Master of Science, University of Toledo, 2018, Civil Engineering

Carbon fiber reinforced polymer (CFRP) reinforcement has been studied as an alternative to steel reinforcement due to steel's high susceptibility to corrosion in bridge girders. The use of deicing salts on roads during extreme cold is the primary cause of the corrosive environment due to salt percolation through cracks. This research manifests the flexural behavior of carbon fiber polymer reinforced beams in prestressed and non-prestressed conditions as well as the variation of the behavior from conventional steel reinforced beams including the design procedure of a prestressed CFRP box section beam through a case study. Unlike steel, CFRP has different stress versus strain relationship - linear without a definite yield point. A review of literature is done regarding the history, properties, applications, and researches in this field. A comparative study is done between the behavior of CFRP reinforced beams using previously tested rectangular and decked bulb T-beams. The study also focuses on the field of application, guidelines, and provisions in different parts of the world, design procedure, characteristics and weaknesses of the material, handling of CFRP in the field, and its design. The application of CFRP as the main reinforcement is scarce because of its brittleness and limited research. However, the strength and lightness make this material ideal for use in the construction industry. It is important that these beams have adequate ductility to prevent sudden failure. Ductility of similar types of beams with conventional and CFRP materials are studied and compared through deformability index. Several methods of calculating ductility are discussed and an ACI method is selected to find the ductility of each beam and a comparative study is done. The behavior of prestressed CFRP tendon is examined when it is used as an alternative to the conventional steel tendon through a case study relating different provisions of code through the design of a prestressed (open full item for complete abstract)

Committee: Douglas Nims (Committee Chair); Liangbo Hu (Committee Member); Luis Mata (Committee Member) Subjects: Civil Engineering

Master of Science, The Ohio State University, 2016, Mechanical Engineering

Due to increasing emphasis on lightweighting to increase fuel efficiency, integration of carbon fiber reinforced polymers (CFRP) with metal structures is necessary. Current adhesive and mechanical fastening methods used for joining CFRP to metals are not ideal due to poor mechanical properties and incompatibility with current manufacturing infrastructure. Consequently, new joining techniques are needed for increasing the use of CFRP. In this research project, a method of creating joints between CFRP and 6061-H18 aluminum was developed by using ultrasonic additive manufacturing (UAM). The UAM process was used to embed dry carbon fiber tows within an aluminum matrix, creating a mechanical joint between the two materials. The joints were then integrated with additional CF fabrics and epoxy, forming a fully integrated CF-Al structure. This technique was used to create CF-Al joints for tensile, cross tensile, and three-point-bend testing. Mechanical test results showed that the UAM constructed joints had superior strength when compared to adhesive single lap joints. Throughout the UAM joint manufacturing process, experimental observations paired with FEA were used to help solve issues with foil tearing, which is a common problem experienced when materials are embedded with UAM.

Committee: Marcelo Dapino (Advisor); Anthony Luscher (Committee Member) Subjects: Aerospace Engineering; Automotive Engineering; Automotive Materials; Engineering; Experiments; Materials Science; Polymers

Doctor of Philosophy (PhD), Ohio University, 1997, Mechanical Engineering (Engineering)

Carbon fibers have become important in matrix reinforcement, thermal, electrical and magnetic applications. The focus of this study is the synthesis of Vapor Grown Carbon Fibers (VGCF) which are produced by the pyrolysis of hydrocarbons over catalytic transition metal particles. A model had been developed to study the formation of catalyst particles and VGCF growth in a flow reactor. The model includes the three distinct phenomena that take place inside a Vapor Grown Carbon Fiber (VGCF) reactor. The phenomena are - heat transfer to the flowing gaseous reactants, particle formation and growth in the flow, and the carbon fiber growth from the catalyst particles. The model predicts the nucleation rates of particles by determination of collision frequency of catalyst molecules which are produced by gas phase reactions. Calculations had been carried out to determine the growth rates of the catalyst particles in the mixture and of the carbon fibers from the catalyst. Results indicate that submicron catalyst particles are produced in the process; consequently, carbon fibers that are formed are submicron in diameter. The model predictions of the catalyst particle growth compare well with results from an experimental VGCF reactor.

Committee: M. Alam (Advisor) Subjects: Engineering, Mechanical

Doctor of Philosophy (PhD), Wright State University, 2020, Engineering PhD

The goal of this project is to investigate fabrication approaches and structure-property relationships of porous and flexible hierarchical hybrid solids suitable for advanced surface-active devices. Multi-scale hierarchical carbon materials are being fabricated by strong covalent attachment of multiwall carbon nanotube(MWCNTs) arrays on flexible carbon fabric substrates in order to enhance the surface area per unit volume. This was done using chemical vapor deposition (CVD) after functionalizing the surface with a plasma-derived nano-oxide coating. Structural and chemical characterization is performed using scanning electron microscope(SEM), energy dispersive spectroscopy(EDS) and x-ray photoelectron spectroscopy(XPS). Surface area estimates have been made by building structural models from Electron Microscopy data and subsequently validated with direct measurement with BET isotherm analyses. It is seen that calculated specific surface area (SSA) of the material via mass increase during the CVD process is in good agreement with BET gas adsorption measurement of the SSA. It has been shown that further modification of these surfaces is very effective for tailoring their wettability for selective infiltration of different fluids. These structures have been infiltrated with responsive polymers such as Poly(N-isopropylacrylamide(PNIPAM)s to fabricate smart stimuli-responsive composites. In addition, palladium nanoparticles(PdNPs) have been attached onto the nanotube carpets. Particle distribution, size variation, and structures have be investigated using Scanning Electron Microscopy (SEM) & Energy Dispersive Spectroscopy (EDS). X-ray photo spectroscopy (XPS) was employed for bonding state analysis. In-depth understanding of catalytic behavior of these hybrid nanocatalysts (Fabric-CNT-Pd system) has been performed by investigating the catalytic reduction of a model water contaminant triclosan(TCS). The reaction rates, efficiency, and durability have been studied (open full item for complete abstract)

Committee: Sharmila M. Mukhopadhyay Ph.D. (Advisor); Nadagouda N. Mallikarjuna Ph.D. (Committee Member); Willie F. Harper, Jr. Ph.D. (Committee Member); Hong Huang Ph.D. (Committee Member); H. Daniel Young Ph.D. (Committee Member) Subjects: Engineering; Materials Science; Nanotechnology

MS, University of Cincinnati, 2018, Engineering and Applied Science: Aerospace Engineering

Carbon nanotubes (CNTs) have extraordinary mechanical, thermal and electrical properties. However, the macroscopic products of CNTs such as sheet and thread, lack these extraordinary physical properties. This reduction in properties for the macroscopic products of CNT is due to the presence of structural defects (disorder-induced symmetry-breaking effects in the sp2 hybridized carbon products), impurities, slipping apart of the short nanotubes in bundles, and random orientation of the CNT strands in sheet and thread. Transferring the physical properties of individual CNTs to the macroscopic scale is a challenging task. To use carbon nanotubes in different applications, intensive research is being performed to improve the mechanical, thermal and electrical properties of CNT sheet and thread. The goal of this work is to investigate methods to improve the mechanical and electrical properties of CNT sheet and thread. The research starts with tuning the CNT synthesis process to produce CNT sheet with fewer structural defects. Also, the effect of this synthesis optimization process on the mechanical and electrical properties of the CNT sheet is investigated. Towards the goal of improving the properties of CNT sheet, further post-processing techniques are studied to improve the orientation of the CNT strands in CNT sheet. It is observed that the mechanical and electrical properties improved due to improved alignment and packing of the CNT strands in the sheet. From the perspective of the application, the hydrophilicity of the CNT sheet is also studied for integrating CNT sheet into textiles. Acid treatment of CNT sheet promoted the hydrophilicity of the CNT sheet. For acid treatment of CNT sheet, hydrogen peroxide and a mixture of H2SO4+HNO3 in 3:1 ratio is used. After analyzing the IG/ID ratio from Raman analysis before and after acid treatment, hydrogen peroxide treated CNT sheet for 48 h showed the best result. Hydrogen peroxide treatment of CNT sheet for 48 h s (open full item for complete abstract)

Committee: Peter Nagy Ph.D. (Committee Chair); Yao Fu (Committee Member); Mark Schulz Ph.D. (Committee Member) Subjects: Nanotechnology

Doctor of Philosophy, University of Toledo, 2016, Chemical Engineering

Concerns over the effects of anthropogenic carbon dioxide (CO2) emissions from fossil-fuel electric power plants has led to significant efforts in the development of processes for CO2 capture from flue gas. Options under consideration include absorption, adsorption, membrane, and hybrid processes. The US Department of Energy (DOE) has set goals of 90% CO2 capture at 95% purity followed by compression to 140 bar for transport and storage. Ideally, the Levelized Cost of Electricity (LCOE) would increase by no more than 35%. Because of the relatively low CO2 concentration in post-combustion flue gas, most of the reported process configurations for membrane systems have sought to generate affordable CO2 partial pressure driving forces for permeation. Membrane Technology and Research, Inc. (MTR) proposed the use of an air feed sweep system to increase the CO2 concentration in flue gas. This process utilizes a two-stage membrane process in which the feed air to the furnace sweeps the flue gas in the second stage to reduce the flow of CO2 in the effluent to 10% of that leaving the furnace. Such a design significantly reduces capture costs but leads to a detrimental reduction in the oxygen concentration of the feed air to the boiler. In this dissertation, the economic viability of combined cryogenic-membrane separation is evaluated. The work incorporates the tradeoff between CO2/N2 selectivity and CO2 permeability that exists when considering the broad range of potential membrane materials. Of particular interest is the use of lower selectivity, higher permeability materials such as polydimethylsiloxane (PDMS). Additional enriching stages are required in a membrane-cryogenic air feed sweep configuration to enable use of these materials and achieve the 90% CO2 recovery and 95% purity targets. The higher CO2 permeance of PDMS significantly reduces the total module membrane area requirement and associated capital cost (CAPEX). However, the lower selectivity increases th (open full item for complete abstract)

Committee: GLENN LIPSCOMB PhD (Committee Chair); MARIA COLEMAN PhD (Committee Member); YAKOV LAPITSKY PhD (Committee Member); CONSTANCE SCHALL PhD (Committee Member); MATTHEW FRANCHETTI PhD (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2013, Mechanical Engineering

The growing demand for superior materials that function as scaffolds for tissue repair and regeneration has served as a catalyst in medicine. The need for artificial or natural replacement or repair of organs, limbs and tissue presents an opportunity to deliver materials with superior biologics, architecture and mechanical properties. Current biomaterials utilized to repair damaged tissue or augment function commonly fail to meet the optimal combination of biomechanical and healing potential. Additionally, limited donor tissue availability and the increased cost of healthcare are driving factors for improving material processing and diagnostic assessment. Currently, metallic materials, such as titanium and stainless steel, function as implants and reinforcements. However, these materials are permanent and rigid and may inhibit natural healing of damaged tissue. Moreover, metallic implants corrode and fracture, causing repetitive injury and excess scar tissue formation. Conversely, polymer-based materials have shown promising results. A limited number of polymer biomaterials have been approved for scaffold and implant applications. Additionally, some polymers have the ability to degrade, an advantageous characteristic for biological applications. Nevertheless, most natural and synthetic biopolymers lack high strength and cannot be utilized as primary scaffolds in load bearing applications. The materials described earlier present shortcomings. The importance of the presented work is that it utilized mass producible materials, modified them for unique cellular environments and developed a computational model to predict cell behavior and facilitate future design endeavors. Specifically, the current analysis focused on preparing carbon-based scaffolds from monolithic, textile, composite, and nanoartifact derivatives. This work was the first to present an understanding between critical properties of carbon materials: crystallinity, orientation, surface (open full item for complete abstract)

Committee: Khalid Lafdi (Advisor); Robert Brockman (Committee Member); Wiebke Diestelkamp (Committee Member); Kevin Hallinan (Committee Member); Panagiotis Tsonis (Committee Member) Subjects: Biomedical Engineering; Materials Science; Mechanical Engineering; Medicine

Master of Science (MS), Wright State University, 2010, Physics

The resistance of three types of bulk carbon nanotube (CNT) materials (floating catalyst CNT yarn, forest grown CNT yarn, and super acid spun CNT fiber) was measured from room temperature to 900 C. Fitting the curves to established conduction equations for disordered materials, competing conduction mechanisms pertaining to the material could be determined. Floating catalyst CNT yarn displayed both semiconductive and metallic isotropic behavior with a resistance minimum, similar to the behavior of crystalline graphite. It was found that, at room temperature, the semiconducting contribution-most likely junctions between CNTs-accounted for 99.99% of the overall resistance. The resistance of forest grown CNT yarn and super acid solution spun CNT fiber decreased monotonically with temperature at a rate similar to amorphous carbon. The impedance of all three materials was also measured to 30 MHz. All three materials followed a series resistor inductor circuit, without any resistance decrease as others have found. Finally, the conductivity and specific conductivity of all three materials was compared to metallic benchmarks. While all three materials had a similar conductivity, the floating catalyst CNT yarn had a significantly higher specific conductivity.

Committee: Gregory Kozlowski PhD (Advisor); Jerry Clark PhD (Committee Member); Benji Maruyama PhD (Committee Member); Jason Deibel PhD (Committee Member); Andrew Hsu PhD (Other); Lok Lew Yan Voon PhD (Other) Subjects: Physics

Doctor of Philosophy (Ph.D.), University of Dayton, 2010, Materials Engineering

The interface between carbon fibers (CFs) and the resin matrix in traditional high performance composites is characterized by a large discontinuity in mechanical, electrical, and thermal properties which can cause inefficient energy transfer. Due to the exceptional properties of carbon nanotubes (CNTs), their growth at the surface of carbon fibers is a promising approach to controlling interfacial interactions and achieving the enhanced bulk properties. However, the reactive conditions used to grow carbon nanotubes also have the potential to introduce defects that can degrade the mechanical properties of the carbon fiber (CF) substrate. In this study, using thermal chemical vapor deposition (CVD) method, high density multi-wall carbon nanotubes have been successfully synthesized directly on PAN-based CF surface without significantly compromising tensile properties. The influence of CVD growth conditions on the single CF tensile properties and carbon nanotube (CNT) morphology was investigated. The experimental results revealed that under high temperature growth conditions, the tensile strength of CF was greatly decreased at the beginning of CNT growth process with the largest decrease observed for sized CFs. However, the tensile strength of unsized CFs with CNT was approximately the same as the initial CF at lower growth temperature. The interfacial shear strength of CNT coated CF (CNT/CF) in epoxy was studied by means of the single-fiber fragmentation test. Results of the test indicate an improvement in interfacial shear strength with the addition of a CNT coating. This improvement can most likely be attributed to an increase in the interphase yield strength as well as an improvement in interfacial adhesion due to the presence of the nanotubes. CNT/CF also offers promise as stress and strain sensors in CF reinforced composite materials. This study investigates fundamental mechanical and electrical properties of CNT/CF using nanoindentation method by designed localiz (open full item for complete abstract)

Committee: Liming Dai PhD (Committee Chair); P. Terrence Murray PhD (Committee Member); Donald Klostermen PhD (Committee Member); James Snide PhD (Committee Member); Jeffry W. Baur PhD (Committee Member); Tia Benson Tolle PhD (Committee Member) Subjects: Materials Science

Doctor of Philosophy in Clinical-Bioanalytical Chemistry, Cleveland State University, 2009, College of Science

Nitric oxide (NO) is an important intercellular messenger that acts in many tissues to regulate a diverse range of physiological and pathological processes. The physiologically implications of NO function are far from being completely understood. The multifaceted reactivity of NO prompted the need for accurate determination of the concentration of this molecule. However, it is difficult to detect nitric oxide, particularly in biological media and near live cells due to its short half-life, a result of its reactivity and the low levels of NO produced in vivo. As a result, the accurate and reliable detection of NO under varying experimental conditions has always posed a challenging task. The main goal was to develop ultra-sensitive electrocatalytic sensors for accurate quantification of NO. We report the fabrication and characterization of improved NO sensors based on electrocatalytic platforms such as ruthenium (colloids, nanoparticles, and nanotubes) and carbon (pastes and nanotubes), acting as catalytic sites for NO oxidation. These sensors are characterized using various surface analytical tools. The electrocatalytic oxidation of NO is assessed by cyclic voltammetry and amperometry both in solution phase and gas phase. Excellent sensitivity and linearity are observed for our modified electrodes towards NO quantification. Our new NO detection sensors also show superior limit of detection and selectivity against common interference species. Our NO sensors are tested for various applications including in the measurement of NO released from human umbilical vein endothelial cells (HUVECs).

Committee: Dr. Mekki Bayachou PhD (Advisor); Dr. Lily Ng PhD (Committee Member); Dr. Robert Wei PhD (Committee Member); Dr. John Turner PhD (Committee Member); Dr. Petru Fodor PhD (Committee Member) Subjects: Chemistry

Master of Science, Miami University, 2025, Mechanical Engineering

Polydimethylsiloxane (PDMS), a versatile silicon-based polymer, is widely used in biomedical devices, microfluidic systems, wearable technology, and electronics due to its mechanical flexibility, optical clarity, electrical conductivity, and biocompatibility. However, its low Young's modulus and tensile strength limit its application in high-stress environments. To enhance its mechanical and functional properties, this study explores the incorporation of carbon fibers (CF) and graphene (Gr) as reinforcements. Despite the potential benefits of these nanomaterials, challenges such as aggregation, void formation, and poor interfacial bonding often compromise composite performance. This research integrates acoustic field (AF) technology into inkjet-based additive manufacturing (AM) to address these issues. The AF enhances material dispersion, reduces defects, and improves bonding between reinforcements and the PDMS matrix. The study evaluates the effects of CF and Gr reinforcements with AF treatment on the mechanical, microstructural, and dynamic properties of PDMS composites. Furthermore, it investigates the impact of different percentages of graphene content on the electrical resistance and mechanical properties graphene-reinforced-PDMS for wearable sensor applications. Results demonstrate that optimal graphene content balances dispersion and aggregation, thus, maximizing mechanical strength and electrical conductivity. By introducing AF-assisted AM, this study provides insights into producing high-performance PDMS composites for advanced applications, particularly in sensors and flexible electronics.

Committee: Muhammad Jahan (Advisor); Yingbin Hu (Committee Member); Zhijiang Ye (Committee Member); Jinjuan She (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, University of Akron, 2024, Polymer Science

Atactic-poly(acrylonitrile) (PAN) is an industrially important polymer material because it is used as a significant precursor for carbon fiber (CF).In CF production, three important heating steps are involved: stabilization, carbonization, and graphitization of wet-spun fiber under tension and different atmospheres. Among them, the initial stabilization process is the most important, as it sets a further high-temperature tolerable structure and thus significantly influences the final mechanical properties of CFs. Therefore, many characterization techniques, including thermal, spectroscopic, scattering, and morphological analyses, have been used to understand complex chemical reactions and stabilized structures of PAN. Even nowadays, the stabilization process is not sufficiently understood due to the difficulty of characterization in solid products which are insoluble in solvents. Our group has recently improved spectral resolution and sensitivity in the solid-state NMR spectrum by combining 13C selective and multiple isotope labeling with state-of-the-art solid-state (ss) NMR techniques. In this dissertation, ssNMR spectroscopy combined with the 13C selective isotope labeling method is used to quantitatively analyze the chemical structures and reactions of PAN and polyacrylonitrile-co-itaconic acid (PAI) with 1mol% itaconic acid (IA) and PAI with 3mol% IA during the stabilization process. First, we investigate the spatial heterogeneity of the chemical reactions in PAN. It is found that both 13C direct polarization magic angle spinning NMR spectra and 1H spin-lattice relaxation time in the laboratory frame (T1H) of the stabilized 13C labeled aPAN films highly depend on the film thickness, which is attributed to different chemical reaction mechanisms at the surface and inner cores due to a limited oxygen diffusivity. For the first time, tunable T1H filtered 2D 13C–13C INADEQUATE NMR selectively observed either the well-stabilized aPAN at the surface or poorly st (open full item for complete abstract)

Committee: Toshikazu Miyoshi (Advisor); Tianbo Liu (Committee Chair); Chunming Liu (Committee Member); Yu Zhu (Committee Member); Mesfin Tsige (Committee Member) Subjects: Chemistry; Materials Science; Physics

Doctor of Philosophy, Case Western Reserve University, 2024, Biology

Adaptive behaviors are critical to animals' survival. The nervous system supports the generation of appropriate behaviors in response to different environments by encoding sensory inputs, integrating and filtering the signals, and producing the appropriate motor outputs. In Aplysia californica, the feeding behaviors are adaptive to food varying in shape, toughness and edibility. A study of the neural circuitry modulating different feeding modes elucidates the functional role of individual neurons and the interaction, coordination and structural organization of the neural network. The multi-action neurons B4/B5 are interneurons in the buccal ganglia that produce different feeding patterns in Aplysia. They have a wide inhibitory effect on multiple key motor neurons and play an important role in rejection behaviors. Previous studies also suggest that they have potential sensory and motor functions. However, these functions are not fully characterized. In this dissertation, we further investigated the sensory and motor functions of the B4/B5 neurons, focusing on the receptive fields of the sensory function and the force generation of the motor function. We also analyzed the behavioral implications related to their ability to transmit signals in both directions. To control the activity in the B4/B5 neurons, we tested a novel technology, carbon fiber electrodes, for its ability to be used intracellularly in a moving system. We then developed a new protocol to adopt this technology to a reduced preparation, making it possible to manipulate individual neurons while monitoring the feeding behaviors. We then controlled the activity in B4/B5 using carbon fiber electrodes and analyzed their impact on the feeding behaviors. The study on the multi-action neurons B4/B5 helps us to understand how adaptive behaviors could be regulated through the multifunctionality of individual neurons. The ability to manipulate neural activity during feeding behaviors also sheds light on ho (open full item for complete abstract)

Committee: Hillel Chiel (Advisor); Hillel Chiel (Committee Chair); Peter Thomas (Committee Member); Gabriella Wolff (Committee Member); Jessica Fox (Committee Member) Subjects: Biology; Neurobiology

Master of Science in Mechanical Engineering, Cleveland State University, 2023, Washkewicz College of Engineering

This research investigates the deformation recovery of 3D-printed Polylactic Acid (PLA) shape memory polymers (SMPs). The study delves into the influence of Fused Deposition Modelling (FDM) parameters, such as nozzle temperature, layer thickness, and printing speed, on the thermomechanical behavior of PLA SMP honeycomb structures. The research identifies optimal printing conditions using the Taguchi approach and explores the cyclic shape memory recovery behavior of the optimized PLA SMP under compression loads. Additionally, the research includes a chapter on the extrusion and printing of uniform-diameter polylactic acid carbon fiber (CFR-PLA) composite filaments. The synthesis of CFR-PLA involves planetary ball milling for composite homogeneity. Extrusion parameters and 3D printing conditions are optimized, and mechanical testing, particularly tensile testing, reveals the composite's strength and flexibility. Fracture surface analysis highlights the behavior of carbon fibers during testing. Altogether, these results advance our understanding of PLA shape memory polymers and CFR-PLA composites, offering insights into material properties, printing parameters, and potential applications in various industries, including robotics, aerospace, and biomedicine.

Committee: Dr. Prabaha Sikder (Advisor); Dr. Mustafa Usta (Committee Member); Dr. Josiah S Owusu Danquah (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2023, Arts and Sciences: Chemistry

Neuroinflammation, oxidative stress, and glutamatergic excitotoxicity are prevalent in several neurological disorders including stroke, substance abuse, and neurodegenerative diseases. Chemical compounds and biomolecules which can ameliorate those conditions are gaining interest for new treatments. Despite many advances in understanding brain anatomy and physiology, the underlying neuropathological mechanisms behind ischemic stroke are still poorly understood. The purine nucleosides adenosine and guanosine have been shown to exhibit neuroprotective behavior in both in vivo and ex vivo models of ischemia. However, real-time detection of guanosine sub-second signaling dynamics in the brain is not understood. Various techniques have been developed for the detection of guanosine in vivo and in in vitro. We have used fast-scan cyclic voltammetry (FSCV), a novel electrochemical technique for real-time detection of the neurochemical release in sub-second timescales at carbon-fiber microelectrodes (CFME). Previously our lab has observed a significant increase in the concentration of guanosine during ischemia with the help of FSCV, showing a neuroprotective effect in ischemia. Despite prior studies, it is still unknown how guanosine released during ischemia is impacted as the function of ischemic severity. Here, we have developed an ex vivo oxygen-glucose deprivation model to investigate the guanosine signaling changes as a function of ischemic severity. Characterization of three different ischemic conditions was studied: normoxia, mild ischemia, and severe ischemia with the help of an optically dissolved oxygen sensor. triphenyl tetrazolium chloride assay and immunohistochemical staining were used to validate these ischemic conditions. Overall, we have successfully developed and maintained three different ex vivo experimental ischemic condition.

Committee: Ashley Ross Ph.D. (Committee Chair); Ryan White Ph.D. (Committee Member); Anthony Grillo Ph.D. (Committee Member) Subjects: Analytical Chemistry

Doctor of Philosophy, The Ohio State University, 2023, Materials Science and Engineering

Rising concerns related to fuel consumption and greenhouse emissions are being addressed by the automotive industry through vehicle lightweighting. Hence to meet the stringent requirements for lightweighting, conventional steel body parts are being replaced with Al alloys, Mg alloys and composite materials. However, the use of dissimilar materials together poses a serious threat of galvanic corrosion leading to accelerated degradation of galvanically coupled body parts. Aiming to develop the automotive closure panels using carbon fiber reinforced plastics (CFRP) inner and an outer aluminum alloy sheet to replace what is now an all-steel design, corrosion studies are performed to determine effective qualification of materials. In the first part of this project, CFRP materials of two types, named as twill and random, coupled with aluminum alloys (AA) 6111 and 6022 in all combinations, are subjected to a Ford laboratory accelerated cyclic corrosion test (CETP: 00.00-L-467) and on-road testing with the help of OSU campus buses for a year. The ability of the laboratory accelerated test to predict the on-road corrosion behavior is assessed by comparing the material volume loss determined using optical profilometer, microscopic images of corroded regions, and measurements of galvanic currents of the coupons exposed to the cyclic test. Analysis of the test results indicated that the coupon combination AA6111 and CFRP-random exhibits the highest corrosion susceptibility whereas AA6022 coupled with CFRP-twill is least susceptible to galvanic corrosion among the combinations used in this study. In the second part of the study, electrochemical behavioral differences between CFRP-twill and -random contributing to the differences in activities when coupled to AA6xxx are evaluated. For this, a copper deposition technique was developed to quantify the extent of electrochemical activity and identify the exact location of electrochemically active sites on the CFRP. Optimization (open full item for complete abstract)

Committee: Gerald S. Frankel Dr. (Advisor); Narasi Sridhar Dr. (Committee Member); Jenifer Locke Dr. (Committee Member) Subjects: Atmosphere; Conservation; Energy; Engineering; Materials Science; Sustainability; Transportation

Doctor of Philosophy, The Ohio State University, 2023, Mechanical Engineering

As emission standards of passenger vehicles become more and more strict, automotive manufacturers are seeking lightweight solutions to increase vehicle's fuel economy. Fibrous reinforced polymers (FRPs) are known to have high strength to weight ratios, and thus, made them good candidates for the application in the automotive industry. FRP is a composite material made of a polymer matrix reinforced with fibers. The inhomogeneity, anisotropy, visco-elasticity/plasticity, mechanical degradation due to temperature/damage, brittleness characteristics of the unidirectional FRP composites bring challenges to determine mechanical responses both experimentally and numerically. In this dissertation, mechanical behavior of unidirectional carbon fiber reinforced polymer (CFRP) made of Toray T700S carbon fiber and G83-CM prepreg system is studied. Specimens are fabricated from 8-ply and 16-ply CFRP plates. An experimental series is performed including tension, compression, and shear coupon tests at various strain rates ranging from 0.001 to 1000 s-1. Anisotropy is studied by conducting tension, compression, and shear coupon tests in different fiber orientations. Thermal dependence of the material is investigated by performing coupon tests under temperatures ranging from 25 °C to 120 °C. CFRP has been found that loading in one direction can potentially lead to damage in other directions. Thus, coupled, and uncoupled damage testing is performed to characterize such behavior. Digital image correlation (DIC) is applied for deformation and strain measurement on the surface of the specimens. The coupon test data and damage test data are used to calibrate the deformation and damage sub-models of the constitutive material model, *MAT_COMPOSITE_TABULATED_PLASTICITY_DAMAGE, also called *MAT_213, in LS-DYNA. The deformation sub-model predicts elasto-plastic behavior, and it uses a strain-hardening-based orthotropic yield function with a non-associated flow rule extended from Tsai-Wu fail (open full item for complete abstract)

Committee: Amos Gilat (Advisor); Prasad Mokashi (Committee Member); Kelly Carney (Committee Member); Jeremy Seidt (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, University of Akron, 2023, Mechanical Engineering

The advancement of composite materials has led to remarkable high-strength and low-weight structures, leading to better fuel efficiency and fewer greenhouse gas emissions, making them a sustainable solution. However, even with the development of composites like carbon fiber reinforced polymers, challenges still exist in safely and efficiently integrating them into structures. The lack of reliable methods to join composites to metals has prevented their use in many structural applications. Even advances in joining technology with adhesives still present problems, as adhesive performance changes drastically with temperature. Furthermore, the damage to composites and adhesives is often unpredictable and challenging to detect. Without understanding how composites interact with other materials, there is room for potential catastrophe. This work investigates the design and characterization of composite and metal joints. The joints' failure characteristics are analyzed through finite element analysis and experimental testing, providing insight into relationships between geometry, temperature, surface preparation, and material properties. Methods to improve performance by implementing novel hybrid and bio-inspired patterned adhesives are introduced, and design considerations are established under extreme environments. Finally, machine learning is used to identify relationships between design parameters, strength, and failure mode. In the end, a framework for safely and efficiently integrating composites into structures is provided, helping establish design techniques to ensure optimal performance.

Committee: Kwek-Tze Tan (Advisor); Gregory Morscher (Committee Member); Patrick Wilber (Committee Member); Sadhan Jana (Committee Member); Xiaosheng Gao (Committee Member) Subjects: Mechanical Engineering

Master of Science in Engineering, Youngstown State University, 2022, Department of Mechanical, Industrial and Manufacturing Engineering

Fracture toughness of 3D printed carbon fiber composite material (Onyx – trademark of Markforged) have been investigated using ASTM recommended specimens and a homemade measuring device for crack tip opening displacement (CTOD) measurements. The measuring device, composed of an extender and an extensometer, was designed to accommodate a dedicated tensile testing extensometer to the ASTM requirements for CTOD measurement. After several design iterations the extender was manufactured using a fused filament deposition 3D printing technique. Kinematic analysis was performed to convert the experimentally obtained displacement values into CTOD values. To assess the accuracy of the fracture toughness measurements performed using the measuring device, 3D printed polylactic acid (PLA) samples have been initially tested. The average fracture toughness value for the PLA samples was 3.53 𝑀𝑃𝑎√𝑚 (standard deviation ± 0.26 𝑀𝑃𝑎√𝑚), which is like the values reported in literature for PLA samples 3D printed using the fused filament deposition technique. The carbon fiber composite fracture toughness samples have been printed from Onyx, which is a combination of chopped carbon fiber embedded into nylon filaments with carbon fiber inlayed into it. Two sets of samples have been printed from Onyx. The first set was printed with a used nozzle for the Onyx filament, and the second one was printed with a brand-new nozzle. The average fracture toughness for the first set of samples was 4.40 𝑀𝑃𝑎√𝑚 with a standard deviation of ± 0.22 𝑀𝑃𝑎√𝑚. For the second set, the average fracture toughness was 3.01 𝑀𝑃𝑎√𝑚 with a standard deviation of ± 0.07 𝑀𝑃𝑎√𝑚. The difference in fracture toughness is related to the printing conditions, which affected the Onyx/carbon fiber inlay ratio and the crack geometry. This research is an important stride in finding new ways to find mechanical

Committee: Virgil Solomon PhD (Advisor); Hazel Marie PhD (Committee Member); Jae Joong Ryu PhD (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering

Doctor of Philosophy in Materials Science and Engineering, Youngstown State University, 2022, Materials Science

Fiber metal laminates (FMLs) are high performance hybrid sandwich structures with composites in between metal plies. These structures were created with an intention to provide the best properties of both the metal and composites and handle high fatigue failure applications such as in the aerospace industry. The composites contain different types of reinforcement materials. Traditionally, the FMLs for the aerospace industry were made using a thermoset composite sandwiched in between different grades of aluminum, especially 2024-T3. The manufacturing also involved multiple laborious steps, tooling, and expensive machines such as autoclaves. Also, to accommodate holes or rivets in such structures, the FMLs were drilled, causing delamination. The objective of this study was to investigate additive manufacturing (AM) as a manufacturing method for addressing such issues. However, to achieve that, it is critical to understand if such a method is applicable to these specialized structures. To accomplish that, in this study two different additive manufacturing techniques were employed. One being Fused Filament Fabrication (FFF) for manufacturing the composites and the second being LPBF (Laser Powder Bed Fusion) for manufacturing the metal plies. Different configurations of the materials with stock 2024-T3 aluminum plies and 3D printed AlSi10Mg metal plies with 3D printed composites manufactured using a closed source printer, Markforged MarktwoTM which uses proprietary materials and an opensource printer, Prusa MK3 with glass fiber reinforced ABS composite were manufactured and tested. The results indicate that AM is a promising technology to pursue as an alternative manufacturing method for highly specialized hybrid structures such as FMLs.

Committee: Pedro Cortes PhD (Advisor); Virgil Solomon PhD (Committee Member); Stefan Moldovan PhD (Committee Member); Eric MacDonald PhD (Committee Member); Gonzalo Carrillo-Baeza PhD (Committee Member) Subjects: Aerospace Materials; Automotive Materials; Engineering; Materials Science