Microstructural effects on the ignition behavior of HMX

The detonation physics community has embraced the idea that initiation of high explosives proceeds from an ignition event through subsequent growth to steady detonation. A weakness of all the commonly used ignition and growth models is that microstructural characteristics are not explicitly incorporated in their ignition and terms. This is the case in spite of a demonstrated, but not well-understood, empirical link between morphology and initiation of energetic materials. Morphological effects have been parametrically studied in many ways, with the majority of efforts focused on establishing a tie between bulk powder metrics and ignition of the pressed beds. More recently, there has been a shift toward characterizing the microstructure of pressed beds in order to understand the underlying mechanisms governing behavior. We have assessed the utility of using a modified James' model as a tool to quantify effects of bed microstructure on ignition behavior. Using this construct, we have studied the ignition behavior of two types of HMX materials in an attempt to quantify effects of microstructure (i.e. mesoscale features) on continuum level ignition behavior. Microstructures of the two HMX materials were characterized using ion bombardment cross sectioning techniques that expose the microstructure of pellets studied in the ignition experiments.