A study was undertaken to determine if light-weighting orbital launch vehicles (rockets) improves lifetime environmental impacts of the vehicle. Light-weighting is performed by a material substitution where metal structures in the rocket are replaced with carbon fiber reinforced polymers (CFRP’s). It is uncertain whether light-weighting the rocket in the same way as traditional vehicles are light-weighted would provide similar environmental benefits. Furthermore, the rocket system is significantly different from traditional vehicles and undergoes an atypical lifecycle, making analysis non-trivial. Seventy rocket configurations were sized using a Parametric Rocket Sizing Model (PRSM) which was developed for this research. Four different propellant options, three staging options, and eighteen different lift capacities were considered. Each of these seventy rockets did not include CFRP’s, thus establishing a baseline. The seventy rockets were then light-weighted with CFRP’s, making a total of seventy pairs of rockets. An environmental Life Cycle Assessment (LCA) was performed on each of the rockets to determine lifetime environmental impacts. During the Life Cycle Inventory (LCI), a Carbon Fiber Production Model was developed to determine the environmental burdens of carbon fiber production and to address issues identified with carbon fiber’s embodied burdens. The results of the LCA were compared across all rockets to determine what effects light-weighting had on environmental impact. The final conclusion is that light-weighting reduces lifetime environmental impacts of Liquid Oxygen-Rocket Propellant 1 and Nitrogen Tetroxide-Unsymmetrical Dimethylhydrazine rockets, while it likely benefits Liquid Oxygen-Liquid Hydrogen rockets. Light-weighting increases lifetime environmental impacts of Solid Propellant rockets.

Le but de ce travail est la caractérisation du comportement au délaminage des composites stratifiés en mode mixte I+II+III, en se focalisant en particulier sur le verrou scientifique que représente le mode III pur. Cette thèse repose sur un travail à la fois expérimental et numérique, validant numériquement les tests existants et ceux développés. La mise en perspective des résultats obtenus a permis, d'un coté, de mieux appréhender l'importance de la distribution des taux de restitution d'énergie, GI, GII et GIII, le long du front de fissure sur le la détermination de la ténacité du composite et d'un autre coté, de proposer et d'améliorer les méthodes de caractérisation. Avant d'évoquer le délaminage en mode mixte, nos efforts se sont d'abord concentrés sur la caractérisation du délaminage en mode III pur. Deux essais de type " Edge Crack Torsion " (ECT) disponibles dans la littérature ont été réalisés. La distribution de GIII le long du front de fissure a été déterminée par la méthode des éléments finis (MEF) en utilisant la technique de fermeture virtuelle de fissure (VCCT). La capacité de ces tests est compromise par : 1. La participation du mode II non nul ; 2. La forte variation de GIII près des bords de l'éprouvette. Ces problèmes rendent la détermination de la ténacité en mode III pur, GIIIC, difficile et imprécise. Par la suite, un nouveau test a été proposé, nommé "Edge Ring Crack Torsion" test (ERCT ou ERT-III). Il s'appuie sur une éprouvette possédant une fissure de front circulaire, l'absence d'extrémités sur le front de fissure permet de supprimer les effets de bords. Après l'optimisation et la modification de la géométrie du dispositif dans le test ERCT original, GIII le long du front de fissure reste presque constant avec très peu de modes parasites. La formule proposée par Tada est appliquée pour déterminer GIIIC. Il est démontré qu'en général, si la variation de GIII est faible le long du front de fissure, la ténacité déterminée par une solution " closed-form " concorde bien avec celle obtenue numériquement. En fait, la répartition de GIII peut être influencée par divers facteurs, tels que la nature des stratifiés, la géométrie du dispositif expérimental et la géométrie des éprouvettes. L'interaction de ces facteurs a été aussi abordée dans cette étude. En outre, une étude numérique de sensibilité aux défauts a permis de vérifier la robustesse de l'essai proposé vis-à-vis de différents défauts qui sont inhérent à tout travail expérimental. Enfin, une géométrie d'éprouvette optimisée est donnée avec une méthodologie permettant de réduire les fluctuations de GIII. L'utilisation de l'éprouvette ERC a été généralisée à la caractérisation du délaminage pour deux autres modes purs : l'essai de traction permet de solliciter ERC en mode I pur et celui de flexion sollicite ERC en mode II pur, nommé ERCTE ou ERC-I et ERCF ou ERC-II, respectivement. Les avantages du test ERCT sont bien conservés. La réalisation des essais ERC-I, ERC-II et ERC-III permet de mesurer la ténacité de chacun des trois modes purs sur des éprouvettes ayant la même géométrie. Finalement, nous avons étudié numériquement la faisabilité de réaliser les essais de délaminage en mode mixte I + II, I + III et I + II + III sur les éprouvettes ERC. Il s'avère que le rapport modal en mode mixte peut être obtenu dans une large gamme en faisant varier la géométrie de l'éprouvette et en combinant les modes de chargement. Aucun mode indésirable n'est présent lors des essais en mode mixte I+II ou en mode mixte I+III. Cependant la distribution de GI, GII et GIII ne sont pas complètement uniforme, mais sa variation reste assez petite. En conclusion, les tests ERC proposés dans cette étude sont prometteurs pour la caractérisation du comportement au délaminage en mode mixte des composites. Il serait possible, dans un avenir proche, de proposer un critère de délaminage en mode mixte I+II+III basé sur une étude utilisant des essais sur éprouvettes ERC. / The aim of this research work is to characterize the delamination behavior of laminate composite materials under the three pure modes and mixed modes, focusing especially on the complex issue of mode III. Both experimental and numerical works were performed, validating the existing and new testing methods. Correlation between the results obtained aims, on the one hand to better understand the distribution of strain energy release rates (GI, GII, GIII) along the crack front; on the other hand, to propose and improve testing methods, and to propose and validate simple approaches for determination of delamination toughness. Pure mode III testing methods are studied. Firstly, two kinds of Edge Crack Torsion tests were carried out, the distribution of GIII along the crack front were determined by finite element analysis (FEA) using virtual crack closure technique (VCCT). The performances of these tests are compromised by the drawbacks: (1) A participation of mode II component cannot be completely eliminated; (2) The distribution of GIII along the crack front is not uniform especially near the sides. After a study of existing tests, a novel mode III testing method was proposed, named Edge Ring Crack Torsion test (ERCT or ERC-III later). In the ERC specimen, the total absence of sides in the circular crack front leads to no edge effects. As a result, pure mode III delamination is achieved and the distribution of GIII along the crack front is quite uniform. In fact, the values of GIII along the crack front are nearly constant after optimizing and modifying the geometry of device in the original ERCT test. A closed-form solution proposed by Tada is applied to determine mode III delamination toughness. In ERCT test, the results calculated by Tada formula agree well with the ones calculated by VCCT when the distribution of GIII is relatively uniform. Actually, a numerical study shows that the distribution of GIII can be affected by different factors related to the nature of laminates tested, the geometry of test device and the geometry of the specimens. The interactive effect of above factors was also discussed in this study. In order to understand the influence of potential defaults on the performance of ERCT test, sensitivity study has been performed on the relative position of the crack front, the circularity of the crack front and the specimen shape. Optimum specimen's relative pre-crack geometry is given and a method for reducing the variation is provided. Then the application of ERC specimen was generalized to other pure delamination modes characterization. Pure mode I can be realized if ERC specimens are loaded in tension, named ERCTE or ERC-I, so can pure mode II if ERC specimens are loaded in flexion, named ERCF or ERC-II. The distribution of the strain energy release rates was also evaluated by FEA using VCCT. These tests keep most advantages of ERC-III test. Pure mode I and pure mode II delamination are achieved respectively and the distribution of GI or GII along the crack front is quite uniform. The realization of ERC-I, ERC-II and ERC-III allows to measure the toughness of each of three pure modes without any interference from geometry of specimens. Finally, we have studied numerically the feasibility to realize the delamination tests in mixed mode I+II, I+III and I+II+III by using ERC specimen. Firstly, the mixed mode ratio can be obtained in a large range by varying the geometry of the specimen and by combining loading modes. Secondly, no unwanted mode is presented for mixed mode I+II and mixed mode I+III; Thirdly, the distribution of strain energy release rates are not completely uniform but its variation is small enough to be accepted. In conclusion, ERC tests are promising testing methods for characterization of mixed mode delamination behavior. It will be possible to propose a mixed mode I+II+III delamination criterion based on the investigation by ERC tests in a close future.

The content of the diploma thesis is evaluation of the usability of carbon composites in the space industry. The aim of this work is to assess whether carbon composites can find application in mechanical systems of passive thermal protection of artificial objects. Model examples demonstrate the principle of operation of selected passive thermal protection. The evaluation is realized based on the results of thermal analysis. Analytical formulas from field theory of heat transfer are used as a calculation method. The diploma thesis consists from two parts. The theoretical part briefly describes the mechanisms of heat transfer, selected types of passive thermal protection and properties and applications of carbon composites. The practical part consists of the assignment, calculation and evaluation of three examples. The results show that carbon composites can compete with commonly used materials for specific requirements.

The diploma thesis deals with the study of bent FRP reinforcements with the main focus on the methods of production of bent FRP reinforcement, examples of their application in structures. The work also mentions the effects of aggressive environments on the durability of FRP. In the practical part, a search of the possibilities of testing the properties of bent FRP reinforcement. Subsequently, an experiment is designed and performed to monitor changes in the properties of straight and bent FRP reinforcement exposed to the alkaline environment and water at 20 °C and 40 °C. Finally, the evaluation of changes in mechanical properties and observation of reinforcements using optical and scanning electron microscopy is performed.

No description available.

No description available.

[pt] O presente trabalho tem como objetivo analisar a utilização de barras constituídas por material compósito para atuarem como reforço de vigas de concreto submetidas à flexão. As barras analisadas são constituídas por polímero reforçado com fibras de carbono (PRFC), material este que apresenta comportamento linear elástico até a ruptura. Este material possui algumas vantagens em relação ao aço, como por exemplo, resistência à tração consideravelmente superior além de não ser suscetível ao fenômeno da corrosão ocasionada por intempéries ambientais. Durante o desenvolvimento do trabalho foi obtido um artigo o qual demonstra resultados de ensaios de laboratório nos quais os autores utilizaram vigas de concreto submetidas a ensaio de flexão por quatro pontos e reforçadas com barras de PRFC. Neste trabalho, o mesmo ensaio foi simulado no software Atena, programa este que realiza análise não linear para estruturas de concreto, considerando a fissuração deste material. Os resultados obtidos pelo software apresentaram consistência com os resultados registrados em laboratório pelos autores. Foi ainda analisada uma viga contínua de concreto submetida a um carregamento uniformemente distribuído. Essa viga foi reforçada com barras de mesmo diâmetro alterando-se apenas o material dessas barras (aço e PRFC). Dessa maneira, foi analisado o valor de carregamento que ocasiona a ruptura da viga. Foram constatadas duas importantes desvantagens das barras de PRFC em relação ao aço. A primeira desvantagem está no custo superior ao aço e por apresentar comportamento elástico até o rompimento, o PRFC não confere à estrutura de concreto uma ruptura dúctil. Os objetivos deste trabalho foram cumpridos e ao final são propostos novos estudos a serem realizados sobre o tema. / [en] The aim of the present work is to analyze the use of bars made of composite material to act as reinforcement for concrete beams subjected to bending. The analyzed bars are constituted by polymer reinforced with carbon fibers (PRFC), a material that presents linear elastic behavior until rupture. This material has some advantages in relation to steel, such as considerably higher tensile strength in addition to not being susceptible to the phenomenon of corrosion caused by environmental conditions. During the development of the work, an article was obtained which demonstrates results of laboratory tests in which the authors used concrete beams subjected to flexion testing by four points and reinforced with PRFC bars. In this work, the same test was simulated in the Atena software, a program that performs non-linear analysis for concrete structures, considering the cracking of this material. The results obtained by the software were consistent with the results recorded in the laboratory by the authors. It was also analyzed a continuous concrete beam subjected to a uniformly distributed load. This beam was reinforced with bars of the same diameter, changing only the material of these bars (steel and PRFC. In this way, the loading value that causes the beam to break when it is reinforced with steel bars and when it is reinforced with PRFC bars of the same diameter was analyzed. Two important disadvantages of PRFC bars in relation to steel have been noted. Due to its elastic behavior until breaking, this composite material does not give the concrete structure a ductile rupture. In addition, its cost is considerably higher than steel bars, since no suppliers of this type of reinforcement have been identified in Brazil, thus increasing the cost to purchase this product. The objectives of this work were accomplished and, in the end, new studies are proposed to be carried out on the theme.

[pt] Este trabalho tem como objetivo avaliar a resistência à força cortante de vigas de concreto reforçado com barras de fibras de vidro e investigar a contribuição dos diferentes mecanismos de transferência do esforço cortante para a resistência final da viga. Um programa experimental foi conduzido, incluindo ensaios para: caracterização do material, para avaliar o efeito de pino, para avaliar o engrenamento dos agregados e, por fim, ensaios de flexão de quatro pontos em vigas. Diferentes parâmetros foram investigados, como a quantidade de barras longitudinais para o efeito de pino, dimensão máxima do agregado graúdo para engrenamento dos agregados e a presença de estribos para os ensaios de vigas. O monitoramento do desenvolvimento da fissura crítica foi realizado com auxílio de correlação de imagem digital (digital image correlation, DIC, em inglês). Os resultados mostraram que não foi evidenciada diferença no comportamento de efeito de pino e de engrenamento dos agregados através dos ensaios realizados. Para os ensaios de vigas, observou-se que todos os espécimes apresentaram ruptura por tração da diagonal crítica e, para vigas sem estribos, a ação do efeito de pino pareceu contribuir significativamente para a resistência ao cisalhamento após a fissura, quando a carga diminui e as deflexões aumentam, resultado do menor engrenamento dos agregados à medida que a fissura se abre. Foi observado que a presença de estribos aumentou em até três vezes a resistência ao cortante das vigas ensaiadas e que houve ruptura do estribo na parte da dobra. / [en] This work aims to evaluate the shear strength of reinforced concrete beams with glass fiber reinforced polymer bars and to investigate qualitatively the contribution of the different shear transfer mechanisms to the final strength of the beam. An experimental program was conducted, including material characterization, dowel action tests, push-off tests, and finally, four-point bending tests on beams. Different parameters were investigated, such as the number of longitudinal bars for dowel action effect, maximum size of the coarse aggregate for aggregate interlock and the presence of stirrups for the beam tests. The monitoring of the development of the critical crack was performed with the aid of digital image correlation (DIC). The results showed that there was no difference in the behavior of the dowel action effect and the aggregate interlock through the tests performed. For beam tests, it was observed that all the specimens exhibited a concrete diagonal tension failure and for beams without stirrups, dowel action seemed to provide significant contribution to the shear strength after the crack, when the load reduces and the deflections increases, resulting from the loss of aggregate interlock as the crack opens. It was also observed that the presence of stirrups increased up to three times the shear strength of the beams tested and that there was rupture of the stirrup at the bent region.

FRP stands for Fiber Reinforced Polymer. FRP materials have yet to be introduced inbridge construction in Sweden. Composite materials can through combined componentsand manufacturing processes be tailored to fit advanced bridge designs. FRP materials arestrong, durable and of low weight. FRP materials give the superstructure reduced weightand are therefore a suitable alternative for industrial prefabrication. This report shows thatFRP materials are possible to use in bridge construction. With the introduction of a specificEurocode we are confident that FRP materials will become a competitive alternative inbridge construction in Sweden in the future. / Broar är förenade med stora kostnader, dels för att bygga och dels för att underhålla ochreparera. FRP står för Fiber Reinforced Polymer är ett erkänt material för många andraanvändningsområden, exempelvis flyg och bilindustri. I Europa finns en mängd FRP-broar,men materialet har ännu inte introducerats i någon bro i Sverige.FRP är ett kompositmaterial som genom olika kombinationer av komponenter ochtillverkningsprocesser kan skräddarsys för den aktuella uppgiften i en konstruktion. FRPmaterialär starka, beständiga och har en låg vikt. Fördelar med FRP inom brokonstruktionär att det ger överbyggnaden en minskad egenvikt och därmed är ett lämpligt alternativ attprefabricera industriellt, då bland annat transport- och lyftbarhet gynnas samt att en högbeständighet ger minskat underhåll.Då ingen litteratur hanterar FRP i Brokonstruktion har de intervjuades åsikter varit mycketviktiga för arbetet. Litteraturstudien har legat till grund för en ökad förståelse för egenskaperutmärkande för olika typer av FRP. Intervjuer har utförts med personer som i dagslägetkommit i kontakt med materialet inom brokonstruktion. Detta har gjorts för att nå ett relevantresultat med möjlighet att kunna identifiera materialets för- respektive nackdelar samtanledningen till det låga användandet i Sverige.Rapporten visar att materialet har positiva egenskaper och är möjligt att använda vidkonstruktion av broar. Det saknas i dagsläget en specifik Eurokod som på ett enhetligt sättredovisar hur materialet ska hanteras. Med införandet av en specifik Eurokod och om en nykompetens arbetas fram inom branschen är vi övertygade om att FRP-material kommer attbli ett konkurrenskraftigt alternativ vid brokonstruktion.

Reinforced cement concrete (RCC) structures have become an important aspect in most of the buildings in our society around the world. Most of the multistoried reinforced concrete buildings house important institutions such as hospitals, schools, government establishments, defense establishments, business centers, sports stadiums, super markets and nuclear power plants. The cost of construction of such multistoried RCC structures is very high, and these structures need to be maintained and restored based on their functionality and importance using repair and retrofit strategies when these structures undergo damage. The steps involved in restoring RCC structures that have damages using repair / retrofit measures consists of identifying the source or cause of damage, assessment of the degree or extent of damage that has taken place using nondestructive techniques. Based on the assessment of degree of damage suitable repair / retrofit strategy using the appropriate repair material is applied to achieve the required load carrying capacity or strength. The present work involves assessing the efficacy of carbon fibre reinforced polymer (CFRP) based system applied on pre-damaged structural members to restore the member’s strength and stiffness through experimental investigations and finite element predictions. To validate the macrolevel properties of predamaged concrete micromechanical analysis, microscale studies and analytical investigations have been conducted. Plain and reinforced concrete test specimens: cylinders, square prisms and rectangular prisms having 25MPa and 35MPa cylinder compressive strengths pre-damaged due to mechanical (monotonic and cyclic loading) and thermal loading (exposure to different temperature and time durations) with applications of CFRP repair subjected to compression is investigated to study the behavior and enhancement in the compressive strength and stiffness after application of repair. Non destructive testing of thermally damaged concrete (exposed to different temperature and exposure time) is conducted using ultrasonic pulse velocity and tomography methods to understand the degradation in the strength and stiffness of thermally damaged concrete. The results of the non destructive testing helps in assessing the amount of repair that can be applied. To validate the macro scale behavior of thermally damaged concrete micro scale studies was performed adopting micro indentation, petrography, Raman spectroscopy, scanning electron miscroscopy (SEM) and Electron probe micro analysis (EPMA). During the event of a fire in RC structures which have been retrofitted. The high temperature caused due to fire tends to make the concrete to deteriorate and the repair material to delaminate. Loss of strength/ stiffness in concrete and delamination of the repair material in a retrofitted structural component in a structure causes instability which results in partial collapse or complete collapse of the structure. Thermal insulation of concrete and the repair material (CFRP) using geo-polymer mortar and simwool thermal fibre blanket exposed to high temperature and different exposure time are experimentally investigated. This is to evaluate the effectiveness of the thermal insulation in protecting epoxy based structural repair material(CFRP) from thermal damage and to minimize the delamination of the repair material when exposed to high temperatures. Slender columns when loaded eccentrically fail at a load much lesser than their actual load carrying capacity. In RC buildings where additional floors need to be added, in those situations slender columns which are already eccentrically loaded tend to get damaged or fail due to additional load which act on them. Therefore to restore such columns experimental and finite element investigations on reinforced concrete slender columns having 25MPa cylinder compressive strength subjected to eccentric monotonic compressive loading with applications of CFRP repair is studied to understand the behavior and the enhancement in load carrying capacity after application of repair. Experimental investigations are conducted to study fracture and fatigue properties of thermally damaged concrete geometrically similar notched plain and reinforced concrete beams having 25MPa cylinder compressive strength exposed to different combinations of temperature and durations with application of repair (CFRP). Nonlinear fracture parameters of thermally damaged concrete is computed which help in understanding the fracture behavior of thermally damaged concrete and application of repair. Effectiveness of CFRP repair and failure behaviour of these beams are studied when these thermally damaged notch concrete beams are subjected to monotonic and cyclic (fatigue) loading. Reinforced concrete slender beams when subjected to unexpected loads such as earthquakes get damaged. The increase in load carrying capacity and fatigue life of reinforced concrete slender beams having 25MPa cylinder compressive strength in flexure subjected to monotonic and cyclic loading with applications of CFRP repair is investigated using experimental and finite element investigations. Finite element analysis of concrete specimens pre-damaged due to mechanical (monotonic and cyclic loading) / thermal loading (exposure to different temperature and time durations) with applications of CFRP repair and assessment of amount of repair required is investigated. Analytical (empirical) models are developed to assess the mechanical properties of concrete (elastic moduli, compressive strength and split tensile strength) exposed to different temperatures and time durations. Nonlinear fracture parameters of geometrically similar plain concrete notch beams exposed to different temperature and time durations are determined. Fracture parameters (stress intensity factor) of thermally damaged plain and reinforced concrete notched beams with application of CFRP have been determined. Effect of size and shape of thermally damaged plain concrete compression members with application of CFRP wrap have been studied. Crack mouth opening displacements (CMOD), strains and crack lengths of thermally damaged plain concrete (PC) notched beams using digital image correlation has also been determined.