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THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Thursday, September 22, 2016
10:30 AM
in Love 295
will be held the
DISSERTATION PROPOSAL DEFENSE
for
David Scripka
“Multilayer Optical Structures for Time-Resolved Meso-Scale Sensing of Shock Compression in Heterogeneous Materials”
Committee Members:
Prof. Naresh Thadhani, Advisor, MSE
Prof. Christopher Summers, MSE
Prof. Seung Soon Jang, MSE
Dr. Zhitao Kang, GTRI
Dr. Keo Springer, Lawrence Livermore National Laboratory
Abstract:
Heterogeneous materials are present in many different engineering, scientific, and industrial applications. Examples range from geologic materials such as soils and rock, to composites such as laminates or energetic particulate compacts. These materials often have complex mechanical behaviors due to their microstructural complexity, and many descriptive and predictive models fail to capture the meso-scale mechanisms that drive macroscopic responses to mechanical loads. This issue is particularly challenging for dynamic loads such as shock compression, where key meso-scale interactions operate on timescales of microseconds to nanoseconds. Consequently, there is a limited understanding of shock responses in many important heterogeneous material systems, and meso-scale models and theories remain largely unvalidated by experimental data. To address this critical knowledge gap, advanced experimental diagnostics that can accurately measure meso-scale material states during shock loading are needed.
The proposed research involves the design and testing of multilayer optical structures, a class of 1-dimensional photonic crystals. These structures have unique optical signatures, which are inherently linked to the physical state of the multilayer. By observing shock loading induced changes in the spectral response of the multilayers, a optically-based pressure sensor can be produced. Unlike other commonly utilized pressure sensors, the multilayers have the potential for significant spatial sensitivity, as localized changes in multilayer physical states will produce corresponding changes in localized spectral responses. Such spectral responses, under both homogeneous and heterogenous shock compression loads, will be investigated using laser-driven shock loading and time-resolved spectroscopy enabled by a spectrograph-coupled streak camera. Concurrently, opto-mechanical simulations utilizing a custom multi-physics framework will be performed, comparing the predictions of theoretical opto-mechanical models to experimental observations. Initial experimental results indicate that the multilayers exhibit a highly time-resolved spectral response to shock compression. Additionally, a spatially-resolved spectral response in a multilayer under a heterogeneous shock load has been successfully demonstrated.
The objective of this research is to establish the potential of multilayer optical structures as time-resolved meso-scale diagnostics through controlled experiments, model development, and simulations. The significance of the proposed work is the development of a new, advanced diagnostic method that can provide insight into the complex shock response of heterogeneous materials.
