Live decomposition imaging of HMX/HTPB based formulations during cook-off in the dual window test vehicle

Thin, cylindrical samples of HMX/HTPB formulations with solids loadings from 85-95% by mass have been heated at 1°C and 10°C minute until a reaction occurred in the new dual window cook-off test vehicle. The test vehicle has captured the response of these formulations, and shown the influence of variables such as confinement, heating rate and sample size. Live imaging of the heated samples revealed that, as with pure nitramine samples, three distinct stages of change take place during heating; phase changes, melting and slow, flameless decomposition with production of gaseous intermediates and finally burning with a luminous flame of the gaseous intermediates. In addition, the binder appears to undergo decomposition before the HMX, darkening along the edge closest to the thermal input before the HMX melts. No apparent volume change has been detected during the beta-delta phase change in HMX, however this could be due to the low-density hand pressed samples, allowing possible occlusions to be present. Prior to violent reaction, flame speeds were measured at approximately 30m/s for high confinement, which reduces by 2-3 orders of magnitude when confinement is lowered.