Detonation of Condensed Explosives

Chéret, Roger

doi:10.1007/978-1-4613-9284-2

Cited by 58 publications

(43 citation statements)

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“…(1) The primary step of thermal excitation and vibrational energy transfer. This process occurs in a sub-ps to one ns regime and proceeds in a highly non-equilibrium manner.…”

Section: Scientific Issues In Detonationmentioning

confidence: 99%

Detonation in Shocked Homogeneous High Explosives

1995

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We have studied shock-induced changes in homogeneous high explosives including nitromethane, tetranitromethane, and single crystals of pentaerythritol tetranitrate (PETN) by using fast time-resolved emission and Raman spectroscopy at a two-stage light-gas gun. The results reveal three distinct steps during which the homogeneous explosives chemically evolve to final detonation products. These are i) the initiation of shock compressed high explosives after an induction period, ii) thermal explosion of shock-compressed and/or reacting materials, and iii) a decay to a steady-state representing a transition to the detonation of uncompressed high explosives. Based on a gray-body approximation, we have obtained the CJ temperatures: 3800 K for nitromethane, 2950 K for tetranitromethane, and 4100 K for PETN. We compare the data with various thermochemical equilibrium calculations. In this paper we will also show a preliminary result of single-shot time-resolved Raman spectroscopy applied to shock-compressed nitromethane.

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“…(1) The primary step of thermal excitation and vibrational energy transfer. This process occurs in a sub-ps to one ns regime and proceeds in a highly non-equilibrium manner.…”

Section: Scientific Issues In Detonationmentioning

confidence: 99%

Detonation in Shocked Homogeneous High Explosives

1995

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“…For detonation, it is generally accepted that hot spots form during the development of instabilities as shock waves pass through the interface or other defects. [1][2][3][4] Despite numerous experimental and theoretical studies, the fundamental processes involved remain controversial. This is due to the complex environment and coupling of thermal, chemical, and mechanical degree of freedom, which is extremely difficult to unravel experimentally.…”

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confidence: 99%

Elucidation of the dynamics for hot-spot initiation at nonuniform interfaces of highly shocked materials

Zybin

Goddard

et al. 2011

Phys. Rev. B

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The fundamental processes in shock-induced instabilities of materials remain obscure, particularly for detonation of energetic materials. We simulated these processes at the atomic scale on a realistic model of a polymer-bonded explosive (3,695,375 atoms/cell) and observed that a hot spot forms at the nonuniform interface, arising from shear relaxation that results in shear along the interface that leads to a large temperature increase that persists long after the shock front has passed the interface. For energetic materials this temperature increase is coupled to chemical reactions that lead to detonation. We show that decreasing the density of the binder eliminates the hot spot. The interaction of shock waves with nonuniform interfaces plays an essential role in the interfacial instabilities in inertial confinement fusion (ICF), in shock-induced RichtmyerMeshkov instabilities (RMIs), and in detonation in heterogeneous polymer-bonded explosives (PBXs). For detonation, it is generally accepted that hot spots form during the development of instabilities as shock waves pass through the interface or other defects.1-4 Despite numerous experimental and theoretical studies, the fundamental processes involved remain controversial. This is due to the complex environment and coupling of thermal, chemical, and mechanical degree of freedom, which is extremely difficult to unravel experimentally. It has also been very difficult theoretically to include the reactive processes involved and yet cover the enormous size and time scales intrinsic to the phenomena.To discover the origin of shock-induced hot-spot formation, we carried out reactive dynamics (RD) using the ReaxFF reactive force field on a realistic model of a real polymerbonded explosive PBX N-106. Energetic materials (EMs) are essential for applications ranging from rocket engines, to building and dam construction, and to armaments. Generally the EM is bound together in a matrix of polymer elastomers to form the PBX that can be molded into various shapes, while providing some control in resisting unintentional detonation due to shocks or friction. Unfortunately, current generations of PBXs are sensitive to accidental detonation, despite many attempts to control the safety by improvements in materials and manufacturing practices. Here we use the ReaxFF reactive force field to examine the effect of shocks on realistic models of polymer-bonded explosives, where we use these simulations to extract the mechanism of hot-spot formation. Then, based on this model, we predict how to change the system to reduce the hot spot, and carry out simulations to validate this prediction.ReaxFF has now been established to provide nearly the accuracy of quantum calculation in the various reaction barriers and rates while providing a computational efficiency nearly that of ordinary molecular dynamics (MD) with ordinary force fields (FFs), enabling us to study the complex processes involved in interfacial instabilities at the atomic scale, providing insights on such phenomenon. Thus ReaxF...

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“…[1][2][3] Experiments that directly probe these molecular processes are central to current research on energetic materials. Results from these experiments complement continuum studies, and together with advances in theory and computational methods can provide a detailed understanding of shockinduced reactions.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Shock-Induced Chemical Decomposition of Sensitized Nitromethane Through Time-Resolved Raman Spectroscopy

et al. 1995

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Molecular processes associated with shock induced chemical decomposition of a mixture of nitromethane with ethylenediamine (0.1 wt%)are examined using time-resolved, Raman scattering. When shocked by stepwise loading to 14.2 GPa pressure, changes in the nitromethane vibrational modes and the spectral background characterize the onset of reaction. The CN stretch mode softens and disappears even as the N02 and CH 3 stretch modes, though modified, retain their identities. The shape and intensity of the spectral background also shows changes characteristic of reaction. Changes in the background, which are observed even at lower peak pressures of 11.4 GPa, are assigned to luminescence from reaction intermediates. The implications of these results to various molecular models of sensitization are discussed.

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Detonation of Condensed Explosives

Cited by 58 publications

References 0 publications

Detonation in Shocked Homogeneous High Explosives

Detonation in Shocked Homogeneous High Explosives

Elucidation of the dynamics for hot-spot initiation at nonuniform interfaces of highly shocked materials

Investigation of Shock-Induced Chemical Decomposition of Sensitized Nitromethane Through Time-Resolved Raman Spectroscopy

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