H. Keo Springer

Mesoscale evolution of voids and microstructural changes in HMX-based explosives during heating through the β-δ phase transition

HMX-based explosives LX-10 and PBX-9501 were heated through the β-δ phase transition. Ultra-small angle x-ray scattering (USAXS) and molecular diffraction were simultaneously recorded as the HMX was heated. Mesoscale voids and structure dramatically change promptly with the β-δ phase transition, rather than with other thermal effects. Also, x-ray induced damage, observed in the USAXS, occurs more readily at elevated temperatures; as such, the dose was reduced to mitigate this effect. Optical microscopy performed during a similar heating cycle gives an indication of changes on longer length scales, while x-ray microtomography, performed before and after heating, shows the character of extensive microstructural damage resulting from the temperature cycle and solid-state phase transition.

Grain-Scale Simulation of Shock Initiation in Composite High Explosives

Many of the safety properties of solid energetic materials are related to microstructural features. The mechanisms coupling microstructural features to safety, however, are difficult to directly measure. Grain-scale simulation is a rapidly expanding area which promises to improve our understanding of energetic material safety. In this chapter, we review two approaches to grain-scale simulation. The first is multi-crystal simulations, which emphasize the role of multi-crystal interactions in determining the response of the material. The second is single-crystal simulations, which emphasize a more detailed treatment of the chemical and physical processes underlying energetic material safety.

Shock initiation experiments with ignition and growth modeling on the HMX-based explosive LX-14

Shock initiation experiments on the HMX-based explosive LX-14 were performed to obtain in-situ pressure gauge data, characterize the run-distance-to-detonation behavior, and provide a basis for Ignition and Growth reactive flow modeling. A 101 mm diameter gas gun was utilized to initiate the explosive charges with manganin piezoresistive pressure gauge packages placed between sample disks pressed to different densities (∼1.57 or ∼1.83 g/cm3 that corresponds to ∼85 or ∼99% of theoretical maximum density (TMD), respectively). The shock sensitivity was found to increase with decreasing density as expected. Ignition and Growth model parameters were derived that yielded reasonable agreement with the experimental data at both initial densities. The shock sensitivity at the tested densities will be compared to prior work published on other HMX-based formulations.