Neste trabalho foi avaliado o desempenho mecânico de um compósito formado por massa cerâmica de porcelanato sendo a matriz e fios de aço o reforço, visando a utilização como cerâmica de revestimento. Com a inserção do fio metálico, teve-se por objetivo aumentar a tenacidade elevando a resistência mecânica ao impacto, proporcionando maior segurança em caso de ruptura acidental. O estudo laboratorial avaliou o comportamento mecânico de corpos de prova sem fios e com a adição de fios. Os fios foram distribuídos longitudinalmente em três configurações. Os corpos possuíam 1600 mm2 de superfície e receberam os fios distribuídos em uma, duas e três camadas perfazendo comprimento respectivamente de 325 mm, 650 mm e 975 mm. Foram realizadas as caracterizações padrões para a cerâmica, expansão após prensagem, retração de secagem, densidade a seco, retração de queima, absorção de água e resistência mecânica à flexão. E adicionalmente foram avaliados: resistência mecânica ao impacto, índice de deformação piroplástica, resistência mecânica à tração e análise da microestrutura. O compósito proporcionou redução de aproximadamente 61% na deformação piroplástica e um acréscimo de aproximadamente de oito vezes na resistência ao impacto. Na análise do compósito, a tensão no fio ficou constante em torno de 800 MPa, mantendo aproximadamente 35% ao seu valor ao natural que era de 2000 MPa. O fio teve grandes perdas em suas características individuais, no entanto sua aplicação na cerâmica em forma de reforço do compósito enriqueceu as propriedades do porcelanato o que proporciona oportunidade de novas aplicações. / This study evaluated the mechanical performance of a composite ceramic body of porcelain with a matrix of steel fibers, for use as a ceramic coating. With the insertion of metallic fiber account was intended to increase the toughness for increasing the mechanical impact resistance, providing greater safety in case of accidental rupture. The study assessed the mechanical behavior of the specimen without fibers and with the addition of fiber. The fibers were distributed longitudinally in three configurations. The bodies had 1600 mm2 and received fibers distributed in one, two or three layers with total length of 325 mm, 650 mm and 975 mm respectively. Characterizations patterns for ceramic, expansion after pressing, drying shrinkage, dry apparent density, firing shrinkage, water absorption and mechanical flexural strength were performed. And we’ve checked also: mechanical impact, index pyroplastic deformation, mechanical tensile strength and microstructural analysis. We found that the composite material gave approximately 61% reduction in pyroplastic deformation and an increase of approximately eight times the impact resistance. In the analysis of the composite stress in the fiber was constant around 800 MPa, holding approximately 35 % of their value to the natural which was 2000 MPa. The fiber had big losses on their individual characteristics, however its application in ceramic composite as increased porcelain ceramic properties which provides opportunity for new applications.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1979. / Vita. / Includes bibliographical references. / by Stuart Forster Cogan. / Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1979.

No description available.

Shear strength of fiber reinforced concrete beams was studied in this research project. Three types of fibers were examined: hooked-end steel fiber, crimped-steel fiber, and crimped-monofilament polypropylene fibers. The experimental program included five beam specimens. Two of the beams were control specimens in which one was reinforced with minimum shear reinforcement according to ACI 318, while the other one did not have any shear reinforcement. Each one of the other three specimens was reinforced with one of the above mentioned fibers by 1% volumetric ratio. In addition to the beam specimens, three prisms were also made for each type fiber to determine their toughness. The aim of this research was to investigate the following questions for medium-high concrete strength 1) to evaluate the effectiveness of each type of fibers on the shear strength, 2) to investigate the shear strength, toughness, crack patterns and near ultimate load crack width of each beam, and 3) to determine if using 1% volumetric ratio of fibers as shear reinforcement in beams would provide adequate strength and stiffness properties comparable to reinforcing steel used as minimum shear reinforcement. The results showed that all three types of fibers increased the shear capacity of the beam specimens more than the beam reinforced with minimum shear reinforcement. Moreover, some of the fibers used could shift the type of failure from a pure shear failure to a combined flexural-shear or pure flexural failure.

O concreto autodensável (CAA) vem conquistando o espaço do concreto convencional (CCV), predominantemente pelo fato de não demandar adensamento, eliminando parte da mão de obra. As propriedades do CAA em seu estado endurecido são maiores do que no concreto convencional por apresentar diferença na distribuição dos poros. Com adição de fibras de aço ao CAA, as propriedades mecânicas são melhoradas principalmente nos esforços de tração na flexão. Relacionado a isso, a presente pesquisa buscou avaliar o comportamento mecânico do CAA com a incorporação de diferentes formas de fibras de aço nos teores de 0,5%, 0,75% e 1,0% nos tipos ancorada, raiada e corrugada e, com diferentes adições minerais: sílica ativa (AS) e fíler calcário (AF). Os compósitos foram submetidos a ensaios tanto no estado fresco como no estado endurecido. No estado fresco, foram executados os ensaios de espalhamento, t500, funil V e caixa L e no estado endurecido os ensaios de resistência à compressão axial, módulo de elasticidade e resistência à tração na flexão. Com o objetivo de analisar o comportamento da zona de transição, todas as misturas sofreram ensaios de microscopia eletrônica de varredura. Os resultados apontaram que foi possível manter as características de adensabilidade do CAA para todas as misturas. O ganho na resistência à compressão foram mais expressivas com as fibras tipo ancorada e corrugada no teor de 1,0% com sílica ativa. No módulo de elasticidade os ganhos não foram significativos. Na resistência à tração na flexão, quando comparado com a resistência à compressão, o maior ganho foi de 8,40% para adição de sílica ativa e de 10,44% para fíler calcário no teor de 1,0% de fibra de aço tipo ancorada. / The autodensible concrete (CAA) has been conquering the space of conventional concrete (CCV), predominantly because it does not demand densification, eliminating part of the workforce. The properties of CAA in its hardened state are larger than in conventional concrete because of the difference in pore distribution. With addition of steel fibers to the CAA, the mechanical properties are improved mainly in the tensile stresses in the flexion. The present study aimed to evaluate the mechanical behavior of the CAA with the incorporation of different forms of steel fibers in the 0.5%, 0.75% and 1.0% in the anchor, corrugated and anchor types, with different mineral additions: active silica (AS) and limestone filler (FA). The composites were tested in both the fresh and hardened state. In the fresh state, the tests of spreading, t500, funnel V and box L and in the hardened state the tests of resistance to axial compression, modulus of elasticity and tensile strength in the flexion were executed. In order to analyze the behavior of the transition zone, all the blends underwent scanning electron microscopy. The results indicated that it was possible to maintain the characteristics of the CAA for all mixtures. The gain in the compressive strength was more expressive with the anchored and corrugated type fibers in the 1.0% content with active silica. In the modulus of elasticity the gains were not significant. In the flexural tensile strength, when compared to the compressive strength, the highest gain was 8,40% for the addition of active silica and 10,44% for limefilter in the content of 1.0% of type steel fiber anchored.

Die exzellenten Eigenschaften einer Keramik beziehen sich auf den hohen Schmelzpunkt, die gute Hochtemperaturfestigkeit sowie hohe Elastizitätsmodul- und Härtewerte. Weiterhin zeichnen sich die anorganisch-nichtmetallischen Werkstoffebesonders durch ihre gute Korrosions- und Verschleißbeständigkeit aus.Bedingt durch die erschwerte Versetzungsbewegung weisen keramische Werkstoffeeine höhere Sprödigkeit auf. Metallische Werkstoffedagegen sind in der Regel duktil und zeigen meist ein duktiles Bruchverhalten. Lokale Spannungsspitzen können durch plastische Verformung abgebaut werden.Das Ziel dieser Arbeit ist es, das grundsätzlich unterschiedliche Werkstofferhalten einer Keramik und eines Metalls miteinander zu kombinieren, um die Bruchzähigkeit des Keramik-Metall-Verbundwerkstoffes zu erhöhenDie fein verteilten Metalle sollen die Rissausbreitung behindern. Es können unterschiedliche Mechanismen wirken. Im Vergleich zur unverstärkten Keramik ist eine höhere Bruchenergie aufzubringen, um den Riss voran zu treiben. Die Erhöhung der Bruchenergie spiegelt sich in einer höheren Bruchzähigkeit wieder.Um eine duktile Phase in einer spröden Zirkoniumdioxidmatrix zu erzeugen, werden für die Untersuchungen unterschiedliche Metalle eingebracht. Dadurch soll die Bruchzähigkeit als Schadenstoleranz gegenüber dem Totalversagen erhöht werden. Die resultierenden Eigenschaften der Keramik-Metall-Verbundwerkstoffewerden analysiert und charakterisiert.Die Untersuchungen umfassen das pulvermetallurgische Einbringen von metallischen Pulvern mit verschiedenen Teilchengrößen sowie die chemische Einbringung von Präkursoren, die in nanokristalline Metallpartikel umgewandelt werden. Dabei kommen verschiedene Metalle mit unterschiedlichen Wechselwirkungen und Spannungen durch thermische Fehlpassungen in der Matrix zur Anwendung. Zusätzlich wird die Auswirkung der Variation der Verstärkungsform (Partikel/Faser) und des Metallgehaltes untersucht.

Die exzellenten Eigenschaften einer Keramik beziehen sich auf den hohen Schmelzpunkt, die gute Hochtemperaturfestigkeit sowie hohe Elastizitätsmodul- und Härtewerte. Weiterhin zeichnen sich die anorganisch-nichtmetallischen Werkstoffebesonders durch ihre gute Korrosions- und Verschleißbeständigkeit aus.Bedingt durch die erschwerte Versetzungsbewegung weisen keramische Werkstoffeeine höhere Sprödigkeit auf. Metallische Werkstoffedagegen sind in der Regel duktil und zeigen meist ein duktiles Bruchverhalten. Lokale Spannungsspitzen können durch plastische Verformung abgebaut werden.Das Ziel dieser Arbeit ist es, das grundsätzlich unterschiedliche Werkstofferhalten einer Keramik und eines Metalls miteinander zu kombinieren, um die Bruchzähigkeit des Keramik-Metall-Verbundwerkstoffes zu erhöhenDie fein verteilten Metalle sollen die Rissausbreitung behindern. Es können unterschiedliche Mechanismen wirken. Im Vergleich zur unverstärkten Keramik ist eine höhere Bruchenergie aufzubringen, um den Riss voran zu treiben. Die Erhöhung der Bruchenergie spiegelt sich in einer höheren Bruchzähigkeit wieder.Um eine duktile Phase in einer spröden Zirkoniumdioxidmatrix zu erzeugen, werden für die Untersuchungen unterschiedliche Metalle eingebracht. Dadurch soll die Bruchzähigkeit als Schadenstoleranz gegenüber dem Totalversagen erhöht werden. Die resultierenden Eigenschaften der Keramik-Metall-Verbundwerkstoffewerden analysiert und charakterisiert.Die Untersuchungen umfassen das pulvermetallurgische Einbringen von metallischen Pulvern mit verschiedenen Teilchengrößen sowie die chemische Einbringung von Präkursoren, die in nanokristalline Metallpartikel umgewandelt werden. Dabei kommen verschiedene Metalle mit unterschiedlichen Wechselwirkungen und Spannungen durch thermische Fehlpassungen in der Matrix zur Anwendung. Zusätzlich wird die Auswirkung der Variation der Verstärkungsform (Partikel/Faser) und des Metallgehaltes untersucht.