In this study, glass and Kevlar® fibers reinforced epoxy composites were manufactured and characterized using different techniques. The effect of thermal exposure on the flexural properties of the composites was investigated to ascertain its suitability for the intended application in cowling panels of light engine aircraft. Thermogravimetric analysis (TGA) was carried out on both reinforced and unreinforced epoxy resin to evaluate their thermal stability at elevated temperatures. Dynamic mechanical thermal analysis was carried out to evaluate the effects of thermal exposure, applied strain and frequency on the dynamic mechanical response of the composites. The effects of the applied resin hardener and thermal exposure on the flexural strength, flexural modulus and dynamic impact response of the composites were also investigated. The flexural properties were determined using 3-point bending test, while the impact test was carried out using Split Hopkinson Pressure Bar (SHPB). TGA analysis of the reinforced and unreinforced epoxy showed no significant weight loss until the test samples were heated above 250°C in an inert atmosphere. Dynamic Mechanical Thermal Analysis (DMTA) on the composites indicated the glass transition temperature to lie between 80 and 100°C. The results of the flexural and impact tests showed that the mechanical integrity of both glass and Kevlar® fiber reinforced epoxy composites remained unimpaired by radiative or convective heat exposure for up to 3 h until the exposure temperature exceeded 200°C. This is much higher than the service temperature of cowling panels of light engine recreational aircrafts. When the manufactured fiber reinforced epoxy composites were exposed to temperature above 200°C matrix degradation occurred, which became very significant when the exposure temperature was higher than 250°C. Extensive delamination and matrix cracking occurred when the composites were exposed to the temperature range 250°C - 300°C for 1 h. Fiber-matrix debonding was not observed in the composite except after failure under impact loading. This is evidence of the fact that the epoxy matrix was adequately wetted by both the glass and Kevlar® fibers resulting in the strong fiber/matrix interfacial bonding. While the Kevlar® reinforced epoxy displayed a better damage tolerance under flexural and impact loading, glass fiber reinforced epoxy showed higher strength but lower damage tolerance. Glass fiber reinforced epoxy also showed more resistance to damage under exposure to thermal flux than Kevlar® reinforced epoxy. Under impact loading, the Kevlar® reinforced composite failed by delamination with no fiber rupture, whereas the glass fiber reinforced epoxy failed by matrix cracking, debonding, fiber rupture and fiber pullout. The results from this research have established the effect of radiative and convective thermal exposure on the mechanical behavior of the fabricated Kevlar® fiber and glass reinforced epoxy composites. The maximum temperature reached on the inner surface of the cowling panels of a typical light engine recreational aircraft due to heat radiations from the engine block has been estimated to be about 65°C. This is lower than the glass transition temperature of the epoxy matrix as obtained from DMTA. The low temperature rise is due to inflow cooling air into the cowling chamber in flight. The results of the current investigations suggest the suitability of composite materials for the intended application. The intensity of thermal exposure, to which the materials will be exposed in such application, may not cause any significant damage to the mechanical integrity of the composite. However, since the difference between the possible exposure temperature and the glass transition temperature is only a little over 20°C, a layer of thermal insulator on the inner surface of the cowling made of fiber reinforced epoxy will be desirable to further sustain the mechanical integrity of the composites when selected for use as choice materials for cowling panels of light engine aircraft.

The production of sand can be a major issue in many young, unconsolidated sandstone formations where there is little to no cement holding the individual sand grains together. When such reservoirs are produced, quite often operators face problems with reduced well productivity and equipment failure. Because of these issues, the industry has developed numerous techniques in its effort to control formation sand production. Sand consolidation is one technology that has been studied and used since the 1940s. The theory behind sand consolidation technology is to place a liquid material which will create a grain to grain contact that will bind individual sand grains together. Most consolidation treatments contain a preflush to clean and wet the surface, the consolidating system to bind the sand grains and give residual strength, and, finally, an overflush to ensure the formation is still able to produce fluids. With the successful placement of this fluid, the sand grains will be locked in placed so that they will not be produced. The technology has gone through many phases of conception since the 1940s; however, most consolidation material that is pumped in the past has been based upon an epoxy or furan backbone. While there are many technologies available, for the purpose of my research, the epoxy technology was experimentally investigated. The testing of the fluid involved investigating numerous additives to obtain the correct residual strength of the sample, as well as the necessary retained permeability. For the epoxy fluid, the optimal preflush, epoxy system and overflush formulations were determined after 250 checkout tests. Based upon these tests, the fluid was optimized to its working time and UCS results. The optimal system included the addition of PA2 to the preflush, along with PA1 and an aromatic amine curing agent to the epoxy system. PA1 and PA2 are adhesion promoter additives which were deemed necessary as a result of the testing. This system was then tested further in a HP/HT cell. While there is still room for improvement with respect to retained permeability, the system still performs very well in terms of UCS.

RESUM Les reïnes epoxi constitueixen un dels polímers més emprats en el món de la industria, si bé presenten una sèrie d’inconvenients, els més importants dels quals són: la seva inherent fragilitat, la seva excessiva resistència tèrmica que en dificulta l’eliminació d’un substrat un cop finalitzada la seva vida útil i l’encongiment que experimenten durant el procés de curat. Per tal de reduir o eliminar aquests problemes aquesta tesi proposa l’ús de polímers hiperramificats així com polímers estrella i copolímers lineal-hiperramificat de bloc com a modificants químics de reïnes comercials. Amb aquesta estratègia s’han aconseguit millorar la tenacitat degut a efectes flexibilitzants o a separacions de fase del modificant en la matriu epoxídica, així com reduir l’encongiment en el curat o la degradabilitat de les reïnes, sense afectar altres propietats de la reïna com la seva Tg o la seva duresa. / ABSTRACT Epoxy resins are one of the most used polymers in the field of technological applications. However, they present some drawbacks being the most important the following: they are inherently brittle materials; they present excessive thermal resistance that limits their reworkability; and the shrinkage they experiment during curing. To overcome these problems this thesis proposes the use of hyperbranched polymers, as well as star polymers and lineal-hyperbranched block copolymers as chemical modifiers of commercially available epoxy resins. With this strategy tougher materials have been obtained due to either a flexibilizing effect or a phase separation of the modifier within the epoxy matrix. Moreover, the shrinkage on curing and the degradability of the thermosets have been improved without compromising other properties of the resin such as its Tg or its hardness.

Some Gulf of Mexico (GOM) wells destroyed by hurricanes have become environment and safety hazard and cannot be abandoned by conventional methods since pumping and circulating cement into the casing is impossible when the platforms have been completely destroyed and toppled. This project tested the curing properties of several epoxy resin systems in different environments. A bisphenol-F/epichlorohydrin (BPF) resin cured by curing agent MBOEA system was successfully tested in the laboratory as a potential plugging material to abandon wells destroyed in the GOM. The BPF/MBOEA resin system had the most suitable curing time in a synthetic seawater environment. The system could be successfully weighted by barite up to 16.8 ppg and cured properly. Weighting allows the resin system fall more efficiently through the casing annulus. This laboratory verification of properties will lead to field test in the test wells.

Orientador: Newton Luiz Dias Filho / Banca: Devaney Ribeiro do Carmo / Banca: Adley Forti Rubira / Resumo: Resinas epoxídicas são uma das mais importantes classes de polímeros termorrígidos usados para aplicações estruturais e como adesivos. Entretanto, os problemas em aplicações de resinas epoxídicas na engenharia incluem a baixa resistência à propagação de trincas devido a sua fragilidade. Para superar esta fragilidade, muitas vezes, dentre os aditivos em formulações multicomponentes de resinas epoxídicas, é utilizado um componente para aumentar a resistência, tais como enchimentos, oligosilsesquioxanos poliédricos (POSS), dendrímeros, etc. POSS (RSiO1,5)n podem ser incorporados em polímeros termorrígidos para melhoramento de suas propriedades térmicas e mecânicas. O uso de POSS nanoestruturados na preparação de polímeros orgânicos pode levar a materiais nanocompósitos. Neste trabalho, um POSS contendo oito grupos ésteres por molécula (MDPS) foi incorporado a uma matriz de polímeros termorrígidos epoxídicos DGEBA/TETA para melhorar suas propriedades mecânicas. Através de ensaios mecânicos foi observado um aumento de aproximadamente 90% (formulação 0,67/5) na resistência a fratura (K1C) com um leve decréscimo no modulo de Young (E). Os valores de Tg, verificados por DMTA mostraram pequeno decréscimo nas composições modificadas. As análises termogravimétricas mostraram que a adição de silsesquioxano não influenciou na estabilidade térmica do material. A cinética de cura foi analisada pelo método de Ozawa. As possíveis e prováveis causas deste significante reforço podem ser atribuídas à formação de uma segunda fase, à miscibilidade residual dos grupos ésteres com a matriz epoxídicas e às interações interfaciais entre a matriz epoxídicas e os cubos de silsesquioxanos devido as suas dimensões nanométricas. / Abstract: Epoxy resins are one of the most important classes of thermosetting polymers used for structural and adhesive applications. However, the current problems in engineering applications of epoxy thermosets include the poor resistance to the crack propagation because they are brittle. To overcome brittleness, among other additives of the multicomponented formulation of the epoxy resin, a toughening agent is often used, such as fillers, polyhedral oligosilsesquioxanes (POSS), dendrimers, etc. POSS, (RSiO1.5)n, can be incorporated into thermosetting polymers to improve their thermal and mechanical properties. The use of such nanosized POSS in the preparation of an organic polymer can lead to a nanocomposite materials. In this work, a POSS containing eight ester groups per molecule (MDPS) was incorporated to an epoxy matrix of DGEBA/TETA thermosetting polymers to improve their mechanical properties. Through the mechanical tests an increase of about 90% (formulation 0,67/5) was observed in the fracture toughness (K1C) with a little decreasing in the module of Young (E). The Tg values verified by DMTA showed smaller values for the compositions with the modifier. The thermogravimetric analyses showed that the addition of the silsesquioxane ester did not influence on the thermal stability of the material. The cure kinetics was analyzed by Ozawa's method. The probable and possible causes of this significant reinforcement can be attributed to the formation of a second inorganic phase, residual miscibility of the ester groups with the epoxy matrix and to interfacial interactions between the epoxy matrix and silsesquioxanes cubes due their nanometric dimensions. / Mestre

The epoxy resin mixture is used for wet filament winding load carrying and electrically insulating tubes for high voltage applications. The cured tubes are key parts of the final products which are subject to qualification. The safe function of the products generally depends on low moisture content. Visual inspection is also an important part of the quality inspection which requires some degree of transparency of the cured tubes. To prepare for future material modifications ABB wishes to evaluate the curing characteristics of some recently developed epoxy/hardener systems. The epoxy resin with the formulation E1/H1 is used as reference. Another type of base epoxy resin E2 and toughened epoxy resin E1 (E1T) are included in the study. Three alternative hardeners H2, H3, and H4 were evaluated. This project is to evaluate different alternative epoxy resin formulations that are promising to be used in the ABB products in the future. These alternative epoxy resin formulations and the reference epoxy resin with the formation E1/H1 were prepared to be compared and evaluated in terms of thermal properties, i.e., glass temperature (Tg), the heat of curing and color of cured epoxy resins. The epoxy resins with alternative formulations which shown relative high Tg values were selected to carry out other analysis, ie., mixing ration optimization, the influence of dissolved water on Tg values, degree of curing and water absorption behavior.

¡uStructure Reinforcement¡v is necessary when the load of a building or bridge has exceeded that for which it was originally designed. Reinforcement is required when there are changes in the function of a building, poor or incorrect design, flood or earthquake damage, revision of government regulations resulting in new specifications for construction materials, or changes in job practices. The concept of structure reinforcement developed in Japan in the 1970¡¦s, and was introduced into Taiwan at the end of the decade. Short operating times, high strength, and economy of space are among the advantages which make the concept attractive. Higher cost, however, has slowed its implementation. The current ratio of new to reinforced construction in developing countries is 6:4; in developed countries 4:6. As Taiwan is now considered a developed country lacking land resources but with strict building regulations, structure reinforcement is more and more in demand. China, on the other hand, is still ranked a developing country, but, due to the current construction boom and weak infrastructure, recent structures often need reinforcement. During the design and calculation of structure reinforcement, the usual choice of reinforcing materials is epoxy resin, special cement, carbon fiber sheets, and carbon steel plates. SB Construction is a medium sized company subject to the natural rise and fall in construction demand. In the past, SB used only special cement as reinforcement material as it had no production line for epoxy resin or carbon fiber steel. This report concerns itself mainly with how, from a business angle, environment analysis and internal management ability can establish a competitive advantage adapted to its own business model and how to evaluate the effectiveness of this strategy. Section One: background and motivation for research, purpose and structure. Section Two: research design, discussion of theory, method and procedures. Section Three: industry analysis, development of structure reinforcement, analysis and comparison of Taiwan and China, and analysis of superior products. Section Four: case study, introduction to the company, changes in strategy, expectations and goals. Last: conclusion and suggestions for adapting to changes in the environment, discussion of strategies for future consideration and further development.

The partial discharges (PD) measurement approach in power equipments is a very important inspection technique for insulation deterioration assessment. The PD based approach possesses the greatest potential for further development. This study proposes a noncontact type acoustic measurement system. We first investigate an acoustic measurement method in the laboratory. To prove the accuracy of the acoustic measurements, we proceed with, in the laboratory, signal-pattern comparison between the acoustic measurement method and the pulse current method. This study creates polar-coordinate and discharge type identification patterns. We propose the use of the q-£p-t patterns, the polar-coordinate patterns and discharge type identification patterns, with mutual cross-reference, to identify the discharge type. Then this study applies the wavelet transform to suppress noises; a wavelet mother function most similar to the acoustic PD signals is chosen and then set the filtering threshold value for the wavelet transform. The signals' features will be extracted after the noises are eliminated. The experimental results indicate that the application of wavelet transform can effectively eliminate the field noises. Next, the features will be used to build the training database for the back-propagation neural network (BNN) to construct the discharge patterns' recognition and identification system. Finally, we apply the finished neural networks to field signal-pattern identification. The proposed acoustic measurement system is applied on line to epoxy-resin transformers, power distributors, and the like. The superior measurement results we obtained shall be able to correctly identify power equipment's PD fault types.

abstract: Polymer and polymer matrix composites (PMCs) materials are being used extensively in different civil and mechanical engineering applications. The behavior of the epoxy resin polymers under different types of loading conditions has to be understood before the mechanical behavior of Polymer Matrix Composites (PMCs) can be accurately predicted. In many structural applications, PMC structures are subjected to large flexural loadings, examples include repair of structures against earthquake and engine fan cases. Therefore it is important to characterize and model the flexural mechanical behavior of epoxy resin materials. In this thesis, a comprehensive research effort was undertaken combining experiments and theoretical modeling to investigate the mechanical behavior of epoxy resins subject to different loading conditions. Epoxy resin E 863 was tested at different strain rates. Samples with dog-bone geometry were used in the tension tests. Small sized cubic, prismatic, and cylindrical samples were used in compression tests. Flexural tests were conducted on samples with different sizes and loading conditions. Strains were measured using the digital image correlation (DIC) technique, extensometers, strain gauges, and actuators. Effects of triaxiality state of stress were studied. Cubic, prismatic, and cylindrical compression samples undergo stress drop at yield, but it was found that only cubic samples experience strain hardening before failure. Characteristic points of tensile and compressive stress strain relation and load deflection curve in flexure were measured and their variations with strain rate studied. Two different stress strain models were used to investigate the effect of out-of-plane loading on the uniaxial stress strain response of the epoxy resin material. The first model is a strain softening with plastic flow for tension and compression. The influence of softening localization on material behavior was investigated using the DIC system. It was found that compression plastic flow has negligible influence on flexural behavior in epoxy resins, which are stronger in pre-peak and post-peak softening in compression than in tension. The second model was a piecewise-linear stress strain curve simplified in the post-peak response. Beams and plates with different boundary conditions were tested and analytically studied. The flexural over-strength factor for epoxy resin polymeric materials were also evaluated. / Dissertation/Thesis / Ph.D. Mechanical Engineering 2011

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-08-10Bitstream added on 2014-06-13T20:33:16Z : No. of bitstreams: 1 pereira_ds_me_ilha.pdf: 5937510 bytes, checksum: c32d623d3e0fbcd57127c9f447e87b2e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Resinas epoxídicas são uma das mais importantes classes de polímeros termorrígidos usados para aplicações estruturais e como adesivos. Entretanto, os problemas em aplicações de resinas epoxídicas na engenharia incluem a baixa resistência à propagação de trincas devido a sua fragilidade. Para superar esta fragilidade, muitas vezes, dentre os aditivos em formulações multicomponentes de resinas epoxídicas, é utilizado um componente para aumentar a resistência, tais como enchimentos, oligosilsesquioxanos poliédricos (POSS), dendrímeros, etc. POSS (RSiO1,5)n podem ser incorporados em polímeros termorrígidos para melhoramento de suas propriedades térmicas e mecânicas. O uso de POSS nanoestruturados na preparação de polímeros orgânicos pode levar a materiais nanocompósitos. Neste trabalho, um POSS contendo oito grupos ésteres por molécula (MDPS) foi incorporado a uma matriz de polímeros termorrígidos epoxídicos DGEBA/TETA para melhorar suas propriedades mecânicas. Através de ensaios mecânicos foi observado um aumento de aproximadamente 90% (formulação 0,67/5) na resistência a fratura (K1C) com um leve decréscimo no modulo de Young (E). Os valores de Tg, verificados por DMTA mostraram pequeno decréscimo nas composições modificadas. As análises termogravimétricas mostraram que a adição de silsesquioxano não influenciou na estabilidade térmica do material. A cinética de cura foi analisada pelo método de Ozawa. As possíveis e prováveis causas deste significante reforço podem ser atribuídas à formação de uma segunda fase, à miscibilidade residual dos grupos ésteres com a matriz epoxídicas e às interações interfaciais entre a matriz epoxídicas e os cubos de silsesquioxanos devido as suas dimensões nanométricas. / Epoxy resins are one of the most important classes of thermosetting polymers used for structural and adhesive applications. However, the current problems in engineering applications of epoxy thermosets include the poor resistance to the crack propagation because they are brittle. To overcome brittleness, among other additives of the multicomponented formulation of the epoxy resin, a toughening agent is often used, such as fillers, polyhedral oligosilsesquioxanes (POSS), dendrimers, etc. POSS, (RSiO1.5)n, can be incorporated into thermosetting polymers to improve their thermal and mechanical properties. The use of such nanosized POSS in the preparation of an organic polymer can lead to a nanocomposite materials. In this work, a POSS containing eight ester groups per molecule (MDPS) was incorporated to an epoxy matrix of DGEBA/TETA thermosetting polymers to improve their mechanical properties. Through the mechanical tests an increase of about 90% (formulation 0,67/5) was observed in the fracture toughness (K1C) with a little decreasing in the module of Young (E). The Tg values verified by DMTA showed smaller values for the compositions with the modifier. The thermogravimetric analyses showed that the addition of the silsesquioxane ester did not influence on the thermal stability of the material. The cure kinetics was analyzed by Ozawa's method. The probable and possible causes of this significant reinforcement can be attributed to the formation of a second inorganic phase, residual miscibility of the ester groups with the epoxy matrix and to interfacial interactions between the epoxy matrix and silsesquioxanes cubes due their nanometric dimensions.