Doctor of Philosophy, The Ohio State University, 1986, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2011, Materials Science and Engineering

Improvements of the anode performances in Li-ions batteries are in demand to satisfy applications in transportation. In comparison with graphitic carbons, transition metal oxides as well as graphene can store over twice amount of lithium per gram. Recently, graphene-based anodes for Li-ion batteries are under extensive development. In this research, lithium storage characteristics in graphene oxide (GO), GO/Manganese acetate (GO/MnAc), GO/manganese oxide (GO/MnOx) composites and Nano Graphene Platelets (NGP) were studied. The prepared GO delivered reversible capacities of 706mAh/g with an average columbic efficiency of 87%. Reversible capacities of 533 mAh/g were observed for GO/MnAc composite. GO/MnOx nanocomposite thermal annealed at 400°C in inert atmosphere exhibited high reversible charge capacity of 798 mAh/g with an average columbic efficiency of 95% and capacity fade per cycle of 1.8%. The EIS spectra of discharge and charge profiles of GO and GO/MnOx composites were analyzed to investigate the kinetics evolution of electrode process at different stages of lithium storage.

Committee: Hong Huang PhD (Advisor); Daniel Young PhD (Committee Member); Chu Kuan-lun PhD (Committee Member); George Huang PhD (Other) Subjects: Alternative Energy; Automotive Materials; Chemistry; Energy; Engineering; Materials Science; Metallurgy; Nanotechnology

Doctor of Philosophy, The Ohio State University, 1987, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, University of Akron, 2008, Civil Engineering

Increasingly, carbon composite structures are being used in aerospace applications. Due to their high strength, high stiffness and low weight properties, they are good candidates for replacing many aerospace structures currently made out of aluminum or steel. Recently, many of the aircraft engine manufacturers have been developing new commercial jet engines which will use composite fan cases. Instead of using traditional composite layup techniques, these new fan cases will use a triaxially braided pattern, which improves case performance. The impact characteristics of composite materials for jet engine fan cases applications have been an important research topic, because federal regulations require that an engine case must be able to contain a blade and blade fragments during an engine blade out event. Once the impact characteristics of these triaxial braided materials are known, computer models can be developed to simulate a jet engine blade out event, thus reducing cost and time for development of these composite jet engine cases. The two main problems that have arisen in this area of research are that the material properties for these materials have not been fully determined, and computationally efficient computer models, which incorporate much of the micro-scale deformation and failure mechanisms, are not available. This research addressed some of the deficiencies present in previous research regarding these triaxial braided composite materials. This research developed new techniques to accurately quantify the material properties of the triaxial braided composite materials. New test methods were developed for the composite constituent, the polymer resin, and representative composite coupons. These methods expanded previous research by using novel specimen designs along with using a non-contact measuring system which was also capable of identifying and quantifying many of the micro-scale failure mechanisms present in the materials. Finally, using the data gathere (open full item for complete abstract)

Committee: Wieslaw Binienda PhD (Advisor) Subjects: Aerospace Materials; Civil Engineering; Engineering; Mechanical Engineering; Mechanics; Polymers

Master of Science, The Ohio State University, 2007, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2007, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2007, Graduate School

Committee: Not Provided (Other) Subjects:

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, 2019, Polymer Engineering Specialization

One type of stimuli-responsive actuator is a bending actuator, which is typically constructed by bonding together two materials with differential volumetric expansion or contraction under a stimulus e.g.solvent quality and temperature. In this dissertation, solvent and temperature sensitive polymer bilayer bending actuators were created in a facile and universal fabrication to scaling up without complicated synthesis and delicate technology. Solvent-responsive bilayer was produced by crosslinking poly(dimethylsiloxane) (PDMS) oligomers in terms of variable fabrication parameters through hydrosilylation. Before vulcanization, the base-tocrosslinker weight ratios determined a crosslinking extent or gel fraction and subsequently, dominated the equilibrium swelling ratio and linear swelling expansion ratio of PDMS rubbers. Except for the base-tocrosslinker weight ratios, the gel fraction of the bottom layer has a predominant impact of the bending extent of the bilayer in terms of the curing time of the bottom layer and deposition order of PDMS layers. The optimum bending degree of the bilayer was estimated by using a simulation model derived from Timoshenko's equation in the case of bimetallic thermostat. Ultimately, the calculated base-to-crosslinker weight ratio of the top layer of the bilayer was significantly corresponded to the experimental data. A different type of bilayer bending actuators with respect to temperature was presented. These temperature-activated actuators containing the phase-change materials would make it potential to detect latent heat in the nature and conduct the thermal-management. A self-contained thermal bending actuator based on a polymer bilayer where the actuation is driven by the expansion and contraction of paraffin wax undergoing solid-to-liquid phase transition. Bilayer films consisting of active, wax-containing polymer layer and passive, wax-free polymer layer were fabricated using commercially available polymers and a commercially (open full item for complete abstract)

Committee: Kevin Cavicchi (Advisor); Mark Soucek (Committee Member); Nicole Zacharia (Committee Member); Li Jia (Committee Member); Alper Buldum (Committee Member) Subjects: Materials Science; Polymer Chemistry; Polymers

Master of Science, Miami University, 0, Mechanical and Manufacturing Engineering

Enhanced performance and multi-functionality in an engineering structure can be achieved by designing composite materials and by tailoring or grading different materials along the structure. Structures can be graded in different directions, for example, along its length and/or thickness or in a radial direction. It is known that non-homogenous distribution of physical parameters (area, inertia, etc.) or material properties (density, modulus, etc.) along the structure can improve its static/dynamic performance and stability. However, axial grading of frequency and temperature dependent viscoelastic polymeric materials, which can contribute to enhanced vibration performance, is not well studied. Therefore, the purpose of this research is to study the axial grading of viscoelastic polymers along the span of the structure to manipulate their spectral characteristics (natural frequency, damping, vibration amplitude, etc.). To this end, piecewise continuous models for axially graded beams are developed and analytical solutions for spectral characteristics are obtained and compared with an associated finite element model. Axially graded beams were fabricated and assembled using 3D printing. Their vibration characteristics were obtained by modal vibration testing and they were validated against the prediction from the model. It is also shown through simulations that optimal grading configurations can be achieved for desired performance metrics.

Committee: Kumar Singh (Advisor); Fazeel Khan (Advisor); Giancarlo Corti (Committee Member) Subjects: Mechanical Engineering

Master of Sciences (Engineering), Case Western Reserve University, 2018, Materials Science and Engineering

The effects of temperature, strain rate, and strain on densification and hardness of direct powder forged metal matrix composites was analyzed. Manufactured by Materion Brush, the MMCs were premixed, mechanically-alloyed, agglomerate powders of Al6061/20%/SiCp/0.7µm and Al6061/40%/SiCp/3.0µm. Open-die direct powder forging was conducted on 80% relative density, green powder compacts under temperatures ranging from 475 to 550 oC, with strain rates from 0.001/s to 0.1/s, and strain levels from -0.16 to -1.51 true strain. Flow stress increased with a decrease in temperature or increase in reinforcement volume fraction and exhibits little softening under the conditions tested in this study. Relative density values up to 97% were achieved in the center region of the ~38 mm diameter DPF billet, requiring forging loads of less than 50 kN, ~15 times lower than unreinforced aluminum in a closed die. Within the chosen range of temperatures and strain rates, strain was determined to have the largest effect on densification. Vickers microhardness show the strongest correlation with density and increases with true strain.

Committee: Matthew Willard (Advisor); John Lewandowski (Advisor); Sunniva Collins (Committee Member) Subjects: Aerospace Materials; Materials Science; Metallurgy

Master of Science, The Ohio State University, 2017, Mechanical Engineering

The forming of composite materials may lead to fiber angle change during the deformation. The change of fiber orientations can lead to changes in mechanical properties of the composite material. Therefore, it is important to know the changes of the fiber orientations in order to calculate effective material properties of the material. The constitutive model for obtaining properties of the composite material has been investigated in this study. Zampaloni originally developed the preferred fiber orientation (PFO) model in his PhD study, in which he tracked the fiber orientation during the composite forming process. He showed that PFO model gives more accurate results compared with the Abaqus/CAE model. The simple tension and shear tests were studied with both Abaqus simulation software, and analytical calculations. Results from both models were compared, and it was shown that compared with Abaqus, the PFO model tracks the fiber angle correctly. The stamping of a hat shape section was also simulated with the PFO model and simulation results were compared with experiments. A good agreement between simulation results and experimental results were obtained, which suggests that the PFO model can predict fiber angle change correctly, and its results are closer to the real forming situation.

Committee: Farhang Pourboghrat (Advisor) Subjects: Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2017, Materials Engineering

In practice, adjacent preform sandwich cores are joined with a simple butt joint without special precautions. When molded, this gap is filled with resin and creates a resin rich area. Stress risers will be amplified under cyclic load, and consequently, the serviceability of the structure will be affected. Designers and researchers are aware of this problem; however, quantifying this effect and its intensity and consequence on the service life of the structures has not yet been developed. Despite pervious findings, limited experimental data backed by a comprehensive root cause failure analysis is available for sandwich under axial static, fatigue and post-fatigue. If such a comprehensive experimental characterization is conducted, specifically understanding the nature of the damage, intensity, and residual strength, then a valid multi-scale damage model could be generated to predict the material state and fatigue life of similar composite structures with/without core joints under in-plane static and fatigue load. This research study characterized the effect of scarf and butt core joints in foam core sandwich structures under in-plane static and fatigue loads (R=0.1 and R= -1). Post-Fatigue tensile tests were also performed to predict the residual strength of such structures. Nondestructive Evaluation Techniques were used to locate the stress concentrations and damage creation. A logical blend of experimental and analytical prediction of the service life of composite sandwich structures is carried out. The testing protocol and the S-N curves provided in this work could be reproducible and extrapolated to any kind of core material. This research study will benefit composite engineers and joint designers in both academia and industry to better apprehend the influence of core joints and its consequence on the functionality of sandwich structures.

Committee: Elias Toubia (Advisor); Paul Murray (Committee Member); Thomas Whitney (Committee Member); Youssef Raffoul (Committee Member) Subjects: Aerospace Engineering; Aerospace Materials; Civil Engineering; Composition; Design; Engineering; Materials Science; Mechanical Engineering; Polymers

Doctor of Philosophy, The Ohio State University, 1986, Graduate School

Committee: Not Provided (Other) Subjects: Physics

Doctor of Philosophy, The Ohio State University, 1972, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, University of Akron, 2014, Mechanical Engineering

The exceptional mechanical (stiffness, strength, etc.) and physical (density, thermal stability, etc.) properties of engineered composite materials make them an excellent candidate for aerospace applications. However, damage development in composites is much different than that of traditionally used materials and is usually very complicated. With the aim at better understanding the damage initiation, development and accumulation in composite materials, various ceramic fiber reinforced ceramics and carbon fiber reinforced polymers were tested and various non-destructive evaluation (NDE) techniques were investigated. Tensile, low cycle fatigue, and high velocity impact damage scenarios were all investigated. Multi-scale models of damage accumulation were developed and implemented and show reasonable agreement with experimental results.

Committee: Gregory Morscher Dr. (Advisor); Tirumalai Srivatsan Dr. (Committee Member); Jon Gerhardt Dr. (Committee Member); Kevin Kreider Dr. (Committee Member); Craig Menzemer Dr. (Committee Member); Andrew Gyekemyesi Dr. (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2013, Civil Engineering

Material system selection for primary structures requires a decision matrix that evaluates not only the initial design but also the full lifecycle economy. The ability to economically repair structural components over time may control initial design decisions, especially for structures tat are routinely repaired such as aircraft components. Composite materials in their virgin condition often provide substantial mechanical and environmental advantages over metals. However, the repair of composite materials has historically been more costly, time-consuming, and mechanically conservative than metallic repair, and thus is a barrier in the continued advancement of their use. The state of the art of composite repair analysis and substantiation in practice is often limited to simplified and conservative methodologies. While these methods of analysis may be acceptable for secondary or tertiary composite structures, the advancement in analysis of repair for primary composite structures must advance in order for composite materials to become a material system of choice. The state of the art of composite repair analysis and substantiation in published theory has advanced to include displacement-based, nonlinear, and fully three-dimensional finite element models; however, these current models also include geometric, loading, and material model simplifications and limitations that inhibit their general application. Given these limitations, the effective and optimal use of composite materials for primary structures over their complete lifecycle, fully developing the capabilities of their advantages over other material systems, is limited. The research herein documents the development of a composite repair model to advance the state of the art by addressing some of the limitations found in the current literature. A constitutive formulation based on a stress-based laminated plate theory was implemented through a finite element numerical solution algorithm to model the stre (open full item for complete abstract)

Committee: William Wolfe (Advisor); Tarunjit Butalia (Advisor); Ethan Kubatko (Committee Member); Gregory Schoeppner (Committee Member); Dean Foster (Committee Member) Subjects: Aerospace Engineering; Civil Engineering; Mechanical Engineering; Mechanics

Master of Science in Chemistry, Youngstown State University, 2010, Department of Chemistry

Fireline TCON, Inc., a ceramics company in Youngstown, Ohio, has developed a unique method for producing co-continuous ceramic/metallic composite materials. These TCON composite materials are usually produced from a reaction of silica with molten aluminum via a process known as reactive metal penetration, producing an interpenetrating phase composite of aluminum oxide and aluminum metal, where silicon is alloyed with aluminum in the metal phase. These composite materials have a variety of interesting properties, such as extremely high tolerance of heat, resistance to corrosion, and high strength. Theoretically, the TCON process can be altered in order to utilize a wide variety of metal oxides other than silica as sacrificial oxides. A class of compounds known as β-aluminas are of particular interest, as these compounds contain open channels within their crystal structure, which may facilitate the TCON reaction or produce a TCON composite with different morphology and properties than have previously been reported. Specifically, the possibility of producing a nano-scale composite is being investigated, due to the nano-scale features of the β-alumina crystalline structure itself. Several different β-alumina compounds have been prepared and transformed via the TCON process. Phases present in the product were analyzed via PXRD, and the morphology of the composite was analyzed via SEM. Several related spinel phases were prepared and transformed for comparison to results for transformed β-alumina. In addition, attempts have been made to produce novel β-alumina structures that would be beneficial as sacrificial oxides in the TCON process. Novel compounds such as SrTi5Mg6O17 that would transform under TCON conditions would result in a number of beneficial properties in the produced composite. These benefits include the presence of aluminum-titanium alloys, which have excellent strength-to-weight ratios.

Committee: Tim Wagner PhD (Advisor); Virgil Solomon PhD (Committee Member); Clovis Linkous PhD (Committee Member) Subjects: Chemistry; Inorganic Chemistry; Materials Science

MS, University of Cincinnati, 2009, Engineering : Aerospace Engineering

Fiber composite materials are ideal engineered materials to carry loads and stresses in the fiber direction due to their high in-plane specific mechanical properties. However, premature failure due to low transverse mechanical properties constitutes a fundamental weakness of composites. A solution to this problem is being addressed through the creation of a nano-reinforced laminated composite (NRLC) materials where carbon nanotubes (CNTs) are grown on the surface of the fiber filaments to improve the matrix-dominated properties. The carbon nanotubes increase the effective diameter of the fiber and provide a much larger interface area for the polymeric matrix to wet the fiber. The objective of this thesis work is to numerically predict the elastic properties of these nano-reinforced fiber composites. Finite Element Method (FEM) is used to evaluate the effective mechanical properties employing a 2D and 3D cylindrical representative volume element (RVE) based on multiscale modeling approach. In continuum mechanics, perfect bonding is assumed between the carbon fiber and the polymer matrix and between the carbon nanotubes and the polymer matrix. In the multiscale modeling approach in this work, cohesive zone approach is employed to model the interface between carbon fiber and polymer matrix and between the CNTs and the polymer matrix. Traction-displacement plots obtained from molecular dynamics simulations are used to derive the constitutive properties of the cohesive zone material model used for CNT-Polymer interface. For NRLC, the cohesive zone material model properties are assumed based on the information found in the literature. Effective material constants are extracted from the solutions of the RVE for different loading cases using theory of elasticity of isotropic and transversely isotropic materials. Experimental mechanical characterization data is used for correlation and validation of numerical results. It is observed that the cohesive zone material model is c (open full item for complete abstract)

Committee: Jandro Abot PhD (Committee Chair); Ala Tabiei PhD (Committee Member); Dong Qian PhD (Committee Member) Subjects: Aerospace Materials; Engineering; Materials Science; Mechanics

PhD, University of Cincinnati, 2007, Engineering : Aerospace Engineering

The design and development of high performance turbomachinery operating in both ambient and high temperature environment in the presence of solid particles requires a thorough knowledge of the fundamental phenomena associated with particulate flow. Because of the serious consequences of turbomachinery erosion on their performance and life expectancy, it is important to have reliable methods for predicting their erosion when solid particles are ingested with the incoming flow. The ingestion of these solid particles over a period of time will reduce the efficiency of the propulsion system, causing increased fuel consumption and reduction in performance and thrust. Many studies, essential to predicting blade surface erosion intensity and pattern, have been conducted at the University of Cincinnati's Propulsion Laboratory in the past. The studies and experiments at the (UC) laboratory were performed in order to obtain a better understanding and a more realistic prediction of erosion rates of various conventional materials and coatings, while varying impingement angle, particle velocity, particle concentration, particle size, temperature and other important erosion parameters. Solid particle erosion is a complicated process which becomes even more complicated when it comes to composite material structures. In composite materials the mechanisms of erosion are complex, difficult to determine and even more difficult to predict due to the non-homogeneity of the material. Attempts were made to understand some of the basic mechanisms of erosion as early as the beginning of the (20th) century and continue even today. Over the years most of the attention of scientists was concentrated toward understanding the mechanisms occurring in conventional materials. However, due to the growing potential of composite materials and their desirable properties, they became a more focal point of interest.

Committee: Dr. Widen Tabakoff (Advisor) Subjects: Engineering, Aerospace