Thin Flyer Impact Initiation Study of Ultrafine CL-20/HMX Co-Crystal Explosive by Varying Barrel Diameter

Abstract

Hexanitrohexaazaisowurtzitane (CL-20) is one of the most powerful explosive materials with potential for development of futuristic miniaturized high performance devices. It has small critical diameter which make it suitable to be initiated by short duration impact generated by small diameter and thin flyer in exploding foil initiators. However, the use of this material is limited due high mechanical sensitivity that strongly influences the safety of a formulation. Therefore, there is a need to improve the sensitivity of CL-20 explosive without compromising in explosive performance. Recently co-crystallization concept has evolved to get the desired insensitivity. In this research work, a new recrystallization method using twin fluid nozzle spray system has been established for making co-crystal of CL-20/HMX (2:1). The explosive co-crystals obtained by this process was characterized and analyzed using particle size analyzer, surface area analyzer, FTIR, FE SEM, X ray diffraction and thermal analytical techniques. It is confirmed the formation of co-crystals and showed that the prepared sample is not a physical mix of CL-20 and HMX. FE SEM analysis showed the particles formed are in the range of 2-5 μm and composed of numerous thin plates of thickness approximately 100 nm. Prototypes of exploding foil initiators using co-crystal of CL-20/HMX explosive were fabricated and the performance was evaluated. Threshold initiation studies were conducted using Bruceton sensitivity test with varying barrel diameter of 0.3 mm, 0.5 mm, 0.9 mm, keeping other parameters same. It was observed that the exploding foil initiators with barrel diameter 0.3mm did not function even at higher voltage and the threshold voltage with barrel diameter 0.5 mm was found to be lower than that of 0.9 mm barrel. It was experimentally found that the barrel diameter has significant effect on threshold voltage as the threshold voltage is reduced by 33% by optimizing barrel diameter from 0.9 mm to 0.5 mm.