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Grosskopf, Paul P. "Mechanical behavior of a ceramic matrix composite material." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42214.
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Monolithic ceramic materials have been used in industry for hundreds of years. These materials have proven their usefulness in many applications, yet, their potential for critical structural applications is limited. The existence of an imperfection in a monolithic ceramic on the order of several microns in size may be critical, resulting in catastrophic failure. To overcome this extreme sensitivity to sman material imperfections, reinforced ceramic materials have been developed. A ceramic matrix which has been reinforced with continuous fibers is not only less sensitive to microscopic flaws, but is also able to sustain significant damage without suffering catastrophic failure.
A borosilicate glass reinforced with several layers of plain weave silicon carbide cloth (Nicalon) has been studied. The mechanical testing which was performed included both flexural and tensile loading configurations. This testing was done not only to determine the material properties, but also to initiate a controlled amount of damage within each specimen.
Several nondestructive testing techniques, including acousto-ultrasonics (AU), were performed on the specimens periodically during testing. The AU signals were monitored through the use of an IBM compatible personal computer with a high speed data acquisition board. Software has been written which manipulates the AU signals in both the time and frequency domains, resulting in quantitative measures of the mechanical response of the material.
This paper will compare the measured AU parameters to both the mechanical test results and data from other nondestructive methods including ultrasonic C-scans and penetrant enhanced X-ray radiography.
Master of Science
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Trandel, Barbara Dawn. "Nondestructive evaluation of a high temperature ceramic matrix composite material." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-01312009-063125/.
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Davies, C. M. A. "Failure mechanisms in glass-ceramic matrix composite laminates." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387305.
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Moro, Marjan. "Nano-Characterization of Ceramic-Metallic Interpenetrating Phase Composite Material using Electron Crystallography." Youngstown State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1340223324.
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Paiva, Denis Valony Martins. "Development of a magneto-dieletric composite based on Y3FE5O12/CATIO3 for microwaves devices." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15155.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoCom o desenvolvimento da tecnologia sem fio, muitos dispositivos eletrÃnicos exigem alta integraÃÃo e que possuam propriedades multifuncionais. Em tal caso, compÃsitos magneto-dielÃtricos tÃm atraÃdo muita atenÃÃo devido as suas propriedades. Nesse sentido, a pesquisa sobre compÃsitos à empregada para a busca de novos materiais. O titanato de cÃlcio (CaTiO3 - CTO) e a granada de Ãtrio e ferro (Y3Fe5O12 - YIG) possuem excelentes propriedades dielÃtricas e ferrimagnÃticas, respectivamente. Este trabalho apresenta a obtenÃÃo do compÃsito ferrimagnÃtico, constituÃdo pelas fases YIG e CTO, atravÃs da rota sintÃtica no estado sÃlido com a utilizaÃÃo de moagem mecÃnica de alta energia. As fases das cerÃmicas foram sinterizadas a 1200ÂC/5h. A DifraÃÃo de Raios-X, a Espectroscopia Raman e MÃssbauer foram essenciais para caracterizaÃÃo estrutural dos compÃsitos. A morfologia das amostras foi elucidada pela Microscopia EletrÃnica de Varredura e auxiliada pela Picnometria a fim de avaliar a densificaÃÃo do material. Adicionalmente, foram realizados experimentos para se avaliar o comportamento elÃtrico e magnÃtico dos compÃsitos na faixa de radiofrequÃncia e de micro-ondas, para depois sugerir uma aplicaÃÃo tecnolÃgica cabÃvel. Os resultados obtidos pela DifraÃÃo de Raio X e da Espectroscopia Raman confirmaram que a sÃntese das fases foi realizada de forma satisfatÃria. As anÃlises qualitativas dos espectros MÃssbauer mostraram boa concordÃncia com os resultados apresentados pela DifraÃÃo de raios-x. Os compÃsitos apresentaram permissividade dielÃtrica praticamente constante na faixa de 50 MHz a 1,5 GHz. Ao analisar o aumento e a diminuiÃÃo da concentraÃÃo em massa de CTO e YIG, respectivamente, foi percebido que os valores de εr aumentaram. A partir dos valores obtidos, pode-se sugerir que o compÃsito sintetizado possui potencial para ser utilizado em dispositivos de micro-ondas, tais como para antenas monopolo.
With the development of wireless technology, many electronic devices require high integration and materials with multifunctional properties. In such a case, magneto-dielectric composites have attracted much attention because they have both magnetic and dielectric properties. In this sense, research on composites is employed to search for new materials. The calcium titanate and yttrium iron garnet possess excellent dielectric properties and ferrimagnetic, respectively. This paper presents the preparation of ferrimagnetic composite, comprising the steps Y3Fe5O12 (YIG) and CaTiO3 (CTO) by the solid state synthetic route with the use of high energy mechanical grinding. The phases of the ceramics were sintered at 1200 Â C for 5 h. The X-ray diffraction, Raman and MÃssbauer Spectroscopy were used to elucidade structural properties of the composites. The morphological characteristics of the samples were elucidated by Scanning Electron Microscopy and supported by Pycnometry to analyze the densification of the material. Furthermore, experiments to evaluate the electrical and magnetic behavior of composites in the range of radiofrequency and microwave were performed and finally an appropriate technological application was suggested. The results obtained by X-Ray Diffraction and Raman spectroscopy confirm that the synthesis of YIG was successfully obtained. The structural characterization of pure and composite samples was performed successfully and the formation of ionic phase in composites YIG-CTO was found, being in the same family of oxide in which the CTO is inserted. Qualitative analysis of the MÃssbauer spectra showed good agreement with the results reported by x-ray diffraction. The dielectric permittivity composites showed almost constant in the range of 50 MHz to 1.5 GHz. Evaluating the increasing and decreasing in mass concentration of CTO and YIG, respectively and it was realized that the values of εr increased. Two profiles was noticed in the compositional series, it can be inferred that the possibility of the reaction of YIG and CTO products may be interfering with the proper measurements.
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Pryce, A. W. "Matrix cracking and stress/strain behaviour of continuous fibre ceramic composite laminates." Thesis, University of Surrey, 1991. http://epubs.surrey.ac.uk/843150/.
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Matrix damage and its effects on mechanical properties have been examined for SiC (Nicalon1) fibre reinforced glass and glass ceramic matrix composites under quasi-static and fatigue loading conditions. Nicalon/Pyrex laminates of different lay-ups have been tested under quasi-static tension. The elastic moduli have been measured and matrix damage monitored as a function of applied strain. The mechanical properties are strongly influenced by the presence of crystalline regions in the matrix which promote microcracking. Laminated plate theory is used to provide bounds to the moduli of the laminates. For unidirectional and simple crossply Nicalon/CAS2 laminates the quasi-static stress/strain behaviour and associated matrix damage accumulation have been examined in detail. The damage development with applied stress was quantified by counts of crack density (in both longitudinal and transverse plies), stiffness loss and cumulative residual strain. The quasi static stress/strain behaviour during continuous tests (accumulating damage) and discontinuous tests (constant damage) have been modelled using a stress analysis based on Aveston, Cooper and Kelly (ACK) theory. The continuous stress/strain behaviour of (0/90) crossply laminates has been modelled using a shear-lag analysis developed previously to describe the transverse ply cracking behaviour of polymer matrix composites. The analysis is modified to account for longitudinal ply cracking. Matrix damage development in unidirectional and (0/90) crossply laminates under quasistatic cycling and high frequency fatigue loading have been studied. For unidirectional laminates stable stress/strain hysteresis loops were obtained during quasi-static cycling, corresponding to stable matrix damage states. These and similar loops obtained after high frequency fatigue are modelled using, the discontinuous stress/strain analysis. It is suggested that the effect of high frequency fatigue is to decrease the interfacial shear strength.
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Gordon, Neal A. "Material Health Monitoring of SIC/SIC Laminated Ceramic Matrix Composites With Acoustic Emission And Electrical Resistance." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1414835900.
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Rabih, Ali. "Élaboration et caractérisation de nanocomposites alumine - zircone à partir de poudres cosynthetisées par voie hydrothermale." Valenciennes, 1997. https://ged.uphf.fr/nuxeo/site/esupversions/337cf2fd-5f79-4072-932a-6fe51f860b1a.
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La synthèse hydrothermale a permis de synthétiser des poudres nanométriques de zircone stabilisée à l'oxyde d'yttrium, d'alumine (boehmite) et d'alumine-zircone. La caractérisation physique (diffraction des rayons x, densité, surface spécifique, analyse thermique différentielle, microscopie électronique. . . ) de ces poudres obtenues pour plusieurs températures de traitement hydrothermal a été réalisée. Les paramètres de cogélification des précurseurs de nitrates de zirconyle et d'aluminium par de la potasse ont été optimisés pour obtenir des poudres composites homogènes a l'échelle micronique. La taille de la poudre de zircone varie entre 13 et 25 nanomètres. La boehmite et l'alumine gamma présentent la même répartition granulométrique comprise entre 30 et 70 nanomètres. Le frittage naturel de ces poudres composites est devenu possible grâce à l'ensemencement du gel par de l'alumine alpha fine. Le comportement au frittage sous charge, la caractérisation des propriétés mécaniques (résistance à la flexion, facteur critique d'intensité de contrainte et dureté) et des microstructures ont été étudiés. Les microstructures obtenues sont nanométriques et présentent une répartition homogène entre les deux phases. La zircone présente est sous forme quadratique non transformable les nanocomposites étudiés à 5 et 50 % en volume de zircone présentent des valeurs de facteur critique d'intensité de contrainte améliorées par rapport à l'alumine pure. La résistance à la flexion pour la composition à 5 % de zircone est comparable par rapport à une alumine fine. Par contre nous observons une diminution de cette résistance à la flexion pour le nanocomposite à 50 % de zircone en raison d'un ensemencement insuffisant. Un essai de thermocompression a permis de réaliser des jonctions parfaites sans aucune aspérité et avec une excellente continuité au niveau des interfaces de nos nanocomposites alumine-zircone, ce qui laisse a priori suggérer un bon comportement superplastique.
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O'Sullivan, David. "Élaboration et caractérisation mécanique des nanocomposites alumine-carbure de silicium." Valenciennes, 1998. https://ged.uphf.fr/nuxeo/site/esupversions/fa8074c9-3bc2-47e1-a75e-41fa9c276467.
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L'objectif de cette étude était de développer un protocole de fabrication de nanocomposites à matrice d'alumine renforcée par des particules nanométriques (< 200 nm) de carbure de silicium utilisant des poudres commerciales et l'eau comme milieu de dispersion, ceci dans un but de faisabilité industrielle. Après la détermination des meilleures conditions de dispersion des poudres d'alumine et de carbure de silicium choisies, les mélanges ont été densifies par pressage à chaud afin d'obtenir des matériaux complètement denses. Malgré la température de frittage plus élevée utilisée pour les nanocomposites (1550°C au lieu de 1400°C), la taille moyenne des grains d'alumine se situant entre 0. 6 et 1. 5 µm est équivalente ou inférieure à celle des grains du matériau monolithique. L'étude des propriétés mécaniques a température ambiante de nanocomposites contenant entre 2. 5 et 25% en volume de SiC a permis de déterminer l'influence de la teneur en dispersoïdes à savoir une augmentation de la résistance en flexion (une valeur de 1 GPA a été obtenue pour le nanocomposite contentant 7. 5% en volume de SiC), une amélioration assez modeste de la ténacité, une légère diminution du module de Young ainsi qu'une faible augmentation de la dureté. L’étude comparative de la résistance au fluage de l'alumine et d'un nanocomposite contenant 5% en volume de SiC a montré que la vitesse de déformation du nanocomposite est 100 fois plus faible que celle de l'alumine pure. Un modèle de blocage du glissement aux joints de grains par les particules de SiC est proposé.
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Jahani, Babak. "Development of an Advanced Composite Material Consisting of Iron Matrix Reinforced with Ultra High Temperature Ceramic Particulate (TiB2) with Optimum Properties." Thesis, North Dakota State University, 2016. https://hdl.handle.net/10365/28089.
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This study was intended to investigate the mechanical properties and microstructure of iron based composite reinforced by ultra high temperature ceramics fabricated by powder metallurgy technique. The fabrication parameters were optimized and composite samples with different volume fraction of TiB2 were fabricated and were subjected to different mechanical tests. The results indicated improving in mechanical properties of Fe-TiB2 composites by increasing the volume fraction of TiB2 up to 20 vol%. More TiB2 particles didn?t improve the mechanical properties of composite, instead adversely affected it due to increasing the chance of agglomeration and porosity in entire microstructure. Another finding showed the twofold characteristic of TiB2 on mechanical properties of composite via increasing the hardness and decreasing the bulk density of composite. Finite Element Analysis (FEA) have also been performed on microstructural based developed models to simulate failure of composites. Numerical simulation results could verify the experimental results.
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Mathieu, Sylvain. "Modélisation du comportement mécanique lors du procédé de mise en forme et pyrolyse des interlocks CMC." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0115/document.
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La simulation des procédés de production des composites à renforts tissés est un enjeu majeur pour les industries de pointe, où leur utilisation s’intensifie. La maitrise des procédés d’obtention des composites à matrice et fibres en céramique, notamment les étapes de mise en forme et de pyrolyse, s’avère primordiale. La connaissance et la simulation du comportement mécanique aux différentes étapes est nécessaire pour optimiser les performances des pièces finales. Deux approches de modélisation macroscopique des renforts tissés épais de composite sont détaillées : une approche continue classique et une approche semi-discrète. Pour cela, une loi de comportement hyperélastique initialement orthotrope est développée. Cette loi est basée sur l’observation phénoménologique des modes de déformation privilégiés, à partir desquels sont proposés des invariants physiques de la transformation. L’identification des paramètres matériaux nécessaires est décrite. Une version modifiée de cette loi, sans contribution en tension, est implémentée dans un élément semi-discret, où le travail en tension est alors pris en compte par des barres discrétisant le tissage réel. Les importantes différences de rigidités entre sollicitations en tension et en cisaillements font des renforts tissés épais des matériaux fortement anisotropes. Leur modélisation numérique met en évidence des phénomènes parasites ou des limitations liés à cette spécificité. Le phénomène de verrouillage en tension est tout d’abord mis en évidence. Une solution basée sur une formulation éléments finis enhanced assumed strain est proposée pour des éléments continus classiques ou semi-discrets. Puis des problèmes liés aux simulations numériques dominées par la flexion sont soulevés : l’hourglassing transverse et l’absence de résistance locale à la courbure. Dans le cas de l’hourglassing transverse, deux méthodes de rigidification de ces modes de déplacement sont proposées : par moyennage des dilatations dans l’élément ou par ajout d’une rigidité matérielle tangente supplémentaire. Pour l’introduction d’une résistance à la courbure, une méthode basée sur l’utilisation purement numérique de plaques rotation free est proposée. Celles-ci permettent le calcul de la courbure induisant, par l’intermédiaire d’un moment de flexion, des efforts internes supplémentaires. Finalement, la modélisation du retour élastique après pyrolyse de la matrice organique à précurseurs céramique est réalisée. Le comportement de la matrice pyrolysée est identifié expérimentalement à l’aide d’une loi hyperélastique isotrope transverse. L’addition de cette loi, qui prend comme référence la préforme déformée, à la loi de comportement initiale du renfort tissé permet de visualiser les déformations obtenues en fin de pyrolyse. Cette modélisation est comparée à des résultats expérimentauxManufacture processes modeling of woven fabrics composites is a major stake for state-of-the-art industrial parts, where their usage is intensifying. Control of all the manufacturing stages of ceramic matrix composites, particularly the forming and pyrolysis steps, is essential. Understanding and simulation of the mechanical behavior at each stage is required to optimize the final product performances. Two macroscopic modeling approaches of thick woven fabric reinforcements are detailed: a continuous classical one and a semi-discrete one. An initially orthotropic hyperelastic constitutive law is thus established. This law is based on a phenomenological observation of the main fabric deformation modes, from where physical invariants of the deformation are suggested. The required material parameters identification is explained. A modified version of this law, without any tensile energetic contribution, is implemented in a semi-discrete element where the tensile work is taken into account by bars that discretize the real weaving. Thick woven reinforcements are highly anisotropic materials due to the large ratio between the tensile rigidity and the others. Their numerical modeling highlights spurious phenomena and limitations related to this specificity. The tension locking is firstly tackled. A remedy based on an enhanced assumed strain finite element formulation is suggested for classical continuum and semi-discrete elements. Problems linked to bending-dominated numerical simulations are brought to attention : transverse hourglassing and lack of local bending stiffness. For the transverse hourglassing situation, two stiffening technics are proposed : averaging the dilatation through the whole element or adding a supplementary tangent material rigidity in a specific direction. The local bending stiffness problem is solved by calculating the curvature inside the element by using rotation free plates. The induced bending moment leads to supplementary internal loads. Finally, the elastic springback following the pyrolysis of the polymer matrix with ceramic precursors is modeled. The constitutive behavior is experimentally identified with a transverse isotropic hyperelastic law. Added to the initial reinforcements’ hyperelastic law, with the preformed fabric as reference configuration, the pyrolysis induced deformations can be visualized. This final model is compared with experimental results
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Sláma, Martin. "Studium přípravy a vlastností biokeramických kompozitů na bázi Ca-fosfátů a ZrO2." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231718.
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The thesis was focused on preparation of bioceramic composite materials containing Ca-phosphates and zirconia fibers using electrophoretic deposition. A series of experiments were aimed at determining the appropriate composition of the suspensions. High-energy milling was used for preparing deposits with good physical and mechanical properties using EPD. The influence of milling time, the amount of monochloroacetic acid in isopropanol slurry indifferent electrolyte LiCl and ZrO2 were evaluated on the course deposition and the resulting properties of the deposits. Influence of sintering temperature, the milling time and the fiber content of ZrO2 on the chemical and structural composition was determined by X-ray analysis, measurement of density and structural analysis using a scanning electron microscope. Mechanical and bioactive properties of sintered deposits were determined depending on the milling time and content of ZrO2 fibers.
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Nowacki, Brenna M. "Verification and Calibration of State-of-the-Art CMC Mechanistic Damage Model." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1461761780.
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Nestler, Daisy Julia. "Beitrag zum Thema VERBUNDWERKSTOFFE - WERKSTOFFVERBUNDE." Doctoral thesis, Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-134459.
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Vielschichtige Eigenschaftsprofile benötigen zunehmend moderne Verbundwerkstoffe und Werkstoffverbunde einschließlich der raschen Entfaltung neuer Fertigungstechnologien, da der monolithische Werkstoff bzw. ein einziger Werkstoff den heutigen komplexen Anforderungen nicht mehr genügen kann. Zukünftige Werkstoffsysteme haben wirtschaftlich eine Schlüsselposition und sind auf den Wachstumsmärkten von grundlegender Bedeutung. Gefragt sind maßgeschneiderte Leichtbauwerkstoffe (tailor-made composites) mit einem adaptierten Design. Dazu müssen Konzepte entwickelt werden, um die Kombination der Komponenten optimal zu gestalten. Das erfordert werkstoffspezifisches Wissen und Korrelationsvermögen sowie die Gestaltung komplexer Technologien, auch unter dem Aspekt der kontinuierlichen Massen- und Großserienfertigung (in-line, in-situ) und damit der Kostenreduzierung bislang teurer Verbundwerkstoffe und Werkstoffverbunde. In der vorliegenden Arbeit wird in vergleichbarer und vergleichender Art und Weise sowie abstrahierter Form ein Bogen über das Gesamtgebiet der Verbundwerkstoffe und Werkstoffverbunde gespannt. Eine zusammenfassende Publikation über dieses noch sehr junge, aber bereits breit aufgestellte Wissenschaftsgebiet fehlt bislang. Das ist der Separierung der einzelnen, fest aufgeteilten Gruppierungen der Verbundwerkstoffe geschuldet. Querverbindungen werden selten hergestellt. Dieses Defizit in einem gewissen Maße auszugleichen, ist Ziel der Arbeit. Besondere Berücksichtigung finden Begriffsbestimmungen und Klassifikationen, Herstellungsverfahren und Eigenschaften der Werkstoffe. Es werden klare Strukturierungen und Übersichten herausgearbeitet. Zuordnungen von etablierten und neuen Technologien sollen zur Begriffsstabilität der Terminologien „Mischbauweise“ und „Hybrider Verbund“ beitragen. Zudem wird die Problematik „Recycling und Recyclingtechnologien“ diskutiert. Zusammenfassend werden Handlungsfelder zukünftiger Forschungs- und Entwicklungsprojekte spezifiziert. Aus dem Blickwinkel der verschiedenen Herstellungsrouten insbesondere für Halbzeuge und Bauteile und der dabei gewonnenen Erkenntnisse werden verallgemeinerte Konzepte für tailor-made Verbundwerkstoffe und Werkstoffverbunde vorgeschlagen („Stellschraubenschema“). Diese allgemeinen Werkstoffkonzepte werden auf eigene aktuelle Forschungsprojekte der Schwerpunktthemen Metallmatrix- und Polymermatrix-Verbundwerkstoffe sowie der hybriden Werkstoffverbunde appliziert. Forschungsfelder für zukünftige Projekte werden abgeleitet. Besonderes Augenmerk gilt den hybriden Verbunden als tragende Säule zukünftiger Entwicklungen im Leichtbau. Hier spielen in-line- und in-situ-Prozesse eine entscheidende Rolle für eine großseriennahe, kosteneffiziente und ressourcenschonende ProduktionComplex property profiles require increasingly advanced composite materials and material compounds, including the rapid deployment of new production technologies, because the monolithic material or a single material can no longer satisfy today's complex requirements. Future material systems are fundamentally important to growth markets, in which they have an economically key position. Tailor-made lightweight materials (tailor-made composites) with an adapted design are needed. These concepts have to be developed to design the optimum combination of components. This requires material-specific knowledge and the ability to make correlations, as well as the design of complex technologies. Continuous large-scale and mass production (in-line, in-situ), thus reducing the costs of previously expensive composite materials and material compounds, is also necessary. The present work spans the entire field of composite materials and material compounds in a comparable and comparative manner and abstract form. A summarizing publication on this still very new, but already broad-based scientific field is not yet available. The separation of the individual, firmly divided groups of the composite materials is the reason for this. Cross-connections are rarely made. The objective of this work is to compensate to some extent for this deficiency. Special consideration is given to definitions and classifications, manufacturing processes and the properties of the materials. Clear structures and overviews are presented. Mapping established and new technologies will contribute to the stability of the terms "mixed material compounds" and "hybrid material compounds". In addition, the problem of recycling and recycling technologies is discussed. In summary, areas for future research and development projects will be specified. Generalized concepts for tailor-made composite materials and material compounds are proposed ("adjusting screw scheme") with an eye toward various production routes, especially for semi-finished products and components, and the associated findings. These general material concepts are applied to own current research projects pertaining to metal-matrix and polymer-matrix composites and hybrid material compounds. Research fields for future projects are extrapolated. Particular attention is paid to hybrid material compounds as the mainstay of future developments in lightweight construction. In-line and in-situ processes play a key role for large-scale, cost- and resource-efficient production
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Nestler, Daisy Julia. "Beitrag zum Thema VERBUNDWERKSTOFFE - WERKSTOFFVERBUNDE: Status quo und Forschungsansätze." Doctoral thesis, Universitätsverlag Chemnitz, 2012. https://monarch.qucosa.de/id/qucosa%3A20009.
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Vielschichtige Eigenschaftsprofile benötigen zunehmend moderne Verbundwerkstoffe und Werkstoffverbunde einschließlich der raschen Entfaltung neuer Fertigungstechnologien, da der monolithische Werkstoff bzw. ein einziger Werkstoff den heutigen komplexen Anforderungen nicht mehr genügen kann. Zukünftige Werkstoffsysteme haben wirtschaftlich eine Schlüsselposition und sind auf den Wachstumsmärkten von grundlegender Bedeutung. Gefragt sind maßgeschneiderte Leichtbauwerkstoffe (tailor-made composites) mit einem adaptierten Design. Dazu müssen Konzepte entwickelt werden, um die Kombination der Komponenten optimal zu gestalten. Das erfordert werkstoffspezifisches Wissen und Korrelationsvermögen sowie die Gestaltung komplexer Technologien, auch unter dem Aspekt der kontinuierlichen Massen- und Großserienfertigung (in-line, in-situ) und damit der Kostenreduzierung bislang teurer Verbundwerkstoffe und Werkstoffverbunde.
In der vorliegenden Arbeit wird in vergleichbarer und vergleichender Art und Weise sowie abstrahierter Form ein Bogen über das Gesamtgebiet der Verbundwerkstoffe und Werkstoffverbunde gespannt. Eine zusammenfassende Publikation über dieses noch sehr junge, aber bereits breit aufgestellte Wissenschaftsgebiet fehlt bislang. Das ist der Separierung der einzelnen, fest aufgeteilten Gruppierungen der Verbundwerkstoffe geschuldet. Querverbindungen werden selten hergestellt. Dieses Defizit in einem gewissen Maße auszugleichen, ist Ziel der Arbeit. Besondere Berücksichtigung finden Begriffsbestimmungen und Klassifikationen, Herstellungsverfahren und Eigenschaften der Werkstoffe. Es werden klare Strukturierungen und Übersichten herausgearbeitet. Zuordnungen von etablierten und neuen Technologien sollen zur Begriffsstabilität der Terminologien „Mischbauweise“ und „Hybrider Verbund“ beitragen. Zudem wird die Problematik „Recycling und Recyclingtechnologien“ diskutiert. Zusammenfassend werden Handlungsfelder zukünftiger Forschungs- und Entwicklungsprojekte spezifiziert. Aus dem Blickwinkel der verschiedenen Herstellungsrouten insbesondere für Halbzeuge und Bauteile und der dabei gewonnenen Erkenntnisse werden verallgemeinerte Konzepte für tailor-made Verbundwerkstoffe und Werkstoffverbunde vorgeschlagen („Stellschraubenschema“). Diese allgemeinen Werkstoffkonzepte werden auf eigene aktuelle Forschungsprojekte der Schwerpunktthemen Metallmatrix- und Polymermatrix-Verbundwerkstoffe sowie der hybriden Werkstoffverbunde appliziert. Forschungsfelder für zukünftige Projekte werden abgeleitet. Besonderes Augenmerk gilt den hybriden Verbunden als tragende Säule zukünftiger Entwicklungen im Leichtbau. Hier spielen in-line- und in-situ-Prozesse eine entscheidende Rolle für eine großseriennahe, kosteneffiziente und ressourcenschonende Produktion.Complex property profiles require increasingly advanced composite materials and material compounds, including the rapid deployment of new production technologies, because the monolithic material or a single material can no longer satisfy today's complex requirements. Future material systems are fundamentally important to growth markets, in which they have an economically key position. Tailor-made lightweight materials (tailor-made composites) with an adapted design are needed. These concepts have to be developed to design the optimum combination of components. This requires material-specific knowledge and the ability to make correlations, as well as the design of complex technologies. Continuous large-scale and mass production (in-line, in-situ), thus reducing the costs of previously expensive composite materials and material compounds, is also necessary. The present work spans the entire field of composite materials and material compounds in a comparable and comparative manner and abstract form. A summarizing publication on this still very new, but already broad-based scientific field is not yet available. The separation of the individual, firmly divided groups of the composite materials is the reason for this. Cross-connections are rarely made. The objective of this work is to compensate to some extent for this deficiency. Special consideration is given to definitions and classifications, manufacturing processes and the properties of the materials. Clear structures and overviews are presented. Mapping established and new technologies will contribute to the stability of the terms "mixed material compounds" and "hybrid material compounds". In addition, the problem of recycling and recycling technologies is discussed. In summary, areas for future research and development projects will be specified. Generalized concepts for tailor-made composite materials and material compounds are proposed ("adjusting screw scheme") with an eye toward various production routes, especially for semi-finished products and components, and the associated findings. These general material concepts are applied to own current research projects pertaining to metal-matrix and polymer-matrix composites and hybrid material compounds. Research fields for future projects are extrapolated. Particular attention is paid to hybrid material compounds as the mainstay of future developments in lightweight construction. In-line and in-situ processes play a key role for large-scale, cost- and resource-efficient production.
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Vantomme, Pascal. "Contribution a l'etude des outillages et de leur lubrification dans le formage du verre creux : evolution vers une lubrification integree." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13112.
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Etude des proprietes de l'interface moule-verre et plus particulierement les phenomenes d'adherence. Trois types de materiaux de construction du moule sont etudies : des ceramiques (siliciures ou carbure de bore), des composites carbone-carbone et des materiaux frittes. Pour chacun de ses materiaux, les problemes de frottement et d'adherence sont etudies. L'analyse tribologique montre que la lubrification est convenable pour de faibles taux de permeabilite
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Vazquez, Calnacasco Daniel. "All-Oxide Ceramic Matrix Composites : Thermal Stability during Tribological Interactions with Superalloys." Thesis, Luleå tekniska universitet, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85513.
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The challenges faced in today’s industry require materials capable of working in chemically aggressive environments at elevated temperature, which has fueled the development of oxidation resistant materials. All-Oxide Ceramic Matrix Composites (OCMC) are a promising material family due to their inherent chemical stability, moderate mechanical properties, and low weight. However, limited information exists regarding their behavior when in contact with other high-temperature materials such as superalloys. In this work three sets of tribological tests were performed: two at room temperature and one at elevated temperature (650 °C). The tests were performed in a pin-on-disk configuration testing Inconel 718 (IN-718) pins against disks made with an aluminosilicate geopolymeric matrix composite reinforced with alumina fibers (N610/GP). Two different loads were tested (85 and 425 kPa) to characterize the damage on both materials. Results showed that the pins experienced ~ 100 % wear increase when high temperature was involved, while their microstructure was not noticeably affected near the contact surface. After high temperature testing the OCMC exhibited mass losses two orders of magnitude higher than the pins and a sintering effect under its wear track, that led to brittle behavior. The debris generated consists of alumina and suggests a possible crystallization of the originally amorphous matrix which may destabilize the system. The data suggests that while the composite’s matrix is stable, wear will not develop uncontrollably. However, as soon as a critical load/temperature combination is attained the matrix is the first component to fail exposing the reinforcement to damage which drastically deteriorates the integrity of the component.
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Oliveira, Cibele Aparecida de [UNESP]. "Otimização do processamento para obtenção de compósitos polímero/cerâmica com propriedades piezo e piroelétricas." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/92050.
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Materiais eletrocerâmicos possuem diversas aplicações, tais como: capacitor de multicamadas, transdutores, sensor piroelétrico e dispositivos eletro-ópticos. Nos últimos anos, tem ocorrido uma crescente demanda por eletrocerâmicas de melhor desempenho e funcionalidade acelerando o desenvolvimento de técnicas de síntese e visando a produção de pós com partículas bem definidas em tamanho, forma e cristalinidade. O método dos precursores poliméricos e a síntese hidrotérmica, tem se destacado entre as demais técnicas, pois são consideradas ideais para a preparação destas partículas. Baseado neste contexto, este projeto teve como objetivo utilizar o método dos precursores poliméricos e a síntese hidrotérmica assistida por microondas para preparar pós com estrutura perovskitas, como o titanato zirconato de chumbo Pb(Zrx,Ti1-x)O3, com tamanho de partículas controlado, boa cristalinidade e estabilidade química. A cerâmica foi associada a um polímero para formar um compósito na forma de filmes. O polímero usado foi fluoreto de polivinideno, PVDF, já conhecido na literatura. Foram controlados o tamanho das partículas cerâmicas e a espessura dos filmes compósitos visando estabelecer um ótimo para as propriedades piezoelétricas e piroelétricas. A polarização tornou-se mais efetiva com a inclusão do polímero condutor a polianilina (PAni). A condutividade foi controlada pelos processos de protonação, desprotonação e reprotonação. Os resultados mostraram que é possível obter filmes compósitos e a melhor proporção foi de 30/70 v/v (cerâmica/polímero) garantindo boas propriedades eletrocerâmicas e ainda a flexibilidade proporcionada pelo polímero. Para a formação do compósito, PZT-PAni-rp/PVDF, a melhor condição encontrada foi para os filmes...
Electroceramic materials have many applications such as multilayer capacitor, transducer, pyroelectric sensor and electro-optical devices. In recent years, there has been a growing demand for electroceramics with better performance and functionality, accelerating the development of synthesis techniques and focusing on the production of powders with well-defined particle size, shape and crystallinity. The polymeric precursor method developed by Pechini and hydrothermal synthesis have stood out among the other techniques and they are considered ideal for the preparation of these particles. Based on this context, this project aimed to use the polymeric precursor method and hydrothermal synthesis assisted by microwave to prepare powders with perovskite structure, such as lead zirconate titanate Pb (Zrx, Ti1-x) O3, with controlled particle size, good crystallinity and chemical stability. The ceramic was associated with a polymer to form a composite in the form of films. The used polymer was polyvinylidene fluoride, PVDF, already known in the literature. We controlled the size of the ceramic particles and the thickness of the composite films to establish the best for the pyroelectric and piezoelectric properties. The polarization has become more effective with the inclusion of the conducting polymer polyaniline (PAni). The conductivity was controlled by the processes of protonation, deprotonation - reprotonation. The results showed that is possible to obtain composite films and the best ratio was 30/70 v / v (ceramic / polymer) electroceramics ensuring good properties and also the flexibility offered by the polymer. To formation the composite PZT-PAni-rp/PVDF, was the best condition found for the films that the PZT was obtained by the method of the polymeric precursor to larger particle sizes and rounded morphology... (Complete abstract click electronic access below)
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Bras, François. "Étude et modélisation de l'endommagement des composites stratifiés SIC-SIC : exploitation d'essais statiques et de type Hopkinson." Cachan, Ecole normale supérieure, 1996. http://www.theses.fr/1996DENS0012.
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La connaissance du comportement dynamique de composites stratifies sic-sic sous sollicitations dynamiques est utile pour dimensionner certaines protections balistiques. Tout d'abord, nous avons choisi, dans ce travail de modélisation et d'identification du comportement, l'échelle mésoscopique du pli orthotrope sic-sic, qui présente l'intérêt de décrire de façon relativement simple les mécanismes de dégradation dans le plan du stratifie, le délaminage n'étant pas aborde. Le comportement du pli élémentaire est étudié au moyen de la mécanique de l'endommagement, avec l'utilisation d'un endommagement retarde, qui permet une description saine de la rupture et la prise en compte des effets dynamiques. Les paramètres du comportement qui peuvent être identifies lors d'essais statiques sont détermines avant de réaliser des essais dynamiques type Hopkinson en compression et en flexion. Nous développons un outil de simulation numérique de ces essais, base sur la théorie des poutres de Timoshenko, appliquée dans un cas hétérogène et non linéaire. Un schéma d'intégration aux différences centrées y est utilise. Pour analyser l'écart existant entre les simulations avec chargement en effort ou en vitesse de la compression dynamique d'une éprouvette, nous avons créé une interface, de rigidité variable, qui montre que les simulations en vitesse y sont très sensibles, contrairement aux simulations en effort. L'effet d'un contact tridimensionnel barre-éprouvette est également étudié. Les essais de flexion mettent aussi en évidence l'influence des conditions aux limites, qui conduit notamment a effectuer une simulation hybride : en vitesse lors du contact barre-éprouvette, en effort sinon. Ainsi, la simulation permet de prévoir qualitativement l'endommagement constate expérimentalement, mais le manque de concordance des données en empêche la quantification. Les perspectives résident alors dans une simulation tridimensionnelle des essais et dans l'amélioration des essais de flexion.
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Matthews, Stephen John. "Cavitation erosion of aluminium alloys, aluminium alloy/ceramic composites and ceramics." Thesis, Coventry University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317927.
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Bulsara, Vatsal N. "Effects of fiber spatial distribution and interphase on transverse damage in fiber-reinforced ceramic matrix composites." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/21429.
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Ellerby, Donald Thomas. "Processing and mechanical properties of metal-ceramic composites with controlled microstructure formed by reactive metal penetration /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/10583.
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Inghels, Eric. "Comportement mecanique de composites a fibres et matrices ceramiques : definition d'une methode d'analyse dans le cas de deux composites tisses a matrice de carbure de silicium." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0036.
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Dans le cas de composites ceramiques a fibres continues, l'existence de plusieurs mecanismes de degradation peut rendre le comportement non-lineaire, la caracterisation necessitant alors une approche specifique a chaque type de materiau. On developpe une telle approche dans le cas de deux composites tisses c/sic et sic/sic. On realise et on interprete des essais mecaniques a partir d'eprouvettes de traction, de flexion et d'eprouvettes entaillees. On propose une approche theorique du comportement mecanique pour illustrer les resultats experimentaux
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Poorteman, Marc. "Fabrication et caractérisation de composites céramiques renforcés par des plaquettes." Valenciennes, 1997. https://ged.uphf.fr/nuxeo/site/esupversions/078152fe-6c38-4759-a136-3513bbe27089.
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Dans le cadre de ce travail, nous avons fabriqué des composites céramiques renforcés par des plaquettes céramiques par des techniques classiques de dispersion et de mise en forme et par frittage sous pression. Ces techniques ont permis d'obtenir des matériaux denses avec une dispersion homogène des plaquettes et une microstructure des grains constituant la matrice comparable dans le cas du matériau monolithique et du composite. Un choix judicieux des couples matrice-plaquettes a permis d'étudier l'influence des contraintes générées lors de la descente en température du frittage suite à la différence de coefficient de dilatation entre la matrice et les plaquettes et de la nature de l'interface sur les propriétés mécaniques du composite. Pour chacun des systèmes étudiés, les mécanismes de renforcement à température ambiante se sont avérés multiples. La contribution de chacun de ces mécanismes au renforcement est fonction des contraintes résiduelles et de la nature de l'interface. Cependant dans tous les cas les plaquettes constituent le défaut critique. L'évolution des mécanismes de renforcement avec la température peut être déterminée par les contraintes présentes à haute température (cas du système ZrO2-SiC), mais également par la présence d'une phase liquide à haute température (cas des systèmes Si3N4-SiC et ZrO2-Al2O3). Nous avons également démontré dans le cas du système Si3N4-SiC que le composite présente une meilleure résistance à la propagation sous-critique à haute température par rapport au matériau monolithique et, dans le cas du système ZrO2-Al2O3, que le composite, comme le matériau monolithique, est superplastique
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Pemberton, Sonya Rachel. "Toughening ceramics : optimising the fracture behaviour of metallic fibre reinforced ceramic matrix composites (MFCs)." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607820.
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Rocabois, Philippe. "Stabilité thermochimique des composites céramiques base SiC : approche thermodynamique et expérimentale du système Si-O-C-N." Grenoble INPG, 1993. http://www.theses.fr/1993INPG0085.
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Les comportements experimentaux des materiaux de synthese contenant silicium, carbone et oxygene ou azote, a haute temperature, et leurs simulations thermodynamiques, presentent des desaccords quantitatifs importants qui peuvent etre expliques par des donnees thermodynamiques peu precises ou incompletes, ou par des cinetiques de reactions particulierement lentes. Pour lever toute ambiguite sur les donnees des composes cristallins, amorphes et gazeux du systeme si-c-n-o de nouvelles mesures d'enthalpie de formation ont ete effectuees par la technique des cellules d'effusion multiples couplee a la spectrometrie de masse. Il a ete mis en evidence que le sio(s) ne constitue pas une phase stable. La temperature de l'eutectique si+sic et les activites du silicium dans le liquide en equilibre avec sic ont ete mesurees. L'etude du ternaire si-n-o a permis de proposer une nouvelle valeur de l'enthalpie de formation de si#2n#2o. En plus des mesures de grandeurs thermodynamiques, l'etude de ces systemes a mis en evidence l'importance des cinetiques de reaction de decomposition (par exemple le faible coefficient d'evaporation de si#3n#4), ou entre phases solides (par exemple si+sio#2 ou sio#2+c). La prise en compte de la reduction des incertitudes sur les donnees thermodynamiques s'est revelee grandement insuffisante pour expliquer les desaccords entre le comportement des fibres et sa simulation. Le comportement de materiaux de synthese a base de sic et le comportement de melanges de phases connues ont ete etudies. Les resultats de ces experiences ont montre que les pressions mesurees de sio(g) et co(g) sont bien plus faibles que les pressions d'equilibre pour les materiaux dont la composition globale est dans le ternaire sic+sio#2+c. Les fibres sicn(o) (ex-pcsz) apparaissent plus stables que les fibres sico (ex-pcs). L'ensemble des resultats exposes peut etre exploite pour aider a expliquer et prevoir les traitements des fibres ceramiques en milieu industriel
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Gasser, Alain. "Sur la modélisation et l'identification du comportement mécanique des composites céramique-céramique à température ambiante." Cachan, Ecole normale supérieure, 1994. http://www.theses.fr/1994DENS0024.
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Une approche générale de l'endommagement des matériaux composites céramique-céramique à fibres est présentée. Des outils de modélisation du comportement jusqu'a rupture, sous chargements complexes, ont été mis en place et appliques aux deux composites étudies (sic-sic tisse et sic-masl stratifié), en tenant compte de la différence de comportement entre traction et compression (due a l'état des fissures, ouvertes ou fermées). Des essais de traction-compression a température ambiante ont été réalises sur ces deux composites, pour différents empilements. Pour le sic-sic tisse, un premier macro-modèle isotrope a montre ses limites dans la description des réseaux de fissures et des chargements complexes. Ainsi, il a été développé un modèle a endommagement anisotrope, qui inclue deux mécanismes de fissuration: le premier prend en compte les fissures perpendiculaires a la direction principale de chargement, le second les fissures perpendiculaires a la direction des fibres. La difficulté de ce modèle se situe dans son identification: les essais uni-axiaux ne sont pas suffisants. Une méthodologie d'identification, comportant un essai biaxial, a été mise en place. Cette loi de comportement a été incluse dans un logiciel permettant de simuler le comportement du matériau sous chargements complexes (comme par exemple un essai de pression interne sur tube), et d'en déterminer les valeurs a rupture. La comparaison avec des essais biaxiaux, réalises au LCTS bordeaux, a permis de vérifier le modèle qualitativement. Le sic-masl se présentant sous forme d'un stratifié, c'est la monocouche qui a été modélisée. Ce méso-modèle comprend trois variables scalaires d'endommagement. Une homogénéisation classique de type stratifie permet de retrouver le comportement global de tous les types d'empilements. L'identification et la vérification du modèle ont été effectuées à l'aide de plusieurs de ces empilements
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Deü, Jean-François. "Rupture des composites stratifiés sous chargement dynamique : apport des méso-modèles avec endommagement retardé." Cachan, Ecole normale supérieure, 1997. http://www.theses.fr/1997DENS0012.
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Cette étude est consacrée a la prévision de l'endommagement et de la rupture de composites stratifies. Pour cela, des méso-modèles de comportement, dans lesquels le stratifie est décrit comme un empilement de couches et d'interfaces interlaminaires, sont utilises en statique. Les effets de l'endommagement sont pris en compte par l'intermédiaire de variables internes supposées uniformes dans l'épaisseur des couches. Une extension de ces modèles aux cas de sollicitations dynamiques est proposée. Elle est basée sur l'utilisation de lois d'endommagement dépendantes du temps, lois appelées retardées. Ces lois introduisent la notion de vitesse maximale d'endommagement. Physiquement, elles sont fondées sur l'idée que la vitesse de propagation des microfissures est finie. Par rapport au cas de sollicitations statiques, le principal paramètre supplémentaire est la vitesse maximale d'endommagement, qui, combinée a la vitesse de propagation des ondes du milieu endommage, introduit une longueur caractéristique dans la modélisation. Les apports de ces modèles vis-à-vis des questions d'unicité, de localisation et de stabilité sont étudiés sur la base de travaux analogues en viscoplasticité. Concernant les problèmes de dépendance au maillage, le modèle développé présente l'intérêt de pouvoir estimer, a priori, la taille des éléments à utiliser. Une discussion sur l'identification des paramètres du modèle est également proposée. Elle est principalement basée sur l'analyse de simulations unidimensionnelles d'essais d'impact plaque-plaque. L'implantation des méso-modèles d'endommagement dans le code de calcul éléments finis de dynamique dyna3d permet de confirmer les apports dus a l'effet retard et de valider l'approche sur des simulations d'essais aux barres d'Hopkinson (essais de compression et flexion dynamique sur composite sic/sic) ainsi que sur un exemple d'impact sur plaque stratifiée sic/mas-l.
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Preiss, Laura. "Nouvelles prothèses intervertébrales en composite céramique : Etude des matériaux, mise en place d'un test multiphysique in vitro et analyse de performances." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI041/document.
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Ce travail de thèse a porté sur de nouveaux implants intervertébraux en céramique. Au cours du projet dans son ensemble (projet européen Longlife), un nouveau matériau et de nouveaux designs d’implants ont été développés, ainsi qu’un nouveau test destiné à simuler les sollicitations subies in vivo par les implants afin d’estimer leur durée de vie. Le nouveau matériau développé est un composite triphasé composé d’une matrice de zircone dopée à l’oxyde de cérium (pour sa résistance au vieillissement), d’une phase globulaire d’alumine α (pour affiner la microstructure) et d’une phase allongée composée d’aluminates de strontium (pour augmenter la ténacité). La première partie du travail a consisté à caractériser ce matériau afin de connaître son comportement en termes de résistance mécanique, stabilité thermique, et de résistance à la stérilisation. Une deuxième partie a été consacrée au développement d’un test multiphysique regroupant les différentes sollicitations attendues par une prothèse in vivo (fatigue axiale, micro-séparation, vieillissement et usure). Il a fallu pour cela s’appuyer sur des simulations numériques qui ont permis de développer le système. Les données de la littérature ont été utilisées afin de choisir les paramètres du test (durée, fréquence, milieu d’essai). Enfin, la dernière partie de ce travail a été la mise à l’épreuve de différents prototypes à travers le test multiphysique et leur caractérisation en cours d’essai. Les principaux résultats de ce travail de thèse sont les suivants : le composite montre un comportement pseudo-plastique sous charge, avec une nette transformation de phase avant rupture, ce qui est positif dans le cadre de son utilisation. De plus, il ne semble pas affecté par la stérilisation. Du point de vue des implants développés, peu passent le test multiphysique. Le design, ainsi que la géométrie (notamment la clearance des échantillons) sont des leviers d’amélioration qui permettront d’augmenter la fiabilité des implantsThis work deals with the development of new intervertebral prostheses, made with ceramics. A whole European project, Longlife, was dedicated to the development of such implants. To achieve this goal, several axes have been followed: the synthesis of a new material, the development of new designs of intervertebral bodies, and the set-up of a new test aimed at reproducing in vitro the different solicitations undergone by an intervertebral implant in vivo. The new material developed is a triphasic composite composed of a matrix of ceria-doped zirconia (insensitive to ageing), a secondary globular phase of α-alumina (to reduce the grain size), and a third, elongated phase composed of strontium aluminates platelets (in order to improve fracture toughness). The first part of this work was to characterize this new material in order to forecast its behaviour under mechanical solicitation, thermal stability and resistance to sterilization. Secondly, the set-up of the new test is exposed. Different steps were chosen (axial fatigue, micro-separation, ageing and wear) in order to reproduce the “real-life” solicitations. To achieve this goal, Finite Elements simulations were performed, allowing the development of specific specimen holders that mimic the fixation of the implants in the vertebrae. The parameters of the test (duration, frequency, medium) were chosen after a details survey of the literature and of standards. At the end, we tested different prototypes trough this new multiphysic assessment set up. As a main result of this thesis, the chosen ceramic composite exhibits a pseudo-plastic behaviour, with a large deformation due to phase transformation before fracture, which is a positive result in the framework of the forecast applications. Moreover, the material doesn’t seem degraded by the sterilization processes. Concerning the multiphysic test, only a few implants resisted it. The design of the implants is a key-point, as well as the geometry (in particular, clearance seems to be critical)
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Antti, Marta-Lena. "All-oxide ceramic matrix composites." Doctoral thesis, Luleå, 2001. http://epubl.luth.se/1402-1544/2001/34/index.html.
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Peng, Fei. "Pressureless sintering and oxidation resistance of zrb2 based ceramic composites." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28208.
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Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.Committee Chair: Robert F. Speyer; Committee Member: George Kardomateas; Committee Member: Preet Singh; Committee Member: Robert L. Snyder; Committee Member: Thomas H. Sanders, Jr.
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Dunyak, Thomas John. "Properties and performance of a ceramic composite component." Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-07282008-134634/.
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Mitre, Leonardo. "Desenvolvimento e avaliação de compósitos cerâmicos de alumina e matriz polimérica contendo adições de nanoestruturas de carbono e elementos antioxidantes." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2011. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=189.
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NenhumaA presença do carbono em materiais refratários modifica a tensão superficial entre o sólido (refratário) e o líquido (metal-escória) diminuindo a penetração do líquido e, consequentemente, reduzindo o processo de corrosão das cerâmicas refratárias durante os processos siderúrgicos. Além deste efeito protetor, o carbono desempenha ainda papel importante quanto à resistência mecânica e ao choque térmico dos tijolos refratários. Nos anos recentes, têm sido desenvolvidos nanocompósitos refratários, incorporando-se na matriz cerâmica uma segunda fase de carbono com dimensões em escala nanométrica. Esta estratégia visa ao desenvolvimento de materiais com desempenhos aprimorados em relação aos materiais hoje utilizados, lançando mão das propriedades mecânicas, térmicas, elétricas e físico-químicas únicas dos nanomateriais de carbono. Duas barreiras tecnológicas, entretanto, devem ser contornadas para o efetivo uso de nanocompostos de carbono em refratários: i) o controle eficiente de sua dispersão na matriz cerâmica e resina polimérica; ii) a melhoria/otimização de sua resistência à oxidação em temperaturas elevadas. Este trabalho teve como objetivos a avaliação dos aspectos termodinâmicos e cinéticos do processo de oxidação de materiais de carbono nanoestruturados (nanotubos de múltiplas paredes, nanofibras e negro de fumo) em compósitos refratários de alumina contendo ligante polimérico. Vale ressaltar que o carbono amorfo proveniente da transformação da resina polimérica é simultaneamente analisado. A análise cinética foi realizada empregando-se a termogravimetria semi-isotérmica e isotérmica, nas quais a amostra é submetida a diferentes patamares de temperatura e aquecida até atingir massa constante. Os dados das diferentes composições foram tratados de forma a obter e ajustar modelos matemáticos que representam o processo de oxidação. Foi também investigado o efeito do acréscimo de elementos com elevada afinidade termodinâmica pelo oxigênio, especificamente boro, titânio e silício, com o objetivo de reduzir ou eliminar a oxidação dos carbonos nanoestruturados incorporados. Utilizando planejamento fatorial de experimentos foi possível avaliar, acompanhar e modelar o comportamento da oxidação dos diferentes compósitos e observar os efeitos de proteção de elementos antioxidantes selecionados sobre a perda de massa dos diferentes nanocarbonos. O modelo cinético básico obtido indica que o processo de oxidação segue o modelo de difusão por poros. As análises obtidas por microscopia eletrônica de varredura (MEV) demonstraram que, para algumas formulações contendo formas nanoestruturadas de carbono e aditivos antioxidantes, houve efeito protetor do carbono, em maior ou menor grau, como evidenciado pelas análises de espectroscopia de energia dispersiva (EDS) efetuadas sob os materiais pós queima. Em determinadas situações foi possível detectar até mesmo formas aparentemente íntegras de carbono nanoestruturado pouco ou nada afetadas pelo processo de oxidação pelo qual o material foi submetido. Estas técnicas permitiram também observar por microscopia eletrônica de varredura, a aparente presença de depósito formado sobre os nanotubos de carbono, sugerindo a presença de composto não determinado, possivelmente um carbeto, o que teria efeito protetor diante do processo oxidativo.
The presence of carbon in refractory materials increases the surface tension between the solid (refractory) and the liquid (metal-slug), decreases the liquid penetration and, consequently, reduces the corrosion of refractory ceramics used in steel-making processes. Besides this protecting effect, carbon also plays an important role in the mechanical strength and thermal shock of refractory bricks. In recent year, refractory nanocomposites have been developed by incorporating a second carbon phase of nanometric dimensions into the ceramic matrix. This strategy aims at the development of materials with improved performance in relation to the currently used materials by taking advantage of the singular mechanical, thermal, electrical, and physical and chemical properties of carbon nanomateriais. Nevertheness, two technological barriers must be overcome for the effective use of carbon nanocomposites in refractory materials: i) the efficient control of dispersion in the ceramic matrix and the polymer resin, ii) improvement of the resistance to oxidation at high temperatures. This study sought to evaluate the thermodynamic and kinectic aspects of the oxidation of nanostructured carbon materials (multi-walled nanotubes (MWNT), nonofibers, and carbon black) in alumina refractory composite using a polymeric ligand. It is worth pointing out that amorphous carbon obtained by the transformation of the polymer resin was analyzed simultaneously. The kinetic analysis was conducted using semi-thermal thermogravimetry. The sample was submitted to different temperature gradients and heated until the mass was constant. Different compositions were tested in order to obtain and adjust mathematical models that represented the oxidation process. The effect of the addition of elements with high thermodynamic affinity for oxygen, specifically boron, titanium, and silica, was investigated seeking to reduce or prevent the oxidation of the incorporated nanostructured carbons. The use of experimental factorial planning allowed the evaluation, follow-up, and modeling of the oxidation behavior of the planned formulations and the observation of the effects of the protection of the antioxidation elements selected on the mass loss of the different nanocarbons. The kinetic model obtained indicates that the oxidation process follows the pore diffusion model.
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Lombardi, John Lang 1968. "Injection solid freeforming of polymer and ceramic composite materials." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282251.
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Solid freeform fabrication processes (SFF) have been the subject of much research and discussion within recent years. Unlike other near net shape manufacturing processes (i.e. conventional injection molding, casting, or bulk machining), SFF techniques fabricate parts "from the ground up" by the sequential deposition and curing of raw material slurry layers upon each other until the final part results. Precise spatial control of deposited layers is achieved through CAD software and hardware interfaced with the SFF apparatus. The development of suitable SFF compatible raw material formulations and appropriate processing parameters are discussed in this dissertation. In particular, a wide range of materials have been fabricated and characterized at AML and ACR using this technique including alumina., crosslinked acrylate, and high molecular weight Nylon 6 thermoplastics. Comparisons are made between the mechanical properties of the SFF and corresponding commercial conventionally processed materials. Finally, the heat transfer and polymerization kinetics associated with three model SFF resin formulations are discussed and compared to corresponding empirical SFF process observations.
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Petla, Harita. "Computational design of ultra-high temperature ceramic composite materials." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Stackpoole, Margaret Mary. "Reactive processing and mechanical properties of polymer derived silicon nitride matrix composites and their use in coating and joining ceramics and ceramic matrix composites /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/10564.
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Whitney, Michael J. (Michael John). "Transformation-mismatch plasticity in zirconia ceramic composites." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43447.
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Graham, Samuel Jr. "Effective thermal condutivity of damaged composites." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/16935.
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Evarts, Jonathan S. "Advanced Processing Techniques For Co-Continuous Ceramic Composites." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1218218162.
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Ren, Guogang. "Fibre reinforced ceramic moulding composites manufacture and characterisation." Thesis, Queen Mary, University of London, 1999. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1710.
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Ceramic materials have considerable attraction for use in applications where the service temperatures are high and where fire performance and non-combustibility are important. Unfortunately most monolithic ceramic materials are extremely brittle which limits their use for structural applications. The development of fibre and particulate reinforced ceramic composites provides a route to achieving increased toughness in the materials, although this is often at the expense of ultimate strengths and/or the process-ability of the materials. Many reinforcing fibres used with ceramics are inherently expensive and manufacturing routes to produce fibre reinforced materials can involve high processing temperatures and are consequently expensive. A key goal of this research therefore is to develop a new type of ceramic matrix composites that combine toughness, strength and process-ability to provide a cost effective structural material. The research described in this thesis has been concerned with the development and characterisation of a series of ceramic compounds that can be moulded at modest temperatures( 130-160" C) and pressures in a manufacturing system that replicates dough moulding compounds (DMC) as used for polymeric matrix composites. The conventional polyester matrix of polymeric DMC has been replaced by a soluble inorganic system which is compounded with fibres, fillers and hardening agents to produce a paste-like or doughy substance The handle-ability of the material is determined by the viscosity of the matrix and the type or amount of fillers and additives present. The research has involved a careful set of experiments in which the formulation of the ceramic DMC has been systematically varied in order to achieve an optimum viscosity for storage and handling together with a further series of experiments studying the hardening and cure of the compounds. The mechanical properties of the compounds have been measured and additional formulation changes have been introduced to maintain desirable processing characteristics while improving mechanical properties, and in particular the impact resistance using instrumented falling weight impact machines. Finally the fire properties of the compounds have been studied using cone calorimetry and indicative furnace testing. The structure of the compound has been studied throughout the programme with various microscopic techniques and thermal analysis systems used to characterise the materials, their dispersion and changes that occurred during processing and after high temperature exposure. The final result of the programme has been the identification of a range of material formulations that can provide a tough moulding compound, capable of high temperature service use, that possesses useful structural properties and which can be processed cheaply at modest temperatures using low cost materials.
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Bischoff, Matthew Lee. "CHARACTERIZATION OF CERAMIC MATRIX COMPOSITE MATERIALS USING MILLIMETER-WAVE TECHNIQUES." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1362655198.
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Mariappan, L. "In-Situ Synthesis Of A12O3_ZrO2_SiCw Ceramic Matrix Composites By Carbothermal Reduction Of Natural Silicates." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/215.
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This thesis outlines the work done on in-situ synthesis of Al2O3-ZrO2-SiCw ceramic composites and their property evaluation. The introductory chapter deals with the literature survey on ceramic matrix composites, properties desirable for structural applications and toughening mechanisms associated with these composites. The role of whisker toughening in ceramic matrix composites, the growth mechanisms involved in whisker growth and the conditions that favour or hamper the whisker growth are also discussed. The advantages and disadvantages of in-situ synthesis of composites as compared to physical mixing are also dealt with. The objective and scope of the work undertaken are outlined at the end.
The second chapter describes the experimental techniques associated with carbothermal synthesis and characterisation of reaction products as well as properties of hot pressed bulk composites. The equipments used for this work are described here.
The third chapter focuses on the results obtained by the carbothermal reduction of mixtures of kaolin, sillimanite and zircon taken in various proportions. The formation of the product phases with respect to variations in temperature, variations in composition and effect of catalyst is analysed with the help of XRD while their morphology is analysed using SEM. The conditions favouring the formation of tetragonal zirconia without the addition of stabilizers is also enumerated here.
The fourth chapter deals with the compaction of these composite powders and the evaluation of some physical, thermal and mechanical properties. Density and porosity, coefficient of thermal expansion, modulus of rupture and fracture toughness of the composite specimens are evaluated and compared with binary and ternary composites made by other methods.
Finally the thesis concludes by summarizing the work done and briefly projecting the areas for future work.
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Nash, James Michael. "An orientation study of Al2IO3/AlCo-continuous ceramic composites." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407408008.
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Saewong, Pakamard. "Erosion of glass and glass-ceramic matrix composites." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300838.
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Owens, Lindsay. "Characterization of Ceramic Composite Materials Using Terahertz Non-Destructive Evaluation Techniques." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1342668277.
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Kraus, Zachary. "Computational tools for preliminary material design of metals and polymer-ceramic nano composites." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51795.
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In this dissertation, algorithms for creating estimated potentials for metals and modeling of nano composites are developed. The efficacy of the algorithms for estimated potentials were examined. The algorithm was found to allow molecular dynamic and Monte Carlo modeling to be included in the potential building process. Additionally, the spline based equations caused issues with the elastic constants and Young’s modulus due to extra local minima. Two algorithms were developed for improved modeling of nano composites: one was a random number generation algorithm for initializing polymer, second was a bonding algorithm for controlling bonds between polymer and nano particle. Both algorithms were effective in their tasks. Additionally, the algorithms for improved nano composite modeling were used for preliminary material design of PMMA metal oxide nano composite systems. The results from the molecular dynamic simulations show the bonding between polymer matrix and nanoparticle has a large effect on the Young’s modulus and if this bonding could be controlled, the tensile properties of PMMA-metal oxide nano composites could be tailored to the applications’ requirements. The simulations also showed bonding had caused changes in the density of the material which than effected the energy on the polymer chain and the Young’s modulus. A model was than developed showing the relationship between density and the chain energy, and density and the Young’s modulus. This model can be used for a better understanding and further improvement of PMMA-metal oxide nano composites.
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Dong, Biqin. "Cement-based piezoelectric ceramic composites for sensor applications in civil engineering /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20DONG.
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Kokan, Julie Runyan. "Microstructure/electrical property correlations in ceramic matrix composites." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19594.
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Schutz, James Branch. "Test methods and analysis for glass-ceramic matrix composites." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13711.
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Lee, Woo Young. "Chemical vapor deposition of dispersed phase ceramic composites." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/11857.
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