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Title: Initiation and growth of reaction in LLM-105
Author: French, Sara
ISNI:       0000 0004 7961 8371
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2019
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The aim of the research conducted in this thesis was to understand the behaviour of LLM-105, a new explosive material, when subjected to impact. Explosive reactivity under impact can be thought of in terms of safety (sensitiveness) and response to shock loading (sensitivity). The experimental work presented addresses both regimes, using hot-spot theory to support the observations made. The literature review discusses material properties that contribute to changes in sensitivity. This motivated modification of LLM-105 to provide different particle sizes and morphologies for assessment and comparison with other explosives. Impact sensitiveness is of particular interest for LLM-105 as there are some discrepancies in the literature data, owing to different methods being used to assess it in different countries and laboratories. Improved methods for characterising impact sensitiveness had to be developed in order to fully evaluate the LLM-105, enhancing a glass anvil drop-weight technique with multiple diagnostics, including high speed camera, mass spectrometer, photodiode and microphone. This equipment provided an ideal research tool for simultaneously assessing the reaction outputs of an explosive, and highlighted limitations of standard techniques used by industry. The characteristics of pristine and modified LLM-105 were evaluated using the drop-weight. It was found that particle size influenced reactive response, though presence of defects had a greater effect on initiation sensitiveness. Also, reaction growth was more strongly related to the particle shape and overall bulk density of the material, likely to be linked to packing efficiency of the particles. It was also found that LLM-105 was more sensitive to impact in general than previously thought, when compared to explosives such as HMX and TATB. The final chapter of this thesis examines LLM-105 behaviour under shock loading. LLM-105 was formulated with a fluoropolymer binder and detonated under a one dimensional shock regime with in-material gauge analysis. Data was acquired for two new LLM-105 formulations with respect to detonation velocity and growth of reaction within the explosive. The results showed that fine particle size LLM-105 has a shorter run distance to detonation than coarse, which is likely caused by the number of potential hot-spot sites available in voids within the pressed formulation.
Supervisor: Jardine, Andrew Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: impact sensitiveness ; shock sensitivity ; LLM-105 ; particle size