The use of timber in building structures is steadily increasing. cross laminated timber (CLT) is an engineered wood product made of an uneven number of layers of lamellas glued at an angle of 90 degrees to each other. This gives CLT high stiffness and strength to bending in all directions, and capability of taking load both in-plane and out-of-plane. Due to the large size of CLT elements, they allow for quick assembly of strong structures. Due to both economic and environmental reasons it is important for producers of CLT to optimize the use of the wood material by using the timber with higher stiffness and strength where it is most needed. This thesis is about evaluating the bending and shear stiffness of CLT elements, when used as plates, depending on the quality of wood used in the different layers. Four-point bending tests are carried out on elements of different compositions and a parametrized finite element model is created. Thus, the model is validated on the basis of experimental tests to evaluate the influence of different quality of different layers. The measured dynamic MoE proved to have good potential to be used as the longitudinal bending stiffness in an FE-model, with a deviation from the experimental tests of less than 1%. There is a strong correlation between the bending stiffness and bending strength of the plates. The effective rolling shear modulus in pine was calculated to be around 170 MPa for pine of dimension 40 x 195 mm2 . Grading the boards into two different classes used for different layers proved to increase the MoE of the plates by 11-17% for 3- and 5-layer CLT.

Due to the cost and difficulty of conducting direct tensile and compression creep testing on engineering ceramics, four-point bending creep test methods are often used as an alternative. Stress distribution in the bending specimen is nonlinear, so a proper interpretation method is needed to get creep properties from data produced by four-point bending creep tests. The method of Hollenberg et al. and the method of Chuang are among the methods to predict the creep parameters from bending creep test data. However, bending creep test methods are often doubted for quantitative creep analysis with reasons like uncertainties from contact point shift or frictional effects in four-point bending creep tests. Finite element simulations of the four-point bending creep tests were performed to evaluate the limitations and abilities of four-point bending creep tests and the methods to predict creep parameters from bend test data. Material model for asymmetric creep behavior (different creep rate in tension and in compression) of ceramics material were developed by modifying the existing symmetric creep model and implemented in the inhouse non-linear finite element code. Explicit finite element method (dynamic relaxation) was successfully used to consider both, the frictional effects between loading rollers and specimen, and asymmetric creep properties of ceramics material. The developed asymmetric creep material model was verified by the simulation of C-ring compression creep test and comparison with published experimental data. It was found that when friction between loading rollers and specimen was not applied in the simulations, both Hollenberg’s and Chuang’s methods well predicted creep parameters from bend creep simulation data. But, when friction was high as in normal bend creep tests, the pre-exponent (A) was highly underestimated. Prediction of stress exponent (n) was not affected much by friction. Bend test set-up with rolling-pins in ASTM C 1211 was recommended to reduce the frictional effects in bend creep tests and a proof simulation was performed. The simulation showed that the test set-up in ASTM C 1211 effectively removed the frictional effect of the frequently used creep test set-up and the effect of bending moment increase due to the rolling of loading pin was minor. / Thesis / Master of Applied Science (MASc)

Introduction. A part of the standard testing procedure on high voltage cables is the measuring of the volume resistivity in the different semi-conductive layers. A need for improvement has been realized because of the increased frequency of testing, which is a result of the recent expansion of cable production of NKT in Karlskrona. Objective. The objectives of the thesis are to firstly discover what the needs are for improvements within the method of conducting volume resistivity measurements on high voltage cables. Secondly, following these discoveries, solving the problems by developing new products. Method. The method for the thesis work is divided into two parts, performing a case study on the current measurement method, and product development for the new solutions. The case study was conducted mainly by gathering empirical data through interviews and observations. The product development process started with ideation for solutions, followed by prototyping, and lastly, a validation process to test the new solutions through experiments and lead used testing. The entirety of the work was conducted through a design thinking approach. Result. From the case study it was discovered that two main issues needed to be addressed, being a new solution for a measurement rig, and a way to streamline the painting and taping process. A new design for a measurement rig was invented. The new solution contains two rigs, which allows for more samples to be heated simultaneously, halving the preheating time when testing four samples from the current measurement method. A preparation station was also created to aid the operators with the taping and painting, which resulted in a 40% reduced time for these tasks. Conclusion. By implementing new products, the measurement method for conducting volume resistivity has been improved by time effectiveness, robustness, and reliability.

This study investigates the mechanical differences between old and newly produced slatted floors through a four-point bending test. To understand to what extent the actual environment has affected the slatted floors, the carbonation depth and corrosion will be examined. The tests showed no mechanical differences between slatted floors which had been in service for a certain amount of years and newly produces ones. Corrosion could be observed on some of the samples but it was not because of the carbonation process. When comparing the calculations of reinforced and pre-stressed concrete slatted floors, the result showed that the pre-stressed floor could carry up to double the load of what the reinforced slatted floor could. The conclusion of this study is, that the pre-stressed slatted floors will certainly hold for at least thirty years and will most likely hold for many years to come.

Les nanomatériaux suscitent depuis quelques décennies de plus en plus d’intérêt tant sur le plan des études fondamentales que sur celui des applications. Parmi ces nouveaux matériaux, les nanotubes de carbone ont attiré beaucoup d’attention au sein de la communauté scientifique à cause de leurs propriétés physiques remarquables. Les travaux présentés dans cette thèse, concernent l’élaboration et la caractérisation de composites solides à base de nanotubes de carbone. Le choix des matériaux s’est porté sur une matrice solide à base de Bromure de Potassium (KBr) et des nanotubes de carbone mono et multifeuillets (SWNT, MWNT). L’étude de ces composites concerne deux aspects : dans un premier temps, l’effet de la charge et de la nature des nanotubes de carbone sur les propriétés électriques et thermiques ont été étudiés. L’étude des propriétés thermiques a été réalisée à l’aide d’une technique photothermique, la photoacoustique, qui présente un grand avantage pour ce type de composites. L’évolution des propriétés thermiques en fonction de la charge a montré un comportement atypique, une augmentation puis une diminution, avec un maximum autour de 2% de charge en nanotubes. Un modèle physique permettant de décrire cette évolution a été proposé. Concernant les propriétés électriques, cette étude a permis de mettre en évidence le phénomène de percolation et d’en déterminer le seuil. Dans un deuxième temps, l’étude a porté sur l’influence du gaz environnant sur les propriétés thermiques et électriques, et sur l’éventuelle utilisation de ces composites comme capteurs de gaz. La caractérisation thermique en présence d’éthanol n’a pas permis de mettre en évidence un changement notable des propriétés thermiques des composites. En revanche, la caractérisation électrique a montré une bonne réponse à ce gaz. L’évolution de la sensibilité en fonction de la charge en nanotubes dans les composites a montré une augmentation pour des charges inférieures à 4% et une stabilisation au-delà. L’influence d’autre gaz comme le dioxyde d’azote et le toluène a été aussi étudié. La réponse électrique au dioxyde d’azote a montré une forte interaction du gaz avec les composites. La réponse au toluène n’a pas montré d’influence de ce gaz sur les propriétés électriques des composites à base de SWNT, cependant, dans le cas des composites à base de MWNT, une réponse électrique comparable à celle de l’éthanol a été observée. / In the recent decades, nanomaterials arouse a growing interest both in their fundamental studies and in their applications. Among these new materials, carbon nanotubes have attracted much attention within the scientific community because of their remarkable physical properties.The work presented in this thesis, involve the preparation and characterization of solid composites based on carbon nanotubes. A solid matrix containing potassium bromide (KBr) and carbon nanotubes, single and multiwalled (SWNT, MWNT) was chosen. The study of these composites involves two aspects: initially, the effect of the loading fraction and the nature of carbon nanotubes on the electrical and thermal properties were investigated. The study of thermal properties was carried out by a photothermal technique, the photoacoustic, which offers great advantages for this type of composites. The evolution of thermal properties according to the loading fraction of nanotubes showed an atypical behavior, an increase followed by a decrease, with a maximum around 2% of nanotubes loading fraction. A physical model describing this evolution has been proposed. Regarding the electrical properties, this study has highlighted the phenomenon of percolation and allowed the determination of the percolation threshold. In a second step, the study focused on the influence of surrounding gas on the thermal and electrical properties, and the possible use of these composites as gas sensors. The thermal characterization with ethanol did not reveal a significant change in thermal properties of composites. However, the electrical characterization showed a good response to this gas. The evolution of the sensitivity depending on the nanotubes loading fraction in the composites showed an increase for loads below 4% and a stabilization beyond this value. The influence of other gases such as nitrogen dioxide and toluene were also studied. The electrical response to nitrogen dioxide showed a strong interaction of the gas with composites. The response to toluene did not show any influence of this gas on the electrical properties of SWNT-based composites, however, in the case of MWNT-based composite, an electrical response similar to that of ethanol was observed.

Zinc Oxide falls under the classification of transparent conductive oxides. They typical optical transmittance of Zinc Oxide is 90% in the visible wavelength region. Though stoichiometric ZnO is an insulator, due to the presence of internal defects such as Zn interstitials and Oxygen vacancies, it exists as a n-type conductor. The other important property of ZnO which could be used by the optical field is its widebandgap. ZnO has a wide bandgap of 3.2eV -3.3eV. The additional advantage of being a direct bandgap semiconductor has increased the probability of using ZnO for short wavelength applications. These practical applications are directly related to the fabrication of homostructural p-n junctions. ZnO can be readily doped n-type. Doping ZnO P-type is very difficult due to its native defects and the self-compensation that occurs during doping. But when P-type doping is obtained in ZnO it could be used in various optical applications such as light emitting diodes and laser diodes. This provided the motivation for this research. Theoretical studies have proposed nitrogen as a suitable material to achieve p-type ZnO. Literature provides a set of conditions that could be used to improve the doping in ZnO films. In this research, a set of these conditions were used to implement p-type doping in ZnO films. A sputtering system with a setup to support two Torus - 5M guns was used to deposit the ZnO films. A codoping technique using an aluminium doped zinc oxide target was the first method. Though an improvement in the nitrogen incorporation was found in this method in the beginning, a further increase in the nitrogen pressure did not show further improvement. A co-sputtering technique of a 99.999% pure ZnO target and a 99.99% pure Zn metal target was the second method. The ZnO target was rf sputtered while the Zn target was dc sputtered using the two guns provided in the deposition chamber. The extra Zinc obtained from sputtering the metallic Zn target was used to improve the incorporation of nitrogen. The films were later deposited in an oxygen ambient where the excess oxygen was used to suppress the oxygen vacancies that act as hole killers during the doping process. Four point probe measurement and Keithley 900 series Hall equipment were used for the electrical characterization of the films. An ORIEL monochromator was used to optically characterize the films. Hitachi S-800 T EDAX analysis system was used to measure the atomic weight % of nitrogen incorporated in the ZnO:N films. Deposition at an oxygen partial pressure of 0.3mT and 0.8mT of nitrogen produced p-type ZnO films. These films showed a carrier absorption in the short wavelength region. The carrier concentration and the mobility obtained for these films were 4.0 x1016 cm-3 and 0.12 cm2 /V-s respectively.

No description available.

No description available.

O fenômeno de fadiga é caracterizado pela deterioração estrutural que um material está sujeito quando submetido a um estado de tensões e de deformações repetidas, resultando assim, em um trincamento do pavimento, que pode até culminar na sua ruptura após um número suficiente de repetições de carregamento. Este processo é considerado como sendo a perda de resistência do material quando solicitado por uma carga repetida. Conhecer a resistência à fadiga de misturas asfálticas torna-se relevante para a formulação das misturas, para o dimensionamento de uma estrutura ou para a escolha de uma adequada solução em uma obra de recuperação do pavimento de uma rodovia. O ensaio laboratorial mais utilizado no Brasil para analisar a fadiga de misturas é o de tração indireta por compressão diametral em corpos de prova cilíndricos, contudo este ensaio apresenta algumas variáveis que diferenciam os resultados obtidos em laboratório com a realidade apresentada em campo. Neste sentido, o presente trabalho analisou o comportamento à fadiga, através do ensaio de flexão em viga quatro pontos, de duas misturas asfálticas: concreto asfáltico com ligante modificado por polímero (COMPAFLEX 60/85) e concreto asfáltico com ligante modificado por polímero e adição de TLA (CAP TLA FLEX). Para obter as vigas de mistura asfáltica optou-se por utilizar uma metodologia de moldagem e compactação das placas em uma usina de asfalto. Após este processo as placas foram serradas para obtenção das vigas nos tamanhos definidos, sendo estas amostras ensaiadas para verificação da densidade aparente e grau de compactação. Com o intuito de atingir o objetivo proposto foram realizados ensaios de fadiga à flexão em quatro pontos, sob modo de carregamento à deformação e tensão controlada, ensaios de fadiga por compressão diametral (tensão controlada) e ensaios de resistência à tração, sendo estes realizados à temperatura de 25°C. Também foi determinado o módulo dinâmico das misturas estudadas para as temperaturas de 15°C, 20°C e 25°C. Os resultados obtidos demonstram que a metodologia escolhida para a moldagem e compactação das placas foi adequada, pois as amostras apresentaram valores de volume de vazios, densidade aparente e grau de compactação semelhantes aos estabelecidos nos projetos das misturas. Em relação aos resultados obtidos nos ensaios de fadiga por compressão diametral a mistura CA-TLA obteve valores de vida de fadiga superiores em relação à mistura CA-E, enquanto no ensaio de flexão em quatro pontos, à deformação controlada, a mistura CA-E apresentou maiores vidas de fadiga. Os resultados dos ensaios de módulo dinâmico das misturas CA-TLA e CA-E foram apresentados através das representações clássicas nas curvas isotérmica, frequência‐temperatura, isócrona, espaço de Black e plano cole‐cole, mostrando que a mistura CA-TLA apresentou maior rigidez em relação a mistura CA-E. / The phenomenon of fatigue is characterized by structural deterioration when a material is subjected to a state of repeated stress and strain cycles, thus resulting in cracking of the pavement which may even result in its failure after a sufficient number of load repetitions. Considering the fatigue resistance of asphalt mixtures becomes relevant for the formulation of mixes, for the design of a pavement structure or for choosing an adequate solution for pavement rehabilitation in highways. The laboratory test commonly employed in Brazil to analyze the fatigue life of asphalt mixes is the indirect tensile test by diametrical compression in cylindrical specimens. However, this test presents some variables that differentiate the results obtained in laboratory with the in situ loading conditions. In this sense, the present work examined the fatigue behavior, through the four points bending beam test, in two asphalt mixtures: asphalt concrete with binder modified by polymer (COMPAFLEX 60/85) and asphalt concrete with binder modified by polymer and TLA (CAP TLA FLEX) addition. To obtain the beams of asphalt mixture, it was chosen to use a methodology of molding and compaction of the slabs in an asphalt plant, after this process the slabs were sawn in order to obtain the beams in set sizes, and these samples tested to verify the apparent density and degree of compaction. For the research, flexural fatigue tests were conducted in four points bending beam under controlled strain and stress modes, fatigue tests by diametrical compression (stress controlled) and tensile strength tests, all these conducted at a temperature of 25°C. It was also determined dynamic modulus of the mixtures at temperatures of 15°C, 20°C and 25°C. The results show that the methodology chosen for molding and compaction of the plates were appropriate because the samples showed targeted values of void volume, bulk density and degree of compaction, similar to those established in the mix design. Regarding the results obtained in fatigue tests by diametrical compression the mixture CA-TLA obtained values higher fatigue life compared to the mix CA-E, while in the bending test on four points, the controlled deformation, the mixture CA-E showed higher fatigue lifes. The test results of dynamic modulus of mixtures CA-TLA and CA-E were presented through classical representations of the isotherm curves, frequencytemperature, isochrone, Black space and cole-cole plane, showing that mixture CA-TLA presented higher stiffness in relation to mixture CA-E.

O fenômeno de fadiga é caracterizado pela deterioração estrutural que um material está sujeito quando submetido a um estado de tensões e de deformações repetidas, resultando assim, em um trincamento do pavimento, que pode até culminar na sua ruptura após um número suficiente de repetições de carregamento. Este processo é considerado como sendo a perda de resistência do material quando solicitado por uma carga repetida. Conhecer a resistência à fadiga de misturas asfálticas torna-se relevante para a formulação das misturas, para o dimensionamento de uma estrutura ou para a escolha de uma adequada solução em uma obra de recuperação do pavimento de uma rodovia. O ensaio laboratorial mais utilizado no Brasil para analisar a fadiga de misturas é o de tração indireta por compressão diametral em corpos de prova cilíndricos, contudo este ensaio apresenta algumas variáveis que diferenciam os resultados obtidos em laboratório com a realidade apresentada em campo. Neste sentido, o presente trabalho analisou o comportamento à fadiga, através do ensaio de flexão em viga quatro pontos, de duas misturas asfálticas: concreto asfáltico com ligante modificado por polímero (COMPAFLEX 60/85) e concreto asfáltico com ligante modificado por polímero e adição de TLA (CAP TLA FLEX). Para obter as vigas de mistura asfáltica optou-se por utilizar uma metodologia de moldagem e compactação das placas em uma usina de asfalto. Após este processo as placas foram serradas para obtenção das vigas nos tamanhos definidos, sendo estas amostras ensaiadas para verificação da densidade aparente e grau de compactação. Com o intuito de atingir o objetivo proposto foram realizados ensaios de fadiga à flexão em quatro pontos, sob modo de carregamento à deformação e tensão controlada, ensaios de fadiga por compressão diametral (tensão controlada) e ensaios de resistência à tração, sendo estes realizados à temperatura de 25°C. Também foi determinado o módulo dinâmico das misturas estudadas para as temperaturas de 15°C, 20°C e 25°C. Os resultados obtidos demonstram que a metodologia escolhida para a moldagem e compactação das placas foi adequada, pois as amostras apresentaram valores de volume de vazios, densidade aparente e grau de compactação semelhantes aos estabelecidos nos projetos das misturas. Em relação aos resultados obtidos nos ensaios de fadiga por compressão diametral a mistura CA-TLA obteve valores de vida de fadiga superiores em relação à mistura CA-E, enquanto no ensaio de flexão em quatro pontos, à deformação controlada, a mistura CA-E apresentou maiores vidas de fadiga. Os resultados dos ensaios de módulo dinâmico das misturas CA-TLA e CA-E foram apresentados através das representações clássicas nas curvas isotérmica, frequência‐temperatura, isócrona, espaço de Black e plano cole‐cole, mostrando que a mistura CA-TLA apresentou maior rigidez em relação a mistura CA-E. / The phenomenon of fatigue is characterized by structural deterioration when a material is subjected to a state of repeated stress and strain cycles, thus resulting in cracking of the pavement which may even result in its failure after a sufficient number of load repetitions. Considering the fatigue resistance of asphalt mixtures becomes relevant for the formulation of mixes, for the design of a pavement structure or for choosing an adequate solution for pavement rehabilitation in highways. The laboratory test commonly employed in Brazil to analyze the fatigue life of asphalt mixes is the indirect tensile test by diametrical compression in cylindrical specimens. However, this test presents some variables that differentiate the results obtained in laboratory with the in situ loading conditions. In this sense, the present work examined the fatigue behavior, through the four points bending beam test, in two asphalt mixtures: asphalt concrete with binder modified by polymer (COMPAFLEX 60/85) and asphalt concrete with binder modified by polymer and TLA (CAP TLA FLEX) addition. To obtain the beams of asphalt mixture, it was chosen to use a methodology of molding and compaction of the slabs in an asphalt plant, after this process the slabs were sawn in order to obtain the beams in set sizes, and these samples tested to verify the apparent density and degree of compaction. For the research, flexural fatigue tests were conducted in four points bending beam under controlled strain and stress modes, fatigue tests by diametrical compression (stress controlled) and tensile strength tests, all these conducted at a temperature of 25°C. It was also determined dynamic modulus of the mixtures at temperatures of 15°C, 20°C and 25°C. The results show that the methodology chosen for molding and compaction of the plates were appropriate because the samples showed targeted values of void volume, bulk density and degree of compaction, similar to those established in the mix design. Regarding the results obtained in fatigue tests by diametrical compression the mixture CA-TLA obtained values higher fatigue life compared to the mix CA-E, while in the bending test on four points, the controlled deformation, the mixture CA-E showed higher fatigue lifes. The test results of dynamic modulus of mixtures CA-TLA and CA-E were presented through classical representations of the isotherm curves, frequencytemperature, isochrone, Black space and cole-cole plane, showing that mixture CA-TLA presented higher stiffness in relation to mixture CA-E.