Disc acceleration experiments and simulation of HMX-based aluminized explosives with PTFE addition

Abstract. The addition of PTFE (polytetrafluoroethylene) to aluminized explosives has been proved to increase the heat of explosion owing to the post-detonation reaction between PTFE and aluminum. PTFE has a high content of fluorine (76%) among fluorinated oxidizers. The formed AlF₃, comparable to Al₂O₃, has a relatively high heat release and high vapor pressure that volatilizes more readily. In this work, several HMX-based polymer bonded explosives (PBXs) containing varying contents of PTFE and specifications of Al were manufactured by acoustic resonance and rotary cutting methods. In order to verify the energy output from Al, a chemically inert material LiF (lithium fluoride), whose physical properties are similar to Al, was used to substitute Al in counterpart formulations. Four pressed charges with dimension of Ø20 mm ×20 mm were used in one disc acceleration shot, a copper disc with thickness of 0.195 mm was attached to one end of the stacked cylindrical charges and the velocity history was recorded by photonic Doppler velocimetry (PDV). Experimental results show that the replacement of HMX by PTFE decreases the detonation pressure and velocity, however, the afterburning between PTFE and Al increase the terminal velocity of the disc. The addition of nano-Al results in a lower terminal velocity of the disc compared with micro-Al, which attributes to the low available aluminum content in nano-Al. The replacement of Al by LiF decreases the terminal velocity of the disc due to the chemical inertness of LiF. In numerical simulation, the JWL (Jones-Wilkins-Lee) parameters of aluminized explosive were obtained from the copper velocity history of corresponding LiF-containing explosive first by genetic algorithm, then the Miller extension parameters were obtained from the copper velocity history of aluminized explosive considering the post-detonation reaction.