Date of Award:

5-2016

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Mechanical and Aerospace Engineering

Committee Chair(s)

Heng Ban, Christ Glorieux

Committee

Heng Ban

Committee

Christ Glorieux

Committee

Randolph V. Lewis

Committee

Michael Wübbenhorst

Committee

Nicholas Roberts

Committee

Carmen Bartic

Committee

Thomas Fronk

Abstract

Thin fibers are prevalent in many engineering materials. Measuring how well heat transfers in such small fibers can be difficult to determine, and previous methods have led to erroneous results. This dissertation details three proposed methods to improve the measurement of the thermal conductivity, thermal diffusivity, and volumetric heat capacity of thin fibers. Of particular interest is natural and synthetic spider silks because previously published values of the natural silk thermal conductivity was similar to copper, an excellent thermal conductor.

The three methods developed are the improved transient electrothermal technique (which was redeveloped to include radiation and convection heat losses and improve accuracy), the 3ω technique (where alternating the power into the fiber allows for a stronger signal to be measured and being able to directly measure all the thermal properties of interest), and the non-contact, photothermal, quantum-dot spectral shape-based fluorescence thermometry method (which takes advantage of the temperature dependent light produced by quantum dots when exposed to laser light).

The results with these methods are that spider silk, while having excellent mechanical properties such as strength and toughness, is not a remarkable thermal conductor. However, the ability to produce synthetic silks with variable properties and the stability and strength of the silk has the potential (with further development) as lightweight, insulative supports in cryogenic systems.

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