Measurement of Porosity in a Composite High Explosive as a Function of Pressing Conditions by Ultra‐Small‐Angle Neutron Scattering with Contrast Variation

Mang, Joseph T.; Hjelm, Rex P.; Francois, Elizabeth

doi:10.1002/prep.200900026

Cited by 27 publications

(20 citation statements)

References 16 publications

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“…The mm-scale pores mentioned in the preceding paragraph are larger than the ones that exist in a real composite explosive [16][17][18]. Direct experimental observation of pore collapse in real explosives is extremely difficult due to the high strain rates and small spatio-temporal scales over which pore collapse occurs, and because the phenomena of interest occur in the bulk of an optically impenetrable material.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of the Collapse of a Cylindrical Pore in the Energetic Material α-RDX

Eason

Sewell

2015

J. dynamic behavior mater.

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Molecular dynamics simulations were used to study the shock-induced collapse of cylindrical pores in oriented single crystals of the energetic material a-1,3,5-trinitroperhydro-1,3,5-triazine (a-RDX). The shock propagation direction was parallel to the [100] crystal direction and the cylinder axis of the initially 35.0 nm diameter pore was parallel to [010]. Features of the collapse were studied for Rankine-Hugoniot shock pressures P s = 9.71, 24.00, and 42.48 GPa. Pore collapse for the weak shock is dominated by visco-plastic deformation in which the pore pinches shut without jet formation and with little penetration of the upstream material into the downstream pore wall. For the strong shock the collapse is hydrodynamiclike and results in the formation of a jet that penetrates significantly into the downstream pore wall. Material flow during collapse was characterized by examining the spread and mixing of sets of initially contiguous molecules and evolution of local velocity fields. Local disorder during collapse was assessed using time autocorrelation functions for molecular rotation. Energy deposition and localization was studied using spatial maps of temperature and pressure calculated as functions of time.

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Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of the Collapse of a Cylindrical Pore in the Energetic Material α-RDX

Eason

Sewell

2015

J. dynamic behavior mater.

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“…The PBX 9501 is composed mainly of the HMX particles embedded within the matrix Estane/BDNPA-F, which can be seen including three kinds of “inclusions”; i.e., the coarse HMX particles, the fine HMX particles, and voids. The parameters in the PSD function for the PBX 9501 used in this study are given by experiment data [21,22], all of them were listed in Table 1, and the subscripts “1”, “2” and “3” represent “the coarse HMX particles,” “the fine HMX particles,” and “the voids,” respectively.…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

The Ubiquitiformal Characterization of the Mesostructures of Polymer-Bonded Explosives

Duan

et al. 2019

Materials

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A nesting ubiquitiform (NU) approach was developed to characterize the mesostructural features of polymer-bonded explosives (PBXs), and then used to predicate some equivalent physical properties of PBXs, which can also be expected to be extended to other composites with complicated internal mesostructures. To verify the availability, two NU models for two kinds of PBX with different compositions are presented, which are PBX 9501 and LX-17, based on which, the equivalent thermal conductivities were calculated. Particularly, it is so encouraging that an analytical expression of the equivalent thermal conductivity was obtained only under a simply assumption of homogeneity. Moreover, it was found that the numerical results calculated by both the recursive algorithm and the analytical expression were in good agreement with the experimental data. In addition, it is also shown that such a physical property as the equivalent thermal conductivity is indeed independent of the meso-configuration of the location distribution of the explosive particles and the voids inside the PBX, which seems consistent with the common expectations and lays the foundations for the application of ubiquitiform to investigating some equivalent properties of composites.

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“…[34]. The MOZ function was chosen because it returns comparable microstructural information to that of the model applied previously to high explosives [5], and unlike the previous model, the MOZ function is not restricted to isotropically scattering systems [25]. For porous systems, in the limit of an infinite fractal aggregate, the model provides a measure of the volume and surface dimensions and the primary void size:

true normalI {(normalQ)}_{i} = I_{oi} {normalQ}^{- D_{f}} {((), 1 +, Q^{2}, {normalr}_{i}^{2})}^{\frac{{normalD}_{normals} + {normalD}_{normalf} - 6}{2}}

true i = normalc, normaly or normalz and,

true {I (normalQ)}_{c} = {⟨ normalI ((), Q, \cos, φ, ,, Q, \sin, φ, , 0) ⟩}_{0 < φ < 2 π}

true {I (normalQ)}_{y} = {⟨ normalI (() 0, Q \sin φ, Q \cos φ) ⟩}_{- \frac{π}{12} < φ + \frac{π}{2} < \frac{π}{12}}

true I (normalQ {)​}_{z} = ⟨ normalI ((), 0,, Q, \sin, φ)

…”

Section: Methodsmentioning

confidence: 99%

“…The current USANS and SANS data were analyzed as a two-phase system using an empirical model that is a special case of the modified Ornstein-Zernike (MOZ) model utilized by Hurd et al [34]. The MOZ function was chosen because it returns comparable microstructural information to that of the model applied previously to high explosives [5], and unlike the previous model, the MOZ function is not restricted to isotropically scattering systems [25]. For porous systems, in the limit of an infinite fractal aggregate, the model provides a measure of the volume and surface dimensions and the primary void size: Here, the intensity components are the averages taken over the azimuthal angle, ϕ (Figure 2), over the indicated domain.…”

Section: Methodsmentioning

confidence: 99%

“…Ultra-and Small-angle scattering techniques employing neutrons (USANS/SANS) or X-rays (USAXS/SAXS) have become valuable tools for probing the microstructure of high explosives over length scales between 0.001-10 μm, fully covering the critical range for hot spot formation [5,15,17,25,26]. A significant advantage of the techniques over other characterization methods is that they can be applied to as-pressed HE parts.…”

Section: Introductionmentioning

confidence: 99%

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Preferred Void Orientation in Uniaxially Pressed PBX 9502

Mang

Hjelm

2020

Propellants Explo Pyrotec

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Ultra-and small-angle neutron scattering techniques were used to study the morphology of voids in directions parallel and perpendicular to the compaction plane of a uniaxially pressed cylinder of PBX 9502. Two-dimensional scattering patterns from samples cut parallel to the compaction plane had circular equal-intensity contours, implying that along this view the voids are circular or randomly oriented. Identical measurements of samples cut perpendicular to the compaction plane produced elliptical equalintensity contours, indicating preferred orientation of voids. Analysis of the two dimensional scattering patterns confirmed that the voids are non-spherical with an average aspect ratio of 1.20, flattened so that the larger dimensions of the voids lie within the compaction plane. Model analysis of the combined ultra-and small-angle neutron scattering curves revealed that the PBX 9502 porosity is interconnected, in the form of aggregates comprised of nonspherical, primary voids. The volume dimension was found to be the same in both directions, indicating that the aggregate is randomly oriented throughout the sample, and that it is the primary voids that are preferentially oriented. Void interfaces with the surrounding matrix were found to be rough or polydisperse, with a common roughness dimension or polydispersity in all directions.

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Measurement of Porosity in a Composite High Explosive as a Function of Pressing Conditions by Ultra‐Small‐Angle Neutron Scattering with Contrast Variation

Cited by 27 publications

References 16 publications

Molecular Dynamics Simulations of the Collapse of a Cylindrical Pore in the Energetic Material α-RDX

Molecular Dynamics Simulations of the Collapse of a Cylindrical Pore in the Energetic Material α-RDX

The Ubiquitiformal Characterization of the Mesostructures of Polymer-Bonded Explosives

Preferred Void Orientation in Uniaxially Pressed PBX 9502

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