Submitted by Caroline Xavier (caroline.xavier@pucrs.br) on 2017-06-30T18:08:23Z No. of bitstreams: 1 DIS_SERGIO_ROBERTO_DA_SILVA_COMPLETO.pdf: 2644731 bytes, checksum: 207623c4aecda0de23cefed577f3f2d6 (MD5) / Made available in DSpace on 2017-06-30T18:08:23Z (GMT). No. of bitstreams: 1 DIS_SERGIO_ROBERTO_DA_SILVA_COMPLETO.pdf: 2644731 bytes, checksum: 207623c4aecda0de23cefed577f3f2d6 (MD5) Previous issue date: 2017-03-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Nowadays, searching for alternatives materials for the construction industry has become imperative. Construction and demolition waste (CDW) and by-products from the thermoelectric industries, such as fly ash, are the subject of studies in several segments of the construction industry. Their use can be one of many significant efforts to achieve a more sustainable construction. This paper studies the influence of the interactions and incorporations of CDW and fly ash on the concrete properties. X-ray diffraction (XRD), X-ray Fluorescence Spectrometry (XRF) and particle size distribution analysis were used to characterize the investigated materials. The mechanical properties (compressive strength and splitting strength) and durability (water absorption and carbonation depth) of concrete with different CDW contents (25%, 50%, 75%, and 100%) were investigated as a coarse aggregate (10%, 15%, 25% and 30%) replacing Portland cement in different water/binder ratios (0.40, 0.45, 0.50, 0, 55 and 0.65). Based on the results, it was observed that the addition of fly ash replacing the Portland cement in concretes with CDW causes a reduction in mechanical properties and durability of concretes in the early ages. However, as the fly ash content increases in concretes with CDW there is an increase in the compressive strength ratio (fc91/fc28), and as the time of exposure to CO2 advances the carbonation coefficient tends to decrease. / A busca de novos materiais para o emprego na ind?stria da constru??o civil se faz necess?rio nos dias atuais. O res?duo da constru??o e demoli??o (RCD) e os subprodutos das ind?strias termoel?tricas como a cinza volante s?o objetos de estudos em diversos segmentos da ind?stria da constru??o civil, e a adi??o destes materiais pode ser um dos esfor?os significativos para se alcan?ar uma constru??o mais sustent?vel. Neste trabalho foram estudadas a influ?ncia das intera??es e incorpora??es de RCD e cinza volante nas propriedades dos concretos. Para a caracteriza??o dos materiais investigados foram utilizadas as t?cnicas de Difra??o de raios X (DRX), an?lise qu?mica por Espectrometria de Fluoresc?ncia de raios X (FRX) e an?lise de distribui??o granulom?trica ? laser. Foram investigadas as propriedades mec?nicas (compress?o axial e tra??o por compress?o diametral) e de durabilidade (absor??o d??gua e resist?ncia ? carbonata??o) dos concretos com diferentes teores de RCD (25%, 50%, 75% e 100%) como agregado gra?do reciclado em substitui??o ao gra?do natural e adi??o de cinza volante (10%, 15%, 25% e 30%) em substitui??o ao cimento Portland em diferentes rela??es ?gua/aglomerante (0,40, 0,45, 0,50, 0,55 e 0,65). Com base nos resultados observou-se que a adi??o de cinza volante em substitui??o ao cimento Portland em concretos com RCD causa uma redu??o nas propriedades mec?nicas e de durabilidade nos concretos nas primeiras idades. Entretanto, ? medida que o teor de cinza volante aumenta nos concretos com RCD h? um aumento na taxa de resist?ncia ? compress?o axial (fc91/fc28), e ? medida que o tempo de exposi??o ao CO2 vai se avan?ando o coeficiente de carbonata??o tende a diminuir.

Submitted by Caroline Xavier (caroline.xavier@pucrs.br) on 2017-08-08T13:47:52Z No. of bitstreams: 1 TES_ALBINO_MOURA_GUTERRES_COMPLETO.pdf: 7255952 bytes, checksum: 781408c060e8988a1e9c63e9d2d0855b (MD5) / Made available in DSpace on 2017-08-08T13:47:52Z (GMT). No. of bitstreams: 1 TES_ALBINO_MOURA_GUTERRES_COMPLETO.pdf: 7255952 bytes, checksum: 781408c060e8988a1e9c63e9d2d0855b (MD5) Previous issue date: 2017-07-04 / The overall objective of this work is to analyze the influence of Si and Mg contents, the percentage of porosity and the effects of hardening precipitation heat treatment on the mechanical properties of Al-Si-Mg alloys. Two alloys: Al-3,8%Si-0,25%Mg (Alloy I) and Al-6,5%Si-0,6%Mg (Alloy II) were prepared and characterized by thermal analysis and optical emission spectroscopy. After that, the alloys were solidified in a metallic mold, with and without degasification. Transversal samples were extracted from solidified ingots to analyze the as-cast structures and mechanical properties (tensile and hardness tests). Part of ingots were submitted to hardening precipitation heat thermal treatments by solutioning at 540?C for 6 hours and artificial aging at 180?C for 4 hours. After the solidification structure analysis in the Alloys I and II in samples along the ingot, it was observed that the grain medium size and the secondary dendrite arm spacing presented small variations that do not influence the variations on the mechanical properties. Regarding porosity, it was noted that Alloy II, which contains a higher content of Si and Fe, presented higher porosity percentage when compared to Alloy I. The degasification process decreased at about 50% porosity volumetric percentage. During the analysis of the mechanical properties of the alloys in the states of crude solidification, it was observed that the samples referring to Alloy II, in the degassed condition, presented higher limits of tensile strength and hardness, 175,5 MPa and 70,7 HB, respectively . Due mainly to the higher content of Si found in alloy II. In relation to the ductility, the Alloy I, in the degassed condition, presented the highest percentage of specific deformation (greater deformation ? = 1.82%), due to the lower percentage of porosity and lower content of Si and Fe. With the treatment (T6), a significant increase in the properties of both alloys can be observed. Alloy II showed the best results with thermal treatment, generating an increase of: 25% in tensile strength, 57% in deformation and 23% in hardness of the samples analyzed. Thus, alloy II, due to the higher percentage of Mg, responded better to the heat treatment. For the analysis of the correlation of the chemical composition, the percentage of porosity and the effects of the thermal treatments with the variation in the mechanical properties, mathematical models were developed that allow to predict the limit of tensile strength, deformation and hardness in Al-Si-Mg. In the analysis of the mathematical models, it was possible to identify the negative effect of the iron and porosity percentages on tensile strength and specific deformation. The increase of silicon and magnesium contents and the application of T6 contributed to higher tensile strength, specific deformation and hardness as well. / O objetivo geral desse estudo foi correlacionar ? composi??o qu?mica, a porosidade e os efeitos dos tratamentos t?rmicos de endurecimento por precipita??o em algumas propriedades mec?nicas em ligas de Al-Si-Mg fundidas. Duas ligas Al-3,8%Si-0,25%Mg (Liga I) e Al-6,5%Si-0,6%Mg (Liga II) foram preparadas e caracterizadas por an?lise t?rmica e espectroscopia de emiss?o ?ptica. Ap?s, foram solidificadas em molde met?lico, com e sem desgaseifica??o. Amostras transversais foram extra?das ao longo do comprimento dos lingotes para an?lises da estrutura de solidifica??o e determina??o das propriedades mec?nicas (ensaios de tra??o e dureza). Parte dos lingotes foram submetidos a tratamentos t?rmicos de endurecimento por precipita??o, com solubiliza??o a temperatura de 540oC por 6 horas, e posterior envelhecimento artificial a temperatura de 180?C por 4 horas. Ap?s as an?lises da estrutura de solidifica??o das Ligas I e II, observou-se que os tamanhos m?dios de gr?o e os espa?amentos dos bra?os dendr?ticos secund?rios apresentaram pequenas varia??es que n?o influenciaram nas varia??es das propriedades mec?nicas. Em rela??o ? porosidade, observou-se que a Liga II, por ter mais Si e Fe na sua composi??o, apresentou maior percentual de porosidade do que a Liga I. O processo de desgaseifica??o reduziu em aproximadamente 50% a porosidade em ambas as ligas. Durante a an?lise das propriedades mec?nicas das ligas nos estados bruto de solidifica??o, observou-se que as amostras referentes ? Liga II, na condi??o desgaseificada, apresentaram maiores limites de resist?ncia ? tra??o e dureza, 175,5 MPa e 70,7 HB, respectivamente, devido principalmente ao maior teor de Si encontrado na Liga II. A Liga I, na condi??o desgaseificada apresentou os maiores percentuais de deforma??o espec?fica (? = 1,82%), devido ao menor percentual de porosidade e menores teores de Si e Fe. Com a aplica??o do tratamento t?rmico (T6), pode-se observar um aumento significativo nas propriedades mec?nicas. Na Liga II, observou-se os melhores resultados com tratamento t?rmico, gerando aumento de: 25% na resist?ncia ? tra??o, 57% na deforma??o e 23% na dureza. Dessa forma, a Liga II por apresentar maior percentual de Mg respondeu melhor ao tratamento t?rmico. Na an?lise da correla??o da composi??o qu?mica, o percentual de porosidade e os efeitos dos tratamentos t?rmicos com a varia??o nas propriedades mec?nicas desenvolveu-se modelos matem?ticos que permitem prever o limite de resist?ncia ? tra??o, deforma??o e dureza em ligas de Al-Si-Mg. Analisando os modelos matem?ticos, identificou-se o efeito negativo do percentual de ferro e porosidade no limite de resist?ncia ? tra??o e deforma??o espec?fica, j? o aumento do teor de sil?cio, de magn?sio e aplica??o do tratamento t?rmico T6 contribu?ram para maiores limites de resist?ncia ? tra??o, percentuais de deforma??o e dureza.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-07-26T16:32:18Z No. of bitstreams: 1 2016 - Marcelly Alves da Silva.pdf: 1109436 bytes, checksum: cf0918f898aa3347f3dda630016df417 (MD5) / Made available in DSpace on 2016-07-26T16:32:18Z (GMT). No. of bitstreams: 1 2016 - Marcelly Alves da Silva.pdf: 1109436 bytes, checksum: cf0918f898aa3347f3dda630016df417 (MD5) Previous issue date: 2016-02-26 / SILVA, Marcelly Alves da. Using of calcium and magnesium lignosulfonate in mixtures with phenol-formaldehyde in particleboard manufacturing. 2016. 33 p. Dissertation (Master in forest and Environmental Sciences). Instituto de Florestas, Universidade Federal Rural do Rio de Janeiro, Serop?dica, RJ, 2016. The purpose of this study was to evaluate the feasibility of using calcium and magnesium lignosulfonate (LS) in the production of Pinus caribaea var. caribaea particleboard panels, used pure and in mixtures with phenol-formaldehyde (FF). It was determined the basic and apparent density of the wood, as well as the physical and chemical properties of adhesives. In order to evaluate the effect of FF replaced by LS on the physical and chemical properties, panels were produced with different concentrations of these adhesives. The experiment consisted of two phases. The first phase was performed under temperature of 160?C and pressing time of 10 mitutes with the following compositions: 100% FF, and LS substitutions in the proportions of 20, 40, 60, 80 and 100%, with three replications each. In the second phase, the first phase of the three treatments with lower performance in the mechanical properties were tested at a temperature of 180?C and to 7 minutes. The results of basic and apparent wood density were 0.54 and 0.60 g/cm?, respectively. In the second stage the temperature increased and decreased of the pressing time were not sufficient to consolidate the panel, becoming not possible to analyze the results of this phase. In respect to the thickness swelling and water absorption, increases in the proportion of lignosulfonate in the mixture also raise up these values. The substitution of the phenol-formaldehyde adhesive of lignosulfonate was satisfactory in attendance the specific norm for mechanical properties by 80%. The lignosulfonate showed efficiency in the use as an adhesive in the production of particleboard in mixtures with phenol formaldehyde, suggesting that this is an alternative of the use of synthetic adhesives. / SILVA, Marcelly Alves da. Utiliza??o de lignosulfonato de c?lcio e magn?sio em misturas com fenol-formalde?do na produ??o de pain?is aglomerados. 2016. 33 p. Disserta??o (Mestrado em Ci?ncias Ambientais e Florestais). Instituto de Florestas, Universidade Federal Rural do Rio de Janeiro, Serop?dica, RJ, 2016. O objetivo deste estudo foi avaliar a viabilidade da utiliza??o do lignosulfonato de c?lcio e magn?sio (LS) na produ??o de pain?is aglomerados de Pinus caribaea var. caribaea, na forma pura e em misturas com fenol-formalde?do (FF). Foram determinadas a densidade b?sica e aparente da madeira, bem como as propriedades f?sicas e qu?micas dos adesivos. De modo a avaliar o efeito da substitui??o de FF por LS sobre as propriedades f?sicas e qu?micas, foram produzidos pain?is com diferentes concentra??es desses adesivos. O delineamento experimental foi constitu?do de duas fases. A primeira fase foi realizada sob a temperatura de 160?C e tempo de prensagem de 10 minutos, com as seguintes composi??es: 100% de FF, e as substitui??es por LS nas propor??es de 20, 40, 60, 80 e 100%, com tr?s repeti??es cada. Na segunda fase, os tr?s tratamentos da primeira fase com desempenho inferior nas propriedades mec?nicas foram testados na temperatura de 180?C em tempos de prensagem de 5 e 7 minutos. Os resultados m?dios da densidade b?sica e aparente da madeira foram de 0,54 e 0,60g/cm?, respectivamente. Na segunda fase, o aumento da temperatura e a diminui??o do tempo de prensagem n?o foram suficientes para consolidar o painel, n?o sendo poss?vel analisar os resultados desta fase. Com rela??o ao inchamento em espessura e absor??o de ?gua, ? medida que aumentou a propor??o de lignosulfonato na mistura elevaram-se tamb?m esses valores. Em at? 80%, a substitui??o do adesivo fenol-formalde?do por lignosulfonato foi satisfat?ria no atendimento a NBR 14810-2 (ABNT,2013) para propriedades mec?nicas. O lignosulfonato apresentou efici?ncia na utiliza??o como adesivo na produ??o de pain?is aglomerados em misturas com fenol-formalde?do, evidenciando que esta ? uma alternativa ? utiliza??o de adesivos sint?ticos.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-02-21T21:14:12Z No. of bitstreams: 1 AnaPaulaPereiraFulco_TESE.pdf: 5611369 bytes, checksum: 90dd17509ac9fc7af5b3bb30ec9b9fd9 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-02-22T20:47:30Z (GMT) No. of bitstreams: 1 AnaPaulaPereiraFulco_TESE.pdf: 5611369 bytes, checksum: 90dd17509ac9fc7af5b3bb30ec9b9fd9 (MD5) / Made available in DSpace on 2018-02-22T20:47:30Z (GMT). No. of bitstreams: 1 AnaPaulaPereiraFulco_TESE.pdf: 5611369 bytes, checksum: 90dd17509ac9fc7af5b3bb30ec9b9fd9 (MD5) Previous issue date: 2017-11-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Materiais comp?sitos de matriz polim?rica refor?ados com fibras de carbono utilizados em estruturas aeron?uticas e aeroespaciais est?o frequentemente sujeitos ? carregamentos c?clicos e condi??es ambientais de temperatura e umidade, que podem provocar degrada??o e at? a falha do componente. O objetivo deste trabalho foi estudar os efeitos do envelhecimento sob exposi??o a temperatura at? 160?C e ? umidade nos mecanismos de dano de comp?sitos carbono/ep?xi submetidos a carregamento c?clico. Um estudo preliminar de envelhecimento acelerado foi inicialmente realizado em comp?sitos unidirecionais AS4/8552 com ciclo exposi??o de 8 h de radia??o UVA-340 a 80?C seguidas de 4 h de condensa??o a 50?C, at? atingir o tempo total de 2.160 h. Os efeitos do envelhecimento do material foram evidenciados pela perda de massa, exposi??o das fibras, altera??es qu?micas, aumento da densidade de trincas em testes de cisalhamento interlaminar e flambagem das fibras em amostras fraturadas em testes de compress?o, embora n?o tenham sido observadas altera??es significativas nas propriedades mec?nicas do material. Com base neste trabalho preliminar, um estudo foi realizado em laminados [02/902]s do mesmo material, utilizando ciclo de exposi??o de 8 h a 160 ?C seguidas de 4 h com umidade relativa de 80% a 70 ?C, at? atingir o tempo total de 2.880 h. Em seguida, as amostras foram submetidas a ensaios de fadiga com controle de carga, com raz?o de tens?es R = 0,1 e frequ?ncia de 5 Hz. Os comp?sitos foram caracterizados por espectroscopia de infravermelho com transformada de Fourier (FTIR), an?lise din?mico mec?nica (DMA), microscopia eletr?nica de varredura (MEV) e varia??o de massa, antes e ap?s a exposi??o higrot?rmica. Amostras de ep?xi puro 8552 foram tamb?m expostas as mesmas condi??es de envelhecimento e caracterizadas por microscopia ?tica (MO), espectroscopia FTIR e varia??o de massa. A partir dos diagramas de vida em fadiga, uma fun??o de deslocamento (shift) foi proposta para a previs?o de n?mero de ciclos para falha de comp?sitos envelhecidos com base em dados de testes de fadiga em comp?sitos n?o envelhecidos. O estudo tamb?m mostrou que a falha por fratura pode n?o ser o melhor par?metro para avalia??o do efeito do envelhecimento higrot?rmico na vida em fadiga de materiais comp?sitos de matriz polim?rica refor?ados com fibras de carbono. Outros par?metros como delamina??o e satura??o de trincas s?o tamb?m essenciais para avaliar a durabilidade desses materiais comp?sitos. / Carbon fiber reinforced polymer (CFRP) composites used in aeronautic and aerospace structures are often exposed to cyclic loading and environmental effects such as temperature and humidity, which can lead to degradation and failure of the component. The objective of this work was to study the effects of aging under exposure to temperature up to 160?C and humidity on the damage mechanisms of carbon/epoxy composites subjected to cyclic loading. Initially, a preliminary accelerated aging study was conducted with unidirectional AS4/8552 samples using an exposure cycle of 8 h of UVA-340 at 80 ?C followed by 4 h of condensation at 80 ?C, for a total exposure period of 2,160 h. The effects of aging were evidenced by weight loss, fiber exposure, chemical changes, increased crack density in interlaminar shear strength tests, and fiber buckling in fractured samples after compression tests, even though no significant changes mechanical properties were observed. Based on this preliminary work, a study was conducted on [02/902]s laminates of the same material, using an exposure cycle of 8 h at 160 ?C followed by 4 h of 80% relative humidity at 70 ?C, for a total exposure period of 2,880 h. Afterwards, stress-controlled tension-tension fatigue tests were conducted using a stress ratio R = 0.1 and frequency of 5 Hz. Composites were characterized using Fourier transform infrared spectroscopy (FTIR), Dynamic Mechanical Analysis (DMA), Scanning Electron Microscopy (SEM) and weight change, before and after hygrothermal exposure. Samples of plain epoxy 8552 were also exposed to the same aging conditions and characterized by optical microscopy (OM), FTIR spectroscopy and weight change. Based on the fatigue life diagrams, a shift function was proposed for the prediction of number of cycles to failure of aged composites based on data from unaged specimens. The study also showed that failure by fracture may not be the best parameter to evaluate the effect of hygrothermal aging on fatigue life of carbon fiber reinforced polymer composites. Other parameters such as delamination and crack saturation are also essential to assess durability of these composites.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-04-02T12:49:22Z No. of bitstreams: 1 GiorgioAndreBritoOliveira_DISSERT.pdf: 3458330 bytes, checksum: 434d48526b1ff4a3e12b0d1b440b6198 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-04-04T14:49:22Z (GMT) No. of bitstreams: 1 GiorgioAndreBritoOliveira_DISSERT.pdf: 3458330 bytes, checksum: 434d48526b1ff4a3e12b0d1b440b6198 (MD5) / Made available in DSpace on 2018-04-04T14:49:23Z (GMT). No. of bitstreams: 1 GiorgioAndreBritoOliveira_DISSERT.pdf: 3458330 bytes, checksum: 434d48526b1ff4a3e12b0d1b440b6198 (MD5) Previous issue date: 2018-02-09 / Os materiais comp?sitos s?o um novo destaque no avan?o tecnol?gico, impondo novas pesquisas relacionadas ao assunto devido a sua crescente demanda nas mais diversas ?reas. Dentre essas pesquisas surgem as que tem como objetivo facilitar as aplica??es desses materiais, atrav?s de uma r?pida apura??o das suas propriedades mec?nicas sem a necessidade de procedimentos experimentais, sendo essa fator primacial na prepara??o de projetos. Assim surgiram os modelos micromec?nicos, que ganharam destaque devido a sua praticidade, como exemplo das equa??es da Regra das Misturas e das equa??es de Halpin-Tsai. Recentemente, novos modelos computacionais vem combinando modelos micromec?nicos e aperfei?oando-os para se ter a m?xima acur?cia, como por exemplo as redes neurais artificiais (RNAs). Com base nisso, este trabalho visa a cria??o de arquiteturas de RNAs capazes de modelar o m?dulo de cisalhamento (G12) e a tens?o ?ltima de tra??o longitudinal (Xt) de comp?sitos unidirecionais. Com as RNAs treinadas e testadas, essas v?o servir como ferramentas computacionais, semelhante a fun??es, em que fornecendo as entradas teremos uma sa?da desejada. Para isso, fez-se necess?rio uma coleta de dados da literatura, que foram divididos em um conjunto de treino e um conjunto de teste, para realiza??o da valida??o cruzada. Se desenvolveram sete tipos de arquiteturas diferentes, tr?s para o G12 e quatro para o Xt, na qual essas possuem entre duas, tr?s e quatro entradas. Dentre esses modelos tr?s deles s?o considerados modelos mistos, que combina valores da sa?da da RNA com os valores obtidos vindos de modelos micromec?nicos, como o modelo de Halpin-Tsai. Ap?s o treinamento das RNAs, foi realizada uma an?lise comparativa dos valores vindos da RNA e dos valores experimentais, e ainda an?lises quantitativas e qualitativas com base no modelo de compara??o (modelo de Halpin-Tsai e modelo da Regra das Misturas), apresentando maiores valores de coeficiente de correla??o e menores valores de erro quadr?tico m?dio. / The composite materials are a new highlight in the technological advancement, consequently leading to the development of new researches due to its growing demand in the most diverse areas. Among these researches, arise those that have the objective to facilitate the application of these materials, through a fast estimation of its mechanical properties, without the need for experimental procedures, with this being the main factor in the projects preparation. Thus the micromechanical models appeared, which gained importance due to its practicality, such as the Mix Rule and the Halpin-Tsai equations. Recently, new computational models are combining micromechanical models and perfecting them to obtain maximum accuracy, as for instance in the Artifical Neural Networks application. Therefore, this work aims to create an Artificial Neural Network (ANN) architecture capable of modeling the shear modulus and ultimate longitudinal stress of unidirectional composites. When the ANN?s are trained and tested, they will serve as computational tools, similar to functions, where an input is supplied to obtain a desired output. To achieve this goal, it was necessary a collection of data in literature, which were divided in a training group and a testing group, with the cross validation between them being performed. Seven different types of architectures were developed, three for the G12 and four for the Xt, each of these with two, three and four inputs. Among these models, three of them are considered mixed models, which combines values from the output of the ANN with values obtained from the micromechanical models, such as the Halpin-Tsai. After the ANN training, a comparative analysis was performed between the values from the ANN and the experimental values, with quantitative and qualitative analysis being performed with the Halpin-Tsai model as a base for comparison, presenting higher values for the correlation coefficient and smaller values for the root mean square error.

Made available in DSpace on 2014-12-17T14:07:08Z (GMT). No. of bitstreams: 1 WagnerLT_TESE.pdf: 4295737 bytes, checksum: feb949970c7901b7da571339c28198a9 (MD5) Previous issue date: 2012-02-29 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Ceramic filters are cellular structures that can be produced by various techniques, among which we highlight the replication method, or method of polymeric sponge. This method consists of impregnating polymeric foam with ceramic slurry, followed by heat treatment, where will occur decomposition of organic material and the sinter of the ceramic material, resulting in a ceramic whose structure is a replica of the impregnated sponge. Ceramic filters have specific properties that make this type of material very versatile, used in various technological applications such as filters for molten metals and burners, make these materials attractive candidates for high temperature applications. In this work we studied the systems Al2O3-LZSA ceramic filters processed in the laboratory, and commercial Al2O3-SiC ceramics filters, both obtained by the replica method, this work proposes the thermal and mechanical characterization. The sponge used in the processing of filters made in the laboratory was characterized by thermogravimetric analysis. The ceramic filters were characterized by compressive strength, flexural strength at high temperatures, thermal shock, permeability and physical characterization (density and porosity) and microstructural (MEV and X-rays). From the results obtained, the analysis was made of the mechanical behavior of these materials, comparing the model proposed by Gibson and Ashby model and modified the effective area and the tension adjusted, where the modified model adapted itself better to the experimental results, representing better the mechanical behavior of ceramic filters obtained by the replica method / Filtros cer?micos processados pelo m?todo da r?plica tem sido objeto de crescentes pesquisas pela versatilidade da t?cnica. O m?todo consiste na impregna??o de uma esponja polim?rica em uma suspens?o cer?mica, seguido de tratamento t?rmico, onde ocorre a decomposi??o do material org?nico e a sinteriza??o do material cer?mico, resultando em um corpo cer?mico, cuja estrutura macrosc?pica ? uma r?plica da esponja impregnada. Filtros cer?micos possuem propriedades especificas que os tornam muito vers?teis, com diferentes aplica??es tecnol?gicas, tais como filtros para metais fundidos e queimadores, tornando esses materiais fortes candidatos para aplica??es ?s altas temperaturas. Neste trabalho foram estudados e desenvolvidos filtros cer?micos dos sistemas Al2O3-LZSA processados em laborat?rio, e de Al2O3-SiC comerciais, ambos obtidos pelo m?todo da r?plica, e caracterizados t?rmica e mec?nicamente. A esponja utilizada no processamento dos filtros feitos em laborat?rio foi caracterizada atrav?s de an?lises t?rmicas (ATG e DrATG). Os filtros cer?micos foram caracterizados mediante an?lises de resist?ncia a compress?o, resist?ncia ? flex?o a altas temperaturas, choque t?rmico, permeabilidade e caracteriza??o f?sica (densidade e porosidade), e microestrutural (MEV e raios X). A partir dos resultados obtidos, foi feita a an?lise do comportamento mec?nico desses materiais, comparando-se o modelo proposto por de Gibson e Ashby e o modelo modificado com a ?rea efetiva e a tens?o corrigida, onde o modelo modificado se adequou melhor aos resultados experimentais, representando melhor o comportamento mec?nico dos filtros cer?micos obtidos pelo m?todo da r?plica

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-10-11T20:53:57Z No. of bitstreams: 1 SistanleyJonesLimaBispo_TESE.pdf: 3279866 bytes, checksum: 4e4c98181eb5b9e3145660daab8debff (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-10-14T20:57:44Z (GMT) No. of bitstreams: 1 SistanleyJonesLimaBispo_TESE.pdf: 3279866 bytes, checksum: 4e4c98181eb5b9e3145660daab8debff (MD5) / Made available in DSpace on 2016-10-14T20:57:44Z (GMT). No. of bitstreams: 1 SistanleyJonesLimaBispo_TESE.pdf: 3279866 bytes, checksum: 4e4c98181eb5b9e3145660daab8debff (MD5) Previous issue date: 2016-06-03 / Esta pesquisa apresenta uma abordagem a cerca do processo de reciclagem do polipropileno refor?ado com fibras de curau? reprocessado. Sendo uma proposta alternativa de refor?o aos comp?sitos polim?ricos. Teores de fibras de 0%, 10%, 20% e 30% foram analisados para verifica??o de suas propriedades mec?nicas comparando-as, inclusive com as propriedades do polipropileno (PP). Os biocomp?sitos granulados foram preparados em uma extrusora. Os corpos de prova foram moldados por processo de inje??o e submetidos aos ensaios mec?nicos de tra??o uniaxial, flex?o em tr?s pontos e impacto. Para verifica??o de danos aos corpos de prova utilizou-se da an?lise por microscopia eletr?nica de varredura (MEV). Estes biocomp?sitos tamb?m foram submetidos a ensaios f?sico - qu?micos de ?ndice de fluidez (IF). Observou-se que os biocomp?sitos de polipropileno com 30% de fibras de curau? apresentaram maior m?dulo de elasticidade e menor resist?ncia ao impacto. Para todos os biocomp?sitos, os valores encontrados nos ensaios de tra??o para os limites de escoamento e tens?o de ruptura n?o sofreram altera??es ? medida que se adicionavam as fibras. Outros pontos relevantes foram o aumento da resist?ncia ? flex?o, a redu??o da degrada??o t?rmica das misturas polipropileno e fibras de curau?, e o n?o comprometimento de uma forma em geral, da fabrica??o dos biocomp?sitos, quando analisados por microscopia eletr?nica de varredura. / This research presents an approach about the polypropylene recycling process reinforced with curau? reprocessed fibers. As an alternative proposal reinforcement to polymeric composites. Levels of 10 %, 20 % and 30 % of fibers in the biocomposites were analyzed to check their mechanical properties comparing them, even with the properties of polypropylene (PP). Pellets biocomposites were prepared by the extrusion process, and the specimens were manufactured by injection process and subjected to mechanical tests of uniaxial tensile, three point bending and impact. To check for damage to the specimens was used to analysis by scanning electron microscopy (SEM). These biocomposites were also subjected to testing physical ? chemistry of index of fluidity (IF). It was observed that the polypropylene biocomposites with 30 % curau? fibers showed higher elastic modulus for both traction and to flexion and less resistance to impact. For all biocomposites, the values found in tensile tests to the limits of flow and maximum voltage have approximate values as they were added the curau? fibers. Another important point was increased resistance to bending in biocomposite as promoting the addition of curau? fibers and decrease as they were reprocessed also decreased thermal degradation of the polypropylene blends and curau? fibers, and no impairment of so in general, the production of biocomposites, when analyzed by scanning electron microscopy.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-06-03T23:57:10Z No. of bitstreams: 1 RicardoAlexDantasDaCunha_DISSERT.pdf: 2552417 bytes, checksum: 6be84ef2bba0ca4028e0191c91836125 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-06-07T22:17:01Z (GMT) No. of bitstreams: 1 RicardoAlexDantasDaCunha_DISSERT.pdf: 2552417 bytes, checksum: 6be84ef2bba0ca4028e0191c91836125 (MD5) / Made available in DSpace on 2016-06-07T22:17:01Z (GMT). No. of bitstreams: 1 RicardoAlexDantasDaCunha_DISSERT.pdf: 2552417 bytes, checksum: 6be84ef2bba0ca4028e0191c91836125 (MD5) Previous issue date: 2015-12-07 / Os materiais comp?sitos de matriz polim?rica v?m sendo utilizados em larga escala nas ?reas industriais tais como aeroespacial, automobil?stica, petrol?fera, por apresentarem um bom desempenho mec?nico, vida ?til elevada e uma rela??o custo/benef?cio. A determina??o das propriedades mec?nicas se faz indispens?vel para a caracteriza??o dos comp?sitos. Desta forma, neste trabalho ser?o obtidas tr?s placas de laminados com matriz polim?rica teraft?lica, refor?ados por um tecido bidirecional de vidro-E e kevlar, ambos confeccionados industrialmente, onde as placas ser?o fabricadas pelo processo de lamina??o manual (Hand lay up). Todos os laminados ter?o cinco camadas de refor?o,como primeiro laminado h?brido sendo composto pelo tecido bidirecional de fibra de vidro-E, intercalado por camadas de fibra kevlar, o segundo ? formado pelo tecido bidirecional de fibra kevlar nas extremidades do laminado (duas camadas), e no centro o tecido de fibra de vidro (tr?s camadas), a terceira placa foi composta apenas pelo tecido bidirecional de fibra de vidro-E. Em seguida, foram confeccionados corpos de prova (CP) mediante norma, para determina??o das propriedades mec?nicas de tra??o e flex?o em tr?s pontos. Ap?s a fabrica??o dos corpos de prova, estes foram imersos em petr?leo e em ?gua do mar. Feito isso, realizou-se um comparativo das propriedades mec?nicas para a condi??o de ensaio no estado seco. Houve um aumento consider?vel nas propriedades estudadas devido o efeito da hibridiza??o nos laminados. / The polymer matrix composite materials are being used on a large scale in the most different industrial fields such as aerospace, automotive, oil, among others, since the industrial perspectives is currently working with materials which have a good mechanical performance at high service life and cost / benefit. Thus, the determination of the mechanical properties is indispensable for the characterization of waste resulting in greater expansion of this type of material. Thus, this work will be obtained three plates laminated with tereft?lica polymeric matrix reinforced by a bidirectional woven E-glass and kevlar both industrially made, where the plates are manufactured by manual lamination process (hand lay-up), all laminates have five enhancement layers, the first hybrid laminate will consist of bidirectional woven E-glass fiber, kevlar fiber interspersed with layers, is formed by the second bidirectional woven kevlar fiber at the ends of the laminate (two layers), and in the center the glass fiber fabric (three layers), the third plate is composed of only the bidirectional woven E-glass fiber. Then were prepared specimens (CP) by standard, to determine the mechanical properties of tensile and bending in three points. After fabrication of the specimens, they were immersed in oil and seawater. After that, there was a comparison of the mechanical properties for the test condition in the dry state. Showing that there was a considerable increase in the properties studied because the effect of hybridization in laminates.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-07-20T21:46:40Z No. of bitstreams: 1 RafaelaLuizPereiraSantos_TESE.pdf: 5717758 bytes, checksum: 765e67dde7c80007f582df680380b1c9 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-07-21T19:39:57Z (GMT) No. of bitstreams: 1 RafaelaLuizPereiraSantos_TESE.pdf: 5717758 bytes, checksum: 765e67dde7c80007f582df680380b1c9 (MD5) / Made available in DSpace on 2016-07-21T19:39:57Z (GMT). No. of bitstreams: 1 RafaelaLuizPereiraSantos_TESE.pdf: 5717758 bytes, checksum: 765e67dde7c80007f582df680380b1c9 (MD5) Previous issue date: 2016-01-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / All-ceramic restorations have been widely used as aesthetic standard in nowadays dentistry, to replace the tooth structure (appearance and function). However, failures associated with chipping and delamination of the veneering porcelain from zirconia substructure still high when compared to metal-ceramic systems. This study aimed address these problems by improving the mechanical strength of veneering porcelain and by improving its adhesion to zirconia substrate. First, the addition of a stronger ceramic second phase (zirconia particles) to feldspathic porcelain was studied. This study began with the preliminary characterization of zirconia synthesized by Complex Polymerization Method (CPM) and commercial zirconia. It was found that the synthesized zirconia did not show improved properties when compared to commercial zirconia. Commercial zirconia powders were thus used thereafter. The influence of the type of powder (pre-sintered or agglomerated) in the mechanical properties and wear of porcelain composites (20vol.%) was evaluated. The pre-sintered powders increased the mechanical strength and wear of the composites compared to agglomerated powders. Then, it was determined the amount of second phase (0-50vol.%) that maximizes the mechanical properties of the porcelain-zirconia composites. It was concluded that the composites with 30vol.% of zirconia showed the best results for wear and flexural strength (198.5MPa). Finally, it was evaluated the influence of the type of surface treatment (sandblasting or holes) and the deposition of a composite interlayer (porcelain reinforced with 30vol.% of zirconia), on the zirconia surface, on the bond strength between the veneering porcelain and the zirconia substructure. The highest bond strength values were found for specimens having simultaneously holes on the surface of zirconia and the composite interlayer between the zirconia substructure and the veneering porcelain (138 ? 19MPa). It was demonstrated that the correct configuration of the interface between the zirconia substructure and the veneering porcelain can lead to all-ceramic restorations with enhanced mechanical strength and improved clinical performance. / Materiais comp?sitos restauradores representam um dos mais bem sucedidos biomateriais na pesquisa moderna, na substitui??o do tecido biol?gico em apar?ncia e fun??o. Nesta linha, a porcelana feldsp?tica tem sido largamente usada em odontologia devido suas interessantes qualidades como estabilidade de cor, propriedades est?ticas, elevada durabilidade mec?nica, biocompatibilidade, baixa condutividade t?rmica e elevada resist?ncia ao desgaste. Entretanto, este material ? fr?gil e pode falhar em ambiente oral devido ao micro-vazamento, baixa resist?ncia ? tra??o, descolagem ou fratura. Assim, para melhorar as propriedades mec?nicas da porcelana, a zirc?nia parcialmente estabilizada com ?tria (Y-TZP) pode ser uma boa alternativa para fortalecer e produzir infraestruturas totalmente cer?micas (coroas e pr?teses parciais fixas). Portanto, este estudo tem por objetivo avaliar as propriedades mec?nicas e caracter?sticas microestruturais da porcelana refor?ada com zirc?nia (3Y-TZP) em diferentes conte?dos e as vari?veis que afetam as propriedades mec?nicas destes materiais. O estudo de caracteriza??o revelou que a zirc?nia comercial apresenta melhores resultados quando comparada com a zirc?nia sintetizada pelo CPM. Assim, os estudos seguintes utilizaram a zirc?nia comercial para todos os testes requeridos. As part?culas de zirc?nia apresentam elevadas propriedades mec?nicas quando comparadas a zirc?nia aglomerada. Os diferentes conte?dos revelam que as propriedades mec?nicas dos comp?sitos aumentam com o aumento do conte?do volum?trico at? 30% vol.% (198,5Mpa), ou seja, maior resist?ncia ? flex?o quando comparada com os outros comp?sitos. Do mesmo modo, a resist?ncia ao desgaste para os comp?sitos com (30%, vol.% de zirc?nia) apresenta valores superiores quando comparado aos demais comp?sitos. Na ades?o cer?mico-cer?mico a porcelana exibe elevada ades?o para a superf?cie de zirc?nia porosa quando comparada a superf?cie rugosa. Os furos superficiais (PZ) e aplica??o de comp?sitos com camada intermedi?ria (RZI) na zirc?nia causam separadamente uma melhoria da resist?ncia ao cisalhamento da zirc?nia-porcelana quando comparados as amostras convencionais de zirc?nia-porcelana (RZ), embora n?o sejam estatisticamente significativas (p>0.05). A presen?a de uma camada intermediaria produz um aumento significativo na for?a de liga??o (~55%) em rela??o as amostras convencionais (RZ). Portanto, a correta a correta configura??o e tratamento superficial podem produzir subestruturas com qualidade e for?a de liga??o adequadas aos requisitos odontol?gicos.

Made available in DSpace on 2014-12-17T14:57:55Z (GMT). No. of bitstreams: 1 EduardoGR_TESE.pdf: 4595986 bytes, checksum: 7a13884531d20feb0680378f1e5403df (MD5) Previous issue date: 2011-10-11 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Ceramics with porous cellular structure, called ceramic foams, have a potential use in several applications, such as: thermal insulation, catalyst supports, filters, and others. Among these techniques to obtain porous ceramics the replication method is an important process. This method consists of impregnation of a sponge (usually polymer) with ceramic slurry, followed by a heat treatment, which will happen the decomposition of organic material and sintering the ceramic material, resulting in a ceramic structure which is a replica of impregnated sponge. Knowledge of the mechanical properties of these ceramics is important for these materials can be used commercially. Gibson and Ashby developed a mathematical model to describe the mechanical behavior of cellular solids. This model wasn?t for describing the ceramics behavior produced by the replica method, because it doesn?t consider the defects from this type of processing. In this study were researched mechanical behavior of porous alumina ceramics obtained by the replica method and proposed modifications to the model of Gibson and Ashby to accommodate this material. The polymer sponge used in processing was characterized by thermogravimetric analysis and scanning electron microscopy. The materials obtained after sintering were characterized by mechanical strength tests on 4-point bending and compression, density and porosity and by scanning electron microscopy. From these results it was evaluated the mechanical strength behavior compared to Gibson and Ashby model for solid cellular structure and was proposed a correction of this model through a factor related to struts integrity degree, which consider fissures present in the structure of these materials besides defects geometry within the struts / Cer?micas com estrutura celular porosa, denominadas espumas cer?micas, possuem o potencial de utiliza??o em uma vasta gama de aplica??es, tais como: isolamento t?rmico, suporte catal?tico, filtros, dentre outras. Dentre as t?cnicas para obten??o destas cer?micas porosas podemos destacar o m?todo da r?plica. Este m?todo consiste na impregna??o de uma esponja (geralmente polim?rica) com uma barbotina cer?mica, seguindo-se um tratamento t?rmico, onde ocorrer? a decomposi??o do material org?nico e sinteriza??o do material cer?mico, resultando em uma cer?mica cuja estrutura ? uma r?plica da esponja impregnada. O conhecimento das propriedades mec?nicas destas cer?micas ? importante para que estas possam ser utilizadas comercialmente. Gibson e Ashby desenvolveram um modelo matem?tico para descrever o comportamento mec?nico de s?lidos celulares, por?m este modelo n?o se mostrou satisfat?rio para descrever o comportamento das cer?micas obtidas pelo m?todo da r?plica, pois o mesmo n?o leva em considera??o os defeitos provenientes deste tipo de processamento. Neste trabalho estudou-se o comportamento mec?nico de cer?micas porosas de alumina obtidas pelo m?todo da r?plica, e a partir desta an?lise se prop?s modifica??es no modelo de Gibson e Ashby para se adequar a este material. A esponja polim?rica utilizada no processamento foi caracterizada atrav?s de an?lise termogravim?trica e microscopia eletr?nica de varredura. Os materiais obtidos ap?s sinteriza??o foram caracterizados atrav?s de testes de resist?ncia mec?nica, tens?o de ruptura ? flex?o (4 pontos) e compress?o, densidade, porosidade e por fim, an?lise microsc?pica por microscopia eletr?nica de varredura. A partir destes resultados avaliou-se o comportamento da resist?ncia mec?nica em compara??o ao modelo de Gibson e Ashby para s?lidos com estrutura celular e foi proposta uma corre??o deste modelo atrav?s de um fator relacionado com o grau de integridade dos filamentos, que considera as trincas presentes na estrutura destes materiais, al?m da geometria dos defeitos no interior dos filamentos