A study has been made of glass fibre reinforced plastic beams in three-point bending. In recent years, the importance of flexural loading in composites has manifested itself in the form of composite leaf springs, helicopter rotors, and other applications. This study is directed at the initiation, growth, characterization and measurement of damage in unidirectional and cross-ply composite beams. Beams were tested in three-point static and cyclic bending. Following damage initiation, either by a machined notch or by repeated cycling, damage growth has been characterized by two damage parameters: a damage depth encompassing a number of broken fibres on the tensile surface at the central load point, and a damage length or delamination parallel to the beam longitudinal axis. A model was developed to predict the compliance, or deflection under applied load, as a function of beam properties and damage dimensions. The model is able to predict the compliance of damaged beams with reasonable accuracy. From fracture mechanics concepts it is shown that the two damage dimensions, depth and length, are related. It is concluded that the increase in compliance, a result of the growing damage dimensions, is related to the growth of the damage depth; the damage length follows from the relation between damage parameters and the compliance follows from the compliance model. The damage state can thus be determined by compliance measurements if the relevant material properties and loading conditions are known. However, in service, compliance measurements may not be practical. Therefore a section of this study is devoted to an alternative damage measurement technique, namely acoustic emission monitoring. Damage initiation, compliance, damage length and damage depth were measured with AE monitoring techniques. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Orientador: Luis Roberto Marcondes Martins / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-26T11:37:31Z (GMT). No. of bitstreams: 1 Bertaglia_PriscilaCamondy_D.pdf: 1620456 bytes, checksum: 044aa4cbf344b86191934f41f4525929 (MD5) Previous issue date: 2015 / Resumo: O objetivo deste estudo in vivo foi avaliar clinicamente através do critério USPHS e a sensibilidade pós-operatória de restaurações Classe I de compósito nanoparticulado, associado a sistemas de união do tipo condicionamento total e autocondicionante. Trinta e duas restaurações de amálgama Classe I foram substituídas por restaurações adesivas. Após a confecção do preparo cavitário, as restaurações foram confeccionadas aleatoriamente, sob isolamento absoluto, utilizando os seguintes grupos (n=8): G1 - Adper Single Bond 2 + Filtek Supreme XT (XT); G2 - Adper Easy One Bond + XT; G3 - Adper Scotchbond + XT; G4 - Clearfil SE Bond + Filtek XT. A sensibilidade pós-operatória foi analisada através de escores antes da substituição (T1) (baseline), após 15 dias (T2), 12 meses (T3) e 24 meses (T4), utilizando-se estímulo frio e escala analógica de dor. A avaliação clínica das restaurações foram realizadas através de exame clínico direto em campo limpo e seco, utilizando o critério USPHS. O preenchimento da ficha de avaliação clínica (estabilidade de cor, integridade marginal, alteração de cor marginal, forma anatômica e cárie secundária) foram realizados nos tempos T2, T3 e T4, por um único avaliador. Ao final das avaliações, os dados foram agrupados e analisados estatisticamente. Ao compararmos a sensibilidade pós-operatória entre os grupos, não houve diferença estatística durante os tempos analisados e todos os grupos se comportaram de maneira semelhante quando avaliamos um único grupo durante os tempos analisamos, obtendo diferença estatística somente no T2, com relação aos demais. Com relação a avaliação clínica através do critério USPHS modificado, podemos observar que o grupo 2 apresentou a pior performance clínica com quantidades expressivas de restaurações com alteração de integridade marginal e de cor marginal, sendo 37,5% que necessitaram troca da restauração (escores Charlie). Os demais grupos se comportaram de maneira semelhante, mantendo-se em nível aceitável após 24 meses. Após a análise dos resultados, podemos concluir que o sistema adesivo autocondicionante de passo único apresentou menor longevidade das restaurações confeccionadas, se comparado aos demais sistemas utilizados, devendo ser utilizado com critério / Abstract: The aim of this in vivo study was to evaluate clinically through the USPHS criteria and postoperative sensitivity in Class I restorations restored with etch-and-rinse and self-etch adhesive system. Thirty-two Class I amalgam restorations are replaced with adhesive restorations. After the cavity preparation, the restorations were made randomly, under rubber dam, using the following groups (n = 8): G1 - 2 Single Bond + Filtek Supreme XT (XT); G2 - Adper Easy Bond + XT; G3 - Adper Scotchbond + XT; G4 - Clearfil SE Bond + XT. Postoperative sensitivity was analyzed using scores before (T1) (baseline), after 15 days (T2), 12 months (T3) and 24 months (T4), using cold stimulus and analog pain scale. The clinical evaluation of restorations were performed by USPHS criteria. The clinical evaluation (color stability, marginal integrity, marginal change color, anatomic form and secondary caries) were performed at the times T2 and T4, by a single evaluator. At the end of the assessment, data were grouped and analyzed statistically. No statistically significant difference when we compared the postoperative sensitivity between groups during the analyzed times and all groups behaved similarly when we evaluated a single group during the time, presenting statistical difference in T2 if we compared to others . The USPHS modified criteria indicated that G2 (EB+XT) had a worse clinical performance with significant amounts of exchanged restorations (37.5% requiring replacement - Charlie scores) with modification of marginal adaptation and marginal staining, . The other groups behaved similarly. The restorations were considered acceptable after 24 months. It is concluded that the one-step self-etching adhesive system showed a lower restoration longevity if compared to other systems used. The 2-step self-etch, 2-step and 3-step etch-and-rinse adhesive systems showed similar clinical results / Doutorado / Dentística / Doutora em Clínica Odontológica

La transmission acoustique de plaques et de coques est un problème présent dans de nombreuses industries, de l'automobile à l'aéronautique en passant par le génie civil. Il s'agit alors, en présence d'une source externe, de limiter le niveau de bruit à l'intérieur d'une cavité enclose par une structure vibrante, qu'il s'agisse d'une voiture, d'un avion ou d'un immeuble.Les matériaux composites sont de plus en plus largement utilisés par toutes les industries du transport, du fait de leur faible masse rapportée à leur grande rigidité. Ces caractéristiques, utiles pour réduire la consommation énergétique des véhicules, sont cependant un handicap lorsqu'il s'agit de limiter le niveau de bruit intérieur. Il est alors nécessaire d'ajouter des protections acoustiques. On s'intéresse dans ce travail à la transmission d'un bruit produit à l'extérieur de la cavité, et à des solutions antibruit passives, utilisant des matériaux poreux absorbants. Ceux-ci, mousses ou laines minérales, présentent en général de bonnes performances acoustiques pour des fréquences élevées, mais nettement mois intéressantes en basses fréquences. Ce travail s'inscrit dans le cadre d'un projet international ayant pour objectif d'étudier la réduction de bruit à travers des structures composites incluant des protections acoustiques passives. Deux axes y sont privilégiés, la modélisation et l'analyse de sensibilité. En effet, les matériaux poreux et composites présentent souvent de grandes incertitudes, dues au procédé de fabrication, à la difficulté de mesure, ou encore simplement à des choix de conception à faire. On cherche donc à s'assurer de la robustesse des solutions étudiées.Cette thèse est organisée en trois parties. La première traite de la modélisation des structures composites et des traitements poroélastiques. On s'intéresse surtout à deux types de structures, les plaques et les cylindres, pouvant dans les deux cas inclure un grand nombre de couches et de matériaux différents. La deuxième partie traite des méthodes d'analyse de sensibilité, et d'applications dans le cas de la transmission acoustique à travers des structures composites. On s'intéressera enfin dans la troisième partie à l'effet du traitement poroélastique, à travers des études numériques et expérimentales. / Acoustic transmission through plates and shells is a problem that appear in many applications, for example in the automotive or aerospace industries, or in civil engineering. The idea is to reduce the noise level inside a caivty enclosed by a vibrating structure, which may be a car, a plane or a building. Composite materials are widely used in the transportation industries due to their light weight and high mechanic resistance, but these features tend to increase the acoustic transparency of the structures, thus making it necessary to add acoustic protections for reducing noise in the enclosed cavity. The most frequently used acoustic protections take the form of layers of poroelastic materials, which are very efficient noise absorbers in high frequencies, but perform less efficiently in lower frequency ranges.This thesis is part of an international project aimed at improving the noise reduction performance of composite structures through passive sound packages. This implies the development of reduced models of acoustic transmission through such structures, and optimization studies on these models. Besides, the robustness of a solution with respect to uncertainties in the model have to be ensured. This thesis is organised in three parts, dealing with numerical modelling, sensitivity analysis for acoustic transmission and the effect of a porous treatment on sound transmission.

The increase in demand for corn ethanol has caused an increase in distiller’s dried grains with solubles (DDGS), which is a byproduct of ethanol production. DDGS is a cheap byproduct and is primarily used for livestock feed filler. DDGS contains oils and proteins from corn and in this research we showed that corn oil and proteins could be extracted with ethanol. Zein protein is the main protein in DDGS and has been shown to have good adhesive properties. This protein was used as a binder in biocomposites with the DDGS after extractions and soy protein isolate (SPI). Mechanical properties and water resistance of the composites were studied. A wood adhesive was also prepared using the zein and cellulose nano-fibrils (CNF) as the adhesive reinforcement. Rheological tests were performed to study the flow property of the adhesive. This research demonstrated the potential of DDGS to be used as a raw material for multiple value-added industrial uses.

Thin unsymmetric carbon fiber reinforced polymeric(CFRP) composite laminates are examined for use of morphing structures using piezoelectric actuation. During fabrication, unsymmetric laminates are able to deform to more than one post-cure room temperature shape. Thin cross-ply laminates will deform to a cylindrical post-cure room temperature shape while thicker non-cross-ply laminates will deform to a saddle shape. Predictions of the deformed post-cure shape will be made by modeling the cure process using analytical and numerical. These models will then serve as expectations for experimental tests. Modeling the fabrication process allowed for characterizing important data such as residual stresses from the cure process, room temperature shapes, and bi-stability of the CFRP composite laminates all of which are needed to accurately model morphing structures. Cross-ply laminates will deform to a symmetric cylindrical shape, cylindrical shape I, after the cure process. Non cross-ply laminates will deform to a non-uniform saddle shape after the cure process. These post-cure room temperature deformation shapes can be used as morphing structures by applying a force large enough to create ”snap” through to the other cylindrical shape, cylindrical shape II. A piezoelectric actuator, bonded to the deformed room temperature shapes, is used to generate this ”snap through force”. Experimental verification was done by fabricating the CFRP composite laminates and comparing the post cure room temperature shapes to the analytical and numerical fabrication models. For morphing structures, experimental verification was done by actuating the piezoelectric actuator and comparing the deformation of cylindrical shape II to analytical and numerical piezoelectric models.

No description available.

No description available.

No description available.

No description available.

Robotic accuracy has long been limited by the compliance of the manipulator. Whether links under bending loads or backlash in gear trains and stretching of belts, the resulting compliance causes a loss of accuracy at the end-effector. Previous research has investigated accuracy of ideally stiff manipulators from many different points of view; however, an overall compliant modeling technique has not been formulated in the literature. This thesis presents a general technique to develop a compliant model for a general six-degree manipulator with the intent of reducing end-effector error for precision manufacturing. Experimental and theoretical work was performed on an American Robot Merlin six-degree of freedom robot. The solution technique assumes each link of the manipulator is subject to stiffnesses in three directions, that is, in the direction of motion, laterally and torsionally. Each of the three stiffnesses is assumed constant, but unknown. Three experimental regimes were established, each covering a successively larger region of the workspace, and 243 data samples were taken within each regime. Samples were taken at twenty-seven data points under nine known loads for each of the first two regimes and at nine locations under twenty-seven loads in the third regime. An OPTOTRAK 3020 non-contact distance-measuring system was used to gather data from twelve sensors for each trial. The results were transformed into three displacements and three rotations of the end-effector. A regression algorithm solved for the unknown stiffnesses of the compliant model based on the measured experimental deflection. Results show that for loads ranging between zero and 445 N, the deflection of the end-effector is predicted within fifteen percent of experimental results for most data points. Furthermore, a load set between zero and 111 N (the stated lift capacity of the manipulator) predicts end point position with an error of less than one-half a millimeter for all tested points. This research provides a technique to quantify the compliance of a general manipulator and develops a model capable of being implemented with open-loop position control with known compliance. / Master of Science