From a single grain to microstructure: How explosive grains interact under shock compression

This dissertation seeks to develop shock compression experiments that are sensitive to microstructural features in plastic explosives. Plastic explosives, or PBXs, are mixtures of high-explosive grains packed together and suspended in polymer binders. These experiments target phenomena occurring on the micron-scale and nanosecond to microsecond time regime, known as the mesoscale. At this scale, shock waves interact with microstructural defects in plastic explosives, producing pockets of heat which can initiate deflagration but remain hard to simulate. The experiments in this work will use shock compression as a tool to pump plastic explosive mixtures with high-temperature hot spots and optically probe the deflagration progress. The future goal is for these experiments to be used by simulations of shock to detonation or shock to deflagration transitions. Compact laser-driven flyer plates will be used on to produce shock to deflagration experiments on many of different PBX compositions. Laser-driven flyer plate production is small scale (sub-mm) and high throughput compared to other shock compression methods. Because of these traits, many different solid explosives with different internal structures can be tested to better understand how the microstructure of a PBX changes the fate of a shock wave interacting with it. This will enrich discussions about the resistance against accidental detonations and inform engineering efforts such as machine learning workflows to predict the performance of specific solid explosive mixtures. First, the introductory principles of shock-to-detonation chemistry will be introduced, including shock waves, basic detonation theory and current understanding of how structured materials create hot spots. Then, this work will explore methods of measuring and quantifying shock-to-deflagration at different time steps within in a lab setting, and the third and fourth chapter will discuss methods to prepare high explosives and measure their internal structure. The chapters proceeding this put these concepts together to tell different stories of how a pocket of energy inside a bomb spread through different structures. The final discussion will be directly measuring shock waves as an initial shock transitions into a full detonation within plastic explosives. Put together, micron-sized defects inside of a plastic bomb interact with shock waves to form pockets of energy which spread inside a bomb to make an explosion; this dissertation will describe that journey. The research described in this study is based on work at the University of Illinois, currently supported by the US Air Force Office of Scientific Research under awards FA9550-19-1-0027 and FA9550-19-1-0318, and the US Army Research Office under award W911NF-19-2-0037. Characterization of materials was carried out in part in the Materials Research Laboratory Central Research Facilities, University of Illinois.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Salvati III, Lawrence

Contributors dc:contributor

• Dlott, Dana D
• Makri, Nancy
• Jain, Prashant K
• Jackson, Nick

• Shock Compression
• Deflagration
• Energetic Materials
• Polymer Bonded Explosives
• Pbx
• Plastic Explosives
• Detonation
• Microscopy
• Emission Pyrometry

Statement dc:rights

• Copyright 2023 Lawrence Salvati III

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/120229

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F120229