Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session V04: Energetic Materials Behavior IRecordings Available
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Chair: Alejandro Strachan, Purdue University Room: Anaheim Marriott Platinum 2 |
Thursday, July 14, 2022 2:00PM - 2:15PM |
V04.00001: Effects of microstructure on shock initiation of insensitive explosives Dana D Dlott, Meysam Akhtar, Lawrence Salvati, Siva K Valluri Understanding the effects of microstructure on shock initiation requires testing methods that can distinguish between energetic materials that have the same composition and the same overall chemistry, but differ only in microstructure. TATB (2,4,6 trinitro 1,3,5 triamino benzene) is an insensitive energetic material with many unique properties. Slight variations in the synthetic procedure can lead to a diverse library of microstructures. We studied 10 different TATB microstructures fabricated in the form of arrays of hundreds of small cylindrical plastic-bonded explosive (PBX) charges. Each charge is shocked by a high-velocity impact with a thin laser-launched flyer plate that produces a short-duration shock so we can time resolve the spectral radiance with a high dynamic range to produce a unique fingerprint and temperature profile for each microstructure, which reveals how the microstructure interacts with a shock to ignite critical hot spots which can grow and interact to produce widespread combustion. |
Thursday, July 14, 2022 2:15PM - 2:30PM |
V04.00002: Multiscale reactive model for 1,3,5-triamino-2,4,6-trinitrobenzene inferred by reactive MD simulations and unsupervised learning Paul Lafourcade, Brenden W Hamilton, Michael Sakano, Pilsun Yoo, Alejandro H Strachan, Jean-Bernard Maillet When high-energy-density materials are subjected to thermal or mechanical aggression at extreme conditions (shock loading), a coupling between the thermo-mechanical and chemical behavior is systematically involved. We develop a reactive model for 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) at the mesoscopic scale where the chemical behavior and thermal transport properties of the system are determined by underlying microscopic reactive simulations. |
Thursday, July 14, 2022 2:30PM - 2:45PM |
V04.00003: Multiple time scale simulations of hotspot development due to dielectric breakdown driven by piezo- and flexo-electricity in energetic materials Ju Hwan Shin, Derek K Messer, Metin Örnek, Steven F Son, Min Zhou We demonstrate using multiphysics/multi-timescale simulations that dielectric breakdown due to electric charge accumulation can lead to hotspot development leading to the initiation of chemical reactions in P(VDF-TrFE)/nAl films comprising a poly(vinylidene fluoride-co-trifluoroethylene) binder and nano-aluminum particles. The development of electric field in the material is driven by flexoelectric and piezoelectric responses of the binder to mechanical loading which has a time scale of hundreds of microseconds. The breakdown process leading to hotspots has a time scale of nanoseconds. A two-step framework for explicit microscale simulations is used. First, the mechanically driven electric field is analyzed using a mechanical-electrostatic model. Next, the transient dielectric breakdown is analyzed using a thermal-electrodynamic model. The temperature field resulting from the breakdown is used to establish the hotspot conditions for the onset of self-sustained chemical reactions. The results demonstrate that temperatures well above the ignition temperatures can be attained. Flexoelectricity plays a primary role and piezoelectricity plays a secondary role. The time to reaction initiation and the time to ignition of the poled films are ~10% shorter than those of the unpoled films. |
Thursday, July 14, 2022 2:45PM - 3:00PM |
V04.00004: Shock to Deflagration Transition of RDX: Role of Microstructure Investigated Through Mesoscale Reactive Model. Brian H Lee, Brenden W Hamilton, James P Larentzos, John K Brennan, Alejandro H Strachan Predictive models for the thermal, chemical, and mechanical properties of high explosives (HEs) at extreme conditions are highly desirable to understand their performance and safety. We introduce a particle-based, reactive model of 1,3,5-trinitro-1,3,5-triazinane (RDX) with molecular resolution utilizing the generalized energy-conserving dissipative particle dynamics with chemical reactions (GenDPDE-RX) method. The model is parameterized from all-atom reactive molecular dynamics simulations, thus, it bridges atomic processes to the mesoscale. We address shortcomings of current state-of-the-art mesoscopic models in reproducing the response of RDX under a range of thermal and shock loading. In addition, the model also correctly portrays the interplay of shock and microstructure in hotspot formation and transition to deflagration. We attribute the vast improvement in accuracy to two distinguishing features: incorporation of a reduced-order chemistry model and a top-down parametrization approach. Exploiting the model’s high computational efficiency, we investigate microscale systems and validate them by investigating size-dependent criticality of RDX hotspots that has been predicted with continuum models. |
Thursday, July 14, 2022 3:00PM - 3:15PM |
V04.00005: Head-to-Head Comparison of Molecular and Continuum Simulations of Shock-Induced Pore Collapse in β-Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine (β-HMX) Puhan Zhao, Pratik Das, Yen t Nguyen, Dilki Perera, Tommy Sewell, H.S. Udaykumar Shock-induced pore collapse in the energetic molecular crystal β-HMX is examined using all-atom molecular dynamics (MD, LAMMPS) and continuum mechanics (SCIMITAR3D) for nearly identical simulation domains under the same impact conditions. Treating MD predictions as ‘ground truth’, a hierarchy of increasingly MD-informed continuum material models was systematically ‘upgraded’ with temperature- and pressure-dependent MD-derived material parameters. Starting with a simple isotropic, elastic-perfectly plastic material model, the model is improved stepwise by adding strain-, strain-rate-, and temperature-dependent isotropic plasticity (Johnson-Cook J2), pressure-dependent melting temperature from MD, and pressure-dependent mechanical properties from MD. Continuum predictions of shear-band patterns, pore-collapse profile and mechanisms, and hotspot formation during collapse of circular and elongated pores using the MD-guided material model are in overall good agreement with MD results. |
Thursday, July 14, 2022 3:15PM - 3:30PM |
V04.00006: Near-Optimal Combination of High Performance and Insensitivity in a Shock Compressed High Explosive Single Crystal Michael Winey, Yoshi Toyoda, Yogendra M Gupta Achieving the desired combination of superior detonation performance and insensitivity to shock initiation has been a long-standing goal in high explosive (HE) science and technology. Having previously established the shock insensitivity of 1,1-diamino-2,2-dinitroethene (FOX-7) single crystals to 20 GPa (extended to 25 GPa in this work), the FOX-7 detonation response was determined through wave profile measurements in ~250 µm thick single crystals shock compressed to 64 GPa. Quite unexpectedly, FOX-7 demonstrated classic Chapman-Jouget (C-J) detonation response – reaction completion in the detonation front (<0.7 ns) at pressures of 44 GPa and higher – not observed in other insensitive high explosives (IHEs). Sound speeds in the compressed detonation products were determined from the measured wave profiles, enabling experimental determination of the C-J state for FOX-7 single crystals. The experimentally determined C-J pressure (35 GPa), detonation wave velocities, and the detonation products equation of state – together with shock insensitivity to 25 GPa – demonstrate that FOX-7 single crystals display a near-optimal combination of high performance and shock insensitivity, not observed in any other HE crystal. |
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