Electronic Theses and Dissertations

Identifier

6240

Date

2018

Document Type

Thesis

Degree Name

Master of Science

Major

Physics

Concentration

Materials Science

Committee Chair

Firouzeh Sabri

Committee Member

Jingbiao Cui

Committee Member

Xiao Shen

Committee Member

Steven Allison

Abstract

Detecting structural damage in a material before complete failure has been a challenge with respect to material access, sensing mechanism resolution, and environmental setting, among other factors. In this work, the feasibility of using thermographic phosphors as a non-contact, instantaneous, and customizable sensing mechanism for detection of structural damage was investigated. The two materials were (1) Sylgard 184 elastomer and (2) silica aerogels. Both materials were impregnated with thermographic phosphors using different methods and tested over a wide range of temperatures. The degree of fracture in either material was gradually increased to represent a complete material failure scenario and a gradual propagation of defect that has not yet led to ultimate failure. The aerogel synthesis methodology was optimized for phosphor application so that either a discrete layer of phosphor would be embedded or a homogeneous mix was created and phoshpor was distributed uniformly throughout the material. The discreteness of the phosphor layer was identified by two distinct points representing the entrance and exit points of the excitation and emission beams. The composite materials (homogeneous and otherwise) were fully characterized, and the sensitivity of the remote, non-contact sensing was evaluated. It was determined that fracture and failure in both aerogel and PDMS could be detected by phosphor thermometry and the limit of its resolution was ultimately determined by the thermal properties of the material, the choice of phosphors, and ambient temperature. In conclusion, thermogrpahic phosphor powders were successfully incorporated at discrete levels and superficially in aerogels and in PDMS materials and as a result can be used as means to interrogate the bulk of the material. Phosphor thermometry proved to be a viable option for remotely identifying structural defects in these two materials, with limitations. The changes in the thermal profile of the materials as a result of material defects were used to infer information about the structural health of the matierla.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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