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1
Palmer, Nathan Reed. "Smart Composites evaluation of embedded sensors in composite materials /." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/palmer/PalmerN0809.pdf.
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As an emerging form of renewable energy, horizontal wind turbines have experienced advancements in improving efficiency and reliability. These advances have pushed the limits of current technology used in wind turbines. Smart blades have been proposed as a method of addressing these limitations. Sensor integration within blade construction is the first step in development of smart blades. Thus, several low cost sensors were chosen, 1 axis strain gages, polyvinylidene fluoride films (PVDF), and single mode fiber optics either coated in acrylate or polyimide. To ensure successful bonding between sensor and composite two surface treatment techniques were developed. The first, dipping of the sensor into a bath of 20% by weight solution of nitric acid and the second was submersion of the sensor in the nitric acid for ten seconds prior to removal. These treatments were compared against sensors not surface treated prior to embedding. These sensors were embedded within samples created of fiberglass and epoxy or vinyl ester resin. Two different material tests were conducted. Tensile testing allowed for evaluation of sensor sensitivity, sensor failure point, material tensile modulus, and material tensile strength. Mode I fracture toughness evaluation, indicated the level of successful bonding which occurred during resin curing. Field Emission Scanning Electron Microscopy (FESEM) was conducted to further confirm the level of bonding between resin and sensor, post fracture. Results for embedded strain gages showed an adverse effect for vinyl ester samples. Epoxy samples fared better, thus concluding manufacturing success for epoxy samples, submersion being preferred, and alternative methods needed for vinyl ester samples. PVDF films had good qualitative FESEM images combined with increasing trends. It was concluded that integration for both resin groups with sensors submerged in nitric acid was successful. Fiber optics coated in acrylate also showed good bonding under FESEM imaging as well as testing. It was thus concluded that submersion was the preferred treatment. Lastly, fiber optics coated in polyimide embedded in vinyl ester composites showed significant drawbacks and it was concluded that alternative methods need exploration. Those embedded in epoxy were successfully integrated and submersion in nitric acid showed the most potential.
2
Klug, Jeremy Hager. "High-performance adhesive systems for polymer composite bonding applications /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/9883.
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Hayes, Brian Steven. "Simulation engineering of polymeric prepreg composite systems /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/9906.
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Li, Wei. "Composite polymer/graphite/oxide electrode systems for supercapacitors." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439309266.
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Buehler, Frédéric Ulysse. "Viscoelastic processing and characterization of high-performance polymeric composite systems /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9880.
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Teh, Kuen Tat. "Impact damage resistance and tolerance of advanced composite material systems." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06062008-170512/.
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Hillermeier, Roman Werner. "Development engineering of advanced polymeric composite systems /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9919.
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Anbarasu, Arungalai. "Characterization of defects in fiber composites using terahertz imaging." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24632.
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Gilbert, Eric Nicholas. "Interlayer modified prepreg systems for customized density applications /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/9889.
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Padipatvuthikul, Pavinee. "Fatigue studies on dental composites and bonding systems." Thesis, University of Liverpool, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485845.
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Introduction: Adhesion has become an important concept in modern restorative dentistry. It offers the ability to bond materials to the tooth without invasive tooth preparation. Numerous in-vitro strength tests have been used to determine the bond strength of adhesive systems. However, because the occlusal forces applied to. a restoration are complex, and made up of a combination of forces, no one test can satisfactorily predict the in-vivo behavior of an adhesive system. The majority of bond strength studies have used monotonic tests to assess the bond strength of materials and between the materials and the tooth. These tests are expedient, but do not simulate the cyclic forces that operate in the mouth. Tests that characterize this type of . stress are called fatigue tests. Fatigue can result in wear and fracture of materials or bonds. .Objectives: To investigate fatigue behavior of modern resin composites and resinbonded joints of both metal to enamel and ceramic to enamel. The main approaches to fatigue assessment, 'Fatigue Limit' and 'Fatigue Life'were compared Materials and Methods: Surface effects of fatigue One hundred and eighty samples of two historical composites1-2 and seven modern composites3 - 9 were subjected to 2000 stress cycles between 0 and 120N or 0 and 400N. Surface damage was measured as the diameter of the fatigue scar and subsurface damage was determined by silver nitrate staining. The hardness of both the surface and subsurface was also determined. Fracture Composite to composite Two hundred and twenty composite disks were fabricated using three materials.7 • 9 After one day, one week, four weeks, and twelve weeks, fifty-five specimens of each material were removed from' water and divided into three groups of fifteen and one group of ten. Each group of samples was treated with one of three bonding systems10- 12 before adding a sec~nd increment. For each material, ten samples were subjected to Shear test in a Universal Testing Machine13 (CHS= 50 mmlmin). The fatigue limit test using fifteen samples per group were used to determine the fatigue limit using the staircase method (Draughn 1979). Metal or Ceramic to Enamel (via resin) Three hundred and forty-two discs of Ni/Cr-alloy14 were cast and treated by either sandblasting with aluminium oxide, or by sandblasting followed by electrolytic-etching in HCI. The disks were bonded to etched enamel with one of three dental bonding systems.1S - 17 One hundred and seventy-one ceramic disks were fabricated by sintering ceramic powder.18 One surface of each disk was etched with porcelain etching-gel19 for fifteen minutes and sandblasted with 50 J.Im A120 3. The prepared disks were then divided into three groups and were bonded to etched enamel using one of three dental bonding systems.1S - 17 Ten specimens of each group were sUbjected to a shear bond test (CHS 50 mm/min) and seventeen specimens of each group to a staircase fatigue test to determine the fatigue limit of the bonds. The remaining specimens from each group were placed in the custom made fatigue testing machine and allowed to cycle to failure between 0-20 kg, 0-10 kg or 0-5 kg (n=10 per load). The number of cycles at failure was analysed by Weibull statistics to determine the fatigue life Results: The surface studies in composites indicated that both surface and subsurface damage increased with increasing load. In general, small-particle composites experienced less damage than the large particle materials. At 12 kg, the surface damage was inversely proportional to the surface hardness, whereas at 40 kg, it was proportional to the subsurface hardness. At both loads, subsurface damage was directly proportion to subsurface hardness. For the composite to composite bonds, the fatigue limit values were approximately 30% of the shear bond strength values and the values were significantly different (p<0.01) for all nine groups. For metal to enamel bonds, the fatigue limit (after 5000 cycles) varied between 10.7 and 16.8 MPa compared to 21.3 and 48 MPa for the shear strength. The values for all groups was significantly different (p<0.001). There was no significant correlation between the shear bond strength and the fatigue limit values (Pearson Correlation P<0.01). For all groups, the threshold stress at which the samples equid withstand over one million cycles (fatigue Life) was 2.5 MPa. For ceramic to enamel bonds, the fatigue limit (after 5000 cycles) varied between 11.41 and 13.74 MPa compared to 21.3 and 48 MPa for the shear strength. The values for all groups were significantly differ~nt (p<0.001). There was no significa~t correlation between the shear bond strength and the fatigue limit values (Pearson Correlation P<0.001). For all groups, the threshold stress at which the samples could withstand over one million cycles (fatigue Life) was 2.5 MPa. Conclusion: Fatigue damage to the surface and subsurface of composite was related to the hardness of the material. The values of the fatigue limit were significantly lower than the shear bond strength values. There was no correlation between fatigue limit and shear bond strength. The long term safety limit for resin bonded joints to enamel is 2.5 MPa. Neither the shear test, nor the fatigue limit test was an accurate predictor of the long-term fatigue behaviour of resin-bonded restorations. A fatigue limit test using 100,000 cycles may be a useful predictor of the fatigue life which, in these studies, was half of the fatigue limit at 100, 000 cycles but the only reliable test is to test to failure. The data presented in this thesis indicated that the shear bond strength is not pred!ctor of long term failure. lClearfil Posterior, Cavex. Holland. 20cclusin. ICI. UK. 3Concise, 3M. USA. 4Admira, VOCO, Germany. 5Grandio. VOCO. Germany. 6Grandio Flow, VOCO, Germany. 7Spectrum, Dentsply, Germany. 8Durafill VS, Heraeus Kulzer, Germany. 9Herculite XRV, Kerr, USA. 10Prime&Bond. Dentsply, Germany. 110ptibond solo plus, Kerr, USA. 12BisGMAffEGDMA. 3M ESPE. USA. 13Nene Instruments Ltd.• UK. 14yerabond II, Aalba Dent Inc., USA. 15Calibra with Prime & Bond Resin, Dentsply, Germany. 16Panavia with ED-Primers. Kuraray, Japan. 17Nexus with Optibond Solo Plus Resin, Kerr, USA. 18Vitadur Alpha, VITA Zahnfabrik. Germany. 19Porcelain Etch-it gels, American Dental Supply. USA.
11
Forbes, Michael F. "Ultrasonic characterization of layered composite systems." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/5633.
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Patel, Ruchi D. "Thermal Aging of Benzoxazine-Epoxy Systems and Their Composites." Thesis, California State University, Long Beach, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10979174.
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New applications of polymers and their composites are arising and replacing traditional materials in the sectors of aerospace, automotive, and civil industries. Polymers and their composites are susceptible to oxidative degradation at high temperatures, especially when approaching but not quite reaching the glass transition temperature (Tg). Although the carbon fibers in these composites are stable at such temperatures, the matrix and especially the fiber-matrix interface can undergo degradation that affects the physical, chemical, and mechanical properties of the structure over time. From an industry point of view, it is important to understand the mechanism of these changes to improve the product quality and lifetime.
This thesis was designed to study the thermal oxidation of the Benzoxazine (BZ) and epoxy-based copolymer system and its composites with differing additives. During the comparison studies, two types of BZ based systems were used. These systems were differentiated by commercially and laboratory formulated systems. The cured specimens were aged at 160 °C, 180 °C, and 200 °C in an air-circulating oven for 24 weeks. The changes in weight, shear strength, flexural strength, and dynamic mechanical properties were recorded for aged samples. Fourier Transform Infrared Spectroscopy (FTIR) analysis was used to observe the changes in the chemical properties of the material after aging. Light microscopy and Dynamic Mechanical Analyzer (DMA) were performed to monitor the initiation of the oxidation-induced surface cracking and the crack number density, and the effect of thermal aging on glass transition temperature ( Tg), respectively.
The aim was to determine the thermal aging mechanism, oxidation thickness growth and crack initiation (damage indicators), and effects of oxidation on the physical, chemical, and mechanical properties of the tested materials. The resulting effects on the thickness of the oxidized layer (TOL) for resin systems and its composites showed that, after prolonged thermal exposure, the degradation mechanism changed from thermal oxidation to thermal degradation. The simultaneous effects of post-curing and thermal degradation lead to the change in Tg during exposure, which was noted from DMA results. Given the addition of epoxy to BZ was shown to be required to adjust the process-required viscosity, this study provides adequate information on mechanical and thermal behaviors of the copolymer resin systems and their composites under prolong isothermal exposure.
13
Chen, Ming. "Electromagnetic radiation calorimetry of thermoplastics, elastomers and composites systems." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54780.
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The application of microwave radiation for processing of glassy and semicrystalline thermoplastics, elastomeric polymers and composites was investigated. The goal of this research was to reveal the relationship between polymer structure and microwave absorptivity, and hence processability. The specimens were subjected to an electric field at 2.45 GHz either inside a rectangular waveguide or in a cylindrical resonant cavity applicator with less than 100 watts applied power. Both travelling wave modes and standing wave modes were examined. Temperatures, powers and times were recorded, leading to the concept of "microwave calorimetry." Low frequency dynamic mechanical and dielectric frequency-temperature spectra were obtained on the materials and combined to conveniently extrapolate structure-property relationships into the GHz region. A correlation was found between the dielectric properties of various polymers and the dipole moments of small molecule analogues. Evaluating heatability was most accurately found to be determined by the magnitude of (εS - ε∞), the oscillator strength. The value of (εS - ε∞) should be used together with the distribution of relaxation times and the activation energies of dipolar dispersion to predict heatability for microwave processing. The critical temperatures, TC, of dielectric loss were obtained from the intercepts of positive slope tangents of heating rate versus temperature plots at 2.45 GHz for polymers. Microwave processing was rapid above the critical temperature where the maximum dielectric loss fell in the 2.45 GHz frequency domain for efficient coupling of energy to the polymers. Shifting the dielectric relaxation spectrum into the microwave region by directly or indirectly increasing the temperature of each sample was unique and of key importance to processability. A schematic model was proposed to explain the behavior of two-phase materials subjected to microwave heating. Combining the heatability, (εS - ε∞), and the dielectric relaxation spectral response was found to be helpful in evaluating formulations of two-phase materials for electromagnetic radiation processing at high frequencies.Ph. D.
14
Mallow, Anne. "Stable paraffin composites for latent heat thermal storage systems." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54406.
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Phase change materials (PCMs) have the ability to store thermal energy as latent heat over a nearly isothermal temperature range. Compared to sensible heat storage, properly chosen PCMs can store an order of magnitude more energy when undergoing phase change. Organic PCMs present several advantages including their non-corrosive behavior and ability to melt congruently, which result in safe and reliable performance. Because of these qualities, organic PCMs have been proposed for use in latent heat thermal storage systems to increase the energy efficiency or performance of various systems such as cooling and heating in buildings, hot water heating, electronics cooling, and thermal comfort in vehicles. Current performance is hindered by the low thermal conductivity, which significantly limits the rate of charging and discharging. Solutions to this challenge include the insertion of high conductivity nanoparticles and foams to increase thermal transport. However, performance validation remains tied to thermal conductivity and latent heat measurements, instead of more practical metrics of thermal charging performance, stability of the composite, and energy storage cost.
This thesis focuses on the use of graphite nanoplatelets and graphite foams to increase the thermal charging performance of organic PCMs. Stability of graphite nanoplatelets in liquid PCM is realized for the first time through the use of dispersants and control of the viscosity, particle distribution, and oxidation. Thermal charging response of stable graphite nanoplatelet composites is compared to graphite foam composites. This study includes a correlation of thermal conductivity and latent heat to material concentration, geometry, and energy storage cost. Additionally, a hybrid PCM storage system of metal foam combined with graphite nanoplatelet PCM is proposed and evaluated under cyclic thermal conditions.
15
Nguyen, Felix Nhanchau. "Improvement of mechanical properties of polymeric composites : experimental methods and new systems /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9907.
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Belijar, Guillaume. "Anisotropic composite elaboration and modeling : toward materials adapted to systems." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30353/document.
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L'objectif de ces travaux de thèse a été de démontrer la possibilité, en se basant sur une approche prédictive, de contrôler avec précision la fonctionnalisation d'un matériau composite, d'isotrope à anisotrope, sous l'application d'un champ électrique. Ces derniers matériaux présentent en effet un fort potentiel pour des applications futures telles que des condensateurs intégrés ou bien encore des composites conducteurs thermiques. Une première approche théorique des différentes forces et mécanismes entrant en jeux lors de l'élaboration de composites anisotropes par chaînage a permis d'identifier les paramètres impactant le procédé d'élaboration. A la suite de cette étude théorique, un modèle de formation de chaînes de particules sous champ électrique a été développé afin de prédire la dynamique de chaînage. Le modèle choisi (méthode moment dipolaire effectif) a permis la simulation de plus de 4500 particules. Les paramètres ayant au préalable été identifiés ont ensuite été mesurés. Pour la permittivité des particules, une méthode de mesure diélectrophorétique a été développée, ce qui est une première dans le cas de particules céramiques. L'élaboration des composites anisotropes a été couplé avec un suivi novateur, en temps réel, d'un marqueur (permittivité) de la formation de chaînes, permettant d'obtenir la dynamique de structuration des particules. Afin de valider l'aspect prédictif du modèle numérique, une comparaison a été effectuée entre la dynamique mesurée et simulée. Les résultats obtenus ont démontré une très bonne fiabilité des prédictions du modèle, même si des progrès sont encore réalisables aux faibles taux de chargement. Dans un dernier temps, une preuve de concept a été démontrée, de la réalisation de composites anisotropes dont les particules sont alignées perpendiculairement au champ électriqueThis study was aimed to demonstrate the possibility, based on a predictive approach, to tailor the structure of a composite from isotropic to anisotropic when applying an electric field. This composites have great potential for future applications such as embed capacitors or thermally conductive composites. A theoretical approach of the forces and mechanisms acting in the elaboration of anisotropic composites by chaining allowed identifying the key parameters. Based on this approach a model of particle chaining under electric field was established to predict the structuration dynamics. This model (effective dipole moment) allowed simulating more than 4500 particles. The parameters previously identified were then measured, and for the particle permittivity, a dielectrophoretic measurement method was developed, which was a first for ceramic particles. The elaboration of anisotropic composites was coupled to a novel on-line monitoring of a chaining marker (permittivity), allowing to obtain the structuration dynamics. To validate the predictive aspect of the model, experimental and numerical dynamics were compared showing the robustness and accuracy of the model, even if improvement is still possible at low filler content. In the last part, a proof of concept was demonstrated of the elaboration of anisotropic composites with fillers oriented normally to the direction of the electric field
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Musch, Janelle C. Riemersma. "Design optimization of sustainable panel systems using hybrid natural/synthetic fiber reinforced polymer composites." Diss., Connect to online resource - MSU authorized users, 2008.
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Thesis (M.S.)--Michigan State University. Dept. of Civil and Environmental Engineering, 2008.Title from PDF t.p. (viewed on Aug. 3, 2009) Includes bibliographical references (p.129-132). Also issued in print.
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Shih, Po-Jen. "On-Line Consolidation of Thermoplastic Composites." Diss., A&T Access:, 1997. http://scholar.lib.vt.edu/theses/public/etd-135510112972690/etd-title.html.
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Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1997."UMI number: 9724066"--T.p. verso. Vita. Includes bibliographical references (p. 182-189). Available electronically via Internet.
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Bushell, Andrew Charles. "The application of laser-generated ultrasound to the testing of aluminium-epoxy bonded systems." Thesis, University of Warwick, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387330.
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Zhou, Yijun. "Polymer-Ceramic Composites for Conformal Multilayer Antenna and RF Systems." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1245240041.
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Salamone, Sam. "Densification of and constitutive laws for ceramic matrix composites and multilayered systems /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/10585.
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Yelle, Daniel Joseph. "Bonding of Wood Fiber Composites Simulating Natural Wood Cell Adhesion Using Lignin Activation Systems." Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/YelleDJ2001.pdf.
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Cen, Lejun. "Fish-like locomotion using flexible piezoelectric composites for untethered aquatic robotics." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45864.
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The capacity of humankind to mimic fish-like locomotion for engineering applications depends mainly on the availability of suitable actuators. Researchers have recently focused on developing robotic fish using smart materials, particularly Ionic Polymer-Metal Composites (IPMCs), as a compliant, noise-free, and scalable alternative to conventional motor-based propulsion systems. In this thesis, we investigate fish-like self propulsion using flexible bimorphs made of Macro-Fiber Composite (MFC) piezoelectric laminates. Similar to IPMCs, MFCs also exhibit high efficiency in size, energy consumption, and noise reduction. In addition, MFCs offer large dynamic forces in bending actuation, strong electromechanical coupling as well as both low-frequency and high-frequency performance capabilities. The experimental component of the presented work focuses on the characterization of an MFC bimorph propulsor for thrust generation in a quiescent fluid as well as the development of a preliminary robotic fish prototype incorporating a microcontroller and a printed-circuit-board (PCB) amplifier to generate high actuation voltage for battery-powered free locomotion. From the theoretical standpoint, a reliable modeling framework that couples the actuator dynamics, hydroelasticity, and fish locomotion theory is essential to both design and control of robotic fish. Therefore, a distributed-parameter electroelastic model with fluid effects and actuator dynamics is coupled with the elongated body theory. Both in-air and underwater experiments are performed to verify the incorporation of hydrodynamic effects in the linear actuation regime. For electroelastically nonlinear actuation levels, experimentally obtained underwater vibration response is coupled with the elongated body theory to predict the thrust output. Experiments are conducted to validate the electrohydroelastic modeling approach employed in this work and to characterize the performance of an MFC bimorph propulsor. Finally, a wireless battery-powered preliminary robotic fish prototype is developed and tested in free locomotion at different frequency and voltage levels.
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Kanelidis, Ioannis [Verfasser]. "Polymer-Nanocrystal Composites: Copolymers, Polymeric Particles and Hybrid Systems / Ioannis Kanelidis." Wuppertal : Universitätsbibliothek Wuppertal, 2012. http://d-nb.info/1022590464/34.
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Liu, Ziqian. "Life cycle assessment of composites and aluminium use in aircraft systems." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8573.
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As a consequence of the gradually expanding aviation network, civil aircrafts
are occupying an increasingly high proportion of the transport industry. Air
transport now dominates the intercity rapid transit, long-distance passenger
transport, international passenger and freight transport, and specific regional
transport, advantaged as it is by fast, convenient, comfortable and safe options.
Nevertheless, the potential adverse impact on the environment of air transport,
specifically, in the case of this research, the pollutants generated during aircraft
production remain a concern.
Using the A319 as the main research object, this thesis will conduct a life cycle
assessment research about its environmental impact. Moreover, it will focus on
the impact brought by the application of composite materials to the entire life
cycle environmental influence of the aircraft, particularly the material production
and disposal process. At the same time, a contrast with the B737-800 aircraft
will be made due to their different composite material use rate.
Firstly, the inventory list is formed by collecting data about the weight and
material of every component in the aircraft, the input and output information of
the composite material manufacturing process, the disposal situation of the
aircraft and the treatment of composite material. Secondly, the impact
assessment of the aircraft is conducted to examine their environmental
influence. During the assessment, each life stage and the whole life cycle of the
aircrafts is assessed, and a comparison between these two aircraft types is
made. Finally, according to the impact assessment result, the environment load
increase brought by the manufacturing of composite material and the decrease
of the environment impact due to the weight reduction character of composite
material is calculated and compared.
From this research, the conclusion that the use of composite material has a
positive effect on decreasing the environmental impact of the whole life cycle of
the aircraft is obtained. This will enable aircraft manufacturers to target these
reas for improvement, to produce more comfortable, environment friendly and
market competitive aircraft.
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Grimaldos, Osorio Nicolas. "Novel Ammonia Storage Materials for SCR Systems : Carbon Materials – Salt Composites." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75167.
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The emissions of nitrogen oxides (NOx) are a serious environmental problem due to its relationship with the formation of smog, acid rain and because they are dangerous for human and animal health. These gases are produced in high quantities in diesel engines used for automotive applications, and different strategies are being used to reduce them, among which are the Selective Catalytic Reduction (SCR) systems. For its operation, it is necessary a supply of ammonia as NOx reducing agent, but the inefficiency at low temperatures of the systems used nowadays has led to the conception of the solid ammonia storage units (ASS). Unfortunately, the materials currently used, i.e. metal halides, do not meet the ammonia supply requirements at low temperatures and have problems of swelling and agglomeration. In order to find a material with better properties for its application as an ammonia sorbent material, MgCl2 composites with different carbon materials (graphite, graphene, and SWCNTs) were prepared by direct mixing and wet impregnation methods, and characterized in this work. Despite the decrease of total storage capacity, improvements were found in thermal stability and mass retention, as well as in sorption and desorption kinetics, making these materials a first result towards the improvement of the solid ammonia storage units.
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Stander, Heinrich. "Interfacial bond properties for ECC overlay systems." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/405.
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Warren, Jeremy. "Optimizing performance in photovoltaic devices based on conjugated poly(phenylene vinylenes)." Akron, OH : University of Akron, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1144257019.
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Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Science, 2006."May, 2006." Title from electronic dissertation title page (viewed 10/11/2006) Advisor, Frank W. Harris; Committee members, Stephen Z. D. Cheng, David A. Modarelli, Judit Puskas, William J. Brittain; Department Chair, Mark D. Foster; Dean of the College, Frank N. Kelley; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Bassett, Julien. "Thermochemical modeling of composite materials for base substrate applications in microelectronic systems." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/18211.
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Hussain, Abid Sayeed. "A finite element study of micromechanical effects in fibre reinforced composites systems." Thesis, University of Manchester, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488454.
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Vantaram, Avinash. "Honeycomb fiber-reinforced polymer sandwich composites for development of aquaculture raceway systems." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3622.
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Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains xi, 107 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 87-89).
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Böhm, Robert, Mike Thieme, Daniel Wohlfahrt, Daniel Sebastian Wolz, Benjamin Richter, and Hubert Jäger. "Reinforcement Systems for Carbon Concrete Composites Based on Low-Cost Carbon Fibers." Molecular Diversity Preservation International MDPI, 2018. https://tud.qucosa.de/id/qucosa%3A33323.
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Carbon concrete polyacrylonitrile (PAN)/lignin-based carbon fiber (CF) composites are a new promising material class for the building industry. The replacement of the traditional heavy and corroding steel reinforcement by carbon fiber (CF)-based reinforcements offers many significant advantages: a higher protection of environmental resources because of lower CO2 consumption during cement production, a longer lifecycle and thus, much less damage to structural components and a higher degree of design freedom because lightweight solutions can be realized. However, due to cost pressure in civil engineering, completely new process chains are required to manufacture CF-based reinforcement structures for concrete. This article describes the necessary process steps in order to develop CF reinforcement: (1) the production of cost-effective CF using novel carbon fiber lines, and (2) the fabrication of CF rebars with different geometry profiles. It was found that PAN/lignin-based CF is currently the promising material with the most promise to meet future market demands. However, significant research needs to be undertaken in order to improve the properties of lignin-based and PAN/lignin-based CF, respectively. The CF can be manufactured to CF-based rebars using different manufacturing technologies which are developed at a prototype level in this study.
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Uddin, Nasir Mohammad Capaldi Franco Farouk Bakhtier. "Modeling and simulations of carbon nanotube (CNT) dispersion in water/surfactant/polymer systems /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3203.
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Almarzouki, Mai. "Influence of polishing systems on the surface roughness of different direct resin composites." Thesis, NSUWorks, 2013. https://nsuworks.nova.edu/hpd_cdm_stuetd/25.
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Background. There are many polishing systems available on the market have been used by many clinicians to improve the color stability, wear resistance and surface smoothness of composite restorations. Several changes have been made in the fabrication of dental resin composites to improve their mechanical strength and esthetic properties. Previous studies have shown that composite resins are susceptible to color instability because of surface roughness and exposure to various staining media, especially red wine, coffee, soda and tea. The purpose of this study was to evaluate the average surface roughness (Ra) and color stability of two direct resin compositespolished with four different polishing systems. Methods. Two resin composites (nanohybrid and nanofill) were evaluated using four polishing systems (Four versus three steps; diamond versus fluted burs). A disk-like specimen of each composite material was fabricated (10 mm in diameter and 2 mm thick). Ten specimens of each composite were randomly assigned to one of four polishing systems. The surface roughness values were measured using the profilometer. In addition, discoloration of the polished composites was evaluated after immersion into different solutions, namely coffee and red wine. The staining of the materials was evaluated using the spectrophotometer. Results. No difference was noted between any of the four different polishing techniques, type of composite and surface roughness (Ra). A one way ANOVA showed that there was a statistical significant difference between color change (ΔE) and polishing techniques, p
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De, Caso y. Basalo Francisco Jose. "Sustainable Composite Systems for Infrastructure Rehabilitation." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/495.
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The development of composite materials by combining two or more constituents with improved mechanical properties, when compared to either of the constituents alone, has existed since biblical times when straw or horse hair was mixed with clay or mud to produce bricks. During the second half of the twentieth century, modern composites known as fiber reinforced polymers (FRP) - consisting of a reinforcing phase (fibers) embedded into a matrix (polymeric resin or binder) - were developed to meet the performance challenges of space exploration and air travel. With time, externally-bonded FRP applications for strengthening of reinforced concrete (RC) structures gained popularity within the construction industry. To date, the confinement of RC columns using FRP systems is a convenient and well established solution to strengthen, repair and retrofit structural concrete members. This technology has become mainstream due to its cost effectiveness, and relative ease and speed of application with respect to alternative rehabilitation techniques such as steel or concrete jackets. However, significant margins exist to advance externally-bonded composite rehabilitation technologies by addressing economic, technological, and environmental issues posed by the use of organic polymer matrices, some of which are addressed in this dissertation. Articulated in three studies, the dissertation investigates the development of a sustainable, reversible, and compatible fiber reinforced cement-based matrix (FRC) composite system for concrete confinement applications in combination with a novel test method aimed at characterizing composites under hydrostatic pressure. Study 1 develops and characterizes a FRC system from different fiber and inorganic matrix combinations, while evaluating the confinement effectiveness in comparison to a conventional FRP system. The feasibility of making the application reversible was investigated by introducing a bond breaker between the concrete substrate and the composite jacket in a series of confined cylinders. The prototype FRC system produced a substantial increase in strength and deformability with respect to unconfined cylinders. A superior deformability was attained without the use of a bond breaker. The predominant failure mode was loss of compatibility due to fiber-matrix separation, which points to the need of improving fiber impregnation to enable a more efficient use of the constituent materials. Additionally semi-empirical linear and nonlinear models for ultimate compressive strength and deformation in FRC-confined concrete are also investigated. Study 2 compares through a life cycle assessment (LCA) method two retrofitting strategies: a conventional organic-based, with the developed inorganic-based composite system presented in Study 1, applied to concrete cylinders by analyzing three life cycle impact indicators: i) Volatile Organic Compound (VOC) emissions, ii) embodied energy, and, iii) carbon foot print. Overall the cement-based composite provides an environmentally-benign alternative over polymer-based composite strengthening system. Results also provide quantitative information regarding the environmental and health impacts to aid with the decision-making process of design when selecting composite strengthening systems. Study 3 is divided into two parts, Part A presents the development of a novel "Investigation of Circumferential-strain Experimental" (ICE) methodology for characterization of circumferential (hoop) strain of composite laminates, while Part B uses the experimental data reported in Part A to explicitly evaluate the effect of FRP jacket curvature and laminate thickness on strain efficiency. Results showed that the proposed ICE methodology is simple, effective and reliable. Additionally, the ultimate circumferential strain values increased with increasing cylinder diameter, while being consistently lower when compared to similar flat coupon specimens under the same conditions. The ultimate FRP tensile strain was found to be a function of the radius of curvature and laminate thickness, for a given fiber ply density and number. The effect of these findings over current design guidelines for FRP confined concrete was also discussed.
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Liang, Ya Palmese Giuseppe R. Lowman Anthony M. "Functional polymer-polymer composites by nano/meso-fiber encapsulation : applications in drug delivery systems and polymer toughening /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3316.
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Zhou, Aixi. "Stiffness and Strength of Fiber Reinforced Polymer Composite Bridge Deck Systems." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/29210.
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This research investigates two principal characteristics that are of primary importance in Fiber Reinforced Polymer (FRP) bridge deck applications: STIFFNESS and STRENGTH. The research was undertaken by investigating the stiffness and strength characteristics of the multi-cellular FRP bridge deck systems consisting of pultruded FRP shapes.
A systematic analysis procedure was developed for the stiffness analysis of multi-cellular FRP deck systems. This procedure uses the Method of Elastic Equivalence to model the cellular deck as an equivalent orthotropic plate. The procedure provides a practical method to predict the equivalent orthotropic plate properties of cellular FRP decks. Analytical solutions for the bending analysis of single span decks were developed using classical laminated plate theory. The analysis procedures can be extended to analyze continuous FRP decks. It can also be further developed using higher order plate theories.
Several failure modes of the cellular FRP deck systems were recorded and analyzed through laboratory and field tests and Finite Element Analysis (FEA). Two schemes of loading patches were used in the laboratory test: a steel patch made according to the ASSHTO's bridge testing specifications; and a tire patch made from a real truck tire reinforced with silicon rubber. The tire patch was specially designed to simulate service loading conditions by modifying real contact loading from a tire. Our research shows that the effects of the stiffness and contact conditions of loading patches are significant in the stiffness and strength testing of FRP decks. Due to the localization of load, a simulated tire patch yields larger deflection than the steel patch under the same loading level. The tire patch produces significantly different failure compared to the steel patch: a local bending mode with less damage for the tire patch; and a local punching-shear mode for the steel patch. A deck failure function method is proposed for predicting the failure of FRP decks. Using developed laminated composite theories and FEA techniques, a strength analysis procedure containing ply-level information was proposed and detailed for FRP deck systems. The behavior of the deck's unsupported (free) edges was also investigated using ply-level FEA.Ph. D.
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Colquhoun, Ross. "Production and characterisation of CorGlaes pure 107 degradable polymer composites." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6352/.
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Phosphate glass fibre polymer composites have the potential to be utilised as degradable orthopaedic implant devices with modifications to the glass fibre composition allowing for materials with tailorable mechanical properties and degradation rates. Accordingly such materials could be advantageous for the development of alternative cranioplasty implant devices. In collaboration with an industrial sponsor, a promising composition of phosphate glass was characterised to assess its potential as a composite reinforcing agent along with the applicability of different composite configurations as possible cranioplasty implants. The CorGlaes® Pure 107 phosphate glass was found to demonstrate suitable dissolution rates for cell culture whilst vibrational spectroscopy and analytical chemistry techniques confirmed its structural features and suitability for fibre manufacturing. The mechanical properties of its bulk and fibre formats were determined to be in line with alternate PG compositions but initial biocompatibility screenings of glass samples using human osteosarcoma cells found this composition to be cytotoxic. This was believed to be due to localised pH changes or from the release of Zn2+ ions towards cytotoxic levels. The absence of a carbonated hydroxyapatite layer formation when immersed in simulated body fluid also indicated that this glass composition possessed no in vitro bioactivity. Composite materials based on CorGlaes® Pure 107 fibres in a polylactic acid (PLA) matrix at a 0.2 fibre volume fraction (Vf) were found to exhibit mechanical properties within the same region as those reported for cranial bones. However rapid dissolution of the reinforcing fibres (due to autocatalysis) led to premature reductions in the composite mechanical properties and resulted in a cytotoxic response during in vitro cell culture. The introduction of a secondary hydroxyapatite filler phase into the CorGlaes® Pure 107 composite to counteract the acidic pH led to changes in the samples mechanical properties and degradation media pH. However this failed to retard the fibre dissolution rate in 0.15Vf composites. At a 0.01Vf, the inclusion of HA produced biocompatible composites compared to the HA free equivalent and was attributed to the reduction of preferential Zn2+ ion release from the glass fibres due to the pH buffering at the fibre-matrix interface. However the low Vf required to achieve biocompatible composites made the CorGlaes® Pure 107 fibres unsuitable as a primary composite reinforcing agent. Consequently phosphate glass fibre composites may be suitable for cranioplasty applications with future hybrid composites allowing for the design of implant materials that are capable of eliciting an immediate in vivo response whilst retaining its long term mechanical properties.
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Al, Haik Mohammad Yousef. "Nanoparticle-based Organic Energy Storage with Harvesting Systems." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/79815.
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A new form of organic energy storage devices (organic capacitors) is presented in the first part of this dissertation. The storage devices are made out of an organic semiconductor material and charge storage elements from synthesized nanoparticles. The semiconducting polymer is obtained by blending poly (vinyl alcohol) and poly (acrylic acid) in crystal state polymers with a known plasticizer; glycerol or sorbitol. Synthesized nanoparticles namely, zinc-oxide (ZnO), erbium (Er), cadmium sulfide (CdS), palladium (Pd) and silver-platinum (AgPt) were used as charge storage elements in fabrication of metal-insulator-semiconductor (MIS) structure. The organic semiconductor and synthesized nanoparticles are tested to evaluate and characterize their electrical performance and properties. Fabrication of the organic capacitors consisted of layer-by-layer deposition and thermal evaporation of the electrode terminals. Capacitance versus voltage (C-V) measurement tests were carried out to observe hysteresis loops with a window gate that would indicate the charging, discharging and storage characteristics. Experimental investigation of various integrated energy harvesting techniques combined with these organic based novel energy storage devices are performed in the second part of this dissertation. The source of the energy is the wind and is harvested by means of miniature wind turbines and vibrations, using piezoelectric transduction. In both cases, the generated electric charge is stored in these capacitors. The performance of the organic capacitors are evaluated through their comparison with commercial capacitors. The results show that the voltage produced from the two energy harvesters was high enough to store the harvested energy in the organic capacitors. The charge and energy levels of the organic capacitors are also reported.
The third part of this dissertation focuses on harvesting energy from a self-induced flutter of a thin composite beam. The composite beam consisted of an MFC patch bonded near the clamped end and placed vertically in the center of a wind tunnel test section. The self sustaining energy harvesting from the unimorph composite beam is exploited. The effects of different operational parameters including the optimum angle of attack, wind speed and load resistance are determined.Ph. D.
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Patil, Sandeep Kesharsingh. "Modeling and simulations of diphasic composites for development of high energy density dielectrics." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Patil_09007dcc804e35ca.pdf.
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Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 21, 2008) Includes bibliographical references.
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Rajayogan, Vinod Engineering & Information Technology Australian Defence Force Academy UNSW. "Autogenous shrinkage in cementitious systems." Awarded by:University of New South Wales - Australian Defence Force Academy. Engineering & Information Technology, 2009. http://handle.unsw.edu.au/1959.4/44250.
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Autogenous shrinkage is of concern in high performance concrete mixtures, when specific properties like strength and durability are enhanced. Factors like low watercement ratio, low porosity and increased hydration kinetics which are associated with high performance concrete mixtures are also responsible for the development of autogenous shrinkage. With about two decades of research into autogenous shrinkage, uncertainties still exist with testing procedure, effect of supplementary cementitious materials, modelling and prediction of autogenous shrinkage. The primary focus of this study is to understand mechanisms which have been postulated to cause autogenous shrinkage like chemical shrinkage and self desiccation. In addition, this study has considered properties like porosity and internal empty voids in the analysis of the causes of bulk volume deformations of the cementitious paste systems with and without mineral admixtures. The study begins with an experimental investigation of chemical shrinkage in hydrating cementitious paste systems with the addition of fly ash, slag and silica fume using the test method recently accepted by the ASTM. This was followed by the experimental investigation of autogenous shrinkage in cementitious paste. The autogenous shrinkage in paste mixtures is studied from an early age (~1.5 hours after addition of water) for cementitious systems at a water-cementitious ratio of 0.32 (w/c 0.25 for limited mixture proportions). A non-contact measurement method using eddy current sensors were adopted. The hydration mechanism of the cementitious paste systems was then modelled using CEMHYD3D, which is a 3 dimensional numerical modelling method successfully used to study, simulate and present the hydration developments in cementitious systems. Properties like chemical shrinkage, degree of hydration, total porosity and free water content; all of which have been obtained from the CEMHYD3D simulation have been cross correlated with the experimental results in order to more comprehensively understand the mechanism contributing to bulk volume change under sealed conditions. The experimental investigations are extended to study the development in concrete with and without mineral admixtures (i.e., silica fume, fly ash and slag). Self desiccation driving the development of autogenous shrinkage has been used extensively across literature but as an alternative the author has proposed using internal drying factor in modelling autogenous shrinkage. The "internal drying factor" is described as the ratio of the empty voids (due to chemical shrinkage) to the total porosity at any point of time of hydration. Independent of the mixture proportions, a linear trend was observed between the autogenous shrinkage strain and increase in internal drying factor. Thus the internal drying factor could be incorporated into semiempirical models while attempting to predict autogenous shrinkage. An increase in the compressive strength of matured concrete at 1 year had a strong correlation to the observed autogenous shrinkage strains irrespective of the cementitious system. It is believed this could be because of the increase in gel-space ratio which is intern linked to the degree of hydration and porosity of the microstructure. The author has obtained strong evidence that the micro-structural changes associated with high strength and durable concrete have a direct impact on the autogenous shrinkage of concrete. Hence, the author suggests that autogenous shrinkage should be investigated and allowable values be stipulated as design criterion in structures that use high strength-high performance concrete.
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Specht, Paul Elliott. "Shock compression response of aluminum-based intermetallic-forming reactive systems." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47559.
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Heterogeneities at the meso-scale strongly influence the shock compression response of composite materials. These heterogeneities arise from both structural variations and differing physical/mechanical properties between constituents. In mixtures of reactive materials, such as Ni and Al, the meso-scale heterogeneities greatly affect component mixing and activation, which, in turn, can induce a chemical reaction. Cold-rolled multilayered composites of Ni and Al provide a unique system for studying the effects of material heterogeneities on a propagating shock wave, due to their full density, periodic layering, and intimate particle contacts. Computational analysis of the shock compression response of fully dense Ni/Al multilayered composites is performed with real, heterogeneous microstructures, obtained from optical microscopy, using the Eulerian hydrocode CTH. Changes in the orientation, density, structure, and strength of the material interfaces, as well as the strength of the constituents, are used to understand the influence microstructure plays on the multilayered composite response at high strain rates. The results show a marked difference in the dissipation and dispersion of the shock wave as the underlying microstructure varies. These variations can be attributed to the development of two-dimensional effects and the nature of the wave reflections and interactions. Validation of the computational results is then obtained through time-resolved measurements (VISAR, PDV, and PVDF stress gauges) performed during uniaxial strain plate-on-plate impact experiments. The experimental results prove that the computational method accurately represents the multilayered composites, thereby justifying the conclusions and trends extracted from the simulations. The reaction response of cold-rolled multilayer composites is also investigated and characterized using uniaxial stress rod-on-anvil impact experiments through post-mortem microscopy and x-ray diffraction. This extensive understanding of the shock compression response of the multilayers systems is contrasted with other composites of Ni and Al, including shock consolidated and pressed (porous) powder compacts. A comprehensive design space is then developed to assist in the understanding and design of Ni/Al composites under conditions of high pressure shock compression. Research funded by ONR/MURI grant No. N00014-07-1-0740.
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Pavlick, Matthew Michael. "Characterization of mechanical properties of advanced polymeric systems evaluated for a cryotank environment." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/18997.
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Subramaniam, C. "Chemorhelogical Modeling Of Amine-Cured Multifunctional Epoxy Resin Systems Used As Matrices In Aerospace Composites." Thesis, Indian Institute of Science, 1994. http://hdl.handle.net/2005/127.
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High performance multifunctional epoxy resin systems are becoming increasingly important as matrix materials for the advanced composites used in aerospace, electronics, automotive and other industries. In a composite based on epoxy resin systems, a three-dimensional network of the matrix is formed around the reinforcing fibre as a result of the chemical reaction between the resin and the curing agent. This chemical process, known as curing, is an important event to he considered in the production of composite components made up of these resin systems. Two process parameters namely viscosity and chemical conversion are of paramount significance in the production of composite materials Curing studies of the resin systems based on these two parameters, would therefore assume great importance in deciding the performance reliability of the end product.
The objectives of the present investigation are
1. to study the cure kinetics of three thermoset resin systems, viz.,
i) epoxy novolac (EPIT)/ diamino diphenyl methane{DDM), ii) trigylcidyl para- ammo phenol (TGPAP)/toluene diamine (TDA) and iii) tetraglycidyl diamino diphenyl methane (TGDDM)/pyridine diamine(PDA) using the cure kinetic models based on chemical conversion (α), Theological conversion (β) and viscosity.
2.to develop a correlation between a and viscosity (η) and modify an existing autocatalytic model based on α, to the viscosity domain and
3.to investigate the cure behaviour of these systems in terms of the TTT cure diagram and its associated models.
EPN/DDM, TGPAP/PDA and TGDDM/PDA resin systems were chosen for the studies to represent a range of functionalities, The cure was monitored using differential scanning calorimetry (DSC), fourier transform infrared (FTIR) and dynamic mechanical analysis (DMA) techniques by following the changes in enthalpy, functional groups and rheology, respectively.
The kinetic parameters namely, order of reaction and activation energy were estimated from dynamic DSC data using the methods of Freeman-Carroll and Ellerstein using nth rate expression. Barton, Kissinger and Osawa methods were employed to find out the activation energy from the peak/equal conversion at different heating rates. Isothermal DSC data were also analyzed using nth order model and it was observed that the data could be fitted satisfactorily only for higher temperatures The results obtained from the analysis of both dynamic and isothermal DSC data using nth order model clearly indicate that this model is inadequate for describing the cure behavior. The isothermal DSC data was analyzed by the autocatalytic models of Hone and Kamal Good correlation was observed with Hum and Kamal models up to 60-70%, 25% and 45% conversions for EPN/DDM, TGPAP/TDA and TCDDM/PDA systems respectively. However, the parameters m and n in Kamal model were found to be temperature dependent for EPN/DDM and TCPAP/TDA systems. The limited applicability of the autocatalytic models IK attributed to the counter-effect offered by the intra-molecular bonding taking place.
The primary amine and epoxy groups conversions obtained from FTIR were analyzed using autocatalytic model and the kinetic parameters were calculated. The reactivity ratio of the primary amine and the secondary amine with epoxy was found to be dependent on temperature in agreement with the recent findings reported m the literature.
The existing models that relate the cure kinetics and the rheological changes, are dual Arrhenius nth order model and autocatalytic model The nth order kinetic model was used to evaluate the kinetic parameters using the viscosity data at different cure temperatures under isothermal conditions As the storage modulus, G' is proportional to the chemical cross links and becomes significant only after the g<4 point, it was used to follow the changes in conversion known as rheoconversion after the gel point The rheoconversion was found by normalizing the G' data with G1^, the storage modulus of the fully cured resin It was used to study the cuie kinetics using an autocatalytic model The kinetic parameters such as rate constant, acceptation and retardation parameters were evaluated and that temperature dependence was established.
While the existing models relate viscosity and conversion only up to gel point the new proposed model, termed VISCON model takes into account the changes up to vitrification. The relation so developed is used to modify the autocatalytic cure model based on chemical conversion. The parameters appearing in this model were evaluated using Levenberg-Marquardt error minimization algorithm. The kinetic parameters obtained are comparable with the values estimated using the DSC data.
All the models cited above represent the microkinetic aspects. The models based on the information of TTT cure diagrams, however, represent the macrokinetic aspects of the cure, as they are based on the cure stages such as gelation and vitrification TTT diagram relates the cure characteristics like cure temperature, cure time, Ta and, indirectly, chemical conversion Hence the ultimate properties of the composite could he predicted and established with the help of the models based on TTT cure diagrams The changes in the storage modulus, G1 and loss modulus, G", were followed to identify the gel and vitrification points of the resin systems at different cure temperatures Gel point and vitrification point were used to generate gelation and vitrification hues in the construction of TTT cure diagrams for EPN/DDM, TGPAP/TDA and TGDDM/PDA resin systems Theoretical TTT diagrams were generated and IBO-T, contours were established using the TTT diagram-based models The cure schedule for the resin systems investigated could be determined from the TTT diagram and the respective rheological data.
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Druce, John W. "Mixed conducting CGO-LSCF Composites for Oxygen Separation in Oxyfuelled Carbon Capture and Storgage Systems." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526368.
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Li, Wai Chung. "Preparation and characterization of noble metal-magnetite hybrid nano/micro composites towards drug delivery and heterogeneous catalysis." HKBU Institutional Repository, 2019. https://repository.hkbu.edu.hk/etd_oa/668.
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This thesis describes the preparation and characterization of core-shell noble metal-magnetite hybrid hollow nanocomposites utilizing hierarchical architecture. The hollow magnetite (hFe3O4) nanoparticles were prepared by hydrothermal method, forming the cavity via Oswald ripening. Further surface modifications involved both inorganic and organic coatings, conferring the intracellular drug delivery ability and the catalytic enhancement. In the first part, a series of hierarchical core-shell nanostructures flower-like hFe3O4@AlOOH was synthesized through solvothermal method and sol-gel process. The formation of cavity accessible hFe3O4@γ-AlOOH was achieved using silica-templated solvothermal treatment where the Kirkendall effect was observed. The morphologies of the as-prepared nanocomposites were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). Then, the nano-encapsulation of platinum drug using hollow magnetite and its derivatives, has been developed with improved loading efficiency via co-solvent system. A dimethylformamide/water co-solvent system was found to be the most efficient system to encapsulate water-insoluble cisplatin. The platinum content was further quantitatively and qualitatively analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and FTIR spectroscopy. The enhancement of loading efficiency could be driven by emulsification due to the diffusion of hydrophobic cisplatin into the hollow cavity of iron oxide nanoparticles. By incorporating water, the loading efficiency of hFe3O4 and hFe3O4@γ-AlOOH increased from 1-2% to 27% and from 6% to 54%, respectively. The grafting of cisplatin on AlOOH nanoflakes might account for the high loading efficiency of flower-like hFe3O4@AlOOH. As a complement to naked hFe3O4, a cell-penetrating poly(disulfide)s (CPD)-decorated hollow iron oxide nanoparticle was synthesized by immobilizing both cysteine and MPTMS as an initiator, followed by in situ polymerization to form hFe3O4-Cys-CPD-CONH2 and hFe3O4-MPS-CPD-CONH2. The morphologies were characterized by TEM/energy-dispersive X-ray spectroscopy (TEM/EDX) and the compositions of the as-prepared iron oxide nanocomposites were characterized by TGA, FTIR and X-ray photoelectron spectroscopy (XPS) and ICP-MS. The CPD coating not only serve as a protective layer, but also prevent the encapsulated cisplatin from a premature release. The hFe3O4-MPS-CPD-CONH2 exhibit promising features for the intracellular delivery of cisplatin, demonstrating a glutathione (GSH)-responsive drug release. Comparing with other hFe3O4 nanoparticles, an enhancement of cellular uptake of hFe3O4-MPS-CPD-CONH2 could be observed by optical microscope, showing rapid accumulation of the hFe3O4-MPS-CPD-CONH2 nanocomposites in the primary human renal proximal tubular epithelial cells (HRPTEpiCs) cell in 2 h. At 24 h, hFe3O4 (F), hFe3O4-MPS (FS) and hFe3O4-MPS-CPD-CONH2 (FSC) together with cisplatin treatment did not cause any significant cytotoxicity to the cells when the particle concentration is less than 10 µg/mL. Interestingly, FSCC showed a certain extent of toxicity with increasing Fe and Pt concentration along with the treated time. It may suggest that the hFe3O4-MPS-CPD-CONH2 nanoparticle, as a cisplatin carrier, could enhance the drug efficiency by increasing cellular uptake of the nanoparticles in HRPTEpiCs together with the boosted cytotoxicity. Based on these data, cisplatin- hFe3O4-MPS-CPD-CONH2 (FSCC) treatments with the concentration less than 20 µg/mL and duration no more than 24 h could maintain around 70% of the cell viability of the HRPTEpiCs. The hypothesis, at which CPD serves as an efficient carrier for intracellular cisplatin delivery, could be confirmed by both microscopic images and the cell viability test. In the second part, a series of Au/Fe3O4 hybrid nanocomposites was prepared to investigate their catalytic efficiencies using 4-nitrophenol reduction as a model system. The flower-like hFe3O4@γ-AlOOH@SiO2-NH2@Au was prepared by using protonated ammonium on hFe3O4@γ-AlOOH@SiO2-NH2 to entangle gold nanoparticles (AuNPs) via electrostatic attraction. In comparison to numerous of catalytic studies, the turnover frequency (TOF) of hFe3O4@γ-AlOOH@SiO2-NH2@Au shows a superior conversion rate up to 7.57 min-1 (4-nitrophenol per Au per min) for the 4-nitrophenol using sodium borohydride as a reductant. A rapid conversion of 4-nitrohpenol was observed using flower like composites that converted the 4-nitrophenol within 2 min. Our result suggests that silica residue hinders the reduction rate of the 4-nitrophenol. A significant deviation from pseudo first order was observed for densely AuNPs-functionalized nanoflower system, hFe3O4@γ-AlOOH@SiO2-NH2@Au2X, which is different from most of the 4-nitrophenol reductions reported in literature. The hFe3O4@γ-AlOOH@SiO2-NH2@Au also demonstrates catalytic activity when heated up to 800 °C before reduction. The recyclability was examined using magnetically recycled hFe3O4@γ-AlOOH@SiO2-NH2@Au, which showed insignificant decrease in the catalytic efficiency. To prove the concept, platinum nanoparticles (PtNPs) immobilized hFe3O4@γ-AlOOH@SiO2-NH2@Pt and hFe3O4@γ-AlOOH@SiO2-NH2@Pt/Au were also prepared via electrostatic attraction to verify the feasibility of endowing modular functionality via post modification.
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Gawrylowicz, Julie. "The construction of facial composites by witnesses with mild learning disabilities." Thesis, Abertay University, 2010. https://rke.abertay.ac.uk/en/studentTheses/4821765e-ab7f-480f-a0e1-65c9291bbc50.
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In a criminal investigation, witnesses may get asked by the police to provide a perpetrator’s description or to generate a composite image of the perpetrator’s face. Due to their elevated vulnerability to victimisation people with a learning disability (LD) may be more likely than other members of the wider community to find themselves in such situations. Research regarding face recognition and description abilities of this group has been to some extent neglected in the eyewitness research literature. Consequently, guidance for practitioners on how to effectively generate facial composite images with LD witnesses is limited. The current research addresses this issue, by investigating basic and applied face recognition and description abilities in individuals with mild learning disabilities (mLD) during a series of experimental studies. Moreover, potential facilitating measures are introduced and assessed. Five studies were conducted during the course of this thesis. In the first study a survey was designed to collect information on currently used composite systems by UK law enforcement agencies and how operators perceive and treat witnesses with LD. The survey findings confirmed the initial assumption that individuals with LD may indeed find themselves in the situation of having to describe a perpetrator’s face to an investigative officer. Furthermore, the results emphasised the lack of guidance available to operators on how to best meet the special needs of this particular witness population. Study 2 investigated basic face recognition and description abilities in people with mLD and revealed that overall they performed at a lower level than the non-LD controls. Despite this finding, mLD individuals as a group performed above chance levels and they displayed variability in performance depending on the introduced measures. iv Studies 3 and 5 investigated these abilities in a more applied setting, namely during the construction of facial composites with contemporary facial composite systems. Study 3 revealed that composites generated with the E-FIT system, a featural system, were considerably poorer than those created by their non-LD counterparts. Studies 4 and 5 attempted to improve mLD individuals’ performance by applying visual prompts and by using a more holistic facial composite system, i.e. EvoFIT. There was little evidence of the former being advantageous for witnesses with mLD, however, EvoFIT significantly enhanced composite construction abilities in the mLD participants. Finally, the practical and theoretical implications of the main findings are discussed.
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Samur, Algan. "Flexible piezoelectric composites and concepts for bio-inspired dynamic bending-twisting actuation." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47680.
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Makhar, Sandeep P. "Mechanical properties of SU-8 and carbon nanotubes reinforced SU-8 from room temperature to high temperatures." Diss., Online access via UMI:, 2006.
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McCague, Colum. "Development of novel composite cement systems for the encapsulation of aluminium from nuclear wastes." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678940.
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Currently in the UK, composite blends of Portland cement (PC) and blastfurnace slag (up to 90%) are commonly used for the encapsulation of low and intermediate level wastes. The high volume replacement of PC is considered necessary in order to to reduce the high heat generation resulting from cement hydration in 500 litre waste packages. While suited to the majority of waste streams, the high pH environment in such systems (usually around 12.5 -13), will cause the corrosion of certain waste metals such as aluminium. Since aluminium is only passive between pH4 - 8.5, the use of an alternative low-pH cement system could serve to reduce/inhibit the corrosion. However, before such cements can be considered, two main research problems must be addressed, as follows: (1) quantitative evaluation of alternative cement systems based on their corrosion performance with aluminium; (2) high heat generation due to the rapid rate of hydration. The research in this thesis was thus divided into two strands, as follows: (1) The design and development of a novel, scientifically robust testing facility for the quantitative monitoring of aluminium corrosion in cement pastes; (2) the development of novel cement composites based on weakly alkaline calcium sulfoaluminate (CSA) cement for the encapsulation of aluminium from nuclear wastes. The output from this research is considered to be of interest to the UK nuclear industry.