Doctoral Dissertations

Zhongzhi Tang

Abstract

"The principal objective of this research is to advance our understanding of how glass breaks. Glass, a material well known for its brittleness, has been used widely but within a frustrating limit of its strength. Generally, strength is not considered as an intrinsic property of glass, due to the difficulty of avoiding the presence of flaws on the sample surface. The fiber drawing system and two-point bending (TPB) equipment developed at Missouri S&T allow the fabrication of pristine glass fibers and failure strain measurements while minimizing the effects of strength limiting critical flaws. Several conditions affect the failure behavior of glasses, including glass composition, thermal history of melts and environmental conditions during the failure tests. Understanding how these conditions affect failure helps us understand how glass fails. In this dissertation, failure strains for many different silicate and borate glasses were measured under a variety of experimental conditions. Failure stresses for various silicate glasses were calculated using values of the nonlinear elastic moduli reported in the literature. Inert intrinsic strengths for alkali silicate glasses were related to the structure and corresponding bond strengths, and the dependence of the inert strengths on faceplate velocity is discussed. Inert failure strains were also obtained for sodium borate glasses. Up to ~40% failure strain was measured for vitreous B₂O₃. The addition of soda to boron oxide increases the dimensionality and connectivity of the glass structure and hence increases its resistance to deformation, as was observed in elasticity and brittleness measurements reported in the literature. The increase in deformation resistance produces lower failure strains, a behavior also seen for alkali silicate and aluminosilicate glasses where the reduction of non-bridging oxygen increases the structure stiffness and leads to lower inert failure strain. Fatigue effects on silicate glasses were studied by measuring the failure strains in water at different temperatures and at different loading rates, and in air with a range of relative humidities. The dominant fatigue reaction for cross-linked network glasses is bond hydrolysis, whereas for alkali modified depolymerized glasses is ion-exchange reaction between alkali ions and water species. The fatigue mechanism difference results in the difference in the humidity sensitivity of the reaction rate. The dominant fatigue reaction also changes at around 50% relative humidity"--Abstract, page iv.

Advisor(s)

Brow, Richard K.

Committee Member(s)

Hilmas, Greg
Huebner, Wayne
Day, D. E.
Dharani, Lokeswarappa R.

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Sponsor(s)

Mo-Sci Corporation
National Science Foundation (U.S.)
United States. Department of Energy

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2011

Journal article titles appearing in thesis/dissertation

  • Two-point bend measurements of failure stress of pristine glass fibers
  • Inert failure strain measurements of sodium borate glass fibers
  • Two-point bend studies of fatigue effects in silicate glasses
  • Environmental fatigue of silicate glasses in humid conditions

Pagination

xvi, 181 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2011 Zhongzhi Tang, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Fibrous composites -- TestingGlass -- FatigueGlass -- FractureGlass -- Mechanical propertiesGlass fibers -- TestingStrains and stresses

Thesis Number

T 9905

Print OCLC #

794777223

Electronic OCLC #

763338508

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