This thesis was concerned on the investigation of mechanical properties of centrally notched and unnotched AS-4/PEEK (APC-2) composite laminates due to static tensile and tension-tension (T-T) fatigue tests empirically and systematically. Then, statistical analyses were used to determine and quantify the significant thermomechanical variables that influence the durability/life of the composite laminates. Typical laminates were made from sixteen prepregs of APC-2 and manufactured by a modified curing process. After drilling one hole with various diameters in the center of the samples respectively, the lay-ups were conducted on tension fracture and T-T fatigue test at different temperatures. From the parametric study we achieved the important results as follows. The cross-ply laminate possesses the higher ultimate strength, fatigue strength and longitudinal stiffness than those of the quasi-isotropic at the same temperature. Notch effect decays the laminate strength seriously, but changes the stiffness irregularly. As test temperature rising both strength and stiffness of lay-ups degrade significantly. Combining both effects of notch and temperature under severe environmental condition, it is found the cross-ply laminate possesses more resistance than that of the quasi-isotropic to cyclic loading. However, the quasi-isotropic laminate is more capable of sustaining the original strength than that of the cross-ply. Finally, the multiple regression analysis results showed that the hygrothermal environmental effects and cyclic loading were decoupled for APC-2 composite system. A semi-empirical model, reliably set up after the said programs, predicts conservative values, and should be adequate for use in preliminary designs. That is the main contribution in this study. Also, for the purposes of design and application, the predicted models efficiently treat experimental data instead of conventional curve-fitting methods.

L'utilisation extensive des matériaux composites dans l'industrie aéronautique nécessite une compréhension étendue de leur comportement mécanique et mécanismes d'endommagement. La prise en compte des effets environnementaux, température et vieillissement humide, dans la prévision du comportement à l'impact, des endommagements et des mécanismes associés reste un sujet encore peu traité actuellement. Dans ce travail différentes conditions de vieillissement humide (dénommées ci-après état neuf, 65% VH, et 90%VH) ont été appliquées au matériau de l'étude. La caractérisation des propriétés du pli et de l'interface ont été effectuée à température ambiante et 80°e. Une attention particulière a été portée à l'identification des propriétés en cisaillement plan. Un modèle d'endommagement progressif basé sur la mécanique de l'endommagement dans les milieux continus est proposé afin de décrire au mieux le comportement du pli élémentaire en prenant en compte les comportements fortement non-linéaires identifiés pour le cisaillement plan de ce matériau. Ce modèle matériau de comportement du pli est combiné avec des lois cohésives d'interface inter-laminaire utilisés dans des simulations numériques d'impact à faible vitesse afin de prédire la réponse mécanique à l'impact et les dommages. Le modèle de matériau a été implémenté dans le code de calcul explicite LS-Dyna. Des essais d'impact à différentes énergies ont été effectués afin de valider par comparaison essais-calcul l'approche utilisée. Une bonne adéquation est observée entre les résultats numériques et expérimentaux du matériau non-vieilli et testé à température ambiante pour ce qui concerne l'historique de la réponse globale et les dommages internes (rupture de fibre, fissures de matrice et délaminages). / The extensive application of composite laminates in aeronautical industries demands a thorough understanding of their mechanical behaviours and damage. The prediction of impact behaviour, impact damage and the associated mechanisms under complex environmental effects remain still an open issue. The effects of various humid ageing conditions (No ageing, 65% relative humidity and 90% relative humidity ageing) and environ mental temperatures (room temperature and 80°C) on the intra-Iaminar and inter-Iaminar properties are characterized. A particular emphasis is laid on the study of different non linear behaviours of in plane shear. A progressive damage model based on continuum damage mechanics is proposed to describe intra laminar mechanical behaviour by taking into account the identified in-plane shear nonlinear phenomenon. This model is then applied in numerical simulation on low velocity impact combined with cohesive law in interface to predict the impact response and associated damage (ie. Fibre failure, matrix cracks and delaminations). The damage model is implemented in LS Dyna as user defined material laws.lmpact tests on laminate coupons with different stratifications are performed to validate the numerical simulation. Good agreement is achieved especially for nonaged material under room temperature between numerical and experimental results in terms of contact force history, platedeflection and impact duration. By means of non-destructive inspection, the impact damage is coherent with predicted results concerning fiber damage location, matrix cracks especially the through thickness delamination.

O objetivo deste trabalho é analisar in vitro a dissipação de tensões em incisivos centrais superiores humanos restaurados com facetas de cerâmica feldspática, através da análise do método dos elementos finitos, considerando cargas funcionais de mastigação e corte dos alimentos, em função de três tipos de preparos utilizados: sem proteção incisal; com proteção incisal em ângulo e com proteção incisal em degrau palatino. Foram utilizadas modelagens bidimensionais de um incisivo central superior e suas estruturas de suporte, simulando três situações: (Primeira modelagem) incisivo central superior com desgaste vestibular (em forma de janela); (Segunda modelagem) incisivo central superior com desgaste vestibular e proteção incisal em plano inclinado; (Terceira modelagem) incisivo central superior com desgaste vestibular, e proteção incisal com degrau palatino. Foi considerada uma carga (P=100N) com uma inclinação de 45 concentrada, simulando a região de contato do incisivo central inferior com o superior durante a mastigação e uma na região de contato topo a topo dos incisivos superior e inferior, simulando o corte dos alimentos. Após a análise dos dados obtidos pela distribuição de tensões, pode-se concluir que quanto à dissipação das tensões em todo o sistema proposto, com a aplicação de carga em 45, não foram observadas mudanças no estado tensional nos três diferentes preparos. Quando foi aplicada carga vertical, simulando o contato de topo, houve variação no estado tensional no sistema do dente com preparo em janela. Nas facetas, com a aplicação de carga em 45, nos preparos em janela e com proteção incisal em plano inclinado o resultado foi semelhante nos valores tensionais enquanto, nas facetas em dentes preparados com proteção incisal com degrau palatino, a distribuição foi mais homogênea tendo valores superiores, mostrando que o abraçamento do dente diminuiu a flexão. / The aim of this study is to analyze in vitro stress dissipation on human maxillary central incisors restored with ceramic feldspathic veneers, through the finite element method. Functional chewing and food cutting loads were evaluated in three types of preparations of teeth: preparation without incisal protection, with incisal angle protection and with incisal protection with palatal step. Two-dimensional modeling of a maxillary central incisor and its supporting structures were used, simulating three conditions: 1) First modeling - maxillary central incisor with facial preparation (window shape); 2) Second modeling - maxillary central incisor with facial preparation and incisal protection on an inclined plane; 3) Third modeling - maxillary central incisor with facial preparation and incisal protection with palatal step. The chosen load (P = 100N) was applied to two different points: one of them to the palatal aspect with an inclination of 45 in order to simulate the contact area of the mandibular and the maxillary central incisors during chewing and the other one to the region of contact with edge-to-edge upper/lower central incisors, simulating food cutting. After analyzing the data obtained from the stress distribution it is possible to conclude that there are no alterations in tensional characteristics of the three different preparations concerning the stress dissipation on the whole proposed system, considering the application of load in 45. When the vertical load was applied, simulating an edge-to-edge contact, a variation in the stress state of tooth with window preparation was observed. For veneers with 45 load application, both the window preparation teeth and teeth with incisal protection on an inclined plane presented similar tensional values. For veneers of prepared teeth with incisal protection with palatal step, the stress distribution was more homogeneous with higher values, showing that tooth embracement reduced flexion.

abstract: The volume of end-of-life photovoltaic (PV) modules is increasing as the global PV market increases, and the global PV waste streams are expected to reach 250,000 metric tons by the end of 2020. If the recycling processes are not in place, there would be 60 million tons of end-of-life PV modules lying in the landfills by 2050, that may not become a not-so-sustainable way of sourcing energy since all PV modules could contain certain amount of toxic substances. Currently in the United States, PV modules are categorized as general waste and can be disposed in landfills. However, potential leaching of toxic chemicals and materials, if any, from broken end-of-life modules may pose health or environmental risks. There is no standard procedure to remove samples from PV modules for chemical toxicity testing in the Toxicity Characteristic Leaching Procedure (TCLP) laboratories as per EPA 1311 standard. The main objective of this thesis is to develop an unbiased sampling approach for the TCLP testing of PV modules. The TCLP testing was concentrated only for the laminate part of the modules, as they are already existing recycling technologies for the frame and junction box components of PV modules. Four different sample removal methods have been applied to the laminates of five different module manufacturers: coring approach, cell-cut approach, strip-cut approach, and hybrid approach. These removed samples were sent to two different TCLP laboratories, and TCLP results were tested for repeatability within a lab and reproducibility between the labs. The pros and cons of each sample removal method have been explored and the influence of sample removal methods on the variability of TCLP results has been discussed. To reduce the variability of TCLP results to an acceptable level, additional improvements in the coring approach, the best of the four tested options, are still needed. / Dissertation/Thesis / Masters Thesis Engineering 2018

Materiais compósitos laminados possuem uma alta eficiência estrutural, mas que é comprometida pela baixa resistência a cargas de impacto. O objetivo deste trabalho é o desenvolvimento de uma metodologia de simulação numérica para a estimativa de danos causados por cargas de impacto a baixas velocidades em placas de material compósito laminado. Ensaios experimentais foram realizados em placas reforçadas com tecidos de fibra de carbono e matriz de resina epóxi. Foram avaliadas três espessuras. Os carregamentos de impacto com uma massa em queda livre foram pontuais e transversais à placa, com intervalos de energia variando entre 5J e 94J, com velocidades inferiores a 6 m/s. As simulações numéricas utilizaram um programa comercial de elementos finitos com integração explícita. Foram avaliados dois critérios de falha da lâmina. O primeiro é o critério de máxima tensão. O segundo é uma proposta de modificação no critério de falha de Hashin, para sua aplicação em laminados reforçados com tecidos bidirecionais. Também foram avaliados quatro diferentes critérios de degradação da lâmina. As evoluções das forças de contato entre o impactador e a placa foram muito bem representadas numericamente. As áreas e os comprimentos dos danos numéricos foram similares ou maiores que os medidos nos resultados experimentais. / Laminate composite materials have high structural efficiency, however it is jeopardized due the low strength to impact loads. The objective of this work is to develop a numerical simulation methodology that estimates the damage in laminate plates caused by low velocity impact. Experimental tests were performed on laminate plates reinforced with weaven carbon fibers and epoxi resine. Three thickness plates were evaluated. The impact loads were transversal and punctual. They were done with drop-test, the impact energy range is between 5J and 94J, and the velocities were lower than 6m/s. The numerical simulations were done with FEM commercial code with explict integration. Two lamina failure criteria were evaluated. The first is the maximum stress. The second is a proposed modification of the Hashin failure criterion in order to be applied on the fabric laminates. Four lamina degradation criteria were evaluated too. The numerical contatct loads between the plate and impactor were well represented. The numerical damaged areas and lengths were similar or greater than the experimental results.

Este trabalho objetivou a manufatura de laminados híbridos metal-fibra (LMF) empregando-se chapas com 0,5 mm de espessura de liga-\'TI\'6\'AL\'4\'V\' com superfícies modificadas por laser de fibra de modo a otimizar a sua adesão com polímero termoplástico poli-sulfeto de fenileno (PPS). Observou-se que a microtextura superficial da liga metálica dependeu fortemente da potência do feixe laser, quando potências mais baixas levaram à verdadeira texturização da superfície metálica, enquanto que potências mais elevadas conduziram à ablação da mesma. A texturização superficial metálica sob laser de baixa potência aparentou ser a condição mais apropriada para a adesão metal-polímero por ancoragem mecânica de macromoléculas, o que foi contrabalanceado por elevados níveis de tensão residual das chapas metálicas, gerando grande distorção das mesmas e inviabilizando sua utilização. O emprego de uma potência intermediária (160 W) mostrou-se propício à otimização entre a adesão física entre metal-polímero e o nível de tensões residuais criado nas chapas metálicas. Concluiu-se que os espécimes extraídos do centro dos laminados metal-fibra exibem uma tensão limite média para falha por cisalhamento interlaminar consideravelmente superior à dos espécimes usinados a partir da borda dos LMF. O LMF manufaturado sob maiores pressão e temperatura exibiu uma maior compactação e melhor consolidação, culminando num máximo desempenho médio sob carga de cisalhamento interlaminar. Evidências de uma correlação entre o mecanismo de falha por cisalhamento interlaminar do corpo de prova e o seu nível de resistência a este tipo de carregamento mecânico foram documentadas e discutidas. / This work aimed at manufacturing hybrid fiber-metal laminates (FML) by employing 0,5 mm-thick \'TI\'6\'AL\'4\'V\'-alloy plaques with fiber laser modified surface in order to optimize metal adhesion with poli-phenylene sulfide (PPS) thermoplastic polymer. The surface microtexture of metallic alloy strongly depended upon the laser power, inasmuch as low-power laser led to true texturization of metal surface, whereas high-power laser light drove to its ablation. Surface metal texturization under low-power laser apparently was the most appropriate condition to metal-polymer adhesion via mechanical entanglement of macromolecules, which was offset by high levels of residual stresses on metallic plaques, bringing them quite warped and useless. The use of an intermediate laser power (160 W) has been shown benign to the optimization between metal-polymer physical adhesion and the residual stress level created in the metal plates. It has been concluded that testpieces machined from the FML central position exhibited average ultimate interlaminar shear strenght considerably higher than those extracted from the FML borders. The FML manufactured under higher pressure and temperature was more compacted and better consolidated, so that it displayed the greatest average performance under interlaminar shear loading. Evidences of a correlation between the failure mechanism by interlaminar shearing of test coupon and its allowance to this type of mechanical loading were documented and discussed.

A radiação gama é uma das tecnologias aplicadas para a esterilização de sistemas de embalagens contendo produtos para a saúde. No processo de esterilização, é fundamental que as propriedades das embalagens sejam mantidas. Neste estudo, duas amostras de embalagens comerciais, no formato de envelope compostas por papel grau cirúrgico de um dos lados e filme plástico laminado do outro, foram irradiadas com raios gama com doses de 25 kGy (taxa de dose de 1,57 kGy/h) e 50 kGy (taxa de dose de 1,48 kGy/h). Uma das amostras de embalagem era constituída por papel de fibras de coníferas e filme plástico laminado de poli(tereftalato de etileno) (PET)/polietileno (PE) e a outra por papel de fibras de coníferas e de folhosas e filme plástico laminado de poli(tereftalato de etileno) (PET)/polipropileno (PP). Os efeitos da radiação nas propriedades físicas e químicas dos papéis e dos filmes plásticos, assim como nas propriedades da embalagem foram estudados. O papel foi o material mais sensível à radiação, sendo a alvura, o pH e as resistências ao rasgo, ao arrebentamento e à tração os parâmetros nos quais foram observadas maiores modificações, em ambas as amostras. Todavia, dos dois tipos de papel, o efeito foi mais pronunciado para a amostra com fibras de conífera e de folhosas. A porosidade dos papéis foi alterada com 50 kGy. No caso dos filmes plásticos, a propriedade com maior modificação foi a resistência à tração, em ambas as amostras. No caso das embalagens, a irradiação diminuiu a resistência da selagem. Os efeitos observados para a dose de 50 kGy foram em média mais pronunciados quando comparados com as modificações nos valores das amostras tratadas com 25 kGy, que é a dose usualmente empregada para esterilização de produtos para a saúde. A dosimetria deste estudo foi realizada nos materiais irradiados com 25 kGy, 40 kGy e 50 kGy, demonstrando sua importância à medida que a variação média para as três doses estudadas foi de 20 %. / Gamma radiation is one of the technologies applied for the sterilization of packaging systems containing products for health. During sterilization process it is critical that the properties of packages are maintained. In this study two samples of commercial pouch packaging comprised of surgical grade paper on one side and the other side multilayer plastic film were irradiated with gamma rays. The following doses were applied 25 kGy (1,57 kGy/h) and 50 kGy (1,48 kGy/h). One packaging sample was paper formed by softwood fibers and multilayer plastic film based on poly(ethylene terephthalate) (PET)/polyethylene (PE). The second type of paper sample was made by a mixture of softwood and hardwood fibers and multilayer plastic film based on polyethylene terephthalate (ethylene) (PET)/polypropylene (PP). The effects of radiation on the physical and chemical properties of papers and multilayer plastic films, as well as the properties of the package were studied. The paper was the more radiation sensitive among the studied materials and radiation effects were more pronounced at brightness, pH, tearing resistance, bursting strength and tensile strength. Nonetheless, worst comparatively effects were noted on the sample made by a mixture of softwood and hardwood fibers. The porosity of paper was enhanced by 50 kGy. In the case of plastic films, radiation effects on tensile strength was the most pronounced property for both samples. In the case of the packaging the sealing resistance decreased with radiation. The effects observed for the treatment at 50 kGy were more pronounced when compared to 25 kGy. This last is the dose which is usually applied to sterilize health products. A dosimetry study was performed during irradiation at 25 kGy, 40 kGy and 50 kGy and its importance may be reported by the average dose variation 20 %.

Aplicações dos laminados híbridos metal-fibra incluem, além da indústria aeronáutica, as indústrias naval e automobilística. Diferentemente do setor aeronáutico, pesquisas sobre impactos mecânicos nas duas outras áreas da mobilidade são freqüentemente limitadas pela disponibilidade de equipamentos laboratoriais, de modo que é desejável o desenvolvimento de procedimentos de baixo custo para a determinação da resistência e tolerância a danos por impacto dos materiais de construção. Neste trabalho, a resistência a danos por impacto transversal do laminado híbrido metal-fibra Glare-5® foi determinada via três diferentes metodologias. A primeira utiliza um aparato sofisticado aparato Laser-Doppler para monitorar a aceleração e desaceleração de um impactador esférico de aço com 5 mm de diâmetro durante o evento do choque mecânico. O segundo método se baseia apenas nos valores de carga (força aplicada) vs. o tempo de impacto para a obtenção da energia absorvida pelo material. O terceiro considera somente os dados da velocidade do impactador, ou projétil, imediatamente antes e após o impacto. Concluiu-se que os valores de energia obtidos segundo as duas primeiras metodologias são similares, com o Laser-Doppler gerando resultados levemente não-conservadores, comprovando assim a possibilidade da derivação da resistência ao impacto do laminado através de um experimento simples e rápido, que utiliza apenas uma célula de carga digital para a monitoração da força aplicada em função do tempo. O terceiro método apresentou resultados substancialmente superiores às duas primeiras metodologias, sendo classificado como inadequado aos propósitos do projeto. Determinou-se que o laminado híbrido Glare-5®; absorve entre 60% e 80% da energia disponibilizada em impactos ditos leves, no intervalo de 1 a 6 Joules. Por fim, comprovou-se que a rigidez do material (módulo de elasticidade) é a propriedade residual (numa base de tolerância a danos) mais clara e consistentemente degradada pelo impacto previamente aplicado ao material. / Applications of hybrid fiber-metal laminates include, besides aeronautical industry, the automotive and naval industries. Unlike aeronautical field, impact research activities in the former areas of mobility industry are frequently limited by available laboratory equipment, so that it would be desirable to develop low-cost procedures to determine impact resistance and tolerance properties of construction materials. In this work, the transversal (trans-thickness) impact resistance and tolerance of hybrid fiber-metal laminate Glare-5® have been determined via three different methodologies. The first one utilizes sophisticated apparatus comprising a Laser-Doppler device to monitor deceleration/re-acceleration of 5 mm-diameter steel-ball impactor during the mechanical shock event. The second approach merely relies on the force (applied load) vs. impact time for determining the absorbed energy during the dynamic process. The third methodology requires only impactor velocity data points, immediately before and after the impact. It has been concluded that the energy values obtained from Laser- Doppler and load cell methods are very similar, with the former method producing slightly non-conservative results, allowing one to rapidly derive the impact resistance of hybrid laminate materials through very simple experimental set-ups employing digital load cells only. The third method presented somewhat higher results as compared to the concurrent techniques, so that it has been considered as inadequate for the research purposes. This study has shown that the fibre-metal laminate Glare absorbs between 60% and 80% of the apported impact energy during light impact events (ranging from 1 to Joules). Last, but not the least, materials stiffness was the most clearly and consistently imparted residual mechanical property (in a damage tolerance basis) due to the previous applied impact loading.

Ziel der vorliegenden Studie war es, bei Keramikveneers zur Frontzahnversorgung den Einfluss des Präparationsdesigns und der Verblendschichtdicke auf die Grenzflächen zwischen Keramik und Komposit sowie zwischen Zahn und Komposit zu untersuchen. Es wurde im speziellen die Grenzflächenadaptation an den zwei Klebefugeninterfaces nach thermozyklischer Beanspruchung und Kausimulation mittels optischer Kohärenztomographie untersucht.:Inhaltsverzeichnis Einführung 3 1. Veneerversorgungen und adhäsiver Verbund 3 2. Adhäsive Defekte an den Verbundzonen 6 3. Methoden zur Untersuchung der Verbundzonen 8 4. Optische Kohärenztomographie 9 Fragestellungen 13 Publikation 14 Zusammenfassung der Arbeit 24 Literaturverzeichnis 28 Erklärung über die eigenständige Abfassung der Arbeit 36 Danksagung 37

In the last few decades, there has been a shift to using more lightweight materials for the potential of fuel consumption reduction. In the Aerospace Industry, conventional metal structures are being replaced by advanced composite structures. The major advantage of an advanced composite structure is the huge reduction in the number of parts and joints required. Also composite materials provide better resistance to creep, corrosion, and fatigue. However, one cannot eliminate all the joints and attachments in an aircraft’s structure. Eliminating structural joints is impractical in present-day aircraft because of the requirements for inspection, manufacturing breaks, assembly and equipment access, and replacement of damaged structures. Currently, composite joints are overdesigned which leads to weight penalties. Understanding how to optimize the ultimate bearing strength of a composite joint by altering the cure cycle might be beneficial to the composite joint design process. This study investigates, through numerical and experimental analysis, the mechanical behavior of double shear joints. The first task is to test Aluminum double shear joint specimens inside the double shear joint fixture at a loading rate of 0.05 in./min. (quasi-static). The second task is to numerically model and validate the aluminum double shear joint specimen. The third task is to test the Unidirectional MTM 49 carbon fiber pre-preg double shear composite joint specimens with two different cure cycles and five different loading rates (0.05 in./min., 0.1 in./min., 1 in./min., 2 in./min. and 6 in./min.). The double shear composite joint specimens are made, using a heat press, with a quasi-isotropic laminate orientation of [0 0 +45 -45 +45 -45 90 90]s. The first cure cycle used is called the alternate cure cycle, which is Cytec’s MTM 49 Unidirectional Carbon Fiber pre-preg material cure cycle, and the second cure cycle used is called the datasheet cure cycle, which is Umeco's MTM 49 Unidirectional Carbon Fiber pre-preg material cure cycle. The recommended datasheet cure cycle and an alternate cure cycle are both compared to see how they affect the mechanical characteristics of the matrix along with the bearing stress. The fourth task is to adjust the Aluminum double shear joint numerical model for the double shear composite joint specimen. The numerical results for both the Aluminum and the composite specimens are in agreement with the experimental results. The theoretical in-plane material properties of the quasi-isotropic laminate were in agreement with the experimental results. One can see that at 0.05 in./min. and 0.1 in./min. (for both cure cycles) the composite double shear specimens carried more load compared to the higher loading rates of 1 in./min., 2 in./min. and 6 in./min. The tensile modulus of elasticity of an Aluminum sample is measured using a crosshead displacement, a strain gage and an extensometer. The crosshead displacement yielded very inaccurate results when compared to the strain gage and the extensometer.