Semester

Summer

Date of Graduation

2010

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Darran Cairns

Abstract

Aerogel materials are of significant interest to numerous applications in many areas of engineering such as oil, gas, aerospace, military, construction, building and apparel because they offer insulating properties that outperform traditional materials by a factor ranging from 2 to 8. Although an aerogel can be manufactured in a clamshell, sleeve or sheet shapes, the most versatile form is a blanket. Aerogel blankets are composites of silica aerogel particles dispersed in a reinforcing fiber matrix that turns the brittle aerogel into a durable and flexible insulating mat.;While aerogel blankets exhibit excellent thermal properties, they are still some concerns over dust mitigation when the blankets are flexed and deformed. The generation of dust is important because it can lead to a degradation of the insulating properties and is not ideal for the work environment during installation for some applications during subsequent uses. In this study, various experimental investigations such as thermal analysis, three-point bending tests and tensile tests have been performed to characterize the thermal insulation properties and degradation level of several commercially-available flexible aerogel blanket materials. The results are reported and discussed in this study. The microstructure of these aerogel blankets are also investigated for better understanding of the failure process. Knowledge of the thermal and mechanical properties are important for the optimization of the design for these heteregeneous materials.;Usage of insulating aerogel blankets in thermal protection systems and heat-sensitive environments, such as infrared suppression around engine and hot components applications, leads to accurate predictions of their thermal properties such as their effective thermal conductivity in such applications. As part of this study, simple theoretical and numerical models have been developed to predict the effective thermal conductivity of flexible aerogel blankets, which consist of fibers, aerogel particles and air-pockets. The theoretical models are thermal conductivity models as a function of aerogel, air-pocket and fiber volume fractions. In the numerical study, the effective thermal conductivity of the aerogel composites is computed with different aerogel particles to fiber volume ratios using the finite element method. The numerical analysis of thermal conductivity is conducted by generating 3D models of the microstructure of the aerogel blanket.;Interesting predictions concerning the effects of air-pocket and aerogel particles volume fractions are observed. For low aerogel particles content (less than 10%), the results of the theoretical and the numerical models show good agreement but discrepancies are observed at high aerogel particles content.

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