A lightweight carbon fiber reinforced polymer (CFRP) sandwich panel has been developed for floor use in commercial office building construction. CFRP laminate skins were combined with low-density rigid polyurethane foam to create a composite sandwich panel suitable for floor use. The CFRP sandwich panel was optimized to withstand code prescribed office-building live loads using a 3D finite element computer program called SolidWorks. The thickness of the polyurethane foam was optimized to meet both strength and serviceability requirements for gravity loading. Deflection ultimately was the controlling factor in the design, as the stresses in the composite materials remained relatively low. The CFRP sandwich panel was then subjected to combined gravity and lateral loading, which included seismic loads from a fictitious 5-story office building located in a region of high seismic risk. The results showed that CFRP sandwich panels are a viable option for use with floors, possessing sufficient strength and stiffness for meeting code prescribed design loads, while providing significant benefits over traditional construction materials.

Due to inadequate lateral stiffness, many reinforced concrete buildings are highly damaged or collapsed in Turkey after the major earthquake. To improve the behavior of such buildings and to prevent them from collapse, repair and/or strengthening of some reinforced concrete elements is required. One of the strengthening techniques is the use of CFRP sheets on the existing hollow brick masonry infill. While using the CFRP sheets their attachment to both structural and non-structural members are provided by CFRP anchor dowels. In this study, by means of the prepared test setup, the pull-out strength capacities of CFRP anchor dowels are measured. The effects of concrete compressive strength, anchorage depth, anchorage diameter, and number of fibers on the tensile strength capacity of CFRP anchor dowel are studied.

Polyacrylonitrile (PAN)/carbon nanotube (CNT) composite fibers were made using various processing methods such as conventional solution spinning, gel spinning, and bi-component gel spinning. The detailed characterization exhibited that the smaller and longer CNT will reinforce polymer matrix mostly in tensile strength and modulus, respectively. Gel spinning combined with CNT also showed the promising potential of PAN/CNT composite fiber as precursor fiber of the next generation carbon fiber. High resolution transmission electron microscopy showed the highly ordered PAN crystal layer on the CNT, which attributed to the enhanced physical properties. The subsequent carbonization study revealed that carbonized PAN/CNT fibers have at least 50% higher tensile strength and modulus as compared to those of carbonized PAN fibers. Electrical conductivity of CNT containing carbon fiber was also 50% higher than that of carbonized PAN fiber. In order to have carbon fiber with high tensile strength, the smaller diameter precursor fiber is preferable. Bi-component gel spinning produced 1-2 µm precursor fiber, resulting in ~1 µm carbon fiber. The tensile strength of the carbonized bi-component fiber (islands fibers) is as high as 6 GPa with tensile modulus of ~500 GPa. Further processing optimization may lead to the next generation carbon fiber.

The goal of this research was to investigate the tensile fatigue behavior of a carbon fiber / epoxy composite material. Specifically, the stress levels at which cracks initiated in static and fatigue loading in the 90 degree plies of a "quasi-cross ply layup" [0/905]S was investigated. For layups which contain them, cracks in composite laminates initiate and propagate from 90 degree plies (including the ubiquitous "quasi-isotropic layup" 0/±45/90). Thus, this work provides valuable insight into the fatigue behavior of the plies which originate fatigue damage. Unidirectional off-axis 90 degree and 10 degree specimens were also tested, but the bulk of testing was done on the cross-ply laminates. The project sponsors, Boeing, were in the process of extending a failure model to the case of fatigue. The body of work presented here provided empirical data for that effort. Several different inspection techniques were used to investigate for cracking in the 90 degree plies, including: x-ray images, edge replicates, dye penetrants, and optical microscopy. Plots of the stress level at which crack initiation occurred will be presented, as well as images illustrating damage development in these layups. Comparisons are made to the experimental results of other investigations of this type of layup. Explorations of the effect of R-ratio (including R = 0.1 and 0.5), loading frequency (including 3, 10, and 30 Hz), and surface roughness (hand polished specimen edges to 1500 grit smoothness) on fatigue crack initiation were also performed. For the most damaging case (10 Hz, R = 0.1, no polishing), the crack initiation strain (0.00276) was one half of the strain at which cracks initiated in static monotonic loading (0.0054), and was 16% of the cross-ply specimen's (0 degree fiber dominated) ultimate strain value of (0.018).

L'objectif de ce travail de thèse est d'étudier le comportement de l'endommagement des matériaux composites sous chargement statique et fatigue par contrôle non destructif (C.N.D) thermographie et soutenu par émission acoustique et la tomographie (CT scan). Pour cela, ce unidirectionnels composite à fibres de verre (GFRP) et discontinue composite à fibres de carbone (DCFC) ont été utilisés comme les éprouvettes qui ont fourni par PSA peugeot citröen, France. Une série d'essais mécaniques a été réalisée pour déterminer le comportement de l'endommagement sous chargement statique et fatigue. Pendant tout des essais mécanique, la thermographie a été utilisé pour l'observation en temps réel pour suivre l'évolution des températures sur la surface de l'éprouvette et supporté par émission acoustique dans certaines conditions. Cette étude a utilisé une forme rectangulaire et se compose d'éprouvettes trouées et non trouées au centre de l'éprouvette. La vitesse de déplacement constante est appliquée pour observer l'effet sur le comportement de l'endommagement sous chargement de traction statique. Sous les essais de fatigue, le paramètre constant de la fréquence et de l'amplitude de stress a été étudiée pour chaque niveau de charge pour avoir les propriétés de fatigue et l'évolution de l'endommagement de l'éprouvette. La tomographie a été utilisée pour confirmer l'apparition de l'endommagement et l'etat du matériau après l'essai de fatigue. L'analyse des résultats de l'expérimentation et de l'observation NDT montré le bon accord entre les résultats mechnical et NDT thermographie avec prise en charge par l'observation de l'émission acoustique en détecter l'apparition et la propagation de l'endommagement de GFRP PRV et DCFC sous chargement de statique en traction. Les essais en fatigue montrent que la dissipation thermique est liée à l'évolution de l'endommagement et également thermographie et peut être utilisé avec succès pour déterminer la limite d'endurance (HCFS) et la courbe de Wöhler du matériau composite. Les résultats par CT scan ont mesurée avec succès les endommagements et l'état du matériau après essai de fatigue du matériau composite. / The aim of this study is to investigate the damage behaviour of composite material in static and fatigue condition with non destructive testing (NDT) thermography method and supported by acoustic emission and also computed tomography (CT) scan. Thermography and acoustic emission are used in real-time monitoring techniques during the test. On the other hand, NDT observation of tomography is used for a post-failure analysis. In order to achive this, continuous glass fiber composite (GFRP) and discontinuous carbon fiber composite (DCFC) have been used as the test specimens which supplied by PSA Company, France. A series of mechanical testing was carried out to determine the damage behaviour under static and fatigue loading. During all the mechanical testing, thermography was used in real-time observation to follow the temperature change on specimen surface and supported by acoustic emission in certain condition. This study used rectangular shape and consist of specimen with and without circular notches (hole) at the center. The constant displacement rate is applied to observe the effect on damage behaviour under tensile static loading. Under fatigue testing, the constant parameter of frequency and amplitude of stress was explored for each load level to have the fatigue properties and damage evolution of specimen. The tomography was used to confirm the appearance of damage and material condition after fatigue testing. The analysis from the experiment results and NDT observation shown the good agreement between mechnical results and NDT thermography with supported by acoustic emission observation in detect the appearance and propagation of damage for GFRP and DCFC under static loading. Fatigue testing shows that thermal dissipation is related to the damage evolution and also thermography and can be successfully used to determine high cycle fatigue strength (HCFS) and S-N curve of fiber composite material. From post failure analysis, CT scan analysis successfully measured and evaluated damage and material condition after fatigue test for fiber composite material. v

Mangotes de transferência têm sido utilizados em grande quantidade em operações de descarga de óleo, principalmente em águas profundas, onde existem cargas estáticas e cíclicas variáveis devido ao ambiente de trabalho. Apesar da grande demanda dessas estruturas, seu comportamento é pouco conhecido e discutido na literatura devido a sua complexidade. Além disso, os materiais utilizados nesse equipamento podem ocasionar um elevado número de falhas, sendo muitas vezes superestimados, deixando o mangote com peso excessivo. Este trabalho objetiva o desenvolvimento de uma metodologia de análise de materiais poliméricos avançados, especificamente fibras de poliaramida e materiais compósitos à base de fibra de carbono, em substituição a materiais tradicionais, utilizando modelos numéricos capazes de prever o comportamento da pressão de ruptura das carcaças e resistência a compressão radial do mangote, além da avaliação em fadiga dos cordonéis à base de poliaramida dessas novas estruturas. Modelos em meso-escala foram desenvolvidos utilizando conceitos de hiperelasticidade e de critérios de falha de materiais compósitos para previsão das tensões e deformações locais em regiões críticas do mangote. Análises numéricas foram realizadas via elementos finitos com o software comercial para auxiliar a elaboração dos modelos e a realização dos cálculos numéricos. Foram realizados ensaios experimentais para validação desses modelos numéricos, bem como para a previsão do comportamento estático e em fadiga dos materiais envolvidos. Foram desenvolvidos dois modelos. Em um modelo foi aplicado pressão interna no mangote para previsão de ruptura das carcaças no qual tem o objetivo de avaliar o desempenho dos novos reforços de poliaramida. No outro modelo foi aplicada uma carga radial na seção central do mangote para prever a resistência ao esmagamento, no qual tem o objetivo de avaliar o desempenho do componente de sustentação em material compósito de fibra de carbono. Os resultados dos modelos numéricos apresentaram boa concordância com os resultados experimentais em grande parte das análises. Também se observou que os novos materiais apresentam um grande potencial de substituição dos materiais tradicionais, bem como um excelente comportamento frente a carregamentos estáticos e dinâmicos envolvidos na aplicação, sendo verificada diminuição significativa de peso e aumento do desempenho. / Offloading hoses have been extensively used at offloading oil operations, especially in deep water, where there are variable static and cyclic loads due to the working environment. Despite the great demand for these structures, their behavior is little known and discussed in the literature due to the complexity. In addition, the materials used in this equipment may lead to a high number of failures, being often overestimated, leading to excessive weight. This work aims to develop a methodology for analysis of advanced polymeric materials, specifically polyaramide fibers and carbon fiber composite materials, in the substitution of traditional materials, using numerical models able to predict the static behavior of the burst pressure of the carcasses and radial compression strength of the hose. In addition, fatigue tests were performed to evaluate the polyaramide cords of these new structures. Meso-scale models were developed using advanced hyperplastic and composite failure criteria concepts to predict local stresses and strains in critical regions of the hose. Numerical analyses were performed using finite elements with commercial software to aid the development of models and to carry out numerical calculations. Several experimental tests were performed to validate numerical models, as well as to forecast the static and fatigue behavior of the materials used. Two models were developed. A model is used to predict the burst pressure of the hose in order to evaluate the performance of the new polyaramide reinforcements cords. In the other model, a radial load was applied in the central section of the hose to predict the crushing strength, in which it has the aim of evaluating the performance of the load-bearing component made with carbon fiber composite material. The results of the computer models showed good agreement with the experimental results in most analyses. It was also found that the studied materials offered considerable potential for the substitution of traditional materials, as well as an excellent behavior under static and dynamic loads related to this application, with a significant weight reduction and increased performance of the new configurations over traditional hoses.

Mangotes de transferência têm sido utilizados em grande quantidade em operações de descarga de óleo, principalmente em águas profundas, onde existem cargas estáticas e cíclicas variáveis devido ao ambiente de trabalho. Apesar da grande demanda dessas estruturas, seu comportamento é pouco conhecido e discutido na literatura devido a sua complexidade. Além disso, os materiais utilizados nesse equipamento podem ocasionar um elevado número de falhas, sendo muitas vezes superestimados, deixando o mangote com peso excessivo. Este trabalho objetiva o desenvolvimento de uma metodologia de análise de materiais poliméricos avançados, especificamente fibras de poliaramida e materiais compósitos à base de fibra de carbono, em substituição a materiais tradicionais, utilizando modelos numéricos capazes de prever o comportamento da pressão de ruptura das carcaças e resistência a compressão radial do mangote, além da avaliação em fadiga dos cordonéis à base de poliaramida dessas novas estruturas. Modelos em meso-escala foram desenvolvidos utilizando conceitos de hiperelasticidade e de critérios de falha de materiais compósitos para previsão das tensões e deformações locais em regiões críticas do mangote. Análises numéricas foram realizadas via elementos finitos com o software comercial para auxiliar a elaboração dos modelos e a realização dos cálculos numéricos. Foram realizados ensaios experimentais para validação desses modelos numéricos, bem como para a previsão do comportamento estático e em fadiga dos materiais envolvidos. Foram desenvolvidos dois modelos. Em um modelo foi aplicado pressão interna no mangote para previsão de ruptura das carcaças no qual tem o objetivo de avaliar o desempenho dos novos reforços de poliaramida. No outro modelo foi aplicada uma carga radial na seção central do mangote para prever a resistência ao esmagamento, no qual tem o objetivo de avaliar o desempenho do componente de sustentação em material compósito de fibra de carbono. Os resultados dos modelos numéricos apresentaram boa concordância com os resultados experimentais em grande parte das análises. Também se observou que os novos materiais apresentam um grande potencial de substituição dos materiais tradicionais, bem como um excelente comportamento frente a carregamentos estáticos e dinâmicos envolvidos na aplicação, sendo verificada diminuição significativa de peso e aumento do desempenho. / Offloading hoses have been extensively used at offloading oil operations, especially in deep water, where there are variable static and cyclic loads due to the working environment. Despite the great demand for these structures, their behavior is little known and discussed in the literature due to the complexity. In addition, the materials used in this equipment may lead to a high number of failures, being often overestimated, leading to excessive weight. This work aims to develop a methodology for analysis of advanced polymeric materials, specifically polyaramide fibers and carbon fiber composite materials, in the substitution of traditional materials, using numerical models able to predict the static behavior of the burst pressure of the carcasses and radial compression strength of the hose. In addition, fatigue tests were performed to evaluate the polyaramide cords of these new structures. Meso-scale models were developed using advanced hyperplastic and composite failure criteria concepts to predict local stresses and strains in critical regions of the hose. Numerical analyses were performed using finite elements with commercial software to aid the development of models and to carry out numerical calculations. Several experimental tests were performed to validate numerical models, as well as to forecast the static and fatigue behavior of the materials used. Two models were developed. A model is used to predict the burst pressure of the hose in order to evaluate the performance of the new polyaramide reinforcements cords. In the other model, a radial load was applied in the central section of the hose to predict the crushing strength, in which it has the aim of evaluating the performance of the load-bearing component made with carbon fiber composite material. The results of the computer models showed good agreement with the experimental results in most analyses. It was also found that the studied materials offered considerable potential for the substitution of traditional materials, as well as an excellent behavior under static and dynamic loads related to this application, with a significant weight reduction and increased performance of the new configurations over traditional hoses.

In order to fulfill increasing production rates, new automated production technologies are required for manufacturing carbon fiber reinforced plastic components for the aerospace industry. Currently, large, double curved composite components have to be manufactured manually, which leads to high process times and poor scalability. As a consequence, a team of cooperating robots with passively adjustable end-effectors was developed, that is capable of handling dry carbon textiles and can be used for layups in double curved molds. This thesis deals with the implementation of a robot program, that performs an automated adjustment of each end-effector to the surface geometry of the manufactured part. The functional principle and the accuracy of the process are evaluated. Further, the automatically adjusted end-effectors are utilized to cooperatively layup carbon plies. The results show, that the accuracy of the automated adjusting process is sufficient to drape carbon fabrics during pick-up and automated layup is possible with this approach. In conclusion, the developed process can be integrated into a fully automated process for future experiments, but hardware inaccuracies should be improved, in order to further enhance the accuracy of the system.

O uso e produção de fibra de carbono têm crescido nas últimas três décadas em diversas aplicações como aeroespacial, automotiva, nuclear, naval e construção civil. Isto é devido ao desempenho que este material possui quando comparado com os tradicionais componentes metálicos. A geração de resíduo de fibra de carbono tem aumentado a cada ano e isto tem impulsionado estudos e aprimoramento dos métodos de recuperação de fibras de carbono. Dentre os mais usuais métodos existentes, pode-se destacar a pirólise. O objetivo do presente trabalho consiste em recuperar fibras de carbono determinando e avaliando os parâmetros do processo de pirólise visando o potencial de reutilização destas fibras em novos compósitos. O compósito utilizado foi doado a partir de um descarte industrial. Para caracterizar o compósito, foram empregadas as técnicas de análise térmica (TGA), espectrometria de massa (QMS), análise estrutural em MEV juntamente com a análise pela energia dispersiva de espectroscopia de raio-X (EDS). Durante o aquecimento em atmosfera inerte, ocorre a liberação de compostos orgânicos proveniente da matriz polimérica, e as fibras de carbono permanecem intactas. As fibras de carbono recuperadas foram analisadas em MEV e EDS a fim de verificar a ocorrência de defeitos superficiais, como, resíduos da matriz polimérica, carbonização, rompimento da fibra entre outros. Os resultados obtidos mostram que pela pirolise feita a 550°C por 1h é possível de se obter fibras de carbono livres da matriz polimérica. Após o processo de pirólise nesta condição as fibras não apresentam poros, fratura do material e carbonização. / The last three decades were marked by the expansion of production and research of carbon fiber in several applications such as automotive, nuclear, navy and construction. This is a result of the extraordinary performance that this material presents when compared with the traditional metallic materials. Each year, there has been an increase of the generation of carbon fiber composite waste which has motivated studies and improvement of the current recovering processes of carbon fiber. Among the most usual methods of recovering, there is the pyrolysis method. The present study aims to recover carbon fiber from polymeric composite while evaluating parameters of the pyrolysis process focusing on the potential of reusing the recovered carbon fiber in new composites. The composite material used in this work had been acquired by donation of an industrial disposal. In order to characterize the composite, thermogravimetric analysis was done (TGA), mass spectrometry (QMS), structural analysis by SEM and analysis by energy dispersive X-ray spectroscopy (EDS). During heating in an inert atmosphere, there were release of organic compounds from the polymeric matrix and the carbon fibers remain untouched. Carbon fibers recovered were analyzed by SEM and EDS to verify the occurrence of superficial defects such as, traces of residual polymer matrix, carbonization, fiber breakage among others. The results show that through pyrolysis held at 550°C for 1 hour it is possible to obtain carbon fibers free of the polymeric matrix. After the pyrolysis process in this condition fibers did not presented pores, carbonization or rupture of the material.

Neste trabalho avaliou-se a influência da forma da seção transversal e da excentricidade do carregamento sobre o efeito de confinamento em pilares de concreto encamisados com polímeros reforçados com fibras (PRF). Para estas avaliações foi utilizada a análise experimental, por meio de ensaios de pilares sob flexo-compressão, e a análise numérica com o método dos elementos finitos. Observou-se que ocorreram reduções significativas dos efeitos de confinamento em pilares de seção quadrada e retangular quando a relação entre o raio de arredondamento dos cantos e o maior lado da seção transversal diminuiu. A influência da relação entre o lado maior e menor, no caso de pilares de seção retangular, não foi tão significativa se comparada ao efeito redutor do raio de arredondamento mencionado anteriormente. Ocorreram ganhos de resistência em todos os pilares ensaiados, indicando que o encamisamento com PRF pode ser utilizado mesmo em situações em que a força de compressão seja aplicada com pequenas excentricidades. O efeito da excentricidade sobre o confinamento dependeu da forma da seção transversal considerada. Em pilares de seção circular a excentricidade reduziu levemente os efeitos de confinamento. Nos pilares de seção quadrada a excentricidade não reduziu significativamente os efeitos de confinamento, sendo que para os menores raios de arredondamento o efeito de confinamento foi até maior na presença da excentricidade. Nos pilares de seção retangular observou-se que aplicando a excentricidade na direção da menor inércia o comportamento foi semelhante ao dos pilares de seção quadrada. Porém, aplicando a excentricidade na direção da maior inércia observou-se um grande efeito de confinamento, maior inclusive que no pilar centrado. / In this work the influence of the cross section shape and eccentricity of the compressive load on the confinement of concrete columns wrapped by fiber reinforced polymer (FRP) was evaluated. Experimental analysis, through flexural compression tests of columns, and numerical analysis developed through the finite element method were used to study these effects. Significant reductions of confinement effects were noticed in square and rectangular cross sections when the ratio of the round off radius to the major side of the column was reduced.The ratio between the major and minor side in rectangular columns was not so important to define the effectiveness of confinement as was the fore mentioned factor. Increases of strength were noticed in all columns tested, showing that FRP wrapping can be successfully used even with small eccentricities of loading. The effect of the eccentricity on the confinement showed to be dependent on the cross section shape. In circular columns the eccentricity of loading reduced the confinement effects. For the square cross section columns tested the confinement was not significantly affected by the eccentricity. In fact, for square columns with low round off radius, the eccentricity increased the confinement effects. Rectangular columns subjected to eccentric loading in the direction of the minor inertia showed a behavior similar to square columns. On the other hand, with the eccentricity applied in the direction of the major inertia, an important confinement effect was observed, more important than in the case of concentric loading.