In this paper we report new experimental results on the shock to detonation transition characteristics of the melt-cast explosive RDX/TNT 60:40, and two PBX explosives, one containing RDX, and the other HMX, with HTPB as the binder in both cases. These experiments employed right-regular cylindrical steel projectiles impacting charges covered by either steel or aluminium barrier plates. Response curves were generated giving the threshold impact velocity for prompt shock initiation as a function of barrier thickness. The results of these experiments showed some general trends. Firstly, the melt-cast explosive was generally more shock sensitive than the PBX formulations. The PBX compositions showed similar shock sensitivities; despite the RDX based material having a higher percentage of nitramine (88%) compared to the HMX material (85%). All the response curves appeared to have at least one discontinuity. For the melt-cast explosive this appeared at thicker barriers than for the PBX formulations. The results of these experiments are discussed in terms of the mechanisms that may be responsible for the observed shape of these response curves.
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