ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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- Creators: Neithalath, Narayanan
- Creators: Mobasher, Barzin
Description
Asphalt binder is a complex viscoelastic hydrocarbon, whose performance depends upon interaction between its physical and chemical properties, both of which are equally important to the successful understanding of the material. Researchers have proposed various models linking linear viscoelastic (LVE) and microstructural parameters. However, none of these parameters provide insight into the relationship in the non- linear viscoelastic NLVE domain. The main goals of this dissertation are two fold. The first goal is to utilize the technique of Laser Desorption Mass Spectroscopy (LDMS) to relate the molecular structure of asphalt binders to its viscoelastic properties. The second goal of the study is to utilize different NLVE characterization tools and analysis procedures to get a clear understanding of the NLVE behavior of the asphalt binders. The goals of the study are divided into four objectives; 1) Performing the LDMS test on asphalt binder to develop at the molecular weight distributions for different asphalts, 2) Characterizing LVE properties of Arizona asphalt binders, 3) Development of relationship between molecular structure and linear viscoelasticity, 4) Understanding NLVE behavior of asphalt binders through three different characterization methods and analysis techniques.
In this research effort, a promising physico-chemical relationship is developed between number average molecular weight and width of relaxation spectrum by utilizing the data from LVE characterization and the molecular weight distribution from LDMS. The relationship states that as the molecular weight of asphalt binders increase, they require more time to relax the developed stresses. Also, NLVE characterization was carried out at intermediate and high temperatures using three different tests, time sweep fatigue test, repeated stress/strain sweep test and Multiple Stress Creep and Recovery (MSCR) test. For the intermediate temperature fatigue tests, damage characterization was conducted by applying the S-VECD model and it was found that aged binders possess greater fatigue resistance than unaged binders. Using the high temperature LAOS tests, distortion was observed in the stress-strain relationships and the data was analyzed using a Fourier transform based tool called MITlaos, which deconvolves stress strain data into harmonic constituents and aids in identification of non-linearity by detecting higher order harmonics. Using the peak intensities observed at higher harmonic orders, non-linearity was quantified through a parameter termed as “Q”, which in future applications can be used to relate to asphalt chemical parameters. Finally, the last NLVE characterization carried out was the MSCR test, where the focus was on the scrutiny of the Jnrdiff parameter. It was found that Jnrdiff is not a capable parameter to represent the stress-sensitivity of asphalt binders. The developed alternative parameter Jnrslope does a better job of not only being a representative parameter of stress sensitivity but also for temperature sensitivity.
ContributorsGundla, Akshay (Author) / Underwood, Benjamin S (Thesis advisor) / Kaloush, Kamil (Thesis advisor) / Mamlouk, Michael S. (Committee member) / Neithalath, Narayanan (Committee member) / Arizona State University (Publisher)
Created2018
Description
This research summarizes the validation testing completed for the material model MAT213, currently implemented in the LS-DYNA finite element program. Testing was carried out using a carbon fiber composite material, T800-F3900. Stacked-ply tension and compression tests were performed for open-hole and full coupons. Comparisons of experimental and simulation results showed a good agreement between the two for metrics including, stress-strain response and displacements. Strains and displacements in the direction of loading were better predicted by the simulations than for that of the transverse direction.
Double cantilever beam and end notched flexure tests were performed experimentally and through simulations to determine the delamination properties of the material at the interlaminar layers. Experimental results gave the mode I critical energy release rate as having a range of 2.18 – 3.26 psi-in and the mode II critical energy release rate as 10.50 psi-in, both for the pre-cracked condition. Simulations were performed to calibrate other cohesive zone parameters required for modeling.
Samples of tested T800/F3900 coupons were processed and examined with scanning electron microscopy to determine and understand the underlying structure of the material. Tested coupons revealed damage and failure occurring at the micro scale for the composite material.
Double cantilever beam and end notched flexure tests were performed experimentally and through simulations to determine the delamination properties of the material at the interlaminar layers. Experimental results gave the mode I critical energy release rate as having a range of 2.18 – 3.26 psi-in and the mode II critical energy release rate as 10.50 psi-in, both for the pre-cracked condition. Simulations were performed to calibrate other cohesive zone parameters required for modeling.
Samples of tested T800/F3900 coupons were processed and examined with scanning electron microscopy to determine and understand the underlying structure of the material. Tested coupons revealed damage and failure occurring at the micro scale for the composite material.
ContributorsHolt, Nathan T (Author) / Rajan, Subramaniam D. (Thesis advisor) / Mobasher, Barzin (Committee member) / Hoover, Christian (Committee member) / Arizona State University (Publisher)
Created2018
Description
Being a remarkably versatile and inexpensive building material, concrete has found tremendous use in development of modern infrastructure and is the most widely used material in the world. Extensive research in the field of concrete has led to the development of a wide array of concretes with applications ranging from building of skyscrapers to paving of highways. These varied applications require special cementitious composites which can satisfy the demand for enhanced functionalities such as high strength, high durability and improved thermal characteristics among others.
The current study focuses on the fundamental understanding of such functional composites, from their microstructural design to macro-scale application. More specifically, this study investigates three different categories of functional cementitious composites. First, it discusses the differences between cementitious systems containing interground and blended limestone with and without alumina. The interground systems are found to outperform the blended systems due to differential grinding of limestone. A novel approach to deduce the particle size distribution of limestone and cement in the interground systems is proposed. Secondly, the study delves into the realm of ultra-high performance concrete, a novel material which possesses extremely high compressive-, tensile- and flexural-strength and service life as compared to regular concrete. The study presents a novel first principles-based paradigm to design economical ultra-high performance concretes using locally available materials. In the final part, the study addresses the thermal benefits of a novel type of concrete containing phase change materials. A software package was designed to perform numerical simulations to analyze temperature profiles and thermal stresses in concrete structures containing PCMs.
The design of these materials is accompanied by material characterization of cementitious binders. This has been accomplished using techniques that involve measurement of heat evolution (isothermal calorimetry), determination and quantification of reaction products (thermo-gravimetric analysis, x-ray diffraction, micro-indentation, scanning electron microscopy, energy-dispersive x-ray spectroscopy) and evaluation of pore-size distribution (mercury intrusion porosimetry). In addition, macro-scale testing has been carried out to determine compression, flexure and durability response. Numerical simulations have been carried out to understand hydration of cementitious composites, determine optimum particle packing and determine the thermal performance of these composites.
The current study focuses on the fundamental understanding of such functional composites, from their microstructural design to macro-scale application. More specifically, this study investigates three different categories of functional cementitious composites. First, it discusses the differences between cementitious systems containing interground and blended limestone with and without alumina. The interground systems are found to outperform the blended systems due to differential grinding of limestone. A novel approach to deduce the particle size distribution of limestone and cement in the interground systems is proposed. Secondly, the study delves into the realm of ultra-high performance concrete, a novel material which possesses extremely high compressive-, tensile- and flexural-strength and service life as compared to regular concrete. The study presents a novel first principles-based paradigm to design economical ultra-high performance concretes using locally available materials. In the final part, the study addresses the thermal benefits of a novel type of concrete containing phase change materials. A software package was designed to perform numerical simulations to analyze temperature profiles and thermal stresses in concrete structures containing PCMs.
The design of these materials is accompanied by material characterization of cementitious binders. This has been accomplished using techniques that involve measurement of heat evolution (isothermal calorimetry), determination and quantification of reaction products (thermo-gravimetric analysis, x-ray diffraction, micro-indentation, scanning electron microscopy, energy-dispersive x-ray spectroscopy) and evaluation of pore-size distribution (mercury intrusion porosimetry). In addition, macro-scale testing has been carried out to determine compression, flexure and durability response. Numerical simulations have been carried out to understand hydration of cementitious composites, determine optimum particle packing and determine the thermal performance of these composites.
ContributorsArora, Aashay (Author) / Neithalath, Narayanan (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Mobasher, Barzin (Committee member) / Chawla, Nikhilesh (Committee member) / Hoover, Christian G (Committee member) / Arizona State University (Publisher)
Created2018
Description
Phase change materials (PCMs) are combined sensible-and-latent thermal energy storage materials that can be used to store and dissipate energy in the form of heat. PCMs incorporated into wall-element systems have been well-studied with respect to energy efficiency of building envelopes. New applications of PCMs in infrastructural concrete, e.g., for mitigating early-age cracking and freeze-and-thaw induced damage, have also been proposed. Hence, the focus of this dissertation is to develop a detailed understanding of the physic-chemical and thermo-mechanical characteristics of cementitious systems and novel coating systems for wall-elements containing PCM. The initial phase of this work assesses the influence of interface properties and inter-inclusion interactions between microencapsulated PCM, macroencapsulated PCM, and the cementitious matrix. The fact that these inclusions within the composites are by themselves heterogeneous, and contain multiple components necessitate careful application of models to predict the thermal properties. The next phase observes the influence of PCM inclusions on the fracture and fatigue behavior of PCM-cementitious composites. The compliant nature of the inclusion creates less variability in the fatigue life for these composites subjected to cyclic loading. The incorporation of small amounts of PCM is found to slightly improve the fracture properties compared to PCM free cementitious composites. Inelastic deformations at the crack-tip in the direction of crack opening are influenced by the microscale PCM inclusions. After initial laboratory characterization of the microstructure and evaluation of the thermo-mechanical performance of these systems, field scale applicability and performance were evaluated. Wireless temperature and strain sensors for smart monitoring were embedded within a conventional portland cement concrete pavement (PCCP) and a thermal control smart concrete pavement (TCSCP) containing PCM. The TCSCP exhibited enhanced thermal performance over multiple heating and cooling cycles. PCCP showed significant shrinkage behavior as a result of compressive strains in the reinforcement that were twice that of the TCSCP. For building applications, novel PCM-composites coatings were developed to improve and extend the thermal efficiency. These coatings demonstrated a delay in temperature by up to four hours and were found to be more cost-effective than traditional building insulating materials.
The results of this work prove the feasibility of PCMs as a temperature-regulating technology. Not only do PCMs reduce and control the temperature within cementitious systems without affecting the rate of early property development but they can also be used as an auto-adaptive technology capable of improving the thermal performance of building envelopes.
The results of this work prove the feasibility of PCMs as a temperature-regulating technology. Not only do PCMs reduce and control the temperature within cementitious systems without affecting the rate of early property development but they can also be used as an auto-adaptive technology capable of improving the thermal performance of building envelopes.
ContributorsAguayo, Matthew Joseph (Author) / Neithalath, Narayanan (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Mobasher, Barzin (Committee member) / Underwood, Benjamin (Committee member) / Liu, Yongming (Committee member) / Arizona State University (Publisher)
Created2018
Description
Nanolaminate materials are layered composites with layer thickness ≤ 100 nm. They exhibit unique properties due to their small length scale, the presence of a high number of interfaces and the effect of imposed constraint. This thesis focuses on the mechanical behavior of Al/SiC nanolaminates. The high strength of ceramics combined with the ductility of Al makes this combination desirable. Al/SiC nanolaminates were synthesized through magnetron sputtering and have an overall thickness of ~ 20 μm which limits the characterization techniques to microscale testing methods. A large amount of work has already been done towards evaluating their mechanical properties under indentation loading and micropillar compression. The effects of temperature, orientation and layer thickness have been well established. Al/SiC nanolaminates exhibited a flaw dependent deformation, anisotropy with respect to loading direction and strengthening due to imposed constraint. However, the mechanical behavior of nanolaminates under tension and fatigue loading has not yet been studied which is critical for obtaining a complete understanding of their deformation behavior. This thesis fills this gap and presents experiments which were conducted to gain an insight into the behavior of nanolaminates under tensile and cyclic loading. The effect of layer thickness, tension-compression asymmetry and effect of a wavy microstructure on mechanical response have been presented. Further, results on in situ micropillar compression using lab-based X-ray microscope through novel experimental design are also presented. This was the first time when a resolution of 50 nms was achieved during in situ micropillar compression in a lab-based setup. Pores present in the microstructure were characterized in 3D and sites of damage initiation were correlated with the channel of pores present in the microstructure.
The understanding of these deformation mechanisms paved way for the development of co-sputtered Al/SiC composites. For these composites, Al and SiC were sputtered together in a layer. The effect of change in the atomic fraction of SiC on the microstructure and mechanical properties were evaluated. Extensive microstructural characterization was performed at the nanoscale level and Al nanocrystalline aggregates were observed dispersed in an amorphous matrix. The modulus and hardness of co- sputtered composites were much higher than their traditional counterparts owing to denser atomic packing and the absence of synthesis induced defects such as pores and columnar boundaries.
The understanding of these deformation mechanisms paved way for the development of co-sputtered Al/SiC composites. For these composites, Al and SiC were sputtered together in a layer. The effect of change in the atomic fraction of SiC on the microstructure and mechanical properties were evaluated. Extensive microstructural characterization was performed at the nanoscale level and Al nanocrystalline aggregates were observed dispersed in an amorphous matrix. The modulus and hardness of co- sputtered composites were much higher than their traditional counterparts owing to denser atomic packing and the absence of synthesis induced defects such as pores and columnar boundaries.
ContributorsSingh, Somya (Author) / Chawla, Nikhilesh (Thesis advisor) / Neithalath, Narayanan (Committee member) / Jiao, Yang (Committee member) / Mara, Nathan (Committee member) / Arizona State University (Publisher)
Created2018
Description
With the growth of global population, the demand for sustainable infrastructure is significantly increasing. Substructures with appropriate materials are required to be built in or above soil that can support the massive volume of construction demand. However, increased structural requirements often require ground improvement to increase the soil capacity. Moreover, certain soils are prone to liquefaction during an earthquake, which results in significant structural damage and loss of lives. While various soil treatment methods have been developed in the past to improve the soil’s load carrying ability, most of these traditional treatment methods have been found either hazardous and may cause irreversible damage to natural environment, or too disruptive to use beneath or adjacent to existing structures. Thus, alternative techniques are required to provide a more natural and sustainable solution. Biomediated methods of strengthening soil through mineral precipitation, in particular through microbially induced carbonate precipitation (MICP), have recently emerged as a promising means of soil improvement. In MICP, the precipitation of carbonate (usually in the form of calcium carbonate) is mediated by microorganisms and the process is referred to as biomineralization. The precipitated carbonate coats soil particles, precipitates in the voids, and bridges between soil particles, thereby improving the mechanical properties (e.g., strength, stiffness, and dilatancy). Although it has been reported that the soil’s mechanical properties can be extensively enhanced through MICP, the micro-scale mechanisms that influence the macro-scale constitutive response remain to be clearly explained.
The utilization of alternative techniques such as MICP requires an in-depth understanding of the particle-scale contact mechanisms and the ability to predict the improvement in soil properties resulting from calcite precipitation. For this purpose, the discrete element method (DEM), which is extensively used to investigate granular materials, is adopted in this dissertation. Three-dimensional discrete element method (DEM) based numerical models are developed to simulate the response of bio-cemented sand under static and dynamic loading conditions and the micro-scale mechanisms of MICP are numerically investigated. Special focus is paid to the understanding of the particle scale mechanisms that are dominant in the common laboratory scale experiments including undrained and drained triaxial compression when calcite bridges are present in the soil, that enhances its load capacity. The mechanisms behind improvement of liquefaction resistance in cemented sands are also elucidated through the use of DEM. The thesis thus aims to provide the fundamental link that is important in ensuring proper material design for granular materials to enhance their mechanical performance.
The utilization of alternative techniques such as MICP requires an in-depth understanding of the particle-scale contact mechanisms and the ability to predict the improvement in soil properties resulting from calcite precipitation. For this purpose, the discrete element method (DEM), which is extensively used to investigate granular materials, is adopted in this dissertation. Three-dimensional discrete element method (DEM) based numerical models are developed to simulate the response of bio-cemented sand under static and dynamic loading conditions and the micro-scale mechanisms of MICP are numerically investigated. Special focus is paid to the understanding of the particle scale mechanisms that are dominant in the common laboratory scale experiments including undrained and drained triaxial compression when calcite bridges are present in the soil, that enhances its load capacity. The mechanisms behind improvement of liquefaction resistance in cemented sands are also elucidated through the use of DEM. The thesis thus aims to provide the fundamental link that is important in ensuring proper material design for granular materials to enhance their mechanical performance.
ContributorsYang, Pu (Author) / Neithalath, Narayanan (Thesis advisor) / Kavazanjian, Edward (Committee member) / Rajan, S.D. (Committee member) / Mobasher, Barzin (Committee member) / Jiao, Yang (Committee member) / Arizona State University (Publisher)
Created2018
Description
A comprehensive study was performed on non-proprietary ultra-high-performance concrete (UHPC) material and several design methods were suggested based on numerous experimental results. Several sets of compression tests, direct tensile tests, and flexural tests were performed on UHPC to provide a better understanding of the mechanisms involved in the mechanical behavior of the fiber reinforced material. In addition to compressive tests, flexural tests, based on ASTM C1609 and EN 14651, were performed. The effect of the strain rate on the UHPC material was also investigated through the high-speed tensile tests at different strain rates. Alongside the usual measurement tools such as linear variable differential transformers (LVDT) and clip gages, digital image correlation (DIC) method was also used to capture the full-range deformations in the samples and localized crack propagations. Analytical approaches were suggested, based on the experimental results of the current research and other research groups, to provide design solutions for different applications and design approaches for UHPC and hybrid reinforced concrete (HRC) sections. The suggested methods can be used both in the ultimate limit state (ULS) and the serviceability limit state (SLS) design methods. Closed form relationships, based on the non-linear design of reinforced concrete, were used in the calculation of the load-deflection response of UHPC. The procedures were used in obtaining material properties from the flexural data using procedures that are based on back-calculation of material properties from the experimental results. Model simulations were compared with other results available in the literature. Performance of flexural reinforced UHPC concrete beam sections tested under different types of loading was addressed using a combination of fibers and rebars. The same analytical approach was suggested for the fiber reinforced concrete (FRC) sections strengthened (rehabilitated) by fiber reinforced polymers (FRP) and textile reinforced concrete (TRC). The objective is to validate the proper design procedures for flexural members as well as connection elements. The proposed solutions can be used to reduce total reinforcement by means of increasing the ductility of the FRC, HRC, and UHPC members in order to meet the required flexural reinforcement, which in some cases leads to total elimination of rebars.
ContributorsKianmofrad, Farrokh (Author) / Mobasher, Barzin (Thesis advisor) / Rajan, Subramaniam Dharma (Committee member) / Hoover, Christian G. (Committee member) / Arizona State University (Publisher)
Created2018
Description
A simplified bilinear moment-curvature model are derived based on the moment-curvature response generated from a parameterized stress-strain response of strain softening and or strain-hardening material by Dr. Barzin Mobasher and Dr. Chote Soranakom. Closed form solutions are developed for deflection calculations of determinate beams subjected to usual loading patterns at any load stage. The solutions are based on a bilinear moment curvature response characterized by the flexural crack initiation and ultimate capacity based on a deflection hardening behavior. Closed form equations for deflection calculation are presented for simply supported beams under three point bending, four point bending, uniform load, concentrated moment at the middle, pure bending, and for cantilever beam under a point load at the end, a point load with an arbitrary distance from the fixed end, and uniform load. These expressions are derived for pre-cracked and post cracked regions. A parametric study is conducted to examine the effects of moment and curvature at the ultimate stage to moment and curvature at the first crack ratios on the deflection. The effectiveness of the simplified closed form solution is demonstrated by comparing the analytical load deflection response and the experimental results for three point and four point bending. The simplified bilinear moment-curvature model is modified by imposing the deflection softening behavior so that it can be widely implemented in the analysis of 2-D panels. The derivations of elastic solutions and yield line approach of 2-D panels are presented. Effectiveness of the proposed moment-curvature model with various types of panels is verified by comparing the simulated data with the experimental data of panel test.
ContributorsWang, Xinmeng (Author) / Mobasher, Barzin (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Neithalath, Narayanan (Committee member) / Arizona State University (Publisher)
Created2015
Description
Composite materials are finally providing uses hitherto reserved for metals in structural systems applications – airframes and engine containment systems, wraps for repair and rehabilitation, and ballistic/blast mitigation systems. They have high strength-to-weight ratios, are durable and resistant to environmental effects, have high impact strength, and can be manufactured in a variety of shapes. Generalized constitutive models are being developed to accurately model composite systems so they can be used in implicit and explicit finite element analysis. These models require extensive characterization of the composite material as input. The particular constitutive model of interest for this research is a three-dimensional orthotropic elasto-plastic composite material model that requires a total of 12 experimental stress-strain curves, yield stresses, and Young’s Modulus and Poisson’s ratio in the material directions as input. Sometimes it is not possible to carry out reliable experimental tests needed to characterize the composite material. One solution is using virtual testing to fill the gaps in available experimental data. A Virtual Testing Software System (VTSS) has been developed to address the need for a less restrictive method to characterize a three-dimensional orthotropic composite material. The system takes in the material properties of the constituents and completes all 12 of the necessary characterization tests using finite element (FE) models. Verification and validation test cases demonstrate the capabilities of the VTSS.
ContributorsHarrington, Joseph (Author) / Rajan, Subramaniam D. (Thesis advisor) / Neithalath, Narayanan (Committee member) / Mobasher, Barzin (Committee member) / Arizona State University (Publisher)
Created2015
Description
In order to verify the dispersive nature of transverse displacement in a beam, a deep understanding of the governing partial differential equation is developed. Using the finite element method and Newmark’s method, along with Fourier transforms and other methods, the aim is to obtain consistent results across each numerical technique. An analytical solution is also analyzed for the Euler-Bernoulli beam in order to gain confidence in the numerical techniques when used for more advance beam theories that do not have a known analytical solution. Three different beam theories are analyzed in this report: The Euler-Bernoulli beam theory, Rayleigh beam theory and Timoshenko beam theory. A comparison of the results show the difference between each theory and the advantages of using a more advanced beam theory for higher frequency vibrations.
ContributorsTschetter, Ryan William (Author) / Hjelmstad, Keith D. (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Mobasher, Barzin (Committee member) / Arizona State University (Publisher)
Created2016