Showing papers in "Propellants, Explosives, Pyrotechnics in 2020"

Non-Shock Ignition Probability of Octahydro-1,3,5,7-Tetranitro-Tetrazocine-Based Polymer Bonded Explosives Based on Microcrack Stochastic Distribution

Abstract: We investigate stochastic microcracks of a heterogeneous microstructure as the primary mechanism determining the non-shock ignition probability of octahydro1,3,5,7-tetranitro-1,2,3,5-tetrazocine-based polymer-bonded explosives. To quantify the ignition probability, we modify the viscoelastic cracking constitutive model by considering randomly distributed microcracks and combine this model with the hot-spot model and the Monte Carlo method. This method is validated by using a standard Steven test simulation, and we quantify how the microcrack stochasticity affects the ignition probability. The high-temperature region clearly changes compared with the case of single microcrack size. The discrepancy in the mechanical response of each element due to the heterogeneous microcracks causes a shear deformation, which increases the temperature. The difference between a uniform distribution and a normal distribution in microcrack size is also discussed. For a given impact velocity, the ignition probability for the normal microcrack size distribution exceeds that for the uniform microcrack size distribution. Although the two distributions have the same mean and variance, the real range in microcrack size corresponding to the normal distribution exceeds that for the uniform distribution. The results show that the sample radius does not significantly affect the ignition probability, whereas the opposite is true for the sample thickness. The ignition-probability curve is obtained in these cases. For sample dimensions of φ70 mm × 13 mm, φ98 mm × 13 mm, φ140 mm × 13 mm, and φ98 mm × 26 mm, the impact velocity thresholds corresponding to ignition probabilities in the range 0 %–99 % are 41.0–43.7, 41.0–44.3, 40.0–44.6, and 62.0–67.2 m/s, respectively, which is consistent with experimental results.

OZM Ball Drop Impact Tester (BIT‐132) vs. BAM Standard Method – a Comparative Investigation

Abstract: Safety, performance, cost efficient synthesis and toxicity are the most important aspects of modern explosives. Sensitivity measurements are performed in accordance with different protocols all around the world. Sometimes the BAM drop hammer does not accurately reflect the sensitivity of an energetic material, in particular the sensitivity of primary explosives. Therefore, we present here preliminary results obtained using the novel ball drop tester (BIT‐132), manufactured by OZM research, following MIL‐STD‐1751 A (method 1016). The ball drop impact sensitivity tester is a device in which a free‐falling steel ball is dropped onto an unconfined sample, and is expected to produce more realistic results than the currently commonly used BAM method. The results obtained using the probit analysis were compared to those from the BAM drop hammer and friction tester. The following sensitive explosives were investigated: HMTD, TATP, TAT, Tetrazene, MTX‐1, KDNBF, KDNP, K2DNABT, Lead Styphnate Monohydrate, DBX‐1, Nickel(II) Hydrazine Nitrate, Silver Acetylide, AgN3, Pb(N3)2 RD‐1333, AgCNO, and Hg(CNO)2.

Development of Propellant Compositions for Vat Photopolymerization Additive Manufacturing

Abstract: A photocurable energetic resin was developed for photopolymerization additive manufacturing. The composition contains 50 wt % RDX, 25 wt % acrylate binder, and 25 wt % energetic plasticizer. The material was characterized in terms of compatibility, printability, mechanical properties and (ballistic) performance. The possibility of printing energetic items of increasing complexity was demonstrated through various print trials. The culmination of the research effort was the firing of a 30 mm gun setup with 3D-printed propellant.