Browsing by Subject "epoxy"
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Item An Experimental Setup to Study the Settling Behavior of Epoxy Based Fluids(2012-07-16) El-Mallawany, Ibrahim IsmailThis thesis is part of a project funded by the Minerals Management Service (MMS) (now Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE)) to study the use of epoxy to plug hurricane damaged wells. Some of the wells destroyed by hurricanes are damaged to an extent that vertical intervention from the original wellhead is not possible. These wells have to be plugged to prevent future flows through the well to protect the environment. Cement is usually the preferred plugging material because it is very cheap compared to other materials like epoxy. However, cement can easily get contaminated by sea water or brines present in wells as completion fluids. Therefore, to be able to use cement it has to be placed at the bottom of the well by drilling an offset well all the way to the bottom of the original well. Epoxy, on the other hand, being much more chemically stable can be placed at the very top of the well and let to settle by gravity without fearing contamination. Therefore, in wells described above, epoxy can be much more economical than cement. Placing epoxy at the top of a well and letting it settle by gravity can also be more economical than using cement in other situations such as in a leaking annulus of a well where circulation in that annulus is not possible, or if a well that has been previously plugged starts leaking again after the rig has been removed. Placing epoxy in the manner described can be achieved without using a rig and therefore, would be much more economical than cement. One of the most important factors in this process is to be able to predict the settling velocity of the epoxy to be able to determine the required setting time of the epoxy so that the epoxy does not set prematurely. In addition, it is important to evaluate whether the epoxy can successfully settle to the bottom and how much of it will adhere to the pipe walls while freefalling. This thesis aims to design, build and run an experimental setup that would help study the settling velocity of epoxy. Some experiments were conducted to assess the effect of different parameters that might affect the settling velocity of the epoxy such as the epoxy?s density, the annulus size and the inclination angle. The results show that the settling velocity was proportional to the epoxy?s density. Also the settling speed was almost double in experiments done at an angle compared to experiments done at vertical position. The annulus size did not have any clear effect on the settling speed. The adhesion to the pipe walls was found to be proportional to the epoxy?s viscosity and angle of inclination and was inversely proportional to the annulus size.Item Modeling Time-dependent Responses of Piezoelectric Fiber Composite(2011-02-22) Li, Kuo-AnThe existence of polymer constituent in piezoelectric fiber composites (PFCs) could lead to significant viscoelastic behaviors, affecting overall performance of PFCs. High mechanical and electrical stimuli often generate significant amount of heat, increasing temperatures of the PFCs. At elevated temperatures, most materials, especially polymers show pronounced time-dependent behaviors. Predicting time-dependent responses of the PFCs becomes important to improve reliability in using PFCs. We study overall performance of PFCs having unidirectional piezoceramic fibers, such as PZT fibers, dispersed in viscoelastic polymer matrix. Two types of PFCs are studied, which are active fiber composites (AFCs) and macro fiber composites (MFCs). AFCs and MFCs consist of unidirectional PZT fibers dispersed in epoxy placed between two interdigitated electrode and kapton layers. The AFCs have a circular fiber cross-section while the MFCs have a square fiber cross-section. Finite element (FE) models of representative volume elements (RVEs) of active PFCs, having square and circular fiber cross-sections, are generated for composites with 20, 40, and 60 percent fiber contents. Two FE micromechanical models having one fiber embedded in epoxy matrix and five fibers placed in epoxy matrix are considered. A continuum 3D piezoelectric element in ABAQUS FE is used. A general time-integral function is applied for the mechanical, electrical, and piezoelectric properties in order to incorporate the time-dependent effect and histories of loadings. The effective properties of PZT-5A/epoxy and PZT-7A/LaRC-SI piezocomposites determined from the FE micromechanical models are compared to available experimental data and analytical solutions in the literature. Furthermore, the effect of viscoelastic behaviors of the LaRC-SI matrix at an elevated temperature on the overall electro-mechanical and piezoelectric constants are examined.Item Thermal protection of high temperature polymer-material-carbon fiber composites(Texas A&M University, 2006-04-12) O'Neal, Justin EarlTwo evaporative-cooling materials were studied which are (i) salt hydrates and (ii) polyacrylic acid for the purpose showing proof of concept of being able to put evaporative-cooling materials into a composite with the Air Force polyimide AFR-PEPAN. The salt hydrates were observed to absorb water and then evaporate water, but due to having a collapsible lattice, made them incapable of reabsorbing water. Polyacrylic acid was mixed into an epoxy sheet at polacrylic acid weight percentages of 5, 10, 12.5. For each weight percentage there was a hydrated epoxy specimen and a dry epoxy specimen. All specimens were individually shot with a hot air stream (temperature approximately 1300C). Temperature readings were taken for each sheet. The hydrated specimen exhibited greater evaporative cooling over its dry counterpart. 12.5 wt% was shown to have the best evaporative cooling mechanism. Experiments were repeated to show that the polyacrylic could reabsorb water. This study illustrates proof of concept utilizing polyacrylic acid as an evaporative cooling material.