Lot Dependence of HMX and TATB formulations in the Los Alamos Gapstick Test

Gapstick is a very sensitive and accurate shock-initiation characterization test, which is useful for HE formulation development, Reactive Flow Model calibration, and HE surveillance. Gapstick alternates HE segments with inert Kynar (PVDF) gaps of gradually increasing in thickness in a rate stick configuration. Piezo-electric gauges capture shock arrival at each HE-inert interface as the detonation travels along the stick. A thickness effect curve is generated with gap thickness(δ) vs average wave speed (V), upon which detonation fails at a critical gap thickness. We present data for HMX formulations prepared with varying HMX types and mixing methods with equal density/porosity but different porous microstructures measured by ultra-small angle X-ray scattering. We found that the measured void size distributions were distinct, and that the mean void diameter correlated with the failure thickness. We present new data for two formulated TATB material lots and illustrate that, like ECOT, Gapstick can detect lot dependence of failure thickness.

LA-UR-25-21077