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Venkatasubramanian, Rajiv. "Composite Nanoparticle Materials for Electromagnetics." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352993374.
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Beglinger, Jarrod (Jarrod Thomas) 1976. "Forming of advanced composite materials." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/31077.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998.Includes bibliographical references (p. 45).
Two significant aspects of advanced composite material forming are examined. First, the fiber deformation of aligned fiber composites formed to double curvature parts is analyzed. Aligned fiber composite lay-ups were formed over hemispherical tools and the fiber deformation was mapped. The data were intended to support the model which predicts trellising of composite fibers in double curvature. The data are, in general, too ambiguous to clearly support this model. Second, springback of woven fiber material-single curvature parts is investigated. A 90° bend was formed for varying laminate lay-ups at varying temperatures via a double diaphragm process. Principal objectives were to qualify the effects of varying lay-ups and temperatures on the net amount of springback observed. The data show that 0/90 woven lay-ups experience more springback than either +45 degree or quasi-isotropic woven lay-ups, and that heating the laminates marginally decreases the springback experienced.
by Jarrod Beglinger.
S.B.
3
Baker, Christopher R. "Assessing Damage in Composite Materials." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1390315001.
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RICHARD, DEEPAK. "LIFECYCLE PERFORMANCE MODEL FOR COMPOSITE MATERIALS IN CIVIL ENGINEERING." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1069787827.
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Shirolkar, Ajay. "A Nano-composite for Cardiovascular Tissue Engineering." Thesis, California State University, Long Beach, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10840053.
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Cardiovascular disease (CVD) is one of the largest epidemic in the world causing 800,000 annual deaths in the U.S alone and 15 million deaths worldwide. After a myocardial infarction, commonly known as a heart attack, the cells around the infarct area get deprived of oxygen and die resulting in scar tissue formation and subsequent arrhythmic beating of the heart. Due to the inability of cardiomyocytes to differentiate, the chances of recurrence of an infarction are tremendous. Research has shown that recurrence lead to death within 2 years in 10% of the cases and within 10 years in 50% of the cases. Therefore, an external structure is needed to support cardiomyocyte growth and bring the heart back to proper functioning. Current research shows that composite materials coupled with nanotechnology, a material where one of its dimension is less than or equal to 100nm, has very high potential in becoming a successful alternative treatment for end stage heart failure. The main goal of this research is to develop a composite material that will act as a scaffold to help externally cultured cardiomyocytes grow in the infarct area of the heart. The composite will consist of a poly-lactic co glycolic acid (PLGA) matrix, reinforced with carbon nanotubes. Prior research has been conducted with this same composite, however the significance of the composite developed in this research is that the nanotubes will be aligned with the help of an electro-magnetic field. This alignment is proposed to promote mechanical strength and significantly enhance proliferation and adhesion of the cardiomyocytes.
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Charles-Harris, Ferrer Montserrat. "Development and Characterisation of Completely Degradable Composite Tissue Engineering Scaffolds." Doctoral thesis, Universitat Politècnica de Catalunya, 2007. http://hdl.handle.net/10803/6054.
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The field of Tissue Engineering has developed in response to the shortcomings associated to the replacement of tissues lost to disease or trauma: donor tissue rejection, chronic inflammation, and donor tissue shortages. The driving force behind Tissue Engineering is to avoid these problems by creating biological substitutes capable of replacing the damaged tissue. This is done by combining scaffolds, cells and signals in order to create living, physiological, three-dimensional tissues.Scaffolds are porous biodegradable structures that are meant to be colonised by cells and degrade in time with tissue generation. Scaffold design and development is mainly an engineering challenge, and is the goal of this PhD thesis.
The main aim of this thesis is to develop and characterise scaffolds for Tissue Engineering applications. Specifically, its objectives are:
1. To study, optimise and characterise two scaffold processing methods: Solvent Casting and Phase Separation. This is done by experiment design analysis.
2. To characterise the degradation, surface properties, and cellular behaviour of the scaffolds produced.
The scaffolds are made of a composite of polylactic acid polymer and a calcium phosphate soluble glass. The comparison of the two processing methods reveals that in general, the solvent cast scaffolds have higher porosities and lower mechanical properties than the phase-separated ones. Two compositions containing 20 weight % and 50 weight % of glass particles were chosen for further characterisations including degradation, surface properties and cellular behaviour.
The degradation of the scaffolds was studied for a period of 10 weeks. The evolution of various parameters such as: morphology, weight loss, mechanical properties, thermal transitions and porosity, was monitored. Scaffolds produced via solvent casting were found to be more severely affected by degradation than phase-separated ones.
The surface properties of the scaffolds were measured by modelling the scaffold pore walls as thin composite films. The morphology, topography, surface energy and protein adsorption of the films was characterised thoroughly. Again, the processing method was critical in determining scaffold properties. Films made via phase-separation processing had markedly different properties due to extensive coating of the glass particles by the polymer. This made the surfaces rougher and more hydrophobic. When the glass particles are not completely coated with polymer, they increase the material's hydrophilic and protein adsorption properties, thus confirming the potential biological benefits of the inclusion of the calcium phosphate glass.
The biological behaviour of the scaffolds was characterised by means of in vitro cell cultures with primary osteoblast stem cells and cells from a stable cell line, under static and dynamic conditions. Their morphology, proliferation and differentiation were monitored. Both types of scaffolds sustained osteblastic cell growth. The solvent cast scaffolds were easily colonised by cells which migrated throughout their structure. The cells on the phase-separated scaffolds, however, tended to form thick layers on the scaffold surface.
Finally, an alternative characterisation technique was explored applying Synchrotron X-Ray Microtomography and in-situ micromechanical testing. These experiments allowed for the qualitative and quantitative analysis of the microstructure of the scaffolds both at rest and under strain. A finite element model of the solvent cast scaffolds was developed and a preliminary analysis was performed. This technique could be used to complement and overcome some of the limitations of traditional mechanical characterisation of these highly porous materials.
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Lee, Jinwook 1966. "Semiconductor nanocrystal composite materials and devices." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8039.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002.Includes bibliographical references.
This thesis describes the synthesis and characterization of semiconductor nanocrystal (quantum dot, QD) embedded composite materials and possible device applications of the resulting luminescent materials. Chemically synthesized ZnS overcoated CdSe, (CdSe)ZnS, QDs are incorporated into a polymer host material. The main challenge in the preparation of QD-polymer composites is the prevention of both phase separation and aggregation of the QDs within the polymer host material, while sustaining the original quantum efficiency of the QDs in their growth solution. Possible ways to incorporate QDs into an optically clear polymer matrix are considered. A guideline for a successful QD-polymer composite is discussed for various polymer systems: ligand polymers, ligand monomer and covalent bonding to a polymer matrix, and in-situ polymerization. The best composite system is based on incorporation of QDs into a poly(laurylmethacrylate) matrix during in-situ polymerization in the presence of TOP ligands. The successful incorporation of QDs into a polymer host material demonstrates the ability to form QD-polymer composite light emitting materials. The emission spans nearly the entire region of saturated and mixed colors with narrow emission profiles. The light emission spectra of QD-polymer composites excited by a blue diode light are also simulated by Monte Carlo methods and compared to the measured spectra from actual devices. The synthesis and characterization of QD-microspheres, which can be used as active fluorescent building blocks, are also described.
(cont.) In order to enhance the stability and compatibility of QDs in a polymer microsphere, the QDs are treated with polymerizable phosphine ligands, small oligomeric phosphine methacrylate (SOPM), and the following homogeneous solution polymerization is investigated to form monodisperse QD-microspheres. The QD-microspheres can store optical information assigned by embedded QDs in multiple codes. The surface functionalization of these capsules could provide a means for attaching capsules to surfaces and allow capsules to assemble into 3D structures.
by Jinwook Lee.
Ph.D.
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Mihai, Iulia. "Micromechanical constitutive models for cementitious composite materials." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/24624/.
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A micromechanical constitutive model for concrete is proposed in which microcrack initiation, in the interfacial transition zone between aggregate particles and cement matrix, is governed by an exterior-point Eshelby solution. The model assumes a two-phase elastic composite, derived from an Eshelby solution and the Mori-Tanaka homogenization method, to which circular microcracks are added. A multi-component rough crack contact model is employed to simulate normal and shear behaviour of rough microcrack surfaces. It is shown, based on numerical predictions of uniaxial, biaxial and triaxial behaviour that the model captures key characteristics of concrete behaviour. An important aspect of the approach taken in this work is the adherence to a mechanistic modelling philosophy. In this regard the model is distinctly more rigorously mechanistic than its more phenomenological predecessors. Following this philosophy, a new more comprehensive crack-plane model is described which could be applied to crack-planes in the above model. In this model the crack surface is idealised as a series of conical teeth and corresponding recesses of variable height and slope. Based on this geometrical characterization, an effective contact function is derived to relate the contact stresses on the sides of the teeth to the net crack-plane stresses. Plastic embedment and frictional sliding are simulated using a local plasticity model in which the plastic surfaces are expressed in terms of the contact surface function. Numerical simulations of several direct shear tests indicate a good performance of the model. The incorporation of this crack-plane model in the overall constitutive model is the next step in the development of the latter. Computational aspects such as contact related numerical instability and accuracy of spherical integration rules employed in the constitutive model are also discussed. A smoothed contact state function is proposed to remove spurious contact chatter behaviour at a constitutive level. Finally, an initial assessment of the performance of the micromechanical model when implemented in a finite element program is presented. This evaluation clearly demonstrates the capability of the proposed model to simulate the behaviour of plain and reinforced concrete structural elements as well as demonstrating the potential of the micromechanical approach to achieve a robust and comprehensive model for concrete.
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Sambasivam, Shamala. "Thermoelastic stress analysis of laminated composite materials." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/72144/.
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In this work thermoelastic stress analysis (TSA) is used to obtain quantitative stress/ strain data from a variety of multi-directional laminated composites. In order to in- terpret the thermoelastic signal correctly the source of the thermoeleastic response has been investigated in detail. In this thesis four possible routines to extract quantitative stress/strain information from thermoelastic data have been explored. A set of carefully selected glass/epoxy composite specimens with designated stacking sequences provided a scheme to identify the source and nature of the thermoelastic response. All of the material properties of the composite laminate were obtained experimentally, to aid an accurate assessment of each routine. The variation in the stress experienced by the laminate in the surface resin layer and ply by ply there after leads to large variations in the temperature change through the thickness. The thermoelastic measurements from dierent laminates revealed a local non-adiabatic condition within the layered medium. Therefore, the implication of applied loading frequency on the heat conduction properties of the laminates was studied. Based on the experimental observation from a representa- tive specimen, numerical models have been developed to understand the nature of the heat transfer in the glass/ epoxy material considered in this work. An analysis of the eect of holes in a variety of laminated components is presented to provide stress concen- tration factors (SCF's) based on TSA data. The conventional, orthotropic surface ply model most often used for thermoelastic stress analysis of composite material is revisited in order to elucidate the invariant nature of the equation. This is an important base for the analysis of structures which are better notated in coordinate system other than Cartesian, or as ratio of thermoelastic measurements in two dierent coordinate systems. The nature of the thermoelastic response in the presence of the in-plane stress gradient is investigated with the aid of numerical and analytical models. An introductory work for quantifying the SCF's around pin-loaded holes in laminated composite based on TSA measurements is also presented. The work presented in this thesis provides a step forward in the application of TSA to the composite materials in a quantitative manner.
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Shokrieh, Mahmood M. (Mahmood Mehrdad). "Progressive fatigue damage modeling of composite materials." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40253.
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A modeling technique for simulating the fatigue behaviour of laminated composite materials with or without stress concentrations, called progressive fatigue damage modeling, is established. The model is capable of simulating the residual stiffness, residual strength and fatigue life of composite laminates with arbitrary geometry and stacking sequence under complicated fatigue loading conditions.The model is an integration of three major components: stress analysis, failure analysis, and material property degradation rules. A three-dimensional, nonlinear, finite element technique is developed for the stress analysis. By using a large number of elements near the edge of the hole and at layer interfaces, the edge effect has been accounted for. Each element is considered to be an orthotropic material under multiaxial state of stress. Based on the three-dimensional state of stress of each element, different failure modes of unidirectional ply under multiaxial states of stress are detected by a set of fatigue failure criteria. An analytical technique, called the generalized residual material property degradation technique, is established to degrade the material properties of failed elements. This analytical technique removes the restriction of the application of failure criteria to limited applied stress ratios. Based on the model, a computer code is developed that simulates cycle-by-cycle behaviour of composite laminates under fatigue loading.
As the input for the model, the material properties (residual stiffness, residual strength and fatigue life) of unidirectional AS4/3501-6 graphite/epoxy material are fully characterized under tension and compression, for fiber and matrix directions, and under in-plane and out-of-plane shear in static and fatigue loading conditions. An extensive experimental program, by using standard experimental techniques, is performed for this purpose. Some of the existing standard testing methods are necessarily modified and improved. To validate the generalized residual material property degradation technique, fatigue behaviour of a 30-degrees off-axis specimen under uniaxial fatigue loading is simulated. The results of an experimental program conducted on 30-degrees off-axis specimens under uniaxial fatigue show a very good correlation with the analytical results. To evaluate the progressive fatigue damage model, fatigue behaviour of pin/bolt-loaded composite laminates is simulated as a very complicated example. The model is validated by conducting an experimental program on pin/bolt-loaded composite laminates and by experimental results from other authors. The comparison between the analytical results and the experiments shows the successful simulation capability of the model.
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Faulk, Joanna (Joanna E. ). "Composite materials in dynamic shipboard structural mounts." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68837.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 18).
The purpose of this thesis is to investigate the viability of replacing traditional metal structural and machinery mounts with padding made of composite material. The two types of padding or isolation materials are represented by steel and CFRP (carbon fiber reinforced polymer). Machinery and instruments in ships are often mounted for two main reasons: they create unwanted vibrations and they need to be isolated from shock and external vibration. In order to analyze this problem, the machinery or instrument plus its padding are modeled as a mass-spring-damper system. The results show that CFRP generally works better for vibration isolation, while steel works better for shock isolation.
by Joanna Faulk.
S.B.
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Del, Pozo León Freddy G. "Coating engineering of composite materials for organic field-effect transistors." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/284993.
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Esta tesis describe el desarrollo de una tecnología para depositar películas delgadas de polímeros aislantes y materiales compuestos, para aplicaciones en transistores orgánicos de efecto de campo (OFETs). Los materiales compuestos se componen de un semiconductor y un aislante. El aislante es el aglutinante y el semiconductor el material activo. Los materiales activos son polímeros o moléculas pequeñas. Los aglutinantes son estirenos, metacrilatos o combinaciones de ambos. A fin de demostrar las capacidades de la tecnología desarrollada, nombrada Bar Assisted Meniscus Shearing (BAMS), películas delgadas de poliestireno sobre Si/SiOx fueron depositadas, espesores típicos en el intervalo de 50 a 80 nm se encontraron, también valores de RMS en el rango de 0,5 a 0,6 nm fueron determinados, y confirma que películas muy lisas fueron formadas con aplicación tentativa a dieléctricos. Poli (3-hexiltiofeno) (P3HT) es ampliamente utilizado en transistores orgánicos de efecto de campo. Materiales compuestos basados en P3HT y poliestireno fueron probados. OFETs basados en materiales compuestos que sólo utilizan un 10% del material activo (P3HT) mostraron una movilidad de 0,1 cm2V-1s-1 y dicho valor coincide con el valor máximo de mobilidad reportado en literatura hasta la fecha para P3HT puro. Es importante destacar que todos los OFETs fabricados por BAMS usando materiales compuestos tienen voltajes de umbral alrededor de cero voltios a pesar de que toda la fabricación y caracterización se llevo a cabo en aire. Los semiconductores poliméricos juegan un papel muy importante dentro de los semiconductores orgánicos, debido a su ventaja de la capacidad de procesamiento. Por otra parte, las moléculas pequeñas carecen de procesabilidad pero en general poseen una alta mobilidad. Así, materiales compuestos se han desarrollaron para añadir procesabilidad a las pequeñas moléculas, pero tratando de mantener una alta mobilidad. Derivados del TTF, dibenzo - tetratiafulvaleno (DB-TTF), ditiofeno - tetratiafulvaleno (DT-TTF) y bis (etylenetio) - tetratiafulvaleno (BET-TTF) fueron las tres moléculas pequeñas investigadas. En primer lugar, películas térmicamente evaporadas de DB-TTF y BET-TTF puros fueron investigadas y su estabilidad en aire evaluada, se encontró que ambos son extremadamente inestables en presencia de oxígeno y agua. La inclusión de BAMs ha demostrado ser eficaz para producir OFETs basados en materiales compuestos. En primer lugar, se investigaron mezclas de poli (-metil-estireno) (PAMS), y DB-TTF. Los OFETs fabricados muestran estabilidad en aire y características de salida y de transferencia como las de un libro de texto, todas con mobilidades aceptables en el rango de 10-3 cm2V-1s-1. También OFETs a base de poliestireno isotáctico y DB-TTF se investigaron y mobilidades en el intervalo de 10-2 cm2V-1s-1 fueron encontradas. Además, una investigación de composiciones para los materiales compuestos se llevo a cabo, variando relaciones de mezcla y el peso molecular del poliestireno. Dicha investigación reveló que la mejor combinación es la relación de DB-TTF y poliestireno para GPC 3000 (PS3000) en una proporción 1: 2. Después de un estudio a fondo se obtuvo una mobilidad promedio para tal mezcla en el rango de 10-1 cm2V-1s-1 y tensiones umbrales cercanas a cero voltios, sin embargo vale la pena destacar que valores de mobilidad tan altos como 0.7 cm2V-1s-1 fueron encontrados. Medidas en función de la temperatura fueron llevadas a cabo y revelaron que el transporte de carga para estos dispositivos (DB-TTF: PS3000 1: 2) apuntan hacia una movilidad independiente de la temperatura, que correctos a nuestro saber y entender es el primer semiconductor orgánico procesado en solución que exhibe tal comportamiento. Otro comportamiento digno de resaltar fue el encontrado cuando los dispositivos constituyen inversores, ganancias tan altas como 300 fueron encontradas, lo que también a la actualidad es el valor de ganancia más alta para inversores orgánicos.This thesis describes the development of a technology to deposit thin films of insulating polymers and composite materials for applications in organic field-effect transistors (OFETs). Composite materials are comprised of a semiconductor and an insulator. The insulator is the binder and the semiconductor the active material. The active materials are either polymers or small molecules. Binders are styrenes, methacrylates or combinations of both. In order to first demonstrate the capabilities of the technology developed, namely Bar Assisted Meniscus Sheering (BAMs), thin films of polystyrene on Si/SiOx were deposited, typical thicknesses in the range of 50 to 80 nm were found, also RMS values in the range of 0.5 – 0.6 nm were found as well, and confirms very smooth films with tentative application as dielectrics. Poly-(3-hexylthiophene) (P3HT) is widely used is organic field-effect transistors. Composite materials comprised of P3HT and polystyrene were tested. OFETs fabricated based on composites which only use a 10 % of the active material exhibited a mobility of 0.1 cm2V-1s-1 such value match the maximum mobility value reported in literature to-date for pure P3HT. It is important to highlight that all OFETs fabricated by BAMS using based on the composites have threshold voltages around zero volts despite the fact that all fabrication and characterization were carried out in air. Polymeric semiconductors plays a very important role inside organic semiconductors, due to their advantage the processability. On the other hand, small-molecules lacks processability but in general possess high mobility than polymeric semiconductors. So, composite materials were devised to add processability to small-molecules, but trying to maintain high mobility. TTF derivatives, dibenzo - tetharthiafulvalene (DB-TTF), dithiophene - tetrathiafulvalene (DT-TTF) and bis(ethylenethio) – tetrathiafulvalene (BET-TTF) were the three small-molecules investigated. First, thermally evaporated films of pure DB-TTF and BET-TTF were investigated and their stability in air assessed, found that both are extremely unstable under the presence of oxygen and water even at ppm levels. The inclusion of BAMs have been proven effective in order to produce OFETs based on composites -- insulator binder and TTF-derivatives. First, poly−(−μετηψλ styrene) PAMS, and DB-TTF composites were investigated. OFETs fabricated shows stability in air and text-book like output and transfer characteristics, all with acceptable mobilities in the range of 10-3 cm2V-1s-1. Also OFETs based on isotactic polystyrene and DB-TTF were investigated reporting mobilities in the range of 10-2 cm2V-1s-1. Further, an screening of compositions for composites were carried out, varying blend ratios and the molecular weight of the polystyrene. The screening was carried out using bottom and top contact devices. The screening revealed that the best performing blend is DB-TTF and polystyrene for GPC 3000 (PS3000) in a ratio 1:2. After an in-depth study have been conducted found average mobility for such blend in the range of 10-1 cm2V-1s-1 and threshold voltages close to zero volts were also found, however is worth to highlight that mobility values as high as 0.7 cm2V-1s-1 were also found. Temperature measurements have been carried out and revealed that the charge transport found for these devices (DB-TTF:PS3000 1:2) point towards a temperature independent mobility, that to the best of our knowledge to-date is the first organic solution processed semiconductor that exhibits such behavior. Also when devices construct inverters gains as high as 300 were found, which also to-date and to the best of our knowledge is the highest gain value for organic based inverters.
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Eskandari, H. (Hamid). "Rate-dependent continuum damage modeling of composite materials." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35696.
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A three-dimensional, phenomenological, tensorial, isotropic, damage model is developed in the framework of continuum damage mechanics for materials whose behavior is governed by elastic deformation coupled with damage. The model was then extended to include isotropic damage for anisotropic materials, as well as rate-dependency behavior caused by damage evolution. The shortcomings of the commonly used scalar variable, as representative of isotropic damage are discussed. It is shown that isotropic damage is best represented by an isotropic tensor of rank four. The damage evolution equations are postulated using strain tensor invariants, based on decomposition of strain energy. The model simulates well the results of static and dynamic uniaxial tension tests on quasiisotropic laminated graphite-epoxy obtained in this study and results, from literature, of uniaxial compression tests on quartzite rock.To determine the material parameters used in the model and to validate the model, a set of material and structural tests, testing a laminate containing a hole, were performed under static and dynamic loading conditions. A tensile version of the Hopkinson bar, suitable for testing of laminated composite materials, is developed to perform dynamic tests. A pulse duration of 200--250 microseconds and peak strain rates of up to 350 s--1 are obtained. Tests performed on a quasi-isotropic lay-up of graphite-epoxy show good repeatability. Comparison of Hopkinson bar tests results with results of tests performed at a quasi-static rate on a hydraulic test machine shows the rate-dependency of this lay-up of graphite-epoxy. Tensile strength and fracture strain are found to be higher for dynamic testing.
The model was evaluated for structural analysis, by implementing the model into a finite element code and analysing a laminate containing a hole. Two techniques are investigated in evaluating the model for structural analysis: stress limiter and mesh limiter. The model is found to be objective with respect to the mesh size. The predicted failure loads using both techniques conform well to the experiments and to the results obtained using one of the existing models.
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Lesko, John James. "Indentation testing of composite materials : a novel approach to measuring interfacial characteristics and engineering properties /." This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03172010-020329/.
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Fenwick, Neal. "Recycling of composite materials using fluidised bed processes." Thesis, University of Nottingham, 1996. http://eprints.nottingham.ac.uk/12837/.
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Lightweight engineering plastics have been increasingly used in automotive applications(3), this tends toward more fuel efficient vehicles(1). Glass reinforced plastics commonly include thermosetting polymers. These cannot be re-moulded, unlike thermoplastics, thus thermoset scrap is currently disposed of in landfill. This is increasingly targeted by legislation(14) and is becoming more expensive. This thesis describes work to maximise resource recovery from scrap thermoset composites. A review of relevant literature identified thermal processes for treating scrap thermoset composites. Combustion is particularly suitable for the mixed and contaminated materials arising from end of life vehicles. The literature showed that heating glass fibres reduced their properties, which is a concern for any thermal recycling process. The methodology of this work is to recover energy from the composite polymer and reuse the incombustible residues. Two experimental processes are reported: Fluidised Bed Co-combustion of Thermoset Composites with Coal. The common composite filler of calcium carbonate captures the sulphur emissions from the coal combustion. Results show that scrap composites can successfully be burned in a commercial scale fluidised bed. Retention of the sulphur from the coal by the composite filler was up to 75 % of the input. Although a technical success, economic analysis shows this disposal to be unviable compared with similar desulphurisation via crushed limestone. Fluidised Bed Thermal Processing Rig for Recovering Glass Fibres. The incombustible constituents of a crushed Sheet Moulding Compound were released from processing above 400 ° C in the fluidised bed test rig. The reinforcing glass fibres were elutriated as monofilaments, suitable for use in a veil product, and recovered from the flue gases. Scanning Electron Microscopy showed that the fibres were intact. The tensile strength of fibres from 450°C processing was reduced by approximately 50% and by 90% from 650°C(73). Strength was also found to reduce with increasing time at a temperature(76) . Flue gas analysis showed that carbon monoxide and hydrocarbons were present. This indicated that full combustion did not take place and the associated heat energy lost. Measured nitrogen oxides and sulphur dioxide concentrations were low. After initial testing, the test rig was refined by the incorporation of a Rotating Screen Collector to separate the fillers and fibres. The fibre contamination was reduced by 50% via this novel equipment. Fibre recovery rates of up to 57% were achieved. Resin Decomposition Model. Results indicate that the resin endothermic energy of decomposition maintained the temperature of the Sheet Moulding Compound significantly below the bed temperature.
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Zafeiropoulos, Nikolaos Evangelos. "Engineering and characterisation of the interface in flax propylene composite materials." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271655.
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Foroutan, Rana. "High strain rate behaviour of woven composite materials." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92165.
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Rbehat, Diana Suleiman Eid. "Development of pyrolysis models of composite materials for fire safety engineering." Thesis, University of Central Lancashire, 2015. http://clok.uclan.ac.uk/11805/.
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The one-dimensional pyrolysis computational tool ThermaKin was used to predict the thermal decomposition behaviour of widely used synthetic polymers (polypropylene (PP) and polyethylene (PE)) with and without additives, in order to investigate the suitability of ThermaKin for novel fire retarded samples, under different thermal and fire conditions. The thermal decomposition of materials was investigated using simultaneous thermal analysis technique (STA) coupled with Fourier Transform Infrared Spectrometry (FTIR) at different heating rates and atmospheres. The results show that thermal decomposition of PP follows single mass-loss step, without formation of residue in nitrogen. It was also found that the pyrolysis shifted towards higher temperature with increase of heating rate at different atmospheres. ThermaKin fitted the TGA curves very well. The thermal decomposition behaviour of polypropylene grafted with 5wt% of maleic anhydride (MA), and reinforced with 5wt% of closite 20A as nanoclay (PP-gMA/NC) was also investigated. The main conclusions from this data are that during the thermal decomposition in different atmospheres, TGA curves showed a single step of decomposition process for all samples. The effect of clay is more pronounced during thermal oxidation. In N2 and air, a two-step reaction mechanism was fitted the experimental curves fairly well. The thermal decomposition of PE, pure and reinforced with different types of carbon fillers (single/multi wall carbon nanotubes, carbon fibres, carbon black and single/few layers of graphene nanosheets), at different loadings (0.1, 0.5 and 1 wt%) and atmospheres were investigated, to determine their suitability as potential fire retardant additives. Results showed that thermal decomposition of PE and its composites/nanocomposites followed a single mass-loss step at a range of temperatures, with no residue formation in N2. The DTG curve in air showed two mass loss rate peaks. The experimental results showed that all loadings of these different additives made no improvement to the thermal stability of PE/MA. In air, the compatibilising agent (MA) improved the thermal stability of pure PE, compared to these composites/nanocomposites at the selected loadings. Mechanisms of single or two-step reaction in N2, and three-step reaction in air for the thermal decomposition of PE with and without additives predicted fairly well the experimental curves. Finally, the work was extended to investigate the performance of ThermaKin to establish a model that is able to predict cone calorimetry results. ThermaKin predicted the burning rate of PE/MA, as a good agreement between the experimental and simulated curves was achieved. Sensitivity analysis was performed to investigate the influence of the variation of the material properties on the modelling results. It was found that the heat of decomposition is the most important parameter of those investigated and needs to be determined most accurately. Heat capacity and thermal conductivity are somewhat important. The absorption coefficient and the reflectivity are of lesser importance. In conclusion, this work shows that the combination of pyrolysis modelling, thermal and chemical analysis techniques provides a strong and powerful tool for generating a comprehensive understanding of the thermal decomposition of novel fire retardant materials. However, further work is needed to study the influence of the changes of the material properties in polymeric material while reinforced with different additives and how this will be reflected on the modelling parameters and mechanism.
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Serra, Tiziano. "Development of 3D-printed biodegradable composite scaffolds for tissue engineering applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/145684.
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The design of smart biodegradable scaffolds plays a crucial role in the regeneration of tissues and restoration of their functionality. Advances in material science and manufacturing and in the understanding on the effects of bio-chemical and bio-physical signals on cell behavior, are leading to a new generation of 3D scaffolds. Recent developments in additive manufacturing, also known as 3D-printing, open new exciting challenges in tissue/organ regeneration by means of the fabrication of complex and geometrically precise 3D structures. This thesis aimed the development and characterization of 3D scaffolds for tissue regeneration. For this, a nozzle-based rapid prototyping system was used to combine polylactic acid and a bioactive CaP glass (coded G5) to fabricate 3-D biodegradable scaffolds. Firstly, optimization of the printing conditions represents a key challenge for achieving high quality 3D-printed structures. Thus, we stress the importance of studying the outcome of the plasticizing effect of PEG on PLA-based blends used for the fabrication of 3D-printed scaffolds. Results indicated that the presence of PEG not only improves PLA processing but also leads to relevant surface, geometrical and structural changes including modulation of the degradation rate of PLA-based 3D printed scaffolds. Secondly, the obtained scaffolds were fully characterized from the physic-chemical point of view. Morphological and structural examinations showed that 3D scaffolds had completely interconnected porosity, uniform distribution of the glass particles, and a controlled and repetitive architecture. In addition, incorporation of G5 particles increased both roughness and hydrophilicity of the scaffolds. Compressive modulus was dependent on the scaffold geometry and the presence of glass. Cell study revealed that G5 glass improved mesenchymal stem cell adhesion after 4 h. Additional biological characterization in terms of the inflammatory response were also carried out. Novel studies have pointed towards a decisive role of inflammation in triggering tissue repair and regeneration, while at the same time it is accepted that an exacerbated inflammatory response may lead to rejection of an implant. Thus, understanding and having the capacity to regulate the inflammatory response elicited by 3D scaffolds aimed for tissue regeneration is crucial. In this context, cytokine secretion and cell morphology of human monocytes/macrophages in contact with biodegradable 3D-printed scaffolds (PLA, PLA/G5 and chitosan ones) with different surface properties, architecture and controlled pore geometry was reported. Results revealed that even though the material itself induced the biggest differences, scaffold geometry also affected on the secretion of cytokines. These findings strengthen the appropriateness of these 3D platforms to study modulation of macrophage responses by specific parameters (chemistry, topography, scaffold architecture). Finally, novel scaffolds composed by two phases (PLA and PLA/G5), for use in guided bone regeneration (GBR) were evaluated. Structural, morphological changes were observed during the in vitro degradation of both PLA and PLA/G5 structures. Although mechanical properties decreased, PLA/G5 scaffolds still showed higher compressive modulus than PLA ones, confirming the reinforcing effect of glass particles after immersion time. In vivo implantation was carried out subcutaneously in mice up to 30 days. Results showed that PLA scaffolds induced mononuclear cell without activating any relevant angiogenic process, while PLA/G5 induced higher presence of multinucleated giant cells and consequently stimulated the vascularization process and further tissue regeneration. The technique/materials combination used in this PhD thesis led to the fabrication of promising fully degradable, mechanically stable, bioactive and biocompatible composite scaffolds with well-defined architectures valuable for TE applications.
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Liu, Ning. "Composite materials impact damage detection using neural networks." Thesis, Aston University, 2002. http://publications.aston.ac.uk/11838/.
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This thesis considers two basic aspects of impact damage in composite materials, namely damage severity discrimination and impact damage location by using Acoustic Emissions (AE) and Artificial Neural Networks (ANNs). The experimental work embodies a study of such factors as the application of AE as Non-destructive Damage Testing (NDT), and the evaluation of ANNs modelling. ANNs, however, played an important role in modelling implementation. In the first aspect of the study, different impact energies were used to produce different level of damage in two composite materials (T300/914 and T800/5245). The impacts were detected by their acoustic emissions (AE). The AE waveform signals were analysed and modelled using a Back Propagation (BP) neural network model. The Mean Square Error (MSE) from the output was then used as a damage indicator in the damage severity discrimination study. To evaluate the ANN model, a comparison was made of the correlation coefficients of different parameters, such as MSE, AE energy, AE counts, etc. MSE produced an outstanding result based on the best performance of correlation. In the second aspect, a new artificial neural network model was developed to provide impact damage location on a quasi-isotropic composite panel. It was successfully trained to locate impact sites by correlating the relationship between arriving time differences of AE signals at transducers located on the panel and the impact site coordinates. The performance of the ANN model, which was evaluated by calculating the distance deviation between model output and real location coordinates, supports the application of ANN as an impact damage location identifier. In the study, the accuracy of location prediction decreased when approaching the central area of the panel. Further investigation indicated that this is due to the small arrival time differences, which defect the performance of ANN prediction. This research suggested increasing the number of processing neurons in the ANNs as a practical solution.
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Megharief, Jihad Dokali. "Behavior of composite castellated beams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ37273.pdf.
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Pathak, Sayali V. "Enhanced Heat Transfer in Composite Materials." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1368105955.
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Ko, Ying-hsiang. "The growth of metal particles in porous glass and the dielectric and optical properties of the composites /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487267024996737.
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Emeric, Pierre Richard. "Characterization of composite materials from temporal thermal response." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539623868.
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There is an increasing interest in the characterization of complex structures with thermographic techniques. Typical of these structures are multilayered systems and fiber reinforced composites where structural thermal response is a function of the combined responses of the constituents. In this work, techniques are presented for measuring the early thermal response. For multilayer structures, the response is reduced to the thermal properties of the constituents. For fiber reinforced composites, the short term response enables detection of the fibers.;A measurement system was developed consisting of an infrared detector focused on a single point on the structure. An input heat flux was provided by either an Argon laser or a flash lamp depending on the configuration. to measure the spatial variations in the thermal response, specimens were mounted on a translation stage.;Initial measurements with the system were performed on multilayered structures. An analytical solution was developed for the thermal response of a two or three layer system, given the thermal properties of the layers. This solution was combined with a nonlinear estimation routine to enable the determination of the properties of the constituents from the thermal properties of the structure. This technique was applied to the characterization of a thermally thin layer on a thermally thick layer. It was also applied to the characterization of the center layer of a three layer structure.;Subsequent measurements were performed on a ceramic composite (reaction bonded silicon nitride reinforced with SiC fibers). Images of the spatial variations in the thermal response were obtained by translation of the composite. to give insights in the significance of the data, a two dimensional analytical solution was developed for the thermal response of a fiber embedded in a matrix material. Predicted responses of the structure were compared with the measured responses.
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Maligno, Angelo Rosario. "Finite element investigations on the microstructure of composite materials." Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/10476/.
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This thesis describes the investigation and development of damage modelling for composites materials at their micro-scale (e.g. fibre, matrix). A damage model for elastic materials, based on a "local" damage approach, has been introduced to predict failure onset and simulate the post-failure behaviour of unidirectional threedimensional representative volume elements (RVE) or unit cells with hexagonal distribution of the fibres over the cross section. The damage model consists of three parts: an elastic model, a failure criterion and the post-failure behaviour. Modifications of von Mises criteria and Maximum Principal Stress criterion have been considered to evaluate failure in the matrix whilst for the fibre in general the Maximum Principal Stress criterion has been used. The damage model has been implemented into the commercial code ABAQUS with subroutines in FORTRAN (UMAT and USDFLD). The material properties in the residual stress analyses are considered temperature dependant to simulate the volumetric contraction during the manufacturing process. Hence, the overall residual stress introduced from curing was determined by considering two ontributions: volume shrinkage of matrix resin from the crosslink polymerization during isothermal curing and thermal contraction of both resin and fibre as a result of cooling from the curing temperature to room temperature. Finally, three different typologies of 3D unit cells have been investigated. The first kind of micro-model is based on a symmetric distribution of the fibres and the unit cells have two phases, i.e.: matrix and fibre. The second typology of unit cells is still based on a uniform architecture but include a three-dimensional interphase between fibre and matrix. As in real composites at their constituent level fibres are randomly distributed. The mutual distance between fibres represents a critical factor for the ultimate mechanical properties of the micro-composites. Hence the last kind of micro-models account for this non-uniform position of fibres within the RVE although they consists of only two phases. FEM analyses have indicated that predicted damage initiation and evolution are clearly influenced by the presence of residual stresses in all the three different typologies of unit cells analysed. The numerical analyses on the numerical models have proved that, in general, the overall mechanical properties are strongly influenced by the presence of residual stress, fibre volume fraction, fibre distribution and interphasial properties. In particular on transverse tensile loading, residual stresses produces beneficial results in terms of ultimate strength while in the case of longitudinal loading (parallel to the fibres) the matrix, due to the high compressive stress, undergoes a premature failure although.
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Hart, Shandon D. (Shandon Dee) 1978. "Multilayer composite photonic bandgap fibers." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32264.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references (leaves 120-126).
Materials and fabrication techniques are developed that lead to the successful fabrication of multilayer composite photonic bandgap fibers. The pertinent background in electromagnetic theory of multilayer dielectric mirrors and optical fibers is surveyed. Materials properties constraints are outlined, with emphasis on those constraints related to processing strategy and ultimate target length scale. Interfacial energy is measured in a chalcogenide glass / organic polymer composite system selected for fiber fabrication. A classical capillary instability model is employed to predict the feasibility of fiber fabrication based on material properties; from this model, quantitative materials selection criteria related to ultimate length scale are derived. Good agreement is found between the calculated materials selection criteria and controlled fiber experiments. The fiber fabrication techniques are described and analyzed; chalcogenide film deposition is characterized using Raman and electron microprobe spectroscopy, and heat transfer during fiber drawing is modeled using a commercial finite-element software package. The developed materials and fabrication processes are used to perform two case studies in novel photonic bandgap fiber fabrication; the first case study deals with externally reflecting omnidirectional 'mirror-fibers', while the second deals with hollow- core light transmitting fibers. The reflecting mirror-fibers consist of a tough polymer core surrounded by multiple coaxial submicron-thick layers of a high-refractive-index glass and a low-index polymer; these layers reflect external light from all incident angles and polarizations in the mid-IR range.
(cont.) Large directional photonic gaps and high reflection efficiencies that are comparable to the best metallic reflectors were measured. In the second case study, the light-transmitting fibers consist of a hollow air core surrounded by multiple alternating layers of the same materials, resulting in large infrared photonic bandgaps. Optical energy is strongly confined in the hollow fiber core, enabling light guidance in the fundamental and up to fourth-order gaps. These gaps are placed at selectable wavelengths within a large selection range, from 0.75 to 10.6 m. Tens of meters of hollow photonic bandgap fibers designed for 10.6 pgm radiation transmission are fabricated. We demonstrate transmission of carbon dioxide (CO2) laser light with high power-density through more than 4 meters of hollow fiber and measure the losses to be less than 1.0 dB/m at 10.6 microns. Thus, fiber waveguide losses are suppressed by orders of magnitude compared to the intrinsic fiber material losses.
by Shandon D. Hart.
Ph.D.
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Souvignier, Chad William. "Solid freeform fabrication of highly loaded composite materials." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/284190.
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Composites are known for their unique blend of modulus, strength, and toughness. This study focuses on two types of composites; organic-inorganic hybrids and the mineralization of highly swollen polymer gels. Both of these composite systems mimic the biological process of composite formation, known as biomineralization. Biomineralization allows for the control of the precipitating phase through an interaction with the organic matrix. This allows higher volume fractions of inorganic material than can be achieved by many traditional processing techniques. Solid freeform fabrication is a processing method that builds materials by the sequential addition of thin layers. As long as the material can easily be converted from a liquid to a solid, it should be amenable for this processing technique. Freeform fabrication has three distinctions from traditional processing techniques that may enable the formation of composite materials with improved mechanical properties. These are the sequential addition of layers, which allows a layer by layer influence of chemistry, the ability to form complex geometries, and finally, extrusion freeform fabrication has been shown to align fibers due to the extrusion of the slurry through a needle. Cracking and shrinkage still play a major role in forming solid parts. The use of an open mesh structure in combination with proper materials selection allowed the formation of highly loaded composite materials without cracking. The modulus values of these materials ranged from 0.1 GPa to 6.0 GPa. The mechanical properties of these materials were modeled.
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Thummalapalli, Vimal Kumar. "Biomimetic Composite T-Joints." University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1323547304.
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Tompson, Carl G. "Radiographic determination of the lay-up influence on fatigue damage development under bearing/bypass conditions." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29689.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Dr. Steve Johnson; Committee Member: Dr. Andrew Makeev; Committee Member: Kyriaki Kalaitzidou. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Mills, John Brean. "Composite materials for microwave frequency agile planar devices." Thesis, University of Oxford, 2003. http://ora.ox.ac.uk/objects/uuid:213e4e33-2816-470f-bb8d-9b36d50e1254.
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The potential of Calcium-Vanadium garnet loaded binary composites for use in the production of planar frequency agile microwave devices has been investigated. A WR90 rectangular waveguide system using the transmission/reflection technique has been used to compare effective medium theory predicted permittivities and permeabilities for unmagnetised and transversely magnetised composites with actual measured composite properties. Use of the the Bruggeman effective medium theory with manufacturer supplied garnet permittivity and values of garnet permeability calculated using simple empirical models were demonstrated to be as accurate as predictions made using the measured properties of the composites' individual constituents. Errors in predicted material properties for unmagnetised and transversely magnetised samples relative to measured data were less than 5% across almost half of the 8.2 -12.4GHz measurement band and within a worst-case error of 15% across the whole band. A series of end-coupled linear microstrip resonators using garnet-loaded composite substrates has been fabricated and tested. Tunabilities in resonance of up to 3.9% at 9.2GHz have been demonstrated for DC magnetic bias fields applied transverse to the microwave magnetic field component. An entirely new and previously unpublished broadband microstrip technique for the measurement of the effective permittivity and permeability of bulk gyromagnetic and gyromagnetic material loaded composite substrates subject to transverse DC magnetic bias fields is presented. This will have wide application in the design of frequency agile microwave integrated circuits.
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Lamm, Adrienne Valerie. "Dislocation Modeling of Mechanical Properties of Nanolayered Composite Materials." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1363615565.
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Bédard, Matthieu. "Optically addressable, integrative composite polymer microcapsules." Thesis, Queen Mary, University of London, 2009. http://qmro.qmul.ac.uk/xmlui/handle/123456789/395.
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The development of remotely addressable tools to encapsulate, store and deliver active materials to living cells is a particularly challenging topic of material science. As drug delivery agents, microcontainers not only require high mechanical stability or to be delivered at target cells, but they should also possess efficient remotely addressable release mechanisms. Light responsive polyelectrolyte capsules are well suited for such purposes. Capsules are constructed using the Layer‐by‐Layer technique where oppositely charged polymers are alternatively deposited on a sacrificial template. The interest for such microcapsules lays in their versatile composition and stimuli‐responsive properties, which can be altered to suit specific needs. The primary aim of this work was to develop polymeric capsules with efficient optically addressable release mechanisms. Previous work on this topic revealed severe flaws in biological environments, especially with regards to the high energy requirements necessary for laser‐induced release and in the very limited knowledge of the fate of microcapsules in living cells. These issues were addressed by developing alternative types of light‐responsive capsules and gaining better understanding of existing ones. Three types of materials were used to sensitize microcapsules to the near‐UV, visible and near‐IR spectral regions: (1) azobenzene‐substituted polymers, (2) gold nanoparticles and (3) photocatalytic porphyrinoid dyes. Various methods were used for the characterization of microcapsules, including laser scanning confocal microscopy, colloidal probe and standard atomic force microscopy, electron microscopy, fluorescence spectrophotometry, UV‐visible spectroscopy and differential scanning calorimetry. Shells were probed for their mechanical stability as well as encapsulation and release behavior based on parameters such as: assembly strategies, shell deformability, permeability, thermal response and response to laser irradiation. This thesis begins with a brief introduction followed by an extensive literature review summarizing the various topics relevant to the work. The materials and methods used in the investigations are catalogued in Chapter 3 . Chapter 4 presents the destructive effects of pulsed UV lasing on polymeric microcapsules and introduces azobenzene‐functionalized capsules with the ability to encapsulate macromolecules by exposure to continuous wave UV light. Chapter 5 looks at the mechanical properties of capsules functionalized with gold nanoparticles as well as their remote release capabilities under near‐IR irradiation. While most of these studies were conducted ex vivo, Chapter 5 concludes with a summary of studies performed in vitro, which demonstrates that it is not only possible to release substances in living cells by light but that the latter also survive in the process. Finally, in Chapter 6, the assembly and light induced destabilization of microcapsules containing porphyrinoid dyes is presented.
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Olivetti, Elsa A. "Composite cathodes for lithium rechargeable batteries." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39554.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references.
The utility of incorporating continuous, nanoscale vanadium oxide phases within preferred domains of self-organizing copolymers was investigated towards the fabrication of composite, nanoarchitectured electrode materials for solid-state rechargeable batteries. In situ growth of cathodic phases within ion-conducting copolymer domains was explored as a means to control morphology and to increase the surface-area-to-volume ratio, thereby increasing the specific electrode area for faradaic reactions and decreasing ion diffusion distances within the electrode-active material. Copolymers of microphase-separating rubbery block and graft copolymers, previously developed as solid electrolytes, provide a matrix for directing the synthesis of an inorganic battery-active phase. The copolymers include poly[(oxyethylene)9 methacrylate]-block-poly(butyl methacrylate) (POEM-b-PBMA) with a domain periodicity of -35 nm made by atom transfer radical polymerization, and poly[(oxyethylene)9 methacrylate]-graft-poly(dimethyl siloxane) (POEM-g-PDMS) with a domain periodicity of-17 nm made by free radical polymerization. The resulting microphase-separated polymer is a structure of alternating hydrophilic (Li-ion conducting) and hydrophobic regions.
(cont.) Sol-gel chemistry involving a vanadium alkoxide precursor enabled the in situ growth of cathode-active vanadium oxide within the continuous ion-conducting POEM domains of the microphase-separated copolymers. Resulting films, termed POEM-b-PBMA/VOx and POEM-g-PDMS/VOx, were freestanding and mechanically flexible. Small angle x-ray scattering and transmission electron microscopy revealed the nanoscale morphology of the composite and confirmed the spatially-selective incorporation of up to 34 wt% VO, in POEM-b-PBMA and 31 wt% in POEM-g-PDMS. Electronically conductive components, necessary for wiring of the lithium-active vanadium oxide domains to the external circuit, were added through a variety of methods. Dispersions of acid-treated and cryo-ground carbon black within POEM-b-PBMA/VOx enabled the cycling of this material as a cathode. Reversible capacities of-~ 40 mAh/g were measured for batteries fitted with a polymer electrolyte doped with LiCF3SO3 and a lithium foil anode. Electrolyte thickness studies indicated battery performance was limited by the ionic conductivity of the solid electrolyte.
(cont.) Using liquid electrolyte resulted in improved capacity (at higher currents) over conventional composite cathodes made from sol-gel derived vanadium oxide without the polymer matrix. The vanadium oxide nanoarchitecture was preserved upon removal of the polymer by heat treatment. The resulting templated vanadium oxide, when repotted with carbon black and binder, exhibited improved capacity at high current over non-templated vanadium oxide cathodes.
by Elsa A. Olivetti.
Ph.D.
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Vasiliu, Andrei. "Masonry columns confined by composite materials: Experimental investigation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7359/.
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This study wants to analyze the effectiveness of different reinforcement typologies for masonry columns, in particular Fiber-Reinforced Polymer (FRP) and FRCM. The behavior of 10 solid – brick columns that are externally wrapped by FRP sheets and 2 unreinforced columns are presented in this study. The specimens are subjected to axial load until failure occurs. Three different confinement schemes were experimentally analyzed in order to evaluate and compare the effectiveness of the proposed strengthening techniques: 1) Grid carbon FRP (CFRP_G); 2) Grid glass FRP (GFRP_G); 3) Uniaxial carbon FRP (CFRP_U). Two different configurations of the reinforcing system were investigated: FRP sheets are applied as external reinforcement along the perimeter of the masonry columns in the form of continuous and discontinuous wrap, respectively. The results, compared with those for un-reinforced columns, indicate an increases in ultimate load, stiffness and ductility.
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Sujidkul, Thanyawalai. "Multi-Physics Modeling of Multifunctional Composite Materials for Damage Detection." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1381874092.
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Dutta, Monojit. "Residual stress measurement in engineering materials and structures using neutron diffraction." Thesis, Open University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301945.
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Emery, Trystan Ross. "Identification of damage in composite materials using thermoelastic stress analysis." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/51292/.
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A quantitative damage assessment methodology for composite materials has been achieved using Thermoelastic Stress Analysis (TSA). The TSA technique provides fullfield data which is collected in a non-contacting and real time manner. The damage assessment methodology proposed requires a means of calibrating and temperature correcting the thermoelastic signal; these are developed and presented in this thesis. The thermoelastic theory for calibrating thermoelastic data from orthotropic bodies has traditionally been based on a stress formulation. There are difficulties in calibrating orthotropic materials in this manner and an alternative calibration routine has been devised and validated. The calibration routine provides the thermoelastic theory as a function of strain and permits a simplified calibration route as the laminate strains are the basis and can be measured in a straightforward manner. During damage propagation in laminated structures the specimen heats. The increase in temperature has a significant effect on the thermoelastic data and necessitates that the thermoelastic data be corrected to remove the effect of temperature from the data. A routine is developed that enables the correction of the thermoelastic data in a point-bypoint manner. By combining the strain calibration and temperature correction procedures a damage assessment methodology has been devised. The application of the methodology is demonstrated on glass / epoxy laminate specimens that are fatigue damaged and the damage state assessed using this method; the extent and type of damage is verified qualitatively using visual inspection methods. The work described is applicable to any orthotropic material. The effect of fatigue damage is assessed by periodically collecting thermoelastic data during the specimen life. This data is analysed using damage metrics based on the calibrated strain obtained from the TSA. The wider application of the TSA damage assessment methodology is considered by assessing the ability to locate subsurface damage. A complementary IR technique is used in conjunction with TSA known as Pulse Phase Thermography (PPT). Initial studies demonstrate the ability to resolve the spatial extents of subsurface damage. The purpose of this step is to guide TSA to areas of concern that can subsequently be assessed using the damage metrics to characterise the effect of damage on the residual life of the component. The strain calibration and temperature correction methods that enable TSA to be applied quantitatively to damaged composite materials have not been accomplished prior to this work. They provide novel methods by which TSA data can be assessed, and their application is not restricted to damage studies alone. The ability to temperature correct TSA data has been shown to be of vital importance if thermoelastic data is to be compared in a quantitative fashion. The strain calibration procedure presented will enable thermoelastic studies to be reported quantitatively and expand the application of TSA particularly in validation studies. The damage assessment methodology presented represents a step forward in the application of TSA to the damage assessment of composite materials.
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Hossain, Kazi Md Zakir. "Extension of the use of cellulose nanowhiskers in composite materials." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/13910/.
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This thesis explores the use of cotton derived cellulose nanowhiskers (CNWs) in composite materials in the form of nanocomposite films, surface modified polymer fibres and also in self-reinforced (SR) composites. Cellulose nanowhiskers (CNWs) were produced from cotton via sulphuric acid hydrolysis process and blended with polylactic acid (PLA) to produce CNW-PLA and was added to hydroxyethyl cellulose (HEC) to manufacture CNW-HEC nanocomposite films. The aggregated morphology and hydrophilicity of CNWs, hydrophobicity of PLA and the solvent used (Chloroform) played a major role in creation of voids within the CNW-PLA nanocomposites. In addition, the aggregated morphology of the CNWs also influenced the surface roughness and light transparency properties of the CNW-HEC films. Improvement in the mechanical, thermal and thermomechanical properties for both types of nanocomposites was achieved due to the reinforcing effect of the rod-like nanowhiskers. An increase in the crystallinity of the nanocomposites indicated that the CNWs induced crystallisation in the matrices. Incorporation of CNWs also had a significant influence on accelerating the degradation profile of the CNW-PLA nanocomposites and reducing the swelling capacity and initial swelling rate for the CNW-HEC films. PLA fibres were also produced with varying diameters (11 µm to 38 µm) via a melt drawing process employing increasing take-up velocities. A higher degree of chain orientation as well as an increase in crystallinity for the thinner fibres was achieved due to strain-induced crystallisation. The variation in PLA fibre diameter also revealed a noticeable influence in their mechanical and moisture absorption properties at various humidity levels. Further, the hydrophobic and smooth surface of the PLA fibres was coated with various blends of CNWs (65 to 95 wt%) and polyvinyl acetate (PVAc) to impart roughness, where PVAc acted as a binder. An increase in tensile modulus and moisture absorption properties were achieved for the CNW/PVAc coated PLA fibres. These surface modified PLA fibres were aligned to produce unidirectional (UD) fibre mats prior to hot compaction (at 95oC) to manufacture SR PLA composites. Incorporation of CNW/PVAc within the SR PLA composites revealed an increase in their flexural and ductile properties compared to the control composite.
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Pierce, Matthew Ryan. "Microvascular Heat Transfer Analysis in Carbon Fiber Composite Materials." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1280944914.
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Lai, Yun. "The study of band gap engineering for phononic crystals and gap structures in phononic quasicrystals /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202005%20LAI.
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Tang, Tian. "Variational Asymptotic Micromechanics Modeling of Composite Materials." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/72.
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The issue of accurately determining the effective properties of composite materials has received the attention of numerous researchers in the last few decades and continues to be in the forefront of material research. Micromechanics models have been proven to be very useful tools for design and analysis of composite materials. In the present work, a versatile micromechanics modeling framework, namely, the Variational Asymptotic Method for Unit Cell Homogenization (VAMUCH), has been invented and various micromechancis models have been constructed in light of this novel framework. Considering the periodicity as a small parameter, we can formulate the variational statements of the unit cell through an asymptotic expansion of the energy functional. It is shown that the governing differential equations and periodic boundary conditions of mathematical homogenization theories (MHT) can be reproduced from this variational statement. Finally, we employed the finite element method to solve the numerical solution of the constrained minimization problem. If the local fields within the unit cell are of interest, the proposed models can also accurately recover those fields based on the global behavior. In comparison to other existing models, the advantages of VAMUCH are: (1) it invokes only two essential assumptions within the concept of micromechanics for heterogeneous material with identifiable unit cells; (2) it has an inherent variational nature and its numerical implementation is shown to be straightforward; (3) it calculates the different material properties in different directions simultaneously, which is more efficient than those approaches requiring multiple runs under different loading conditions; and (4) it calculates the effective properties and the local fields directly with the same accuracy as the fluctuation functions. No postprocessing calculations such as stress averaging and strain averaging are needed.
The present theory is implemented in the computer program VAMUCH, a versatile engineering code for the homogenization of heterogeneous materials. This new micromechanics modeling approach has been successfully applied to predict the effective properties of composite materials including elastic properties, coefficients of thermal expansion, and specific heat and the effective properties of piezoelectric and electro-magneto-elastic composites. This approach has also been extended to the prediction of the nonlinear response of multiphase composites. Numerous examples have been utilized to clearly demonstrate its application and accuracy as a general-purpose micromechanical analysis tool.
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Lee, Bok W. "Application of variational-asymptotical method to laminated composite plates." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/20695.
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Sanga, Essau C. M. "Microwave assisted drying of composite materials : modelling and experimental validation." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38271.
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Model materials with discretely varying loss factors under microwave fields, were studied with respect to drying characteristics. In the first part numerical simulations were conducted to study the fluid flow and heat transfer in a rectangular microwave cavity where cylindrical samples were heated by microwave. The Reynolds numbers studied in this work were 2800, 5600 and 11200 based on the entrance diameter to the rectangular microwave cavity. Heat transfer results in terms of Nusselt numbers for the Reynolds number ranges studied are presented and discussed.In the second part of the study a mathematical model was developed to describe heat and mass transfer of a model material under microwave fields. The dynamic temperature and moisture profiles of cylindrical composite samples subjected to microwave and convective energy were determined and validated at microwave power density levels of 0.20 W/g, 0.3 W/g and 0.4 W/g based on initial weight of the sample. Model results were compared with experimental data and found to agree within 1.0--2.6%. Predicted temperature profiles at selected locations within the model material were also showed a good agreement with experimental data. However, a significant discrepancy between the numerical and experimental temperature results occurred after t > 30 minutes. This might have been due to localized overheating, or to mathematical model overestimation.
Lastly, a quality evaluation of the dried samples was also performed. Quality attributes evaluated were surface color, shrinkage and rehydration capacity. Samples dried as a special case of biological material were of better quality when compared to other samples.
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Lemieux, Stéphane. "Thermal expansion study of particulate reinforced aluminum matrix composite materials." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20505.
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The thermal expansion behavior of Duralcan particle reinforced composite materials was investigated. Initially, the temperature dependence of the CTE of Al-Si alloy containing SiC reinforcement particles ranging from 10 to 40% in volume was experimentally examined and compared with standard theoretical model predictions. In addition, the effects of reinforcement volume fraction and nature of the composite constituents during thermal cycling between 25 and 350ºC were determined for Al-Si alloy containing between 10 and 40% SiC particles and Al alloy having 40% alumina in volume. Accurate experimental CTE measurements were made using a high precision Thermomechanical Analyzer system. Silicon carbide reinforced composite average CTE values were bounded by two elastic CTE theoretical models consisting of Schapery and Kerner predictions over the 25--350ºC interval for reinforcement volume fractions between 10 and 40%. The CTE mismatch between the particles and the matrix does not appear to be the only factor influencing the expansion response of the composites. Indeed, the nature of the composite constituents also plays an important role by influencing the ductility and bonding of the particle-matrix interface.
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Bekiaris, Nikolaos 1970. "Selection of composite materials for the construction of large ships." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88344.
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Kuryak, Chris A. (Chris Adam). "Nanostructured thin film thermoelectric composite materials using conductive polymer PEDOT:PSS." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79270.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 65).
Thermoelectric materials have the ability to convert heat directly into electricity. This clean energy technology has advantages over other renewable technologies in that it requires no sunlight, has no moving parts, and is easily scalable. With the majority of the unused energy in the United States being wasted in the form of heat and the recent mandates to reduce greenhouse gas emissions, thermoelectric devices could play an important role in our energy future by recovering this wasted heat and increasing the efficiency of energy production. However, low conversion efficiencies and the high cost of crystalline thermoelectric materials have restricted their implementation into modem society. To combat these issues, composite materials that use conductive polymers have been under investigation due to their low cost, manufacturability, and malleability. These new composite materials could lead to cheaper thermoelectric devices and even introduce the technology to new application areas. Unfortunately, polymer composites have been plagued by low operating efficiencies due to their low Seebeck coefficient. In this research, we show an enhanced Seebeck coefficient at the interface of poly(3,4- ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) spin coated onto silicon substrates. The maximum Seebeck coefficient achieved was 473 uV/K with a PEDOT:PSS thickness of 7.75 nm. Furthermore, the power factor of this interface was optimized with a 15.25 nm PEDOT:PSS thickness to a value of 1.24 uV/K2-cm, which is an order of magnitude larger than PEDOT:PSS itself. The effect of PEDOT:PSS thickness and silicon thickness on the thermoelectric properties is also discussed. Continuing research into this area will attempt to enhance the power factor even further by investigating better sample preparation techniques that avoid silicon surface oxidation, as well as creating a flexible composite material of PEDOT:PSS with silicon nanowires..
by Chris A. Kuryak.
S.M.
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Hager, Elizabeth A. (Elizabeth Ann). "Composite gelatin delivery system for bone regeneration." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32844.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, June 2005.Includes bibliographical references (p. 38-39).
In this thesis, the chemical/mechanical properties and biocompatibility of gelatin were investigated to produce a gelatin scaffold for the release of bone morphogenetic proteins (BMPs) from composite particles. This delivery system, designed to regenerate bone, holds much promise as an alternative to bone grafts. The chemical properties of gelatin were examined through zeta potential measurements, swelling studies, optical microscopy, environmental scanning electron microscopy (ESEM), and collagenase degradation. Compressive tests and mercury porosimetry were performed to study the mechanical and structural properties of the scaffold. The biocompatibility of the scaffold was determined through cell optical imaging and DNA quantification studies. Based on findings of this research, the material choices were made and the synthesis method for the gelatin scaffold was developed. Gelatin A, 300B, derived from bovine collagen, with an isoelectric point of [approx.] 9, was selected. Crosslinking was accomplished by reacting 10 w/v% glutaraldehyde with 10 w/v% gelatin solution. The most effective crosslinking condition was found to be 5 hours at room temperature. Glycine rinses were conducted to cap any non- reacted (toxic) aldehyde groups, and the necessary length of time was found to be at least 48 hours at 37⁰C. Finally, based on pore size distribution and mechanical stability, an optimal lyophilization method was developed with initial freezing at -20⁰C for 1 day, followed by lyophilization of the scaffold for 1-2 days. In terms of mechanical properties of the gelatin and amount of protein delivered, the most effective loading of poly(lactic-co-glycolic acid)/apatite/protein composite particles was found to be 10% of the mass of the gelatin.
by Elizabeth A. Hager.
S.B.
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Guazzone, Federico. "Engineering of substrate surface for the synthesis of ultra-thin composite Pd and Pd-Cu membranes for H₂ separation." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-011006-123013/.
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Liu, Jian. "Fabrication of composite materials with addition of graphene platelets." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5484/.
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This PhD project set out to tackle the disadvantages of brittleness and low corrosion resistance that ceramics and mild steel bear respectively by developing ceramic and metallic nanocomposites using nanostructured fillers. Graphene platelets (GPLs) as newly emerging carbon materials were chosen as the reinforcing fillers. Two types of nanocomposites were fabricated and their mechanical or corrosion resistant properties were characterized. Alumina (Al2O3) based nanocomposites reinforced with GPLs were sintered and GPL/Nickel (Ni) nanocomposites were produced using an electrodeposition technique. The results show that the mechanical properties of the ceramic matrices are significantly improved by adding nano fillers. Toughening mechanisms induced by GPLs, such as pull-out, crack deflection and crack bridging are observed. On the other hand, the mechanical and corrosion resistance properties of Ni matrix are greatly enhanced by the addition of GPLs. In addition, the higher percentage of GPLs results in finer and more uniform Ni microstructures, leading to the higher hardness and corrosion resistance.
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Dow, Douglas Donald. "Finite Element and Experimental Analyses of Hybrid Joints Subjected to Fully Reversed Flexure Fatigue Loading." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/DowDD2008.pdf.
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