Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
Displaying 1 - 10 of 172
Description
Laminated composites are increasingly being used in various industries including <br/>automotive and aerospace. Under a variety of extreme loading conditions such as low and <br/>high-velocity impacts and crash, laminated composites delaminate. To understand how and<br/>when delamination occurs, two types of laboratory tests are conducted - End-notched <br/>Flexure (ENF) test and Double Cantilever Beam (DCB) test. The ENF test is designed to <br/>find the mode II interlaminar fracture toughness, and the DCB test, the mode I interlaminar <br/>fracture toughness. In this thesis, thermopressed Honeywell Spectra Shield® 5231 <br/>composite specimens made of ultra-high molecular weight polyethylene (UHMWPE), <br/>manufactured under two different pressures (3000 psi and 6000 psi), are tested in the <br/>laboratory to find its delamination properties. The test specimen preparation, experimental <br/>procedures, and data reduction to determine the mode I and mode II interlaminar fracture <br/>properties are discussed. The ENF test results show a 15.8% increase in strain energy <br/>release rate for the 6000 psi specimens when compared to the 3000 psi specimens. <br/>Conducting the DCB tests proved to be challenging due to the low compressive strength <br/>of the material and hence required modifications to the test specimens. An estimate of the <br/>mode I interlaminar fracture toughness was found for only two of the 6000 psi specimens.
ContributorsRyder, Chandler (Author) / Rajan, Subramaniam (Thesis director) / Khaled, Bilal (Committee member) / Neithalath, Narayanan (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
Fibromyalgia (FM) is a chronic musculoskeletal disorder characterized by widespread pain, fatigue, and a variety of other comorbid physiological and psychological characteristics, including a deficit of positive affect. Recently, the focus of research on the pathophysiology of FM has considered the role of a number of genomic variants. In the current manuscript, case-control analyses did not support the hypothesis that FM patients would differ from other chronic pain groups in catechol-O-methyltransferase (COMT) and mu-opioid receptor (OPRM1) genotype. However, evidence is provided in support of the hypothesis that functional single nucleotide polymorphisms on the COMT and OPRM1 genes would be associated with risk and resilience, respectively, in a dual processing model of pain-related positive affective regulation in FM. Forty-six female patients with a physician-confirmed diagnosis of FM completed an electronic diary that included once-daily assessments of positive affect and soft tissue pain. Multilevel modeling yielded a significant gene X environment interaction, such that individuals with met/met genotype on COMT experienced a greater decline in positive affect as daily pain increased than did either val/met or val/val individuals. A gene X environment interaction for OPRM1 also emerged, indicating that individuals with at least one asp allele were more resilient to elevations in daily pain than those homozygous for the asn allele. In sum, the findings offer researchers ample reason to further investigate the contribution of the catecholamine and opioid systems, and their associated genomic variants, to the still poorly understood experience of FM.
ContributorsFinan, Patrick Hamilton (Author) / Zautra, Alex (Thesis advisor) / Davis, Mary (Committee member) / Lemery-Chalfant, Kathryn (Committee member) / Presson, Clark (Committee member) / Arizona State University (Publisher)
Created2011
Description
I examined the role of children's or teacher's effortful control (EC) in children's academic functioning in early elementary school in two separate studies. In Study 1, I tested longitudinal relations between parents' reactions to children's displays of negative emotions in kindergarten, children's EC in first grade, and children's reading or math achievement in second grade (N = 291). In the fall of each school year, parents reported their positive or negative reactions and parents and teachers reported on children's EC. Standardized achievement tests assessed achievement each spring. Results from autoregressive panel mediation models demonstrated that constructs exhibited consistency across study years. In addition, first-grade EC mediated relations between parents' reactions (i.e., a difference composite of positive minus negative reactions) at kindergarten and second-grade math, but not reading, achievement. Findings suggest that one method of promoting math achievement in early school is through the socialization of children's EC. In Study 2, I examined relations between teachers' EC, teachers' reactions to children's negative emotions, the student-teacher relationship (STR), and children's externalizing behaviors or achievement among 289 second-graders and their 116 teachers. Results from mixed-model regressions showed that negative reactions and teacher-reported STR mediated relations between teachers' EC and math achievement. In addition, teacher-reported STR mediated links between teachers' EC and externalizing problems across reporters and between teachers' EC and reading achievement. Tests of moderated mediation indicated that a high-quality STR was negatively associated with externalizing problems and high levels of teachers' negative reactions were negatively related to math achievement only for students low in EC. In tests of moderation by social competence, teachers' reports of high-quality STRs tended to be negatively associated with externalizing problems, but relations were strongest for students not high in social competence. For students low in social competence only, children's reports of a high-quality STR was related to lower reading achievement. These results highlight the utility of considering whether and how teachers' own intrinsic characteristics influence classroom dynamics and students' academic functioning outcomes.
ContributorsSwanson, Jodi Michelle (Author) / Valiente, Carlos (Thesis advisor) / Bradley, Robert H (Thesis advisor) / Kochenderfer-Ladd, Becky (Committee member) / Lemery-Chalfant, Kathryn (Committee member) / Arizona State University (Publisher)
Created2011
Description
Nuclear magnetic resonance (NMR) is an important phenomenon involving nuclear magnetic moments in magnetic field, which can provide much information about a wide range of materials, including their chemical composition, chemical environments and nuclear spin interactions. The NMR spectrometer has been extensively developed and used in many areas of research. In this thesis, studies in two different areas using NMR are presented. First, a new kind of nanoparticle, Gd(DTPA) intercalated layered double hydroxide (LDH), has been successfully synthesized in the laboratory of Prof. Dey in SEMTE at ASU. In Chapter II, the NMR relaxation studies of two types of LDH (Mg, Al-LDH and Zn, Al-LDH) are presented and the results show that when they are intercalated with Gd(DTPA) they have a higher relaxivity than current commercial magnetic resonance imaging (MRI) contrast agents, such as DTPA in water solution. So this material may be useful as an MRI contrast agent. Several conditions were examined, such as nanoparticle size, pH and intercalation percentage, to determine the optimal relaxivity of this nanoparticle. Further NMR studies and simulations were conducted to provide an explanation for the high relaxivity. Second, fly ash is a kind of cementitious material, which has been of great interest because, when activated by an alkaline solution, it exhibits the capability for replacing ordinary Portland cement as a concrete binder. However, the reaction of activated fly ash is not fully understood. In chapter III, pore structure and NMR studies of activated fly ash using different activators, including NaOH and KOH (4M and 8M) and Na/K silicate, are presented. The pore structure, degree of order and proportion of different components in the reaction product were obtained, which reveal much about the reaction and makeup of the final product.
ContributorsPeng, Zihui (Author) / Marzke, Robert F (Thesis advisor) / Dey, Sandwip Kumar (Committee member) / Neithalath, Narayanan (Committee member) / Chamberlin, Ralph Vary (Committee member) / Mccartney, Martha Rogers (Committee member) / Arizona State University (Publisher)
Created2013
Description
Using data from an eight-year longitudinal study of 214 children's social and emotional development, I conducted three studies to (1) examine patterns of agreement for internalizing (INT) and externalizing (EXT) symptomatology among different informants (mothers, fathers, teachers, and adolescents) using a recently developed structural equation modeling approach for multi-trait, multi-method data; (2) examine the developmental trajectories for INT and EXT and predict individual differences in symptom development using temperament and parenting variables; and (3) describe patterns of INT and EXT co-occurrence and predict these patterns from temperament and parenting. In Study 1, longitudinal invariance was established for mothers', fathers' and teachers' reports over a six-year period. Sex, age, and SES did not substantially moderate agreement among informants, although both sex and age were differentially related to symptomatology depending on the informant. Agreement among teachers and mothers, but not among mothers and fathers, differed by domain of symptomatology, and was greater for EXT than for INT. In Study 2, latent profile analysis, a person-centered analytic approach, did not provide easily interpretable patterns of symptom development, a failure that is likely the result of the relatively modest sample size. Latent growth curve models, an alternative analytic approach, did provide good fit to the data. Temperament and parenting variables were examined as predictors of the latent growth parameters in these models. Although there was little prediction of the slope, effortful control was negatively related to overall levels of EXT, whereas impulsivity and anger were positively related. Mutually responsive orientation, a measure of the parent-child relationship, was a more consistent predictor of EXT than was parental warmth. Furthermore, the relation between mutually responsive orientation and EXT was partially mediated by inhibitory control. Across informants, there were few consistent predictors of INT. In Study 3, latent profile analysis was used to classify individuals into different patterns of INT and EXT co-occurrence. In these models, a similar class structure was identified for mothers and for teachers. When temperament and parenting were examined as predictors of co-occurring symptomatology, few significant interactions were found and results largely replicated prior findings from this data set using arbitrary symptom groups.
ContributorsSulik, Michael John (Author) / Eisenberg, Nancy (Thesis advisor) / Spinrad, Tracy L (Thesis advisor) / Lemery-Chalfant, Kathryn (Committee member) / Wolchik, Sharlene A (Committee member) / Arizona State University (Publisher)
Created2013
Description
This study focused on investigating the ability of a polymeric-enhanced high-tenacity fabric composite called CarbonFlex to mitigate damages from multi-natural hazards, which are earthquakes and tornadoes, in wood-framed structures. Typically, wood-framed shear wall is a seismic protection system used in low-rise wood structures. It is well-known that the main energy dissipation of the system is its fasteners (nails) which are not enough to dissipate energy leading to decreasing of structure's integrity. Moreover, wood shear walls could not sustain their stiffness after experiencing moderate wall drift which made them susceptible to strong aftershocks. Therefore, CarbonFlex shear wall system was proposed to be used in the wood-framed structures. Seven full-size CarbonFlex shear walls and a CarbonFlex wrapped structures were tested. The results were compared to those of conventional wood-framed shear walls and a wood structure. The comparisons indicated that CarbonFlex specimens could sustain their strength and fully recover their initial stiffness although they experienced four percent story drift while the stiffness of the conventional structure dramatically degraded. This indicated that CarbonFlex shear wall systems provided a better seismic protection to wood-framed structures. To evaluate capability of CarbonFlex to resist impact damages from wind-borne debris in tornadoes, several debris impact tests of CarbonFlex and a carbon fiber reinforced storm shelter's wall panels were conducted. The results showed that three CarbonFlex wall panels passed the test at the highest debris impact speed and the other two passed the test at the second highest speed while the carbon fiber panel failed both impact speeds.
ContributorsDhiradhamvit, Kittinan (Author) / Attard, Thomas L (Thesis advisor) / Fafitis, Apostolos (Thesis advisor) / Neithalath, Narayanan (Committee member) / Thomas, Benjamin (Committee member) / Arizona State University (Publisher)
Created2013
Description
The main objective of this study is to develop an innovative system in the form of a sandwich panel type composite with textile reinforced skins and aerated concrete core. Existing theoretical concepts along with extensive experimental investigations were utilized to characterize the behavior of cement based systems in the presence of individual fibers and textile yarns. Part of this thesis is based on a material model developed here in Arizona State University to simulate experimental flexural response and back calculate tensile response. This concept is based on a constitutive law consisting of a tri-linear tension model with residual strength and a bilinear elastic perfectly plastic compression stress strain model. This parametric model was used to characterize Textile Reinforced Concrete (TRC) with aramid, carbon, alkali resistant glass, polypropylene TRC and hybrid systems of aramid and polypropylene. The same material model was also used to characterize long term durability issues with glass fiber reinforced concrete (GFRC). Historical data associated with effect of temperature dependency in aging of GFRC composites were used. An experimental study was conducted to understand the behavior of aerated concrete systems under high stain rate impact loading. Test setup was modeled on a free fall drop of an instrumented hammer using three point bending configuration. Two types of aerated concrete: autoclaved aerated concrete (AAC) and polymeric fiber-reinforced aerated concrete (FRAC) were tested and compared in terms of their impact behavior. The effect of impact energy on the mechanical properties was investigated for various drop heights and different specimen sizes. Both materials showed similar flexural load carrying capacity under impact, however, flexural toughness of fiber-reinforced aerated concrete was proved to be several degrees higher in magnitude than that provided by plain autoclaved aerated concrete. Effect of specimen size and drop height on the impact response of AAC and FRAC was studied and discussed. Results obtained were compared to the performance of sandwich beams with AR glass textile skins with aerated concrete core under similar impact conditions. After this extensive study it was concluded that this type of sandwich composite could be effectively used in low cost sustainable infrastructure projects.
ContributorsDey, Vikram (Author) / Mobasher, Barzin (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Neithalath, Narayanan (Committee member) / Arizona State University (Publisher)
Created2012
Description
The main objective of this study is to investigate the mechanical behaviour of cementitious based composites subjected dynamic tensile loading, with effects of strain rate, temperature, addition of short fibres etc. Fabric pullout model and tension stiffening model based on finite difference model, previously developed at Arizona State University were used to help study the bonding mechanism between fibre and matrix, and the phenomenon of tension stiffening due to the addition of fibres and textiles. Uniaxial tension tests were conducted on strain-hardening cement-based composites (SHCC), textile reinforced concrete (TRC) with and without addition of short fibres, at the strain rates ranging from 25 s-1 to 100 s-1. Historical data on quasi-static tests of same materials were used to demonstrate the effects including increases in average tensile strength, strain capacity, work-to-fracture due to high strain rate. Polyvinyl alcohol (PVA), glass, polypropylene were employed as reinforcements of concrete. A state-of-the-art phantom v7 high speed camera was setup to record the video at frame rate of 10,000 fps. Random speckle pattern of texture style was made on the surface of specimens for image analysis. An optical non-contacting deformation measurement technique referred to as digital image correlation (DIC) method was used to conduct the image analysis by means of tracking the displacement field through comparison between the reference image and deformed images. DIC successfully obtained full-filed strain distribution, strain versus time responses, demonstrated the bonding mechanism from perspective of strain field, and corrected the stress-strain responses.
ContributorsYao, Yiming (Author) / Barzin, Mobasher (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Neithalath, Narayanan (Committee member) / Arizona State University (Publisher)
Created2013
Description
This study focuses on implementing probabilistic nature of material properties (Kevlar® 49) to the existing deterministic finite element analysis (FEA) of fabric based engine containment system through Monte Carlo simulations (MCS) and implementation of probabilistic analysis in engineering designs through Reliability Based Design Optimization (RBDO). First, the emphasis is on experimental data analysis focusing on probabilistic distribution models which characterize the randomness associated with the experimental data. The material properties of Kevlar® 49 are modeled using experimental data analysis and implemented along with an existing spiral modeling scheme (SMS) and user defined constitutive model (UMAT) for fabric based engine containment simulations in LS-DYNA. MCS of the model are performed to observe the failure pattern and exit velocities of the models. Then the solutions are compared with NASA experimental tests and deterministic results. MCS with probabilistic material data give a good prospective on results rather than a single deterministic simulation results. The next part of research is to implement the probabilistic material properties in engineering designs. The main aim of structural design is to obtain optimal solutions. In any case, in a deterministic optimization problem even though the structures are cost effective, it becomes highly unreliable if the uncertainty that may be associated with the system (material properties, loading etc.) is not represented or considered in the solution process. Reliable and optimal solution can be obtained by performing reliability optimization along with the deterministic optimization, which is RBDO. In RBDO problem formulation, in addition to structural performance constraints, reliability constraints are also considered. This part of research starts with introduction to reliability analysis such as first order reliability analysis, second order reliability analysis followed by simulation technique that are performed to obtain probability of failure and reliability of structures. Next, decoupled RBDO procedure is proposed with a new reliability analysis formulation with sensitivity analysis, which is performed to remove the highly reliable constraints in the RBDO, thereby reducing the computational time and function evaluations. Followed by implementation of the reliability analysis concepts and RBDO in finite element 2D truss problems and a planar beam problem are presented and discussed.
ContributorsDeivanayagam, Arumugam (Author) / Rajan, Subramaniam D. (Thesis advisor) / Mobasher, Barzin (Committee member) / Neithalath, Narayanan (Committee member) / Arizona State University (Publisher)
Created2012
Description
Concrete design has recently seen a shift in focus from prescriptive specifications to performance based specifications with increasing demands for sustainable products. Fiber reinforced composites (FRC) provides unique properties to a material that is very weak under tensile loads. The addition of fibers to a concrete mix provides additional ductility and reduces the propagation of cracks in the concrete structure. It is the fibers that bridge the crack and dissipate the incurred strain energy in the form of a fiber-pullout mechanism. The addition of fibers plays an important role in tunnel lining systems and in reducing shrinkage cracking in high performance concretes. The interest in most design situations is the load where cracking first takes place. Typically the post crack response will exhibit either a load bearing increase as deflection continues, or a load bearing decrease as deflection continues. These behaviors are referred to as strain hardening and strain softening respectively. A strain softening or hardening response is used to model the behavior of different types of fiber reinforced concrete and simulate the experimental flexural response. Closed form equations for moment-curvature response of rectangular beams under four and three point loading in conjunction with crack localization rules are utilized. As a result, the stress distribution that considers a shifting neutral axis can be simulated which provides a more accurate representation of the residual strength of the fiber cement composites. The use of typical residual strength parameters by standards organizations ASTM, JCI and RILEM are examined to be incorrect in their linear elastic assumption of FRC behavior. Finite element models were implemented to study the effects and simulate the load defection response of fiber reinforced shotcrete round discrete panels (RDP's) tested in accordance with ASTM C-1550. The back-calculated material properties from the flexural tests were used as a basis for the FEM material models. Further development of FEM beams were also used to provide additional comparisons in residual strengths of early age samples. A correlation between the RDP and flexural beam test was generated based a relationship between normalized toughness with respect to the newly generated crack surfaces. A set of design equations are proposed using a residual strength correction factor generated by the model and produce the design moment based on specified concrete slab geometry.
ContributorsBarsby, Christopher (Author) / Mobasher, Barzin (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Neithalath, Narayanan (Committee member) / Arizona State University (Publisher)
Created2011