Date of Award

12-1-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Aeronautics and Astronautics

First Advisor

Carl Hartsfield, PhD

Abstract

Carbon nanotube materials are promising multifunctional materials for incorporation into aerospace structures because of their high tensile strength, high electrical conductivity, and low density. This research aimed to characterize the mechanical failure mechanisms of carbon nanotube fibers and examine the effects of the space environment on their material properties. Tensile tests were conducted at varying strain rates and on fibers of varying gage lengths to examine the underlying molecular failure mechanisms and impact of defects on fiber strength. Tensile strength and elastic modulus were observed to increase with increasing strain rate and decrease with increasing gage lengths. The observed effects were similar to those observed for polymeric fiver materials. Atomic oxygen exposure was found to severely degrade the tensile strength and electrical conductivity of CNT yarns after an exposure equivalent to one year in Low Earth Orbit. Intense ultraviolet radiation did not significantly impact the mechanical or electrical properties of the fibers after an exposure equivalent to 3 years in Low Earth Orbit.

AFIT Designator

AFIT-ENY-DS-18-D-036

DTIC Accession Number

AD1067789

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