Using Rock Sugar Crystals as a Surrogate Material for HE Crushing, Diagnosed by Micro-Computed-Tomography*

The detonation properties of PBXs depend on both the bulk void fraction, and the manner in which voids are distributed. The latter depends on how HE crystals crush up and, for a PBX, how the binder flows. Thus, if we would engineer void structure in pressed pieces, then we must understand the complex transformation that occurs during the pressing process. Most explosives are brittle and closely resemble sucrose in their mechanical properties. For this reason, table sugar has often been used as a mechanical mock. Here we crush a good-quality rock sugar, and diagnose its damage structure via micro-Computed-Tomography (CT). A large grain size is used to enable study of crushing over many generations before spatial resolution is compromised. About 50 grains are crushed, in nine discrete increments, in a test cell optimized for the purpose. CT scans are performed following each increment, on material that is stationary in the frame of the cell. Rock sugar will also be pressed in a traditional die-punch setup to similar levels of compaction and particle size distribution measured with a Camsizer X-2. In addition to observation of qualitative features; we’ll pass the starting structure on to the CartaBlanca++ code, so as to quantitatively compare experiments and computations—the primary question being, what type of constitutive models produce the most realistic crushing behavior?