Made available in DSpace on 2014-12-17T14:57:59Z (GMT). No. of bitstreams: 1 WalneyGS_TESE.pdf: 2269904 bytes, checksum: 6e832698b2804a3e69b2353dde562cad (MD5) Previous issue date: 2014-12-30 / The adhesive mortars are a mixture of cement, sand, and additives to polymers that retain the mixing water and promotes adherence, being used in setting on various ceramic substrates. The sand used in the production of these mortars is from the riverbeds, and with the increasing restriction of these sands extraction by environmental agencies, and often having to be transported over long distances to the consumer center. This work aims to design and physical and mechanical characterization of ecological adhesive mortar with total replacement of natural sand by sand from the crushing of limestone, and the addition of mineral ash biomass of cane sugar in partial replacement cement used in the production of adhesive mortar , aiming compositions that meet the regulatory specifications for use adhesive mortar. Standardized tests to determine the tensile bond strength (NBR 14081-4), determination of open time (NBR 14081-3) and determination of slip (NBR 14081-5) were performed. Were also conducted trials squeeze flow in different formulation, the mortar with addition of 15 % gray biomass of cane sugar for cement mortars as well as the total replacement of natural sand by sand limestone crushing, got the best performance among the mortars studied, it was found that the addition of biomass to replace cement is perfectly feasible due to its pozzolanic activity, which contributed to this reduction in the cement matrix formation of adhesive mortar / As argamassas colantes s?o a mistura de cimento e areia, aditivadas com pol?meros que ret?m ?gua de amassamento e promovem a ader?ncia, sendo utilizadas na fixa??o da cer?mica sobre diversos substratos. A areia utilizada na produ??o dessas argamassas, proveniente dos leitos dos rios, tem sua extra??o submetida ? restri??o cada vez maior por parte dos ?rg?os ambientais e, muitas vezes, precisa ser transportada a grandes dist?ncias at? chegar ao centro consumidor. Este trabalho tem por objetivo a formula??o e a caracteriza??o f?sica e mec?nica de argamassa colante ecol?gica com a substitui??o total da areia natural por areia proveniente de britagem de rocha calc?ria, bem como com a adi??o mineral de cinza de biomassa de cana-de-a??car em substitui??o parcial do cimento utilizado na produ??o das argamassas colantes, visando composi??es que atendam ?s especifica??es normativas de utiliza??o de argamassa colante. Foram realizados ensaios normatizados de determina??o da resist?ncia de ader?ncia ? tra??o (NBR 14.081-4), determina??o do tempo em aberto (NBR 14.081-3) e determina??o do deslizamento (NBR 14.081-5). Foram realizados, ainda, ensaios de squeeze flow nas diferentes formula??es. A argamassa com adi??o de 15% de cinza de biomassa de cana-de-a??car em substitui??o ao cimento, bem como a substitui??o total da areia natural por areia de britagem calc?ria, obteve o melhor desempenho entre as argamassas estudadas. Foi verificado que a adi??o de biomassa em substitui??o ao cimento ? perfeitamente vi?vel, devido a sua atividade pozol?nica, que contribuiu para essa redu??o de cimento na matriz de forma??o da argamassa colante

As argamassas colantes são produtos constituídos por areia natural ou artificial, ligantes e aditivos químicos que cumprem uma função de adesivo para assentamento de revestimentos em pisos e paredes. Sob o ponto de vista reológico, a argamassa colante é um material multifásico formado por uma pasta que envolve agregados minerais. Atualmente, o único teste preconizado em norma a fresco é o ensaio de deslizamento, que apesar de ter baixo custo e relativa facilidade de execução em laboratório. As grandes desvantagens desse método são: imprecisão e a baixa repetibilidade, além de ser insuficiente para efetuar uma avaliação mais completa desses produtos no estado fresco. Assim, técnicas de caracterização reológica (Squeeze Flow, Pull Out Flow e reometria rotacional) foram especificadas e aplicadas, como alternativa tecnológica para avaliação de argamassas colantes. Porém, o potencial da configuração tradicional do ensaio de Squeeze Flow e a reometria rotacional foram pouco explorados neste tipo de argamassa. Neste estudo foi necessário empreender ajustes de configuração. O objetivo desta dissertação foi o de aplicar métodos de caracterização reológica em argamassas colantes de mercado (ACI e ACIII) de certo fabricante e ACI formulada em laboratório composta por areias com morfologias diferentes que permitissem identificar suas características relevantes no estado fresco, avaliar a influência dos parâmetros experimentais do método de Squeeze Flow (principalmente em relação à configuração e parâmetros), avaliar a adesividade das argamassas no estado fresco e aplicar o método de reometria rotacional para avaliação das energias de mistura e reológica. Os experimentos para avaliação das configurações e parâmetros do ensaio de Squeeze Flow e Pull Out Flow mostraram que tais métodos foram sensíveis para diferenciar as argamassas e refletiram o que, na prática, é percebido: ACIII (Argamassa Colante do Tipo III) tem maior consistência que ACI (Argamassa 7 Colante do Tipo I), além de mostrar que são sensíveis às diferentes taxas de deslocamento, teores de água e morfologia de agregados. Já a reometria rotacional mostrou-se sensível para identificar e diferenciar a cinética de mistura das argamassas colantes ACI e ACIII. Os resultados indicaram que o tempo de mistura de 150 segundos foi eficiente e suficiente para homogeneizar e estabilizar as argamassas testadas, e que a argamassa do tipo ACI apresenta maior dificuldade de mistura e resulta em uma suspensão com maior viscosidade e tensão de escoamento do que a argamassa ACIII. Por fim, a aplicação dos métodos de caracterização reológica em argamassas ACI compostas por areias com morfologias diferentes, indicou que o método de Squeeze Flow mostrou ser sensível para diferentes teores de água, em argamassas compostas por areia artificial. As curvas de carga de compressão da argamassa ACI com areia artificial mostraram serem superiores às formuladas argamassas com areia natural, indicando que, com a mesma proporção de insumos e teor de água (volume), as argamassas não possuem perfis reológicos similares. / Adhesive mortars are products constituted of natural or artificial sand, binder (cement) and chemical additives which serve as an adhesive for laying floor and wall tiles. From the rheological point of view, the adhesive mortar is a multiphase material consisting of a paste that coats mineral aggregates. Currently, the only test done is the slip test, which has low cost and has a relatively easy execution. The disadvantage of this method is not to have a good repeatability and is not sufficient to evaluate products in fresh state. Thus, techniques of rheologic characterization (flow squeeze, pull out flow and rotational rheometry) were applied as technologic alternatives for evaluation of adhesive mortars. However, the potential of the traditional configuration of the Squeeze Flow test and rotational rheometry were not explored in this type of product due to the requirement of configuration settings. The purpose of this dissertation is to apply advanced methods for rheological characterization of adhesive mortars in order to identify important characteristics of fresh-state application; evaluation of the influence of the squeeze-flow experimental method (mainly due to configuration and parameters); applied rheometry techniques to evaluate the mixing energy; and to evaluate the adhesiveness of fresh mortars. The evaluation of the configuration and parameters of the Squeeze Flow and Pull Out Flow showed that the methods were sensible enough to differentiate mortars in the same way that is perceived in practice: ACIII has greater consistency than ACI, also shows that are sensitive to different rates of displacement, water content and morphology of aggregates. The mixing and rotational rheometry showed that the method is sensitive to identify and differentiate the kinetics of mixing for ACI and ACIII mortars. The results indicate that the mixing time of 150 seconds was effective to homogenize and disperse the mortars. The mixing and flow torque values are higher for ACI than for ACIII, indicating that ACI is more difficult to be mixed and has a higher viscosity and yield stress than ACIII.

O presente trabalho propõe o entendimento do comportamento no estado fresco de argamassas colantes, com base na caracterização reológica e físico-química de diferentes composições comerciais, servindo de base para analisar o fenômeno de deslizamento, a partir do ensaio estabelecido na norma brasileira. Para isso, foi utilizado o ensaio “Squeeze flow” (escoamento por compressão axial), empregado na caracterização de argamassas de revestimento no laboratório de microestrutura do CPqDCC da EPUSP, como ferramenta de análise do comportamento de argamassas colantes. Neste ensaio, o escoamento do material decorre da aplicação de uma carga de compressão sobre a amostra no estado fresco, a qual ocasiona deslocamentos no seu interior devido a esforços de cisalhamento radiais originados durante o fluxo. O critério de seleção das argamassas colantes comerciais (tipo AC-I) se baseou nos resultados do ensaio de deslizamento, escolhendo-se duas com resultado muito abaixo do limite especificado, duas com resultado próximo do limite e outras duas com resultado acima do mesmo. A composição química e física foi caracterizada com o objetivo de embasar a análise dos resultados obtidos no “Squeeze flow”. A separação da fração fina das argamassas na peneira no.200 contribuiu para o conhecimento da viscosidade da pasta e da sua influência no comportamento reológico das argamassas. Foi observado que as argamassas estudadas apresentam diferenças de composição físico-química e de comportamento reológico. As diferenças de comportamento reológico das argamassas decorrem, provavelmente, de ação sinérgica de alguns parâmetros da composição, com destaque para a distribuição granulométrica. O “Squeeze flow” mostrou-se uma ferramenta adequada na caracterização das argamassas colantes e contribuiu para explicar o deslizamento estabelecido na norma brasileira, pela proposição de modelos hipotéticos de comportamento. / Present thesis proposes the study of plastic-state behaviour of dry-set mortars based on the rheological and physicochemical characterization of different commercially available dry-set mortar compositions. Such characterization served as basis for the analysis of dry-set mortar slip phenomena using the tests recommended by brazilian standards (NBR). The Squeeze Flow test (slip by axial compression) originally used for coating mortars characterization by the EPUSP CPqDDC Microstructure Laboratory was adopted as a test tool for analysing the dry-set mortar behaviour. In the mentioned test the material slip is obtained by compressing the sample in its plastic state which caused internal displacements due to radial shearing tensions originated during the mentioned slip. The dry-se mortars (all of them AC-I type) used in the study were selected based in the slip tests results against brazilian standards specified limits resulting in the selection of two dry-set mortars below the specified limit, two dry-set mortars close to the specified limit and dry-set mortars above the specified limit. Chemical and physical compositions were characterized in order to serve as basis for Squeeze Flow results analysis. Fine fraction segregation, using number 200 sieve contributed to understanding of plastic-state mortar viscosity and its influence in mortar rheological behaviour. It was observed diverse physicochemical and rheological behaviour among the studied dry-set mortars. The rheological behaviour diversity of dry-set mortars were due to the synergy among some composition parameters, specially the granular distribution. The Squeeze Flow was considered a suitable tool for the characterization of dry-set mortars and contributed to develop hypotetical behaviour models that allowed to explain the slip as stated by brazilian standards.

The consolidation time is the time available for the application of adhesive mortar on the substrate. The NBR 14081-1 does not specify a method of test to determining the consolidation time, however, the standard of enforcement procedures of covering floors and walls with ceramic tiles (NBR 13755 and NBR 13754) establish 2 h and 30 min as the minimum time. By considering the significant differences between the formulations, the presence of polymeric additives, besides the evolution of cement and additions, a study about how and when the consolidation of adhesive mortar happens is needed. Then, it was looked for to evaluate and determine the time of consolidation of adhesive mortars of the types ACI, ACII and ACIII by Squeeze flow and Pull out flow tests in different time intervals (30, 60, 120, 180, 240 and 300 min) in fresh state. The test methods shown to be sensitive for the determination of consolidation time of adhesive mortars, indicating the increase of the viscosity and of the adhesion of the mortar over time. For mortars in which the consolidation occurred during the time period studied, this time made up to 180 minutes after mixing. From this period the adhesive mortars suffered losses in their rheological characteristics, which would cause difficulties in the settlement stages of ceramic plates and later problems in its performance and durability. On the other hand, the tensile bond strength tests showed great variability imparing a correlation with the rheological tests. / O tempo de consolidação é o período disponível para a aplicação da argamassa colante no substrato. A NBR 14081-1 não especifica um método de ensaio para a determinação do tempo de consolidação, já as normas de procedimento de execução de revestimento de pisos e paredes com placas cerâmicas (NBR 13755 e NBR 13754) estabelecem 2 h e 30 min como tempo mínimo. Considerando as diferenças significativas entre as formulações, a presença de aditivos poliméricos, além da evolução dos cimentos e das adições, faz-se necessário um estudo sobre como e quando se dá a consolidação da argamassa colante. Em virtude disso, procurou-se avaliar e determinar o tempo de consolidação das argamassas colantes dos tipos ACI, ACII e ACIII por meio dos ensaios de Squeeze flow e Pull out flow, em diferentes intervalos de tempo (30, 60, 120, 180, 240 e 300 min) no estado fresco. Os métodos de ensaio mostraram-se sensíveis para a determinação do tempo de consolidação das argamassas colantes, indicando o aumento da viscosidade e da adesão da argamassa com o passar do tempo. Para as argamassas em que o tempo de consolidação ocorreu durante o período estudado, este tempo deu-se aos 180 minutos após a mistura. A partir deste período as argamassas colantes sofreram perdas nas suas características reológicas o que poderá causar dificuldades nas etapas de assentamento das placas cerâmicas e posteriormente, problemas no seu desempenho e durabilidade. Já os ensaios de resistência de aderência à tração apresentaram grande variabilidade prejudicando uma correlação com os ensaios reológicos.

A conformação em torno elétrico é um dos métodos utilizados na fabricação de peças cerâmicas, principalmente utilitários e decorações. Porém nem todas as massas cerâmicas possuem plasticidade adequada para serem torneadas. A porcelana fosfática é um desses exemplos devido à composição de 50 % de cinza de ossos bovinos, 25 % de caulim e 25 % de feldspato. Uma massa de porcelana comercial de alta temperatura, branca e com boa plasticidade foi a referência de massa propícia para se trabalhar no torno elétrico e foi feito a caracterização desse material como distribuição granulométrica, picnometria a gás, composição química por fluorescência de raio X (FRX) e difração de raio X (DRX). Os mesmos métodos de caracterização foram feitos na porcelana fosfática. O limite de Atterberg foi utilizado como técnica para medir os teores de água das massas e a reometria por squeeze flow foi o método de análise para diferenciar massas cerâmicas plásticas e não-plásticas. Testes no torno elétrico foram feitos para concluir sobre melhoria na plasticidade da porcelana fosfática através da adição de aditivo como bentonita e polímero à base de éter celulose (MHEC). Adição de 4 % de bentonita na porcelana fosfática aumentou o índice de plasticidade de Atterberg em cerca de 100 % e as curvas de squeeze flow ficaram próximos das curvas do material de referência, apresentando assim plasticidade suficiente para fabricar peças no torno elétrico. / Throwing on electric wheel is one of techniques used to forming ceramic wares as tableware and decorative. However, ceramic body needs to have enough plasticity for hands working on throwing wheel. The phosphatic porcelain composition is 50 % of bone ash, 25 % of kaolin and 25 % of feldspar and generally has low plasticity. A commercial porcelain for throwing on the electric wheel was used as default and compared with the phosphatic porcelain. Raw material characterization as particle size distribution analysis, gas pycnometry, chemical composition by x-ray fluorescence (XRF), zeta potential and x-ray diffraction (XRD) was doing to compare both porcelains. Atterberg limits were used to measure moisture content of ceramic body and rheometry was evaluated by squeeze flow technique to determine the viscosity difference between porcelain and phosphatic porcelain. Test on the throwing wheel were made to verify plasticity improvement by addition of bentonite or a polymer based on ether cellulose (MHEC). The 4 % of bentonite addition increased about 100 % the Atterberg limit and the consequent change in the squeeze flow curves demonstrate to be similar with reference and with enough plasticity to throwing on the electric wheel. Keyword: Phosphatic porcelain. Plasticity. Throwing wheel. Bentonite. Squeeze flow.

A conformação em torno elétrico é um dos métodos utilizados na fabricação de peças cerâmicas, principalmente utilitários e decorações. Porém nem todas as massas cerâmicas possuem plasticidade adequada para serem torneadas. A porcelana fosfática é um desses exemplos devido à composição de 50 % de cinza de ossos bovinos, 25 % de caulim e 25 % de feldspato. Uma massa de porcelana comercial de alta temperatura, branca e com boa plasticidade foi a referência de massa propícia para se trabalhar no torno elétrico e foi feito a caracterização desse material como distribuição granulométrica, picnometria a gás, composição química por fluorescência de raio X (FRX) e difração de raio X (DRX). Os mesmos métodos de caracterização foram feitos na porcelana fosfática. O limite de Atterberg foi utilizado como técnica para medir os teores de água das massas e a reometria por squeeze flow foi o método de análise para diferenciar massas cerâmicas plásticas e não-plásticas. Testes no torno elétrico foram feitos para concluir sobre melhoria na plasticidade da porcelana fosfática através da adição de aditivo como bentonita e polímero à base de éter celulose (MHEC). Adição de 4 % de bentonita na porcelana fosfática aumentou o índice de plasticidade de Atterberg em cerca de 100 % e as curvas de squeeze flow ficaram próximos das curvas do material de referência, apresentando assim plasticidade suficiente para fabricar peças no torno elétrico. / Throwing on electric wheel is one of techniques used to forming ceramic wares as tableware and decorative. However, ceramic body needs to have enough plasticity for hands working on throwing wheel. The phosphatic porcelain composition is 50 % of bone ash, 25 % of kaolin and 25 % of feldspar and generally has low plasticity. A commercial porcelain for throwing on the electric wheel was used as default and compared with the phosphatic porcelain. Raw material characterization as particle size distribution analysis, gas pycnometry, chemical composition by x-ray fluorescence (XRF), zeta potential and x-ray diffraction (XRD) was doing to compare both porcelains. Atterberg limits were used to measure moisture content of ceramic body and rheometry was evaluated by squeeze flow technique to determine the viscosity difference between porcelain and phosphatic porcelain. Test on the throwing wheel were made to verify plasticity improvement by addition of bentonite or a polymer based on ether cellulose (MHEC). The 4 % of bentonite addition increased about 100 % the Atterberg limit and the consequent change in the squeeze flow curves demonstrate to be similar with reference and with enough plasticity to throwing on the electric wheel. Keyword: Phosphatic porcelain. Plasticity. Throwing wheel. Bentonite. Squeeze flow.

This study aims to better understand the behavior of magnetorheological (MR) fluids operated in the non-conventional squeeze mode through the use of a custom designed rheometer. Squeeze mode is the least understood of the three operational modes of MR fluid and thus its potential has yet to be realized in practical applications. By identifying the behavior of MR fluid in this mode, the foundation for future development of MR technology will be laid. Using the limited amount of literature available on squeeze-mode operation in conjunction with conventional principles associated with MR technology, a custom rheometer was designed and fabricated. A detailed account of the design considerations and background information on the fundamentals incorporated into the design are provided. The squeeze-mode rheometer was used to evaluate a variety of MR fluids to observe trends that may exist across fluids. Specifically, fluids of different ferrous particle volume fractions were considered. Through testing, common trends in fluid stiffness were observed for multiple fluids tested with the squeeze-mode rheometer. When operated in squeeze mode, activated MR fluid has shown to provide substantial resistance to compressive loading, possibly making it attractive for low-displacement high-load systems. The primary observation from the tests is that the activated fluid's stiffness progressively increases over the duration of fluid operation. This phenomenon is due to severe carrier-fluid separation coupled with the formation of ferrous particle aggregate clumps in the fluid. This effect is further explored in this research. / Master of Science

Long fiber reinforced thermoplastic composites are used for creating lightweight, but mechanically sound, automotive components. Injection molding is a manufacturing technique commonly used for traditional thermoplastics due to its efficiency and ability to create complex geometries. Injection molding feedstock is often in the form of pellets. Therefore, fiber composites must be chopped for use in this manufacturing method. The fibers are cut to a length of 13 mm and then fiber attrition occurs during processing. The combination of chopping the fibers into pellets and fiber breakage creates a distribution of mostly short fiber lengths, with some longer fibers remaining. Discontinuous fiber reinforcements are classified as long for aspect ratios greater than 100. For glass fibers, that distinction occurs at a length of 1 mm, and for carbon fibers 0.5 mm. Traditional composite materials and manufacturing processes utilize continuous fibers with a controlled orientation and length. The use of chopped discontinuous fibers requires a method to predict the orientation of the fibers in the final molded piece because mechanical properties are dependent on fiber length and orientation. The properties and behavior of the flow of a fiber reinforced polymer composite during molding are directly related to the mechanical properties of the completed part. Flow affects the orientation of the fibers within the polymer matrix and at locations within the mold cavity. The ability to predict, and ultimately control, flow properties allows for the efficient design of safe parts for industrial uses, such as vehicle parts in the automotive industry. The goal of this work is to test material characterization techniques developed for measuring and predicting the orientation of fiber reinforced injection molded thermoplastics using commercial grade long carbon fiber (LCF) reinforced nylon 6,6 (PA 6,6). Forty weight percent LCF/PA 6,6 with a weight averaged fiber length of 1.242 mm was injection molded into center gated disks and the orientation was measured experimentally. A Linux based Numlab flow simulation process that utilizes the finite element method to model the flow and orientation of fiber reinforced materials was tested and modified to accurately predict the orientation for this composite and geometry. Fiber orientation models used for prediction require the use of empirical parameters. A method of using non-lubricated squeeze flow as an efficient way to determine the strain reduction factor, , and Brownian motion like factor, CI, parameters for short glass fiber polypropylene orientation predictions using the strain reduction factor (SRF) model was extended to use with the LCF/PA 6,6 composite. The 40 weight percent LCF/PA 6,6 material was compression molded and underwent non-lubricated squeeze flow testing. The flow was simulated using finite element analysis to predict the fiber orientation using the SRF model. The empirical parameters were fit by comparing the simulated orientation to experimentally measured orientation. This is a successful method for predicting orientation parameters that is significantly more efficient than optimizing the parameters based on fitting orientation generated in injection molded pieces. The determined orientation parameters were then used to reasonably predict the fiber orientation for the injection molded parts. The authors proved that the experimental and simulation techniques developed for the glass fiber reinforced polypropylene material are valid for use with a different, more complex material. / Doctor of Philosophy / Fibers reinforce thermoplastic polymers to create lightweight, but mechanically sound, automotive parts. Thermoplastics flow when heated and harden when cooled. This work compares two of the commonly used thermoplastics, polypropylene (plastic grocery bags, food storage containers) with a glass fiber reinforcement and a form of nylon called PA 6,6 with a carbon fiber reinforcement. Injection molding is a manufacturing technique commonly used for un-reinforced thermoplastics due to its efficiency and ability to create complicated shapes. Injection molding feedstock is often in the form of pellets. Therefore, fiber composites must be chopped for use in this manufacturing method. The fibers are cut to a length of 13 mm and then fiber breakage occurs in the injection molder. The combination of chopping the fibers into pellets and fiber breakage creates a range of lengths. This distribution consists of mostly short fiber lengths, with some longer fibers remaining. Discontinuous fiber reinforcements are classified as long for aspect ratios (the ratio of length over diameter) greater than 100. For glass fibers, that distinction occurs at a length of 1 mm, and for carbon fibers 0.5 mm. Traditional composite materials and manufacturing processes utilize continuous fibers with a controlled orientation and length, such as the weave pattern one might see in a carbon fiber hood. The use of chopped fibers requires a method to predict the orientation of the fibers in the final molded piece because mechanical properties are dependent on fiber length and orientation. The way that the plastic flows during molding is directly related to the mechanical properties of the completed part because flow affects the way that the fibers arrange. The ability to predict, and ultimately control, flow properties allows for the efficient design of safe parts for industrial uses, such as vehicle parts in the automotive industry. The goal of this work is to test the techniques developed for measuring and predicting the orientation of fiber reinforced injection molded thermoplastics using commercial grade long carbon fiber (LCF) reinforced nylon 6,6 (PA 6,6). LCF/PA 6,6 with an average fiber length of 1.242 mm was injection molded into a disk and the orientation was measured experimentally. A computer flow simulation process that utilizes the finite element method to model the flow and orientation of fiber reinforced materials was tested and modified to accurately predict the orientation for this composite and geometry. Fiber orientation models used for prediction require the use of parameters. There is no universal method for determining these parameters. A method of using non-lubricated squeeze flow as an efficient way to determine the parameters for short glass fiber polypropylene orientation predictions was extended to use with the LCF/PA 6,6 composite. The LCF/PA 6,6 material was compression molded and underwent non-lubricated squeeze flow testing. The flow was modeled to predict the fiber orientation. The empirical parameters were fit by comparing the simulated orientation to experimentally measured orientation. This is a successful method for predicting orientation parameters. The determined orientation parameters were then used to reasonably predict the fiber orientation for the injection molded parts. The authors proved that the experimental and simulation techniques developed for the glass fiber reinforced polypropylene material are valid for use with a different, more complex material.

Carbon mat thermoplastics (CMT) consisting of 12.7 mm or 25.4 mm long, 7.2 micrometer diameter, chopped carbon fibers in a polypropylene (PP) or poly(ethylene terephthalate) (PET) thermoplastic matrix were manufactured using the wetlay technique. This produces a porous mat with the carbon fibers well dispersed and randomly oriented in a plane. CMT composites offer substantial cost and weight savings over typical steel construction in new automotive applications. In production vehicles, automotive manufacturers have already begun to use glass mat thermoplastic (GMT) materials that use glass fiber as the reinforcement and polypropylene as the matrix. GMT parts have limitations due to the maximum achievable strength and stiffness of the material. In this study the glass fibers of traditional GMT are replaced with higher strength and higher stiffness carbon fibers. The tensile strength and modulus and the flexural strength and modulus of the CMT materials were calculated for fiber volume fractions of 10-25%. Additionally, the length of the fiber (12.7 mm or 25.4 mm) was varied and four different fiber treatments designed to improve the bond between the fiber and the matrix were tested. It was found that the fiber length had no effect on the mechanical properties of the material since these lengths are above the critical fiber length. The tensile and the flexural moduli of the CMTs were found to increase linearly with the FVF up to 25% FVF for some treatments of the fibers. For the other treatments the linearly increasing trend was valid up to 20% FVF, then stiffness either stayed constant or decreased as the FVF was increased from 20% to 25% . The strength versus FVF curves showed trends similar to those of the modulus versus FVF curves. It is shown that choosing an appropriate sizing can extend the usable FVF range of the CMT by at least 5%. Published micromechanical relations over-predicted the tensile modulus of the composite by 20-60%. An empirical fiber efficiency relation was fit to the experimental data for the tensile modulus and the tensile strength giving excellent agreement with the experimental results. Flow tests simulating the compression molding process were conducted on the CMT to determine what factors affect the flow viscosity of the CMT. The melt viscosity of the neat PP was measured using cone and plate rheometry at temperatures between 180°C–210°C and was fit with the Carreau relation. The through thickness packing stress of the CMT mat was measured for FVFs of 8-40% and was found to follow a power law behavior based on the local bending of fibers up to a FVF of 20.9%. Above this FVF the power law exponent decreases, and this is attributed to fracture of some of the fibers. Heated platens were used to isothermally squeeze the CMT at axial strain rates of 0.02-6 s^-1. The plot of the load-displacement behavior for the 10% FVF CMT was similar in shape to that for a fluid with a yield stress. For FVFs of 15-25% the load-displacement curves showed a load spike at the beginning of the flow, then followed the curve for a fluid with a yield stress. The matrix was burned off the squeezed samples, and the remaining carbon mat was dissected and visually inspected. It was found that fiber breakage increased and fiber length decreased as the FVF of the sample was increased. / Ph. D.

Investigation of material behaviour in a squeeze flow geometry provides an impor- tant technique in rheology and it is relevant also from the technological point of view (some types of dampers, compression moulding). To our best knowledge, the sque- eze flow has not been solved for fluids-like materials with pressure-dependent material moduli. In the main scope of the present thesis, an incompressible fluid whose visco- sity strongly depends on the pressure is studied in both the perfect-slip and the no-slip squeeze flow. It is shown that such a material model can provide interesting departures compared to the classical model for viscous (Navier-Stokes) fluid even on the level of analytical solutions, which are obtained using some physically relevant simplificati- ons. Numerical simulation of a free boundary problem for the no-slip squeeze flow is then developed in the thesis using body-fitted curvilinear coordinates and spectral collocation method. An interesting behaviour is expected especially in the corners of the computational domain where the stress singularities are normally located. Unfor- tunately, numerical results reveal some fundamental drawbacks related to the physical model and its possible improvement is discussed at the end of the thesis.