Date of Award

2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Advisor

Frederic Sansoz

Abstract

Flexible thermal protection materials made from two-dimensional woven ceramics fibers are of significant interest for hypersonic inflatable aerodynamic decelerators being developed by NASA for future missions on Mars and other planets. A key component of the thermal shield is a heat-resistant outer ceramic fabric that must withstand harsh aero-thermal atmospheric entry conditions. However, a predictive understanding of heat conduction processes in complex woven-fiber ceramic materials under deformation is currently lacking. This dissertation presents a combined experimental and computational study of thermal conductivity in alumina-based Nextel-440 and silicon carbide Hi-Nicalon 5-harness-satin woven fabrics, using the hot-disk transient plane source method and computational multiscale thermo-mechanical modeling by finite-element analysis. The objective is to create a physics-based model for the anisotropic heat conduction in flexible two-dimensional ceramic materials and quantify and understand the effect of deformation and gas pressure over the out-of-plane thermal conductivity. We find, both experimentally and theoretically, that thermal conductivity of woven fabrics rises in both in-plane and out-of-plane directions, as the transverse load increases. Air gap conduction is shown to play a major role in the insulation capabilities of these materials. The proposed modeling methodology accurately captures the experimental heat conduction results and should be applicable to more complex loading conditions and different woven fabric materials, relevant to extreme high temperature environments.

Language

en

Number of Pages

120 p.

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