predict since they depend strongly on …

Modeling And Simulation Of The Thermoforming Process In Thermoplastic-Matrix Composite Materials, Philip M. Bean

Electronic Theses and Dissertations

Thermoplastic-matrix composite materials have unique advantages over traditional thermosets including faster processing, improved fracture toughness, and recyclability. These and other benefits have caused increasing interest in the use of these materials in both aerospace and automotive industries. Due to the differences in behavior, these materials require a different type of manufacturing process to thermoset matrix composites. This manufacturing process generally involves using pre manufactured tape-layers. These layers, containing both thermoplastic-matrix and fiber-reinforcement, are aligned to the desired orientation, and stacked up into a “tailored blank” using an automated tape layup machine. They are then heated to the thermoplastic melting temperature …

Feasibility Of Hybrid Thermoplastic Composite-Concrete Load Bearing System, Camerin M. Seigars

Electronic Theses and Dissertations

Thermoplastic composites have many advantages over thermoset composites such as being recyclable, rapidly manufacturable, and more impact resistant. The goal of this thesis is to assess the feasibility of using thermoplastic composites in structural applications through literature review, mechanical testing, design of a load-bearing hybrid composite-concrete structures, and the implementation of thermoplastic composites for tensile reinforcement of concrete. The study had four objectives covering the stated goal.

1. Conduct a literature review to direct thermoplastic material selection
2. Characterize thermoplastic material mechanical properties using standardized mechanical testing
3. Design a hybrid composite-reinforced concrete beam, and
4. Develop thermoplastic shear connectors to develop composite action …

Performance Test And Numerical Simulation Of An Adjustable Implant For Treating Vocal Fold Paralysis, Hai Zi

Electronic Theses and Dissertations

Unilateral vocal fold paralysis (UVFP) is one of the most common laryngeal diseases that affect human voice and speech production. It often causes incomplete glottal closure, resulting in voice symptoms including hoarseness, voice fatigue and increased voice effort. One common treatment of UVFP is Thyroplasty Type I, which uses a thyroplasty implant to medialize the paralyzed vocal fold and restore the normal vibration of the vocal fold. However, the surgical outcome is extremely sensitive to the size and shape of the implant. Currently, modifications in the implant size and shape rely upon surgical intuition and experience. The level of voice …

Microwave Acoustic Saw Resonators For Stable High-Temperature Harsh-Environment Static And Dynamic Strain Sensing Applications, Anin K. Maskay

Electronic Theses and Dissertations

High-temperature, harsh-environment static and dynamic strain sensors are needed for industrial process monitoring and control, fault detection, structural health monitoring in power plant environments, steel and refractory material manufacturing, aerospace, and defense applications. Sensor operation in the aforementioned extreme environments require robust devices capable of sustaining the targeted high temperatures, while maintaining a stable sensor response. Current technologies face challenges regarding device or system size, complexity, operational temperature, or stability.

Surface acoustic wave (SAW) sensor technology using high temperature capable piezoelectric substrates and thin film technology has favorable properties such as robustness; miniature size; capability of mass production; reduced installation …

Dynamic Modeling And Extreme Tension Analysis Of Mooring System For A Floating Offshore Wind Turbine, Wei Ting Hsu

Electronic Theses and Dissertations

For offshore wind industry, exploiting the dynamic behaviors of mooring lines is of increasing importance in floating offshore wind turbine (FOWT) mooring system design. Currently, the design philosophy for structures and moorings is based on principles and practices adopted in offshore oil and gas, including mooring systems that are optimized for applications in deeper waters. However, the design of FOWT mooring systems is facing several challenges, including installation costs, the stability of light-weight minimalistic platforms, and shallow water depths (50-300m). The extreme tension in mooring lines of a light displacement platform in shallow water is dominated by snap loads. Hence …

Modeling Of A Head - Neck Assembly Drop Tower Impact Test Using Abaqus, Hussein Sharqi Owaid

Electronic Theses and Dissertations

There are numerous potential causes of traumatic brain injury (TBI) and concussions, including traffic accidents, contact during sports and falls. Protection from these injuries is paramount because of the problems that result from TBI, such as loss of thinking and memory capability. Head impact from falls, especially in elderly, can also result in severe to fatal injury and some effects of brain injury are often not visible. For these reasons and more a need exists for protective head gear that can keep persons safe during at risk physical activity and that can protect fall prone persons from accidental injuries. Part …

Transformation Of Nonlinear Waves In The Presence Of Wind, Current, And Vegetation, Haifei Chen

Electronic Theses and Dissertations

Accurate prediction of extreme wave events is crucial for the safe maritime activities and offshore operations. Improved knowledge of wave dissipation mechanisms due to breaking and vegetation leads to accurate wave forecast, protecting life and property along the coast. The scope of the thesis is to examine the wave transformations in the presence of wind, current, and vegetation, using a two-phase flow solver based on the open-source platform OpenFOAM. The Reynolds-Averaged Navier-Stokes (RANS) equations are coupled with a Volume of Fluid (VOF) surface capturing scheme and a turbulence closure model. This RANS-VOF model is adapted to develop a numerical wind-wave-current …

Feasibility Of Using 3d Printed Molds For Thermoforming Thermoplastic Composites, Sunil Bhandari

Electronic Theses and Dissertations

This thesis presents a novel combined experimental and numerical mechanics approach for characterizing 3D printed thermoplastic materials by the fused deposition modeling process for thermoforming thermoplastic composites. The implications of this work are:

1. a methodology for model-based performance evaluation of 3D printed structural parts, and
2. an improved design of 3D printed molds for composites manufacturing, which has potential for material innovations and scaled-up applications in additive manufacturing.

The thesis formulates basic criteria for selection of thermoplastic polymer used for the 3D printed mold based on forming temperatures. The thesis creates a lattice and shell finite element model of the 3D …