You searched for +publisher:"Virginia Tech" +contributor:("Philen, Michael K.").
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Virginia Tech
1.
De La Hunt, Melina Renee.
Fluidic Flexible Matrix Composite Wafers for Volume Management in Prosthetic Sockets.
Degree: MS, Mechanical Engineering, 2015, Virginia Tech
URL: http://hdl.handle.net/10919/52786 
► Persons with transfemoral (above knee) and transtibial (below knee) prostheses experience changes in the volume of their residual limb during the course of the day.…
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▼ Persons with transfemoral (above knee) and transtibial (below knee) prostheses experience changes in the volume of their residual limb during the course of the day. These changes in volume unavoidably lead to changes in quality of fit of the prosthesis, skin irritations, and soft tissue injuries. The associated pain and discomfort can become debilitating by reducing one's ability to perform daily activities. While significant advancements have been made in prostheses, the undesirable pain and discomfort that occurs due to the volume change is still a major challenge that needs to be solved. The overall goal of this research is to develop smart prosthetic sockets that can accommodate for volume fluctuations in the residual limb. In this research, fluidic flexible matrix composite wafers (f2mc) are integrated into the prosthetic socket for volume regulation. The f2mc's are flexible tubular elements embedded in a flexible matrix. These tubular elements are connected to a reservoir, and contain an internal fluid such as air or water. Fluid flow between the tubes and reservoir is controlled by valves. A linear finite element model has been created to better understand output response and stiffness of the f2mc wafers for different design variables. Results demonstrate that wind angle, latex thickness, and material selection can be used to tailor the wafers for different applications. Through experiments, f2mc's have been shown to achieve nearly 100% strain through the thickness when pressurized to about 482.6 kPa (70 psi). The displacement results shown through these tests show great promise in applications of socket integration to compensate for volume change.
Advisors/Committee Members: Philen, Michael K. (committeechair), West, Robert L. (committee member), Tarazaga, Pablo Alberto (committee member).
Subjects/Keywords: Smart prosthetic socket; Fluidic flexible matrix composite; Volume management
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APA (6th Edition):
De La Hunt, M. R. (2015). Fluidic Flexible Matrix Composite Wafers for Volume Management in Prosthetic Sockets. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/52786
Chicago Manual of Style (16th Edition):
De La Hunt, Melina Renee. “Fluidic Flexible Matrix Composite Wafers for Volume Management in Prosthetic Sockets.” 2015. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/52786.
MLA Handbook (7th Edition):
De La Hunt, Melina Renee. “Fluidic Flexible Matrix Composite Wafers for Volume Management in Prosthetic Sockets.” 2015. Web. 26 Feb 2021.
Vancouver:
De La Hunt MR. Fluidic Flexible Matrix Composite Wafers for Volume Management in Prosthetic Sockets. [Internet] [Masters thesis]. Virginia Tech; 2015. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/52786.
Council of Science Editors:
De La Hunt MR. Fluidic Flexible Matrix Composite Wafers for Volume Management in Prosthetic Sockets. [Masters Thesis]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/52786
Virginia Tech
2.
Hyde, Griffin Nicholas.
Investigation into the Local and Global Bifurcations of the Whirling Planar Pendulum.
Degree: MS, Aerospace Engineering, 2019, Virginia Tech
URL: http://hdl.handle.net/10919/91395
► This report details the investigation into the Whirling Planar Pendulum system. The WPP is a pendulum that is spun around a vertical spin axis at…
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▼ This report details the investigation into the Whirling Planar Pendulum system. The WPP is a pendulum that is spun around a vertical spin axis at a controllable horizontal offset. This system can be used to investigate what are known as local and global bifurcations. A local bifurcation occurs when the single equilibrium state (corresponding to the pendulum hanging straight down) when spun at low speeds, bifurcates into three equilibria when the spin rate is increased beyond a certain value. The global bifurcations occur when the system experiences sinusoidal forcing near certain equilibrium conditions. The resulting chaotic oscillations are investigated using Melnikov’s method, which determines when the sinusoidal forcing results in chaotic motion. This chaotic motion comes in two types, which cause the system to behave in different ways. Melnikov’s method, and results from a simulation were used to determine the parameter values in which the pendulum experiences each type of chaos. It was seen that at certain parameter values, the WPP experiences both types of chaos, supporting the observation that these types of chaos are not necessarily independent of each other, but can merge and interact.
Advisors/Committee Members: Woolsey, Craig A. (committeechair), Southward, Steve C. (committee member), Philen, Michael K. (committee member).
Subjects/Keywords: Chaos theory; Bifurcation theory; Whirling Planar Pendulum
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APA (6th Edition):
Hyde, G. N. (2019). Investigation into the Local and Global Bifurcations of the Whirling Planar Pendulum. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/91395
Chicago Manual of Style (16th Edition):
Hyde, Griffin Nicholas. “Investigation into the Local and Global Bifurcations of the Whirling Planar Pendulum.” 2019. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/91395.
MLA Handbook (7th Edition):
Hyde, Griffin Nicholas. “Investigation into the Local and Global Bifurcations of the Whirling Planar Pendulum.” 2019. Web. 26 Feb 2021.
Vancouver:
Hyde GN. Investigation into the Local and Global Bifurcations of the Whirling Planar Pendulum. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/91395.
Council of Science Editors:
Hyde GN. Investigation into the Local and Global Bifurcations of the Whirling Planar Pendulum. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/91395
Virginia Tech
3.
Hull, Brandon Tristan.
Examination of Mechanical Stretching to Increase Alignment in Carbon Nanotube Composites.
Degree: MS, Aerospace Engineering, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/52629
► Individual carbon nanotubes have been theoretically and experimentally proven to be the strongest and stiffest materials discovered to date with tensile strengths ranging from 1-5…
(more)
▼ Individual carbon nanotubes have been theoretically and experimentally proven to be the strongest and stiffest materials discovered to date with tensile strengths ranging from 1-5 TPa and elastic modulus values as high as 150 GPa. In this work, the recent development of continuous sheets of CNTs, produced by Nanocomp Technologies Inc ., are investigated for their potential as reinforcement in polymer matrix composite (PMC) materials. The potential of these nanotube-based PMC materials have been reported by researchers at Florida State University (FSU). Through the use of mechanical stretching procedures to increase the alignment of the nanotubes within the CNT sheets, the tensile strength and Young's modulus of the composites in the FSU study averaged 3081 MPa and 350 GPa, respectively. These values are for composites fabricated from 40% stretched CNT sheets and are 48% and 107% improvements over composites fabricated from the pristine, unstretched CNT sheets. However, the test specimens used in the FSU study consisted of a single CNT ply and each coupon was individually stretched and cured for testing. Therefore, the process used to generate the coupons which exhibited these high mechanical properties would be difficult to scale to a usable size for aerospace structural components. In the current study, a scalable process has been developed in which 2-ply, 3" x 3" panels of CNT and resin composites are fabricated. An apparatus and methodology for mechanically stretching the CNT sheets used in these composite panels has also been developed. After initial testing was conducted with the CNT composites and the coupons exhibited significant elongation at failure, along with the absence of a linear elastic region, conventional test standards for material testing were deemed impractical. For this reason, new mechanical testing methodologies have been developed to determine the mechanical properties of specific strength and specific modulus of CNT-polymer composites.
In order to obtain the maximum benefits of a fiber in any matrix in terms of stiffness and strength, it is preferable to align the high strength and stiffness fibers in the direction of loading. Given that these CNT sheets essentially consist of billions of short, discontinuous CNTs of 2-3mmin length, the process of mechanical stretching is used in an attempt to align these tubes in the direction of the applied tensile load. Here we have explored methodologies for stretching, fabricating, and mechanical testing. Having identified a process which seems viable, an examination into the effect of the mechanical stretching to increase the alignment of the nanotubes within the CNT sheets, and thus to increase the material properties of the 2-ply composites constructed from them, is conducted. In order to correlate the enhancements in the mechanical properties with the increased alignment of the CNTs, polarized Raman spectroscopy techniques have been used. Lastly, Scanning Electron Microscopy (SEM) is used to examine the effect of stretching on the pristine CNT…
Advisors/Committee Members: Seidel, Gary D. (committeechair), Grimsley, Brian William (committee member), Philen, Michael K. (committee member).
Subjects/Keywords: Carbon Nanotube; Composite Fabrication; Mechanical Stretching; Composite Tensile Testing; Raman Spectroscopy
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APA (6th Edition):
Hull, B. T. (2013). Examination of Mechanical Stretching to Increase Alignment in Carbon Nanotube Composites. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/52629
Chicago Manual of Style (16th Edition):
Hull, Brandon Tristan. “Examination of Mechanical Stretching to Increase Alignment in Carbon Nanotube Composites.” 2013. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/52629.
MLA Handbook (7th Edition):
Hull, Brandon Tristan. “Examination of Mechanical Stretching to Increase Alignment in Carbon Nanotube Composites.” 2013. Web. 26 Feb 2021.
Vancouver:
Hull BT. Examination of Mechanical Stretching to Increase Alignment in Carbon Nanotube Composites. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/52629.
Council of Science Editors:
Hull BT. Examination of Mechanical Stretching to Increase Alignment in Carbon Nanotube Composites. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/52629
Virginia Tech
4.
Marshall, Peter Johannes.
Acoustic Analysis of Spacecraft Cavities using the Boundary Element Method.
Degree: MS, Aerospace Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/83460
► Spacecraft structures are subject to a series of load environments during their service life, with the most severe of these occurring during the spacecraft's launch…
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▼ Spacecraft structures are subject to a series of load environments during their service life, with the most severe of these occurring during the spacecraft's launch and ascension through the atmosphere. In particular, acoustic loads imposed on stowed satellites within the launch vehicle fairing can result in high mechanical loads on sensitive spacecraft hardware. These acoustic loads have the potential to damage important components and as such it is necessary to accurately characterize and predict the acoustic launch environment for a given mission. This research investigates the Sound Pressure Level (SPL) that can be measured in and around spacecraft cavities resulting from a known excitation and the resultant structural responses. Linear finite element analysis (FEA) is coupled with the Boundary Element method (BEM) to analyze spacecraft acoustic environments and corresponding structural responses at low frequencies on the order of the structural modes.
Analytical capability for predicting acoustic environments inside the launch vehicle has improved significantly in recent years; however, while it is easy to perform an analysis and obtain results, the modeling effort can become unnecessarily complicated and analytical data can be hard to interpret. This work seeks to alleviate unnecessary complexity in the low-frequency regime of acoustic modeling by examining the fundamentals of coupled BEM-FEM analysis and applying simplification to a spacecraft model where possible to achieve results verified against direct field acoustic testing (DFAT) methods.
Advisors/Committee Members: Kapania, Rakesh K. (committeechair), McQuigg, Thomas Dale (committee member), Philen, Michael K. (committee member).
Subjects/Keywords: Acoustics; Spacecraft Structures; Boundary Element Method
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APA (6th Edition):
Marshall, P. J. (2018). Acoustic Analysis of Spacecraft Cavities using the Boundary Element Method. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/83460
Chicago Manual of Style (16th Edition):
Marshall, Peter Johannes. “Acoustic Analysis of Spacecraft Cavities using the Boundary Element Method.” 2018. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/83460.
MLA Handbook (7th Edition):
Marshall, Peter Johannes. “Acoustic Analysis of Spacecraft Cavities using the Boundary Element Method.” 2018. Web. 26 Feb 2021.
Vancouver:
Marshall PJ. Acoustic Analysis of Spacecraft Cavities using the Boundary Element Method. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/83460.
Council of Science Editors:
Marshall PJ. Acoustic Analysis of Spacecraft Cavities using the Boundary Element Method. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/83460
Virginia Tech
5.
Offenberger, Sean Alan.
Investigation of Zinc Oxide Nanowires for Impedance Based Structural Health Monitoring.
Degree: MS, Aerospace Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/82502
► The goal of this work is to investigate the piezoelectricity of composite laminates embedded with layers of zinc oxide (ZnO) nanowires. ZnO nanowire embedded composites…
(more)
▼ The goal of this work is to investigate the piezoelectricity of composite laminates embedded with layers of zinc oxide (ZnO) nanowires. ZnO nanowire embedded composites have the potential to sense and actuate giving the potential for these smart composites to serve the function of being load bearing structures and monitoring the integrity of the structure. This work examines the piezoelectric characteristics of composite beams by investigating their electromechanical coupling in the form of vibration under the presence of electrical excitation. With the help of a mathematical model, piezoelectric constants are estimated for these samples. A layer of ZnO nanowires were grown on plane woven fiberglass fabric that was incorporated into a carbon fiber epoxy composite. The beam deflection velocity was measured as a varying voltage was applied to the composite. Using Hamilton's Principle and Galerkin's method of weighted residuals, a mathematical model was derived to estimate piezoelectric constants for the composites from the experimental data. Piezoelectric properties were determined using vibrational testing and a mathematical model. Piezoelectric constants h31, g31, and d31 were estimated to be 9.138 E7 V/m, 6.092 E-4 Vm/N, and 2.46 E-14 respectively. To demonstrate the electromechanical coupling, ZnO nanowire composites were bonded to Al beams that were progressively damaged to determine if a change in electrical impedance could be observed to correspond to the change in structural impedance of the host beam. Changes in impedance were detected by a change in root mean squared deviation damage metric M. A significant correlation was shown between increasing damage in the host beam and an increase in damage metric M.
Advisors/Committee Members: Philen, Michael K. (committeechair), Patil, Mayuresh J. (committee member), Seidel, Gary D. (committee member).
Subjects/Keywords: Smart Materials; Piezoelectrics; Zinc Oxide Nanowires; Impedance-Based Structural Health Monitoring
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APA (6th Edition):
Offenberger, S. A. (2018). Investigation of Zinc Oxide Nanowires for Impedance Based Structural Health Monitoring. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/82502
Chicago Manual of Style (16th Edition):
Offenberger, Sean Alan. “Investigation of Zinc Oxide Nanowires for Impedance Based Structural Health Monitoring.” 2018. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/82502.
MLA Handbook (7th Edition):
Offenberger, Sean Alan. “Investigation of Zinc Oxide Nanowires for Impedance Based Structural Health Monitoring.” 2018. Web. 26 Feb 2021.
Vancouver:
Offenberger SA. Investigation of Zinc Oxide Nanowires for Impedance Based Structural Health Monitoring. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/82502.
Council of Science Editors:
Offenberger SA. Investigation of Zinc Oxide Nanowires for Impedance Based Structural Health Monitoring. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/82502
Virginia Tech
6.
Ojeda Romero, Juan Andre.
Dual Satellite Coverage using Particle Swarm Optimization.
Degree: MS, Aerospace Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/50627
► A dual satellite system in a Low Earth Orbit, LEO, would be beneficial to study the electromagnetic occurrences in the magnetosphere and their contributions to…
(more)
▼ A dual satellite system in a Low Earth Orbit, LEO, would be beneficial to study the electromagnetic occurrences in the magnetosphere and their contributions to the development of the aurora events in the Earth's lower atmosphere. An orbit configuration is sought that would increase the total time that both satellites are inside the auroral oval. Some additional objectives include minimizing the total fuel cost and the average angle between the satellites' radius vectors. This orbit configuration is developed using a series of instantaneous burns applied at each satellite's perigee. An analysis of the optimal solutions generated by a Particle Swarm Optimization method is completed using a cost function with different weights for the time, fuel, and angle terms. Three different scenarios are presented: a single burn case, a double burn case, and a four burn case. The results are calculated using two different orbital mechanics models: an unperturbed two-body simulation and a two-body simulation with added Earth's equatorial bulge effects. It is shown that the added perturbation reduces the total event time in the optimal solutions generated. Specific weights for the cost function are recommended for further studies.
Advisors/Committee Members: Philen, Michael K. (committeechair), Earle, Gregory D. (committee member), Sultan, Cornel (committee member).
Subjects/Keywords: particle swarm optimization; space weather; aurora borealis; orbital mechanics; satellite coverage
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APA (6th Edition):
Ojeda Romero, J. A. (2014). Dual Satellite Coverage using Particle Swarm Optimization. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50627
Chicago Manual of Style (16th Edition):
Ojeda Romero, Juan Andre. “Dual Satellite Coverage using Particle Swarm Optimization.” 2014. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/50627.
MLA Handbook (7th Edition):
Ojeda Romero, Juan Andre. “Dual Satellite Coverage using Particle Swarm Optimization.” 2014. Web. 26 Feb 2021.
Vancouver:
Ojeda Romero JA. Dual Satellite Coverage using Particle Swarm Optimization. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/50627.
Council of Science Editors:
Ojeda Romero JA. Dual Satellite Coverage using Particle Swarm Optimization. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/50627
Virginia Tech
7.
Degl'Incerti Tocci, Corrado.
Analysis of Composites using Peridynamics.
Degree: MS, Aerospace Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/25351
► Since the last century a lot of effort has been spent trying to analyze damage and crack evolution in solids. This field is of interest…
(more)
▼ Since the last century a lot of effort has been spent trying to analyze damage and crack evolution in solids. This field is of interest because of the many applications that require the study of the behavior of materials at the micro- or nanoscale, i.e. modeling of composites and advanced aerospace applications. Peridynamics is a recently developed theory that substitutes the differential equations that constitute classical continuum mechanics with integral equations. Since integral equations are valid at discontinuities and cracks, peridynamics is able to model fracture and damage in a more natural way, without having to work around mathematical singularities present in the classical continuum mechanics theory. The objective of the present work is to show how peridynamics can be implemented in finite element analysis (FEA) using a mesh of one-dimensional truss elements instead of 2-D surface elements. The truss elements can be taken as a representation of the bonds between molecules or particles in the body and their strength is found according to the physical properties of the material. The possibility implementing peridynamics in a finite element framework, the most used method for structural analysis, is critical for expanding the range of problems that can be analyzed, simplifying the verification of the code and for making fracture analysis computationally cheaper. The creation of an in-house code allows for easier modifications, customization and enrichment if more complex cases (such as multiscale modeling of composites or piezoresistive materials) are to be analyzed. The problems discussed in the present thesis involve plates with holes and inclusions subjected to tension. Displacement boundary conditions are applied in all cases. The results show good agreement with theory as well as with empirical observation. Stress concentrations reflect the behavior of materials in real life, cracks spontaneously initiate and debonding naturally happens at the right locations. Several examples clearly show this behavior and prove that peridynamics is a promising tool for stress and fracture analysis.
Advisors/Committee Members: Seidel, Gary D. (committeechair), Patil, Mayuresh J. (committee member), Philen, Michael K. (committee member).
Subjects/Keywords: peridynamics; multiscale; carbon nanotube; finite element analysis; truss; micromechanics
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APA (6th Edition):
Degl'Incerti Tocci, C. (2014). Analysis of Composites using Peridynamics. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/25351
Chicago Manual of Style (16th Edition):
Degl'Incerti Tocci, Corrado. “Analysis of Composites using Peridynamics.” 2014. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/25351.
MLA Handbook (7th Edition):
Degl'Incerti Tocci, Corrado. “Analysis of Composites using Peridynamics.” 2014. Web. 26 Feb 2021.
Vancouver:
Degl'Incerti Tocci C. Analysis of Composites using Peridynamics. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/25351.
Council of Science Editors:
Degl'Incerti Tocci C. Analysis of Composites using Peridynamics. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/25351
Virginia Tech
8.
Capps, Ryan Anthony.
Fatigue Characteristics of Pressurized Artificial Muscles.
Degree: MS, Aerospace Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/49702
► Pressurized artificial muscles show promise in both standard aircraft actuation operations and in morphing structures as an alternative to currently used actuation systems due to…
(more)
▼ Pressurized artificial muscles show promise in both standard aircraft actuation operations and in morphing structures as an alternative to currently used actuation systems due to their high power-to-weight ratio. Pressurized artificial muscles have already demonstrated the necessary force production to be utilized as an alternative actuation mechanism. In order to better understand the feasibility of using pressurized artificial muscles as a standard actuation mechanism it is necessary to determine the life cycle of pressurized artificial muscles under high pressures, loads, and strains, and how muscle geometry and materials effect the life cycle of the artificial muscle.
This thesis presents a study to determine the fatigue characteristics of pressurized artificial muscles to address the issues noted above. The life cycle of the pressurized artificial muscle is examined at high internal pressures and high strains. The materials composing the pressurized artificial muscle, and the artificial muscle geometry are changed throughout the study to determine their effect on the life cycle of a pressurized artificial muscle. Finally a morphing aileron utilizing pressurized artificial muscles as the actuation mechanism is fatigue tested.
Fatigue testing results show that pressurized artificial muscle fatigue life is dependent on both actuator materials and geometry. Latex rubber bladders were shown to perform better than bladders of other materials. Increasing the wall thickness of the latex bladder increased the life cycle of the pressurized artificial muscles. Additionally, casting the pressurized artificial muscle in a cylindrical polyurethane resin matrix increased the life cycle of the actuator, and increasing the diameter of this resin matrix further increased the life cycle of the actuator.
Advisors/Committee Members: Philen, Michael K. (committeechair), Patil, Mayuresh J. (committee member), Tarazaga, Pablo Alberto (committee member).
Subjects/Keywords: Fatigue; Pressurized Artificial Muscles
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APA (6th Edition):
Capps, R. A. (2014). Fatigue Characteristics of Pressurized Artificial Muscles. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/49702
Chicago Manual of Style (16th Edition):
Capps, Ryan Anthony. “Fatigue Characteristics of Pressurized Artificial Muscles.” 2014. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/49702.
MLA Handbook (7th Edition):
Capps, Ryan Anthony. “Fatigue Characteristics of Pressurized Artificial Muscles.” 2014. Web. 26 Feb 2021.
Vancouver:
Capps RA. Fatigue Characteristics of Pressurized Artificial Muscles. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/49702.
Council of Science Editors:
Capps RA. Fatigue Characteristics of Pressurized Artificial Muscles. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/49702
Virginia Tech
9.
Singh, Raymond Charan.
Modeling Energy Harvesting From Membrane Vibrations using Multi-physics Modeling.
Degree: MS, Aerospace Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/76793
► Given the ever-growing need for device autonomy and renewable sources of energy, energy harvesting has become an increasingly popular field of research. This research focuses…
(more)
▼ Given the ever-growing need for device autonomy and renewable sources of energy, energy harvesting has become an increasingly popular field of research. This research focuses on energy harvesting using the piezoelectric effect, from vibrating membrane structures by converting mechanical energy into electric energy. Specific applications of this research include powering components of bio-inspired micro air vehicles (MAVs), which require long range with as little regular maintenance as possible, and powering sensors for structural health monitoring on otherwise inaccessible locations (the roof of the Denver Int'l Airport is a good example). Coming up with an efficient, high-fidelity model of these systems allows for design optimization without the extensive use of experimental testing, as well as a deeper understanding of the physics involved. These are the twin goals of this research. This work describes a modeling algorithm using COMSOL, a multi-physics software, to predict the structural mechanics of and subsequent power harvested from a piezoelectric patch placed on a prestressed membrane structure. The model is verified by an FE comparison of the modeled system's dynamic response. For a 0.5 x 0.5 x 0.001 m nylon membrane with a 0.1 x 0.1 x 0.001 m piezoelectric patch placed on its corner, a maximum power output of ~10 microwatts was achieved, using a resistance of 100 Ohms and exciting the system around resonance. When the patch was placed on the side of the membrane, the power output was ~100 milliwatts. The ultimate goal is to estimate the energy harvested by a network of these piezoelectric patches and optimize the harvesting system based on the size, shape and location of the patches.
Advisors/Committee Members: Kapania, Rakesh K. (committeechair), Philen, Michael K. (committee member), Sultan, Cornel (committeecochair).
Subjects/Keywords: Piezoelectric; Energy Harvesting; Computational Methods; Membranes
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APA (6th Edition):
Singh, R. C. (2012). Modeling Energy Harvesting From Membrane Vibrations using Multi-physics Modeling. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/76793
Chicago Manual of Style (16th Edition):
Singh, Raymond Charan. “Modeling Energy Harvesting From Membrane Vibrations using Multi-physics Modeling.” 2012. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/76793.
MLA Handbook (7th Edition):
Singh, Raymond Charan. “Modeling Energy Harvesting From Membrane Vibrations using Multi-physics Modeling.” 2012. Web. 26 Feb 2021.
Vancouver:
Singh RC. Modeling Energy Harvesting From Membrane Vibrations using Multi-physics Modeling. [Internet] [Masters thesis]. Virginia Tech; 2012. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/76793.
Council of Science Editors:
Singh RC. Modeling Energy Harvesting From Membrane Vibrations using Multi-physics Modeling. [Masters Thesis]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/76793
Virginia Tech
10.
Allen, David William.
Development of a Value System and Mission Architecture for the Exploration of the Oceans of Europa.
Degree: MS, Aerospace and Ocean Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/78175
► Of all of the bodies in the solar system, Europa is perhaps the most enticing. Based on several lines of evidence, Europa, a moon of…
(more)
▼ Of all of the bodies in the solar system, Europa is perhaps the most enticing. Based on several lines of evidence, Europa, a moon of Jupiter, is believed to have an ocean of liquid water beneath several kilometers of ice. This ocean is likely in contact with Europa's rocky core, making Europa's ocean one of the most likely places for life to exist in the solar system outside of Earth. This thesis provides an outline of the technology required for a mission that travels to Europa, penetrates the ice, and explores the ocean below.
In order to create this outline, this thesis first provides background on previous missions to the outer planets. A discussion of the science requirements is presented and then a value system by which designs are evaluated is developed. Current technologies and the design alternatives are presented and evaluated using the value system. A final mission architecture and concept of operations are then presented.
Advisors/Committee Members: Woolsey, Craig A. (committeechair), Philen, Michael K. (committee member), Moore, William (committee member), McCue, Leigh (committeecochair).
Subjects/Keywords: Europa; Planetary Exploration; Autonomous Underwater Vehicles; Melt Probes
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APA (6th Edition):
Allen, D. W. (2014). Development of a Value System and Mission Architecture for the Exploration of the Oceans of Europa. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78175
Chicago Manual of Style (16th Edition):
Allen, David William. “Development of a Value System and Mission Architecture for the Exploration of the Oceans of Europa.” 2014. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/78175.
MLA Handbook (7th Edition):
Allen, David William. “Development of a Value System and Mission Architecture for the Exploration of the Oceans of Europa.” 2014. Web. 26 Feb 2021.
Vancouver:
Allen DW. Development of a Value System and Mission Architecture for the Exploration of the Oceans of Europa. [Internet] [Masters thesis]. Virginia Tech; 2014. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/78175.
Council of Science Editors:
Allen DW. Development of a Value System and Mission Architecture for the Exploration of the Oceans of Europa. [Masters Thesis]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/78175
11.
Rocker, Samantha Nicole.
Piezoresistivity Characterization of Polymer Bonded Energetic Nanocomposites under Cyclic Load Cases for Structural Health Monitoring Applications.
Degree: MS, Aerospace Engineering, 2019, Virginia Tech
URL: http://hdl.handle.net/10919/91427
► The ability to characterize both deformation and damage in real time within materials of high energetic content, such as solid rocket propellant, is of great…
(more)
▼ The ability to characterize both deformation and damage in real time within materials of high energetic content, such as solid rocket propellant, is of great interest in experimental mechanics. Common energetic ammonium perchlorate, in the fonn of crystal particles, was embedded in polymer binders (ie PDMS and epoxy) and investigated under a variety of meÂchanical and thermal loads. Carbon nanotubes, conductive tube-shaped molecular structures of carbon atoms, have been demonstrated in prior proofs of concept to induce substantial electrical response change when dispersed in composites which are experiencing strain. With the introduction of carbon nanotubes in the energetic composites investigated herein, the electrical response of the material systems was measured as a change in impedance with applied strain. Elastomer-bonded energel.ks were t.esl.ed under monotonic compression and cyclic compression, and expanded exploration was done on these material systems with the additional particulate of aluminum powder, allowing for varied particulate sizes and conductivity enhancement of the overall composite. The magnitude of the resulting piezoresistive change due to strain and microscale damage was observed to increase dramatically in material systems enhanced by MWCNT networks. Local heating was used to explore thermal loading on epoxy-bonded energetic material systems, and sensing of permanent damage to the material through its CNT network was proven through a permanent change in the electrical response which was exclusive to the CNT-enhanced material systems. These results demonÂstrate valid structural health monitoring (SHM) applications for embedded carbon nanotube sensing networks in particulate energetic composites, under a variety of load cases.
Advisors/Committee Members: Seidel, Gary D. (committeechair), Philen, Michael K. (committee member), Kapania, Rakesh K. (committee member).
Subjects/Keywords: Structural health monitoring; Piezoresistivity; Nanocomposites; Multifunctional composites; Energetics; Carbon nanotubes; Damage detection
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APA (6th Edition):
Rocker, S. N. (2019). Piezoresistivity Characterization of Polymer Bonded Energetic Nanocomposites under Cyclic Load Cases for Structural Health Monitoring Applications. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/91427
Chicago Manual of Style (16th Edition):
Rocker, Samantha Nicole. “Piezoresistivity Characterization of Polymer Bonded Energetic Nanocomposites under Cyclic Load Cases for Structural Health Monitoring Applications.” 2019. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/91427.
MLA Handbook (7th Edition):
Rocker, Samantha Nicole. “Piezoresistivity Characterization of Polymer Bonded Energetic Nanocomposites under Cyclic Load Cases for Structural Health Monitoring Applications.” 2019. Web. 26 Feb 2021.
Vancouver:
Rocker SN. Piezoresistivity Characterization of Polymer Bonded Energetic Nanocomposites under Cyclic Load Cases for Structural Health Monitoring Applications. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/91427.
Council of Science Editors:
Rocker SN. Piezoresistivity Characterization of Polymer Bonded Energetic Nanocomposites under Cyclic Load Cases for Structural Health Monitoring Applications. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/91427
12.
Berry, Seth David.
Experimental Characterization of Mode I Fracture Toughness of Reinforced Carbon Fiber Laminate with Nano-Cellulose and CNT Additives.
Degree: MS, Aerospace Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/72132
► Effective treatment of carbon fiber components to improve delamination resistance is vital to the application of such materials since delamination is one of the biggest…
(more)
▼ Effective treatment of carbon fiber components to improve delamination resistance is vital to the application of such materials since delamination is one of the biggest concerns regarding the use of composites in the aerospace sector. Due to the significant application benefit gained from increased stiffness to density ratio with composite materials, innovative developments resulting in improved through-thickness strength have been on the rise. The inherent anisotropy of composite materials results in an added difficulty in designing structural elements that make use of such materials. Proposed techniques to improve the through-thickness strength of laminar composites are many and varied; however all share the common goal of improving inter-laminar bond strength.
This research makes use of novel materials in the field of wet flocking and Z-pinning. Cellulose nanofibers (CNFs) have already demonstrated excellent mechanical properties in terms of stiffness and strength, originating at the nano-scale. These materials were introduced into the laminate while in a sol-gel suspension in an effort to improve load transfer between laminate layers. The effect of CNFs as lightweight renewable reinforcement for CFRPs will be investigated. Carbon nanotube (CNT) additives were also considered for their beneficial structural properties.
Advisors/Committee Members: Seidel, Gary D. (committeechair), Philen, Michael K. (committee member), Goodell, Barry (committee member).
Subjects/Keywords: Delamination; Carbon Fiber; CNT; Nano-Cellulose; Z-pin; Fracture Toughness
…Virginia Tech Sustainable Biomaterials Department at the Institute for Critical Technology and… …Sciences Circle, Virginia Tech
Seth D. Berry
Chapter 3. Experimental Methods
13
Figure 3.3…
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APA (6th Edition):
Berry, S. D. (2016). Experimental Characterization of Mode I Fracture Toughness of Reinforced Carbon Fiber Laminate with Nano-Cellulose and CNT Additives. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/72132
Chicago Manual of Style (16th Edition):
Berry, Seth David. “Experimental Characterization of Mode I Fracture Toughness of Reinforced Carbon Fiber Laminate with Nano-Cellulose and CNT Additives.” 2016. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/72132.
MLA Handbook (7th Edition):
Berry, Seth David. “Experimental Characterization of Mode I Fracture Toughness of Reinforced Carbon Fiber Laminate with Nano-Cellulose and CNT Additives.” 2016. Web. 26 Feb 2021.
Vancouver:
Berry SD. Experimental Characterization of Mode I Fracture Toughness of Reinforced Carbon Fiber Laminate with Nano-Cellulose and CNT Additives. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/72132.
Council of Science Editors:
Berry SD. Experimental Characterization of Mode I Fracture Toughness of Reinforced Carbon Fiber Laminate with Nano-Cellulose and CNT Additives. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/72132
13.
Chung, Howard Jenn Yee.
Towards a Self-Powered Structural Health Monitoring Smart Tire.
Degree: MS, Aerospace Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/71375
► This work investigates the feasibility of developing a self-powered structural health monitoring (SHM) smart tire using piezoelectric materials. While this work is divided into two…
(more)
▼ This work investigates the feasibility of developing a self-powered structural health monitoring (SHM) smart tire using piezoelectric materials. While this work is divided into two components: SHM and energy harvesting, the context of smart tire in this work is defined as the development of a SHM system that (i) has self-powering capabilities, and (ii) addresses the potential of embedding sensors. The use of impedance based SHM on a tire is severely limited due to the low stiffness and high damping characteristics of the tire. This work propose the use of a high voltage impedance analyzer, and the addition of electrical circuit to enhance the damage detection process. Experimental work was conducted on an aluminum beam and on a tire section with commercially available piezoelectric sensors. The use of a high voltage impedance analyzer was demonstrated to provide insight on damage type and damage location. Two sensors were connected in parallel as an effective sensory system, and was shown to reduce interrogation time, but reduce damage identification sensitivity. With added electrical circuits, a belt separation on the tire was successfully detected by the shift in electrical impedance signature. For the energy harvesting portion of this work, a bimorph piezoelectric energy harvester model was derived using extended Hamilton's principle and the linear constitutive relations of piezoelectric materials. Comparison of model with experimental data at increasing loading conditions demonstrated the monotonic increase in voltage output, with linear asymptotes at extreme loading conditions (short-circuit and open-circuit). It also demonstrated the existence of an optimal resistive load for maximum power output. To address the ability to embed sensors, an existing fabrication process to grow arrays of ZnO nanowires in carbon fiber reinforced polymer was used in this work. Comparison of power generation from a composite beam with ZnO nanowires with a composite beam without ZnO nanowires demonstrated the power generation capabilities of the nanowires. A maximum peak voltage of 8.91 mV and peak power of 33.3 pW was obtained. After the application of 10V DC, a maximum of 45 pW was obtained. However, subsequent application of 20V DC reduced the maximum peak power output to 2.5 pW. Several attempts to increase power generation including adding a tip mass and changing the geometry of the composite beam were conducted. Finally, the theoretical voltage frequency response function obtained from the theoretical piezoelectric constant and dielectric constant of a single ZnO nanowire were compared to the experimental voltage frequency response function. The discrepancies were discussed.
Advisors/Committee Members: Philen, Michael K. (committeechair), Tarazaga, Pablo Alberto (committeechair), Kurdila, Andrew J. (committee member).
Subjects/Keywords: Piezoelectric; Impedance-Based Structural Health Monitoring; Energy Harvesting; Zinc Oxide Nanowires; Smart Tires; Smart Materials
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APA (6th Edition):
Chung, H. J. Y. (2016). Towards a Self-Powered Structural Health Monitoring Smart Tire. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/71375
Chicago Manual of Style (16th Edition):
Chung, Howard Jenn Yee. “Towards a Self-Powered Structural Health Monitoring Smart Tire.” 2016. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/71375.
MLA Handbook (7th Edition):
Chung, Howard Jenn Yee. “Towards a Self-Powered Structural Health Monitoring Smart Tire.” 2016. Web. 26 Feb 2021.
Vancouver:
Chung HJY. Towards a Self-Powered Structural Health Monitoring Smart Tire. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/71375.
Council of Science Editors:
Chung HJY. Towards a Self-Powered Structural Health Monitoring Smart Tire. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/71375
14.
Rubenking, Samuel Kim.
Dual Mode Macro Fiber Composite-Actuated Morphing Tip Feathers for Controlling Small Unmanned Aircraft.
Degree: MS, Aerospace Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/78433
► The transition of flight from manned to unmanned systems has led to new research and applications of technology within the field that, until recently, were…
(more)
▼ The transition of flight from manned to unmanned systems has led to new research and applications of technology within the field that, until recently, were previously thought to be unfeasible. The industry has become interested in alternative control surfaces and uses for smart materials. A Macro Fiber Composite (MFC), a smart material, takes advantage of the piezoelectric effect and provides an attractive alternative actuator to servos in the Small Unmanned Aerial Systems (SUAS) regime of flight. This research looks to take MFC actuated control surfaces one step further by pulling inspiration from and avian flight. A dual mode control surface, created by applying two sets of two MFCs to patch of carbon fiber, can mimic the tip feathers of a bird. This actuator was modeled both using Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD). Real-world static testing on a feather confirmed preliminary FEA results, and wind tunnel tests simulating assumed cruise conditions confirmed the feather would not exhibit any adverse structural behaviors, such as flutter or aeroelastic divergence. From its modeled performance on a wing using CFD, the MFC feather proved to be a success. It was able to produce a wing that, when compared to a traditional rectangular wing, yielded 73% less induced drag and generated proverse yaw. However, the MFC feathers alone, in the configuration tested, did not produce enough roll authority to feasibly control an aircraft.
Advisors/Committee Members: Kochersberger, Kevin Bruce (committeechair), Seidel, Gary D. (committee member), Philen, Michael K. (committee member).
Subjects/Keywords: Macro Fiber Composites; Proverse Yaw; Induced Drag; Artificial Feather; Smart Materials
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APA (6th Edition):
Rubenking, S. K. (2017). Dual Mode Macro Fiber Composite-Actuated Morphing Tip Feathers for Controlling Small Unmanned Aircraft. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78433
Chicago Manual of Style (16th Edition):
Rubenking, Samuel Kim. “Dual Mode Macro Fiber Composite-Actuated Morphing Tip Feathers for Controlling Small Unmanned Aircraft.” 2017. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/78433.
MLA Handbook (7th Edition):
Rubenking, Samuel Kim. “Dual Mode Macro Fiber Composite-Actuated Morphing Tip Feathers for Controlling Small Unmanned Aircraft.” 2017. Web. 26 Feb 2021.
Vancouver:
Rubenking SK. Dual Mode Macro Fiber Composite-Actuated Morphing Tip Feathers for Controlling Small Unmanned Aircraft. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/78433.
Council of Science Editors:
Rubenking SK. Dual Mode Macro Fiber Composite-Actuated Morphing Tip Feathers for Controlling Small Unmanned Aircraft. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/78433
15.
Crosser, Kara Elizabeth.
Heat Transfer Assessment of Aluminum Alloy Corrugated Naval Ship Deck Panels under VTOL Aircraft Thermal Loads.
Degree: MS, Aerospace Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/72947
► The behavior of aluminum alloy ship deck panels under the thermal loads of Vertical Take-off-and Landing (VTOL) capable aircraft has become a question of interest…
(more)
▼ The behavior of aluminum alloy ship deck panels under the thermal loads of Vertical Take-off-and Landing (VTOL) capable aircraft has become a question of interest with the introduction of new primarily aluminum alloy ships to the U.S. Naval Fleet. This study seeks to provide an initial investigation of this question by examining the transient transfer of heat through aluminum alloy ship deck panels under application of the local heat transfer similar to that of a VTOL aircraft exhaust plume core in typical operation.
In this study, a jet stream intended to replicate the key physics of the core of a VTOL aircraft plume was impinged onto the upper surface of aluminum alloy corrugated deck panel test specimen. Temperature measurements are taken via thermocouples on the face of the specimen opposite the impingement to evaluate heat transfer through the specimen. This data is used to assess the effects of variation in the geometry of the corrugation between specimen. Qualitative temperature distributions were also gathered on the impingement surface via thermal imaging. A quantitative assessment of the heat paths for transverse and vertical heat transfer was made based on a thermal resistance model, leading to a conceptual description of predominant heat flow paths in the specimen, specifically weld lines between the corrugation and the flat plate surfaces.
In support of this, thermal images indicated that the weld lines provided paths for heat to be pulled away from the center of heat application more rapidly than over the rest of the surface. Ultimately, heat transfer through the specimen was found to be more dependent on the flow conditions than the variations in geometry of the deck panels due to the low variation in thermal resistance across the plate. A recommendation is made based upon this observation to use the deck panels similarly to heat exchanges by adding a small amount of through-deck airflow in the areas of high heat load.
Advisors/Committee Members: Lowe, Kevin Todd (committeechair), Philen, Michael K. (committee member), Schetz, Joseph A. (committee member).
Subjects/Keywords: Heat Transfer; Aluminum Alloy; Convection Coefficient
…surroundings.
3.3 Virginia Tech Hot Jet Facility
The Virginia Tech Hot Jet was used in this study… …at the Virginia Tech Advanced Propulsion and
Power Lab in Blacksburg, VA. The jet is driven… …Figure 7: Image of Virginia Tech Hot Jet Facility at the Advanced Propulsion and Power… …Laboratory
Figure 8: Schematic of Virginia Tech Hot Jet Facility
3.4 Experimental Specimen…
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APA (6th Edition):
Crosser, K. E. (2016). Heat Transfer Assessment of Aluminum Alloy Corrugated Naval Ship Deck Panels under VTOL Aircraft Thermal Loads. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/72947
Chicago Manual of Style (16th Edition):
Crosser, Kara Elizabeth. “Heat Transfer Assessment of Aluminum Alloy Corrugated Naval Ship Deck Panels under VTOL Aircraft Thermal Loads.” 2016. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/72947.
MLA Handbook (7th Edition):
Crosser, Kara Elizabeth. “Heat Transfer Assessment of Aluminum Alloy Corrugated Naval Ship Deck Panels under VTOL Aircraft Thermal Loads.” 2016. Web. 26 Feb 2021.
Vancouver:
Crosser KE. Heat Transfer Assessment of Aluminum Alloy Corrugated Naval Ship Deck Panels under VTOL Aircraft Thermal Loads. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/72947.
Council of Science Editors:
Crosser KE. Heat Transfer Assessment of Aluminum Alloy Corrugated Naval Ship Deck Panels under VTOL Aircraft Thermal Loads. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/72947
Virginia Tech
16.
Shukla, Himanshu.
Nonlinear Analysis and Control of Aeroelastic Systems.
Degree: PhD, Aerospace Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/71468
► Presence of nonlinearities may lead to limit cycle oscillations (LCOs) in aeroelastic systems. LCOs can result in fatigue in wings leading to catastrophic failures. Existence…
(more)
▼ Presence of nonlinearities may lead to limit cycle oscillations (LCOs) in aeroelastic systems.
LCOs can result in fatigue in wings leading to catastrophic failures. Existence of LCOs for
velocities less than the linear flutter velocity has been observed during flight and wind tunnel
tests, making such subcritical behavior highly undesirable. The objective of this dissertation
is to investigate the existence of subcritical LCOs in aeroelastic systems and develop state
feedback controllers to suppress them. The research results are demonstrated on a two degree
of freedom airfoil section model with stiffness nonlinearity.
Three different approaches are developed and discussed. The first approach uses a feedback
linearization controller employing the aeroelastic modal coordinates. The use of modal coordinates results in a system which is linearly decoupled making it possible to avoid cancellation
of any linear terms when compared to existing feedback linearization controllers which use
the physical coordinates. The state and control costs of the developed controller are compared to the costs of the traditional feedback linearization controllers. Second approach
involves the use of nonlinear normal modes (NNMs) as a tool to predict LCO amplitudes
of the aeroelastic system. NNM dynamics along with harmonic balance method are used
to generate analytical estimates of LCO amplitude and its sensitivities with respect to the
introduced control parameters. A multiobjective optimization problem is solved to generate optimal control parameters which minimize the LCO amplitude and the control cost.
The third approach uses a nonlinear state feedback control input obtained as the solution
of a multiobjective optimization problem which minimizes the difference between the LCO
commencement velocity and the linear flutter velocity. The estimates of LCO commencement velocity and its sensitivities are obtained using numerical continuation methods and
harmonic balance methods. It is shown that the developed optimal controller eliminates any
existing subcritical LCOs by converting them to supercritical LCOs.
Advisors/Committee Members: Patil, Mayuresh J. (committeechair), Philen, Michael K. (committee member), Sultan, Cornel (committee member), Woolsey, Craig A. (committee member).
Subjects/Keywords: Aeroelasticity; Control; Limit cycle oscillations; Optimization; Subcritical; Supercritical
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APA (6th Edition):
Shukla, H. (2016). Nonlinear Analysis and Control of Aeroelastic Systems. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/71468
Chicago Manual of Style (16th Edition):
Shukla, Himanshu. “Nonlinear Analysis and Control of Aeroelastic Systems.” 2016. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/71468.
MLA Handbook (7th Edition):
Shukla, Himanshu. “Nonlinear Analysis and Control of Aeroelastic Systems.” 2016. Web. 26 Feb 2021.
Vancouver:
Shukla H. Nonlinear Analysis and Control of Aeroelastic Systems. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/71468.
Council of Science Editors:
Shukla H. Nonlinear Analysis and Control of Aeroelastic Systems. [Doctoral Dissertation]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/71468
Virginia Tech
17.
Wu, Yue.
4D combustion and flow diagnostics based on tomographic chemiluminescence (TC) and volumetric laser-induced fluorescence (VLIF).
Degree: PhD, Aerospace Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/73554
► Optical diagnostics have become indispensable tools for the study of turbulent flows and flames. However, optical diagnostics developed in the past have been primarily limited…
(more)
▼ Optical diagnostics have become indispensable tools for the study of turbulent flows and flames. However, optical diagnostics developed in the past have been primarily limited to measurements at a point, along a line, or across a two-dimensional (2D) plane; while turbulent flows and flames are inherently four-dimensional (three-dimensional in space and transient in time). As a result, diagnostic techniques which can provide 4D measurement have been long desired. The purpose of this dissertation is to investigate two of such 4D diagnostics both for the fundamental study of turbulent flow and combustion processes and also for the applied research of practical devices. These two diagnostics are respectively code named tomographic chemiluminescence (TC) and volumetric laser induced fluorescence (VLIF). For the TC technique, the emission of light as the result of combustion (i.e. chemiluminescence) is firstly recorded by multiple cameras placed at different orientations. A numerical algorithm is then applied on the data recorded to reconstruct the 4D flame structure. For the VLIF technique, a laser is used to excite a specific species in the flow or flame. The excited species then de-excite to emit light at a wavelength longer than the laser wavelength. The emitted light is then captured by optical sensors and again, the numerical algorithm is applied to reconstruct the flow or flame structure. This dissertation describes the numerical and experimental validation of these two techniques, and explores their capabilities and limitations. It is expected that the results obtained in this dissertation lay the groundwork for further development and expanded application of 4D diagnostics for the study of turbulent flows and combustion processes.
Advisors/Committee Members: Ma, Lin (committeechair), Lowe, Kevin T. (committee member), Xiao, Heng (committee member), Philen, Michael K. (committee member).
Subjects/Keywords: Optical diagnostics; Tomography; Laser-induced fluorescence
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APA (6th Edition):
Wu, Y. (2016). 4D combustion and flow diagnostics based on tomographic chemiluminescence (TC) and volumetric laser-induced fluorescence (VLIF). (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/73554
Chicago Manual of Style (16th Edition):
Wu, Yue. “4D combustion and flow diagnostics based on tomographic chemiluminescence (TC) and volumetric laser-induced fluorescence (VLIF).” 2016. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/73554.
MLA Handbook (7th Edition):
Wu, Yue. “4D combustion and flow diagnostics based on tomographic chemiluminescence (TC) and volumetric laser-induced fluorescence (VLIF).” 2016. Web. 26 Feb 2021.
Vancouver:
Wu Y. 4D combustion and flow diagnostics based on tomographic chemiluminescence (TC) and volumetric laser-induced fluorescence (VLIF). [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/73554.
Council of Science Editors:
Wu Y. 4D combustion and flow diagnostics based on tomographic chemiluminescence (TC) and volumetric laser-induced fluorescence (VLIF). [Doctoral Dissertation]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/73554
Virginia Tech
18.
Yari Boroujeni, Ayoub.
Fatigue, Fracture and Impact of Hybrid Carbon Fiber Reinforced Polymer Composites.
Degree: PhD, Engineering Mechanics, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/84223
► The excellent in-plane strength and stiffness to-weight ratios, as well as the ease of manufacturing have made the carbon fiber reinforced polymer composites (CFRPs) suitable…
(more)
▼ The excellent in-plane strength and stiffness to-weight ratios, as well as the ease of manufacturing have made the carbon fiber reinforced polymer composites (CFRPs) suitable structural materials for variety of applications such as aerospace, automotive, civil, sporting goods, etc. Despite the outstanding performance of the CFRPs along their fibers direction (on-axis), they lack sufficient strength and performance in the out-of-plane and off-axis directions. Various chemical and mechanical methods were reported to enhance the CFRPs' out-of-plane performance. However, there are two major drawbacks for utilizing these approaches: first, most of these methods induce damage to the carbon fibers and, therefore, deteriorate the in-plane mechanical properties of the entire CFRP, and second, the methods with minimal deteriorating effects on the in-plane mechanical performance have their own limitations resulting in very confined mechanical performance improvements. These methods include integrating nano-sized reinforcements into the CFRPs' structure to form a hybrid or hierarchical CFRPs.
In lieu to all the aforementioned approaches, a relatively novel method, referred to as graphitic structures by design (GSD), has been proposed. The GSD is capable of grafting carbon nanotubes (CNTs) onto the carbon fibers surfaces, providing high concentration of CNTs where they are most needed, i.e. the immediate fiber/matrix interface, and in-between the different laminae of a CFRP. This method shows promising improvements in the in-plane and out-of-plane performance of CFRPs. Zinc oxide (ZnO) nanorods are other nano-sized reinforcing structures which can hybridize the CFRPs via their radially growth on the surface of carbon fibers. Among all the reported methods for synthesizing ZnO nanorods, hydrothermal technique is the most straightforward and least destructive route to grow ZnO nanorods over carbon fibers.
In this dissertation, the GSD-CNTs growth method and the hydrothermal growth of ZnO nanorods have been utilized to fabricate hybrid CFRPs. The effect of different ZnO nanorods growth morphologies, e.g. size distribution and alignment, on the in-plane tensile performance and vibration attenuation capabilities of the hybrid CFRPs are investigated via quasi-static tension and dynamical mechanical analysis (DMA) tests, respectively. As a result, the in-plane tensile strength of the hybrid CFRPs were improved by 18% for the composite based on randomly oriented ZnO nanorods over the carbon fibers. The loss tangent of the CFRPs, which indicates the damping capability, increased by 28% and 19% via radially and randomly grown ZnO nanorods, respectively.
While there are several studies detailing the effects of dispersed nanofillers on the fracture toughness of FRPs, currently, there are no literature detailing the effect of surface GSD grown CNTs and ZnO nanowire -on carbon fiber- on the fracture toughness of these hybrid composites. This dissertation probes the effects of surface grown nano-sized reinforcements on the fracture toughness…
Advisors/Committee Members: Al-Haik, Marwan (committeechair), Case, Scott W. (committeechair), Patil, Mayuresh J. (committee member), Hajj, Muhammad R. (committee member), Philen, Michael K. (committee member).
Subjects/Keywords: carbon fiber; hybrid composites; carbon nanotubes; ZnO nanorods; mechanical characterization; finite element modeling; fatigue
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APA (6th Edition):
Yari Boroujeni, A. (2017). Fatigue, Fracture and Impact of Hybrid Carbon Fiber Reinforced Polymer Composites. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/84223
Chicago Manual of Style (16th Edition):
Yari Boroujeni, Ayoub. “Fatigue, Fracture and Impact of Hybrid Carbon Fiber Reinforced Polymer Composites.” 2017. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/84223.
MLA Handbook (7th Edition):
Yari Boroujeni, Ayoub. “Fatigue, Fracture and Impact of Hybrid Carbon Fiber Reinforced Polymer Composites.” 2017. Web. 26 Feb 2021.
Vancouver:
Yari Boroujeni A. Fatigue, Fracture and Impact of Hybrid Carbon Fiber Reinforced Polymer Composites. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/84223.
Council of Science Editors:
Yari Boroujeni A. Fatigue, Fracture and Impact of Hybrid Carbon Fiber Reinforced Polymer Composites. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/84223
Virginia Tech
19.
Allen, David William.
Gait and Morphology Optimization for Articulated Bodies in Fluids.
Degree: PhD, Aerospace Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/72272
► The contributions of this dissertation can be divided into three primary foci: input waveform optimization, the modeling and optimization of fish-like robots, and experiments on…
(more)
▼ The contributions of this dissertation can be divided into three primary foci: input waveform optimization, the modeling and optimization of fish-like robots, and experiments on a flapping wing robot. Novel contributions were made in every focus.
The first focus was on input waveform optimization. This goal of this research was to develop a means by which the optimal input waveforms can be selected to vibrationally stabilize a system. Vibrational stabilization is the use of high-frequency, high-amplitude periodic waveforms to stabilize a system about a desired state. The contributions presented herein develop a technique to choose the ``best" input waveform and a discussion of how the ``best" input waveform changes with the definition of ``best."
The next focus was the optimization of a fish-like robot. In order to optimize such robots, a new model for fish-like locomotion is developed. An optimization technique that uses numerous simulations of fish-like locomotion was used to determine the best gaits for traveling at various speeds. Based on these results, trends were found that can determine the optimal gait using a couple relatively simple functions.
The final focus was experimentation on a flapping wing robot in a wind tunnel. These experiments determined the performance of the flapping wing robot at a variety of flight conditions. The results of this research were presented in manner that is accessible to the larger aircraft design community rather than only to those specializing in flapping flight.
Advisors/Committee Members: Woolsey, Craig A. (committeechair), Philen, Michael K. (committee member), Patil, Mayuresh J. (committee member), Hajj, Muhammad R. (committee member).
Subjects/Keywords: Bio-inspired Vehicles; Optimization; Averaging; Geometric Control
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APA (6th Edition):
Allen, D. W. (2016). Gait and Morphology Optimization for Articulated Bodies in Fluids. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/72272
Chicago Manual of Style (16th Edition):
Allen, David William. “Gait and Morphology Optimization for Articulated Bodies in Fluids.” 2016. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/72272.
MLA Handbook (7th Edition):
Allen, David William. “Gait and Morphology Optimization for Articulated Bodies in Fluids.” 2016. Web. 26 Feb 2021.
Vancouver:
Allen DW. Gait and Morphology Optimization for Articulated Bodies in Fluids. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/72272.
Council of Science Editors:
Allen DW. Gait and Morphology Optimization for Articulated Bodies in Fluids. [Doctoral Dissertation]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/72272
Virginia Tech
20.
Al Haik, Mohammad Yousef.
Nanoparticle-based Organic Energy Storage with Harvesting Systems.
Degree: PhD, Engineering Mechanics, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/79815
► A new form of organic energy storage devices (organic capacitors) is presented in the first part of this dissertation. The storage devices are made out…
(more)
▼ A new form of organic energy storage devices (organic capacitors) is presented in the first part of this dissertation. The storage devices are made out of an organic semiconductor material and charge storage elements from synthesized nanoparticles. The semiconducting polymer is obtained by blending poly (vinyl alcohol) and poly (acrylic acid) in crystal state polymers with a known plasticizer; glycerol or sorbitol. Synthesized nanoparticles namely, zinc-oxide (ZnO), erbium (Er), cadmium sulfide (CdS), palladium (Pd) and silver-platinum (AgPt) were used as charge storage elements in fabrication of metal-insulator-semiconductor (MIS) structure. The organic semiconductor and synthesized nanoparticles are tested to evaluate and characterize their electrical performance and properties. Fabrication of the organic capacitors consisted of layer-by-layer deposition and thermal evaporation of the electrode terminals. Capacitance versus voltage (C-V) measurement tests were carried out to observe hysteresis loops with a window gate that would indicate the charging, discharging and storage characteristics. Experimental investigation of various integrated energy harvesting techniques combined with these organic based novel energy storage devices are performed in the second part of this dissertation. The source of the energy is the wind and is harvested by means of miniature wind turbines and vibrations, using piezoelectric transduction. In both cases, the generated electric charge is stored in these capacitors. The performance of the organic capacitors are evaluated through their comparison with commercial capacitors. The results show that the voltage produced from the two energy harvesters was high enough to store the harvested energy in the organic capacitors. The charge and energy levels of the organic capacitors are also reported.
The third part of this dissertation focuses on harvesting energy from a self-induced flutter of a thin composite beam. The composite beam consisted of an MFC patch bonded near the clamped end and placed vertically in the center of a wind tunnel test section. The self sustaining energy harvesting from the unimorph composite beam is exploited. The effects of different operational parameters including the optimum angle of attack, wind speed and load resistance are determined.
Advisors/Committee Members: Hajj, Muhammad R. (committeechair), Case, Scott W. (committee member), Philen, Michael K. (committee member), Ragab, Saad A. (committee member).
Subjects/Keywords: Energy Storage Devices; Energy Harvesting; Organic Semiconducting Polymers; Nanoparticles; Composites; Fluttering
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APA (6th Edition):
Al Haik, M. Y. (2016). Nanoparticle-based Organic Energy Storage with Harvesting Systems. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/79815
Chicago Manual of Style (16th Edition):
Al Haik, Mohammad Yousef. “Nanoparticle-based Organic Energy Storage with Harvesting Systems.” 2016. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/79815.
MLA Handbook (7th Edition):
Al Haik, Mohammad Yousef. “Nanoparticle-based Organic Energy Storage with Harvesting Systems.” 2016. Web. 26 Feb 2021.
Vancouver:
Al Haik MY. Nanoparticle-based Organic Energy Storage with Harvesting Systems. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/79815.
Council of Science Editors:
Al Haik MY. Nanoparticle-based Organic Energy Storage with Harvesting Systems. [Doctoral Dissertation]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/79815
Virginia Tech
21.
Leslie, Brian Robert.
Design, Analysis, and Testing of Nanoparticle-Infused Thin Film Sensors for Low Skin Friction Applications.
Degree: PhD, Aerospace Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/19199
► Accurate measurement of skin friction in complex flows is important for: documentation and monitoring of fluid system performance, input information for flow control, development of…
(more)
▼ Accurate measurement of skin friction in complex flows is important for: documentation and monitoring of fluid system performance, input information for flow control, development of turbulence models and CFD validation. The goal of this study was to explore using new materials to directly measure skin friction in a more convenient way than available devices. Conventional direct measurement skin friction sensors currently in use are intrusive, requiring movable surface elements with gaps surrounding that surface, or require optical access for measurements. Conventional direct measurement sensors are also difficult to apply in low shear environments, in the 1-10 Pa range. A new thin, flexible, nanoparticle infused, piezoresistive material called Metal Rubber" was used to create sensors that can be applied to any surface. This was accomplished by using modern computerized finite element model multiphysics simulations of the material response to surface shear loads, in order to design a sensor configuration with a reduced footprint, minimal cross influence and increased sensitivity. These sensors were then built, calibrated in a fully-developed water channel flow and tested in both the NASA 20x28 inch Shear Flow Control Tunnel and a backwards facing step water flow. The results from these tests showed accurate responses, with no amplification to the sensor output, to shear levels in the range of 1-15 Pa. In addition, the computer model of these sensors was found to be useful for studying and developing refined sensor designs and for documenting sources of measurement uncertainty. These encouraging results demonstrate the potential of this material for skin friction sensor applications.
Advisors/Committee Members: Schetz, Joseph A. (committeechair), Philen, Michael K. (committee member), Seidel, Gary D. (committee member), Claus, Richard O. (committee member).
Subjects/Keywords: Aerospace; Fluid Dynamics; Skin Friction; Sensor; Instrumentation; CFD; FEM; Turbulent; Design
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APA (6th Edition):
Leslie, B. R. (2012). Design, Analysis, and Testing of Nanoparticle-Infused Thin Film Sensors for Low Skin Friction Applications. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/19199
Chicago Manual of Style (16th Edition):
Leslie, Brian Robert. “Design, Analysis, and Testing of Nanoparticle-Infused Thin Film Sensors for Low Skin Friction Applications.” 2012. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/19199.
MLA Handbook (7th Edition):
Leslie, Brian Robert. “Design, Analysis, and Testing of Nanoparticle-Infused Thin Film Sensors for Low Skin Friction Applications.” 2012. Web. 26 Feb 2021.
Vancouver:
Leslie BR. Design, Analysis, and Testing of Nanoparticle-Infused Thin Film Sensors for Low Skin Friction Applications. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/19199.
Council of Science Editors:
Leslie BR. Design, Analysis, and Testing of Nanoparticle-Infused Thin Film Sensors for Low Skin Friction Applications. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/19199
Virginia Tech
22.
Bean, Jacob Jon.
Design and Analysis of an Active Noise Canceling Headrest.
Degree: PhD, Aerospace Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/94626
► This dissertation is concerned with the active control of local sound fields, as applied to an active headrest system. Using loudspeakers and microphones, an active…
(more)
▼ This dissertation is concerned with the active control of local sound fields, as applied to an active headrest system. Using loudspeakers and microphones, an active headrest is capable of attenuating ambient noise and providing a comfortable acoustic environment for an occupant. A finite element (FE) model of an active headrest is built and analyzed such that the expected noise reduction levels could be quantified for various geometries as well as primary sound field conditions. Both plane wave and diffuse primary sound fields are considered and it is shown that the performance deteriorates for diffuse sound fields. It is then demonstrated that virtual sensing can greatly improve the spatial extent of the quiet zones as well as the attenuation levels. A prototype of the active headrest was constructed, with characteristics similar to those of the FE model, and tested in both anechoic and reverberant sound fields. Multichannel feedforward and feedback control architectures are implemented in real-time and it is shown that adaptive feedback systems are capable of attenuating band-limited disturbances. The spatial attenuation pattern surrounding the head is also measured by shifting the head to various positions and measuring the attenuation at the ears. Two virtual sensing techniques are compared in both feedback and feedforward architectures. The virtual microphone arrangement, which assumes that the primary sound field is equivalent at the physical and virtual locations, results in the best performance when used in a feedback system attenuating broadband disturbances. The remote microphone technique, which accounts for the transfer response between the physical and virtual locations, offers the best performance for tonal primary sound fields. In broadband sound fields, a causal relationship rarely exists between the physical and virtual microphones, resulting in poor performance.
Advisors/Committee Members: Woolsey, Craig A. (committeechair), Fuller, Christopher R. (committeechair), Schiller, Noah Harrison (committee member), Philen, Michael K. (committee member), Sultan, Cornel (committee member).
Subjects/Keywords: Active headrest; active noise control; adaptive control; hybrid control; finite element modeling
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APA (6th Edition):
Bean, J. J. (2018). Design and Analysis of an Active Noise Canceling Headrest. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/94626
Chicago Manual of Style (16th Edition):
Bean, Jacob Jon. “Design and Analysis of an Active Noise Canceling Headrest.” 2018. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/94626.
MLA Handbook (7th Edition):
Bean, Jacob Jon. “Design and Analysis of an Active Noise Canceling Headrest.” 2018. Web. 26 Feb 2021.
Vancouver:
Bean JJ. Design and Analysis of an Active Noise Canceling Headrest. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/94626.
Council of Science Editors:
Bean JJ. Design and Analysis of an Active Noise Canceling Headrest. [Doctoral Dissertation]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/94626
Virginia Tech
23.
Sengezer, Engin Cem.
Multifunctional Nanocomposites and Particulate Composites with Nanocomposite Binders for Deformation and Damage Sensing.
Degree: PhD, Aerospace Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/78782
► At present, structural health monitoring efforts focus primarily on the sensors and sensing systems for detecting instances and locations of damage through techniques such as…
(more)
▼ At present, structural health monitoring efforts focus primarily on the sensors and sensing systems for detecting instances and locations of damage through techniques such as X-ray, micro CT, acoustic emission, infrared thermography, lamb wave etc., which only detect cracks at relatively large length scales and rely heavily on sensors and sensing systems which are external to the material system. As an alternative to conventional commercially available SHM techniques, the current work explores processing-structure-property relationships starting from carbon nanotube (CNT) based nanocomposites to particulate composites with nanocomposite binder/matrix materials, i.e. hybrid particulate composites to investigate deformation and damage sensing capabilities of inherently sensing materials and structures through their piezoresistive (coupled electro-mechanical) response. Initial efforts focused on controlling the dispersion of CNTs and orientation of CNT filaments within nanocomposites under dielectrophoresis to guide design and fabrication process of nanocomposites by tuning CNT concentration, applied AC electric field intensity, frequency and exposure time. It is observed that a combination of exposure time to AC electric field and the AC field frequency are the key drivers of filament width and spacing and that the network for filament formation is much more efficient for pristine CNTs than for acid treated functionalized CNTs. With the knowledge obtained from controlling the morphological features, AC field-induced long range alignment of CNTs within bulk nanocomposites was scaled up to form structural test coupons. The morphology, electrical and mechanical properties of the coupons were investigated. The anisotropic piezoresistive response both for parallel and transverse to CNT alignment direction within bulk composite coupons under various loading conditions was obtained. It is observed that control of the CNT network allows for the establishment of percolation paths and piezoresistive response well below the nominal percolation threshold observed for random, so called well-dispersed CNT network distributions. The potential for use of such bulk nanocomposites in SHM applications to detect strain and microdamage accumulation is further demonstrated, underscoring the importance of microscale CNT distribution/orientation and network formation/disruption in governing the piezoresistive sensitivities. Finally, what may be the first experimental study in the literature is conducted for real-time embedded microscale strain and damage sensing in energetic materials by distributing the CNT sensing network throughout the binder phase of inert and mock energetic composites through piezoresistive response for SHM in energetic materials. The incorporation of CNTs into inert and mock energetic composites revealed promising self-diagnostic functionalities for in situ real-time SHM applications under quasi-static and low velocity impact loading for solid rocket propellants, detonators and munitions to reduce the stochastic nature…
Advisors/Committee Members: Seidel, Gary D. (committeechair), Philen, Michael K. (committee member), Case, Scott W. (committee member), Patil, Mayuresh J. (committee member).
Subjects/Keywords: Carbon Nanotube; Alignment; Dielectrophoresis; Raman Spectroscopy; Nanocomposites; Particulate Composites; Energetics; Piezoresistivity; Strain Sensing; Damage Sensing; Digital Image Correlation; Instrumented Charpy Impact
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APA (6th Edition):
Sengezer, E. C. (2017). Multifunctional Nanocomposites and Particulate Composites with Nanocomposite Binders for Deformation and Damage Sensing. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78782
Chicago Manual of Style (16th Edition):
Sengezer, Engin Cem. “Multifunctional Nanocomposites and Particulate Composites with Nanocomposite Binders for Deformation and Damage Sensing.” 2017. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/78782.
MLA Handbook (7th Edition):
Sengezer, Engin Cem. “Multifunctional Nanocomposites and Particulate Composites with Nanocomposite Binders for Deformation and Damage Sensing.” 2017. Web. 26 Feb 2021.
Vancouver:
Sengezer EC. Multifunctional Nanocomposites and Particulate Composites with Nanocomposite Binders for Deformation and Damage Sensing. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/78782.
Council of Science Editors:
Sengezer EC. Multifunctional Nanocomposites and Particulate Composites with Nanocomposite Binders for Deformation and Damage Sensing. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/78782
Virginia Tech
24.
Parsons, Shawn M.
Strain-based Topology Optimization of a 2D Morphing Transitional Surface.
Degree: MS, Aerospace Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/83961
► Morphing aircraft offer many benefits. However, the design of stiff yet flexible structures still provides many obstacles to fully exploring and realizing morphing structures. Due…
(more)
▼ Morphing aircraft offer many benefits. However, the design of stiff yet flexible structures still provides many obstacles to fully exploring and realizing morphing structures. Due to this, many morphing challenges remain open. Topology optimization is a type of structural optimization that optimizes the material layout of a structure based on imposed boundary conditions and load paths. This type of optimization is promising for solving morphing design challenges but many of the optimized structures are not suited for traditional manufacturing and material arrangements. Multi-material additive manufacturing is an emerging technology that can produce a single structure with many different materials integrated in custom geometries. This could be the solution to realizing topology optimized structures. Despite the rich amount of current research in morphing aircraft, many challenges still remain open and topology of morphing structures could provide the solution to these morphing challenges.
Advisors/Committee Members: Philen, Michael K. (committeechair), Tarazaga, Pablo Alberto (committee member), Raj, Pradeep (committee member), Canfield, Robert Arthur (committee member).
Subjects/Keywords: Topology; structures; morphing aircraft
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APA (6th Edition):
Parsons, S. M. (2018). Strain-based Topology Optimization of a 2D Morphing Transitional Surface. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/83961
Chicago Manual of Style (16th Edition):
Parsons, Shawn M. “Strain-based Topology Optimization of a 2D Morphing Transitional Surface.” 2018. Masters Thesis, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/83961.
MLA Handbook (7th Edition):
Parsons, Shawn M. “Strain-based Topology Optimization of a 2D Morphing Transitional Surface.” 2018. Web. 26 Feb 2021.
Vancouver:
Parsons SM. Strain-based Topology Optimization of a 2D Morphing Transitional Surface. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/83961.
Council of Science Editors:
Parsons SM. Strain-based Topology Optimization of a 2D Morphing Transitional Surface. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/83961
Virginia Tech
25.
Williams, Eric Andrew.
The Development of Actuators for the Whole Skin Locomotion Robot.
Degree: PhD, Mechanical Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/46786
► The Whole Skin Locomotion robot propels itself using a motion similar to the cytoplasmic streaming exhibited by an amoeba. In the robot there are embedded…
(more)
▼ The Whole Skin Locomotion robot propels itself using a motion similar to the cytoplasmic streaming exhibited by an amoeba. In the robot there are embedded ring actuators which evert the material of the robot to produce forward motion. The robot benefits from a highly flexible exterior allowing it to squeeze into constricted passageways or collapsed structures. The development of actuators for such a motion is performed by a shape memory alloy composite actuator. Unlike a typical composite model which utilizes a homogenization of fiber and matrix properties our model is developed for line loads produced in individual shape memory alloy wires onto the rod structure. The load vectors are determined in the deformed configuration of the actuator to account for the highly deformed actuator profiles that would be seen in operation. Also the load requirements for such actuators are developed in terms of the constriction forces and functional design limits are established. In addition, a helical spring backbone design is considered and stiffness properties for general helical springs are determined. The contact of spring coils is included in the analysis and a coupled constitutive model is developed for the spring when coils are in contact. The static design of helical springs for use in the actuators is performed and deformation and load restrictions are determined for subsequent design efforts.
Advisors/Committee Members: Hong, Dennis W. (committeechair), West, Robert L. (committee member), Philen, Michael K. (committee member), Williams, Christopher Bryant (committee member), Vick, Brian (committee member).
Subjects/Keywords: helical spring; contact; actuator; design; rod theory; shape memory alloy; composite
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APA (6th Edition):
Williams, E. A. (2014). The Development of Actuators for the Whole Skin Locomotion Robot. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/46786
Chicago Manual of Style (16th Edition):
Williams, Eric Andrew. “The Development of Actuators for the Whole Skin Locomotion Robot.” 2014. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/46786.
MLA Handbook (7th Edition):
Williams, Eric Andrew. “The Development of Actuators for the Whole Skin Locomotion Robot.” 2014. Web. 26 Feb 2021.
Vancouver:
Williams EA. The Development of Actuators for the Whole Skin Locomotion Robot. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/46786.
Council of Science Editors:
Williams EA. The Development of Actuators for the Whole Skin Locomotion Robot. [Doctoral Dissertation]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/46786
Virginia Tech
26.
Kapoor, Hitesh.
Isogeometric Finite Element Code Development for Analysis of Composite Structures.
Degree: PhD, Aerospace Engineering, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/50567
► This research endeavor develops Isogeometric approach for analysis of composite structures and take advantage of higher order continuity, smoothness and variation diminishing property of Nurbs…
(more)
▼ This research endeavor develops Isogeometric approach for analysis of composite structures and take advantage of higher order continuity, smoothness and variation diminishing property of Nurbs basis for stress analysis of composite and sandwich beams and plates. This research also computes stress concentration factor in a composite plate with a hole. Isogeometric nonlinear/linear finite element code is developed for static and dynamic analysis of laminated composite plates. Nurbs linear, quadratic, higher-order and
k-refined elements are constructed using various refinement procedures and validated with numerical testing. Nurbs post-processor for in-plane and interlaminar stress calculation in laminated composite and sandwich plates is developed. Nurbs post-processor is found to be superior than regular finite element and in good agreement with the literature. Nurbs Isgoemetric analysis is used for stress analysis of laminated composite plate with open-hole. Stress concentration factor is computed along the hole edge and good agreement is obtained with the literature. Nurbs Isogeometric finite element code for free-vibration and linear dynamics analysis of laminated composite plates also obtain good agreement with the literature. Main highlights of the research are newly developed 9 control point linear Nurbs element,
k-refined and higher-order Nurbs elements in isogeometric framework. Nurbs elements remove shear-locking and hourglass problems in thin plates in context of first-order shear deformation theory without the additional step and compute better stresses than Lagrange finite element and higher order shear deformation theory for comparatively thick plates i.e. a/h = 4. Also, Nurbs Isogeometric analysis perform well for vibration and dynamic problems and for straight and curved edge problems.
Advisors/Committee Members: Kapania, Rakesh K. (committeechair), Batra, Romesh C. (committee member), Philen, Michael K. (committee member), Clay, Stephen Brett (committee member).
Subjects/Keywords: Nurbs Isogeometric analysis; k-refinement procedure; shear-deformable plates and beams; nonlinear analysis; interlaminar stress
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APA (6th Edition):
Kapoor, H. (2013). Isogeometric Finite Element Code Development for Analysis of Composite Structures. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/50567
Chicago Manual of Style (16th Edition):
Kapoor, Hitesh. “Isogeometric Finite Element Code Development for Analysis of Composite Structures.” 2013. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/50567.
MLA Handbook (7th Edition):
Kapoor, Hitesh. “Isogeometric Finite Element Code Development for Analysis of Composite Structures.” 2013. Web. 26 Feb 2021.
Vancouver:
Kapoor H. Isogeometric Finite Element Code Development for Analysis of Composite Structures. [Internet] [Doctoral dissertation]. Virginia Tech; 2013. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/50567.
Council of Science Editors:
Kapoor H. Isogeometric Finite Element Code Development for Analysis of Composite Structures. [Doctoral Dissertation]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/50567
Virginia Tech
27.
Ferhat, Ipar.
Development and Application of Modern Optimal Controllers for a Membrane Structure Using Vector Second Order Form.
Degree: PhD, Aerospace Engineering, 2015, Virginia Tech
URL: http://hdl.handle.net/10919/53513
► With increasing advancement in material science and computational power of current computers that allows us to analyze high dimensional systems, very light and large structures…
(more)
▼ With increasing advancement in material science and computational power of current computers that allows us to analyze high dimensional systems, very light and large structures are being designed and built for aerospace applications. One example is a reflector of a space telescope that is made of membrane structures. These reflectors are light and foldable which makes the shipment easy and cheaper unlike traditional reflectors made of glass or other heavy materials. However, one of the disadvantages of membranes is that they are very sensitive to external changes, such as thermal load or maneuvering of the space telescope. These effects create vibrations that dramatically affect the performance of the reflector.
To overcome vibrations in membranes, in this work, piezoelectric actuators are used to develop distributed controllers for membranes. These actuators generate bending effects to suppress the vibration. The actuators attached to a membrane are relatively thick which makes the system heterogeneous; thus, an analytical solution cannot be obtained to solve the partial differential equation of the system. Therefore, the Finite Element Model is applied to obtain an approximate solution for the membrane actuator system.
Another difficulty that arises with very flexible large structures is the dimension of the discretized system. To obtain an accurate result, the system needs to be discretized using smaller segments which makes the dimension of the system very high. This issue will persist as long as the improving technology will allow increasingly complex and large systems to be designed and built. To deal with this difficulty, the analysis of the system and controller development to suppress the vibration are carried out using vector second order form as an alternative to vector first order form. In vector second order form, the number of equations that need to be solved are half of the number equations in vector first order form.
Analyzing the system for control characteristics such as stability, controllability and observability is a key step that needs to be carried out before developing a controller. This analysis determines what kind of system is being modeled and the appropriate approach for controller development. Therefore, accuracy of the system analysis is very crucial. The results of the system analysis using vector second order form and vector first order form show the computational advantages of using vector second order form.
Using similar concepts, LQR and LQG controllers, that are developed to suppress the vibration, are derived using vector second order form. To develop a controller using vector second order form, two different approaches are used. One is reducing the size of the Algebraic Riccati Equation to half by partitioning the solution matrix. The other approach is using the Hamiltonian method directly in vector second order form. Controllers are developed using both approaches and compared to each other. Some simple solutions for special cases are derived for vector second order form…
Advisors/Committee Members: Sultan, Cornel (committeechair), Woolsey, Craig A. (committee member), Kapania, Rakesh K. (committee member), Philen, Michael K. (committee member).
Subjects/Keywords: Thin / membrane structures; piezoelectric actuators; smart materials; control of structures; distributed control; vector second order form.
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APA (6th Edition):
Ferhat, I. (2015). Development and Application of Modern Optimal Controllers for a Membrane Structure Using Vector Second Order Form. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/53513
Chicago Manual of Style (16th Edition):
Ferhat, Ipar. “Development and Application of Modern Optimal Controllers for a Membrane Structure Using Vector Second Order Form.” 2015. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/53513.
MLA Handbook (7th Edition):
Ferhat, Ipar. “Development and Application of Modern Optimal Controllers for a Membrane Structure Using Vector Second Order Form.” 2015. Web. 26 Feb 2021.
Vancouver:
Ferhat I. Development and Application of Modern Optimal Controllers for a Membrane Structure Using Vector Second Order Form. [Internet] [Doctoral dissertation]. Virginia Tech; 2015. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/53513.
Council of Science Editors:
Ferhat I. Development and Application of Modern Optimal Controllers for a Membrane Structure Using Vector Second Order Form. [Doctoral Dissertation]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/53513
28.
Wang, Haoting.
Experimental and Modeling Study of the Thermal Management of Li-ion Battery Packs.
Degree: PhD, Aerospace Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/79660
► This work reports the experimental and numerical study of the thermal management of Li-ion battery packs under the context of electric vehicle (EV) or hybrid…
(more)
▼ This work reports the experimental and numerical study of the thermal management of Li-ion battery packs under the context of electric vehicle (EV) or hybrid EV (HEV) applications. Li-ion batteries have been extensively demonstrated as an important power source for EVs or HEVs. However, thermal management is a critical challenge for their widespread deployment, due to their highly dynamic operation and the wide range of environments under which they operate. To address these challenges, this work developed several experimental platforms to study adaptive thermal management strategies. Parallel to the experimental effort, multi-disciplinary models integrating heat transfer, fluid mechanics, and electro-thermal dynamics have been developed and validated, including detailed CFD models and lumped parameter models. The major contributions are twofold. First, this work developed actively controlled strategies and experimentally demonstrated their effectiveness on a practical sized battery pack and dynamic thermal loads. The results show that these strategies effectively reduced both the parasitic energy consumption and the temperature non-uniformity while maintaining the maximum temperature rise in the pack. Second, this work established a new two dimensional lumped parameter thermal model to overcome the limitations of existing thermal models and extend their applicable range. This new model provides accurate surface and core temperatures simulations comparable to detailed CFD models with a fraction of the computational cost.
Advisors/Committee Members: Ma, Lin (committeechair), Lowe, Kevin T. (committee member), Philen, Michael K. (committee member), Xiao, Heng (committee member).
Subjects/Keywords: Thermal management; Li-ion battery pack; actively controlled cooling; lumped parameter thermal model; wind tunnel test
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APA ·
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APA (6th Edition):
Wang, H. (2017). Experimental and Modeling Study of the Thermal Management of Li-ion Battery Packs. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/79660
Chicago Manual of Style (16th Edition):
Wang, Haoting. “Experimental and Modeling Study of the Thermal Management of Li-ion Battery Packs.” 2017. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/79660.
MLA Handbook (7th Edition):
Wang, Haoting. “Experimental and Modeling Study of the Thermal Management of Li-ion Battery Packs.” 2017. Web. 26 Feb 2021.
Vancouver:
Wang H. Experimental and Modeling Study of the Thermal Management of Li-ion Battery Packs. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/79660.
Council of Science Editors:
Wang H. Experimental and Modeling Study of the Thermal Management of Li-ion Battery Packs. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/79660
29.
Xu, Wenjiang.
Three Dimensional Laser Diagnostics for Turbulent Flows and Flames.
Degree: PhD, Aerospace Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/79912
► Due to their scientific significance and practical applications, turbulent flows and flames have been under extensive and intensive research for a long time. Turbulent flows…
(more)
▼ Due to their scientific significance and practical applications, turbulent flows and flames have been under extensive and intensive research for a long time. Turbulent flows and flames of interests to practice inherently have three-dimensional (3D) spatial structures, and therefore diagnostic techniques that can instantaneously resolve their 3D spatial features have long been desired and probably are needed to ultimately answer some of the open research questions. The goal of this dissertation thus is to investigate such diagnostics and demonstrate their capability and limitations in a range of turbulent flows/flames. To accomplish this goal, this dissertation developed and evaluated the following three diagnostic methods: tomographic chemiluminescence (TC), volumetric laser induced fluorescence (VLIF), and super-resolution planar laser induced fluorescence (SR-PLIF).
First, 3D flame topography of well-controlled laboratory flames was measured with TC method and validated by a simultaneous 2D Mie scattering measurement. The results showed that the flame topography obtained from TC and the Mie scattering agreed qualitatively, but quantitative difference on the order of millimeter was observed between these two methods. Such difference was caused by the limitations of the TC method. The first limitation involves TC's reliance on chemiluminescence of nascent radicals (mainly CH*) in reacting flows, causing ambiguity in the definition of flame front and limiting its applications to certain types of reactive flow only. The second limitation involves TC's inability to study an isolated region of interest because the chemiluminescence is emitted everywhere in the flame.
Based on the above understanding of the TC technique, the second part of this dissertation studied a VLIF method to overcome the above limitations of the TC technique. Compared with the TC technique, the VLIF method can be used in either reacting or non-reacting flow and on any particular region of interest. In the VLIF technique, the fluorescence signal was generated by exciting a target species with a laser slab of certain thickness. The signal was recorded by cameras from different perspectives, and then a VLIF tomographic algorithm was applied to resolve the spatial distribution of the concentration of the target species. An innovative 3D VLIF algorithm was proposed and validated by well-designed experiment. This model enables analysis of VLIF performance in terms of signal level, size of the field of view in 3D, and accuracy. However, due to the limited number of views and the tomographic reconstruction itself, the spatial resolution of VLIF methods is limited.
Hence, the third part of this dissertation investigated a SR-PLIF method to provide a strategy to improve the spatial resolution in two spatial directions, and also to extend the measurement range of scanning 3D imaging strategies. The SR-PLIF method used planar images captured simultaneously from two (or more) orientations to reconstruct a final image with resolution enhanced or blurring…
Advisors/Committee Members: Ma, Lin (committeechair), Lowe, Kevin T. (committee member), Philen, Michael K. (committee member), Xiao, Heng (committee member).
Subjects/Keywords: Optical diagnostics; Tomography; Laser induced fluorescence
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APA ·
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MLA ·
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APA (6th Edition):
Xu, W. (2017). Three Dimensional Laser Diagnostics for Turbulent Flows and Flames. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/79912
Chicago Manual of Style (16th Edition):
Xu, Wenjiang. “Three Dimensional Laser Diagnostics for Turbulent Flows and Flames.” 2017. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/79912.
MLA Handbook (7th Edition):
Xu, Wenjiang. “Three Dimensional Laser Diagnostics for Turbulent Flows and Flames.” 2017. Web. 26 Feb 2021.
Vancouver:
Xu W. Three Dimensional Laser Diagnostics for Turbulent Flows and Flames. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/79912.
Council of Science Editors:
Xu W. Three Dimensional Laser Diagnostics for Turbulent Flows and Flames. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/79912
Virginia Tech
30.
Zhang, Zhiye.
Modeling, Analysis, and Experiments of Inter Fiber Yarn Compaction Effects in Braided Composite Actuators.
Degree: PhD, Aerospace and Ocean Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/29162
► The braided composite actuator is a pressure-driven muscle-like actuator capable of large displacements as well as large blocking forces. It consists of an elastomeric tube…
(more)
▼ The braided composite actuator is a pressure-driven muscle-like actuator capable of large displacements as well as large blocking forces. It consists of an elastomeric tube reinforced by a sleeve braided by high performance fibers.
In addition to the actuation properties, this actuator can also exhibit a large change in stiffness through simple valve control when the working fluid has a high bulk modulus. Several analytical models have been previously developed that capture the geometrical and material nonlinearities, the compliance of the inner liner, and entrapped air in the fluid. The inter fiber yarn compaction in the fiber layer, which is shown to reduce the effective closed-valve stiffness, is studied. A new analytical model for uniformly deformed actuators is developed to capture the compaction effect. This model considers the inter fiber yarn compaction effect and the fiber extensibility as well as the material and geometric nonlinearities. Analysis and experimental results demonstrate that the new compaction model can improve the prediction of the response behavior of the actuator.
The compaction model is improved by considering the yarn bending stiffness. The governing equations are derived and the solution algorithm is presented.
Advisors/Committee Members: Philen, Michael K. (committeechair), Kapania, Rakesh K. (committee member), Patil, Mayuresh J. (committee member), Priya, Shashank (committee member).
Subjects/Keywords: Braided Composite Actuators; Variable Stiffness Structures; Compaction Model; Smart Materials
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Record Details
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Zhang, Z. (2012). Modeling, Analysis, and Experiments of Inter Fiber Yarn Compaction Effects in Braided Composite Actuators. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/29162
Chicago Manual of Style (16th Edition):
Zhang, Zhiye. “Modeling, Analysis, and Experiments of Inter Fiber Yarn Compaction Effects in Braided Composite Actuators.” 2012. Doctoral Dissertation, Virginia Tech. Accessed February 26, 2021.
http://hdl.handle.net/10919/29162.
MLA Handbook (7th Edition):
Zhang, Zhiye. “Modeling, Analysis, and Experiments of Inter Fiber Yarn Compaction Effects in Braided Composite Actuators.” 2012. Web. 26 Feb 2021.
Vancouver:
Zhang Z. Modeling, Analysis, and Experiments of Inter Fiber Yarn Compaction Effects in Braided Composite Actuators. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2021 Feb 26].
Available from: http://hdl.handle.net/10919/29162.
Council of Science Editors:
Zhang Z. Modeling, Analysis, and Experiments of Inter Fiber Yarn Compaction Effects in Braided Composite Actuators. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/29162
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