Engineering Science and Materials Commons^™

Electromechanical Fatigue Properties Of Dielectric Elastomer Stretch Sensors Under Orthopaedic Loading Conditions, Andrea Karen Persons

Theses and Dissertations

Fatigue testing of stretch sensors often focuses on high amplitude, low-cycle fatigue (LCF) behavior; however, when used for orthopaedic, athletic, or ergonomic assessments, stretch sensors are subjected to low amplitude, high-cycle fatigue (HCF) conditions. As an added layer of complexity, the fatigue testing of stretch sensors is not only focused on the life of the material comprising the sensor, but also on the reliability of the signal produced during the extension and relaxation of the sensor. Research into the development of a smart sock that can be used to measure the range of motion (ROM) of the ankle joint during …

Fluid-Structure Interaction Of Nrel 5-Mw Wind Turbine, Mohamed Sayed Elkady Abd-Elhay

Theses and Dissertations

Wind energy is considered one of the major sources of renewable energy. Nowadays, wind turbine blades could exceed 100 m to maximize the generated power and minimize produced energy cost. Due to the enormous size of the wind turbines, the blades are subjected to failure by aerodynamics loads or instability issues. Also, the gravitational and centrifugal loads affect the wind turbine design because of the huge mass of the blades. Accordingly, wind turbine simulation became efficient in blade design to reduce the cost of its manufacturing. The fluid-structure interaction (FSI) is considered an effective way to study the turbine's behavior …

Computational Aerothermodynamic Analysis Of Satellite Trans-Atmospheric Skip Entry Survivability, John J. Runco

Theses and Dissertations

Computational aerothermodynamic analysis is presented for a spacecraft in low Earth orbit performing an atmospheric skip entry maneuver. Typically, atmospheric reentry is a terminal operation signaling mission end-of-life and, in some instances, executed for spacecraft disposal. A variation on reentry – skip entry – is an aeroassisted trans-atmospheric maneuver in which a spacecraft utilizes the effects of aerodynamic drag in order to reduce energy prior to a terminal entry, pinpoint a targeted entry, or change orbital elements such as inclination. Spacecraft performing a skip entry enable new modes of maneuver to enhance operations in nominal or possibly contested mission environments. …

Finite Element Analysis (Fea) Study Of The Thermal Stress Concentrations In Planar-Type Sodium Sulfur (Nas) Secondary Batteries, Jeffrey P. Colker

Theses and Dissertations

The importance of a reliable and safe way to store energy, and allow for on-demand usage, has led to much research in the field of secondary battery development. The thesis herein explores a technology that has shown promising results when implemented in large-scale energy grid applications. Though the technology has proven viable in both load-leveling on existing grids as well as serving to legitimize renewable energy sources, the development of such advanced battery systems is not without challenge. Sodium-sulfur (NaS) secondary cells have shown promising results when implemented in the aforementioned energy storage applications. One of the main drawbacks to …

Field And Laboratory Study Of The Flàajökull Glacier, Iceland, William Russell Jacobson, Jr.

Theses and Dissertations

The increased surface melting of the outlet glaciers of the Vatnajökull Ice Cap has a profound affect on the dynamics of the ice-bed couple and landform genesis. Soft-bedded glaciers are largely inaccessible, which creates a problem. One challenge is to understand the complex interactions of the glacier bed and its resultant depositional and deformational landform systems. This study investigates an outlet glacier from the Vatnajökull Ice Cap, described herein as the Fláajökull glacier system. To circumvent some of these problems, three separate projects were conducted in this dissertation: (1) magnetic fabric study of effective pressure (difference between the ice-overburden pressure …

Primary Creep In Astm A325 Bolts Under Simulated Fire Loading, Mohammad Matar

Theses and Dissertations

At room temperature, small creep effects are present on steel structures. This is not the case at fire condition where the temperature is much higher than room temperature; in this case creep can be significant, and should be taken into consideration. Since fire hazard can happen in any building, creep effect must be taken into consideration when designing a building. Creep strain behaves as a function of time, temperature and stress. As the temperature increases, the creep strain increases. Similarly, the longer the temperature at a given stress on the structure, the more the creep strain present.

The smallest component …

Characterization Of Carbon-Fiber Reinforced Polyetherimide Thermoplastic Composites Using Mechanical And Ultrasonic Methods, Mohannad A. Alhaidri

Theses and Dissertations

Continuous fiber-reinforced thermoplastics (CFRT) have the potential for being a mass-produced material for high-performance applications. The primary challenge of using CFRT is achieving fiber wet-out due to the high viscosity of thermoplastics. This results in higher temperatures and pressures required for processing the composites. Co-mingling thermoplastic fibers with a reinforcing fiber, potentially, can enable better wetting by reducing the distance the matrix needs to flow. This could result in shorter cycle times and better consolidation at lower temperatures and pressures. In this study, a polyetherimide (PEI) fiber was comingled with carbon fibers (CF). The resultant fibers were woven into fabrics …

Experimental And Analytical Characterization Of Regenerated/Nano Cellulose Composites, Issam I A Qamhia

Theses and Dissertations

Fiber-reinforced composite materials are increasingly used for structural and engineering purposes. In particular, composites reinforced with natural fiber systems are becoming more and more popular due to their biodegradability and abundance; added to that other properties such as transparency, dimensional stability and good mechanical behavior. However, major issues remain to properly understand their behavior and enable their widespread use.

In this thesis, the mechanical behavior of cellulose fiber/epoxy composites is investigated. The natural fiber systems studied fall into three categories: unidirectional regenerated cellulose fibers, triaxially braided quasi-isotropic regenerated cellulose fibers and micro-fibrillated cellulose in the form of nanocellulose scaffolds. Different …

Measuring And Modeling The Mechanical Properties Of Bicycle Tires, Andrew Erwin Dressel

Theses and Dissertations

It has been shown that tire deformation can play an important role in the stability and handling of a bicycle. It is expected that an accurate understanding of tire behavior is necessary for correct understanding of rider behavior and that correct understanding of rider behavior is necessary for optimizing bicycle design. That certainly has been the case for motorcycles.

Several instances of published bicycle tire stiffness data exist, but they seldom agree with each other, do not all measure the same properties, and often are missing key pieces of test configuration data, such as tire size, rim width, inflation pressure, …

Material Behavior Characterization Of A Thin Film Polymer Used In Lithium-Ion Batteries, Michael James Martinsen

Theses and Dissertations

The use of lithium-ion batteries in the automotive industry has become increasingly popular. As more hybrid and electric vehicles take to the road an understanding of how these batteries will behave structurally will be of greater concern. Impact testing can give a valuable overview of the strengths and weaknesses of a battery's design, however, these tests can be time consuming, expensive, and dangerous. Finite element analysis can deliver a reliable low cost approximation of physical testing results. The accuracy of FE results depends greatly on the mathematical representation of the material properties of Li-ion battery components. In this study, the …

Analysis Of Multi-Directional Recycled Jute Fiber Composite Behavior Using Experimental, Numerical, And Analytical Methods, Patrick Severson

Theses and Dissertations

Composite materials are increasing in popularity as a material of choice in many engineering applications. Major industries using composites include automotive, construction, and sports equipment. Most of the knowledge, research, and technology that will help decrease the cost of composite materials have been aimed at developing synthetic fibers as the reinforcing constituent.

This thesis characterizes jute fibers obtained as a byproduct from the coffee industry to determine if they can be viable in composite manufacturing. Experimental analysis, finite element analysis, and analytical modeling are used to characterize jute fiber based composites. Experimental analysis consists of jute fiber bundle tensile testing …

Experimental Methods To Characterize Nonlinear Vibration Of Flapping Wing Micro Air Vehicles, Adam P. Tobias

Theses and Dissertations

For urban combat reconnaissance, the flapping wing micro air vehicle concept is ideal because of its low speed and miniature size, which are both conducive to indoor operations. The focus of this research is the development of experimental methods best suited for the vibration testing of the wing structure of a flapping wing micro air vehicle. This study utilizes the similarity of a beam resonating at its first bending mode to actual wing flapping motion. While computational finite element analysis based on linear vibration theory is employed for preliminary beam sizing, an emphasis is placed on experimental measurement of the …