4D micro-scale, phase-contrast X-ray imaging and computed tomography of HMX-based polymer-bonded explosives during thermal runaway

High-resolution synchrotron x-ray radiography with computed tomography is used to observe the evolution of porosity created by thermal exposure in two HMX-based polymer-bonded explosive compositions; LX-04 and BX-63. The measurements were made in situ, over an extended period of time, during which t...

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Bibliographic Details
Published in:Combustion and flame 2021-04, Vol.226, p.478-489
Main Authors: Parker, G.R., Eastwood, D.S., Storm, M., Vitharana, K., Heatwole, E.M., Lopez-Pulliam, I., Broilo, R.M., Dickson, P.M., Martinez, A., Rau, C., Bourne, N.K.
Format: Article
Language:English
Subjects:
Auto-ignition
Combustion
Composition
Computed tomography
Confinement
Contact angle
Contact melting
Convective burn
Damage
Explosive behavior
Fluoropolymers
HMX
Ignition
Morphology
PBX (explosives)
Polymers
Porosity
Radiography
Synchrotron radiation
Synchrotrons
Thermal runaway
X ray imagery
X-ray radiography
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Summary:High-resolution synchrotron x-ray radiography with computed tomography is used to observe the evolution of porosity created by thermal exposure in two HMX-based polymer-bonded explosive compositions; LX-04 and BX-63. The measurements were made in situ, over an extended period of time, during which the samples were heated on a slow-rate thermal trajectory. The tests ended with thermal-runaway to ignition after which the samples were consumed by combustion. The primary means of damage appears to be from mechanical debonding of the HMX-binder interface with secondary contribution from chemical decomposition. Confinement and binder properties affect the amount of porosity and permeability that develops. Additionally, observations were made describing the emergence and structure of an internal ignition volume, the formation and transport of a pre-ignition melt layer, and how the early stages of combustion were affected by material morphology, mechanical confinement and melt. The contact angle between molten HMX and the fluoropolymer, Viton A, is also presented. For the first time we have time-resolved x-ray images of ignition in sufficient detail to verify the mechanism of cookoff in polymer-bonded explosive compositions.
ISSN:0010-2180
1556-2921
DOI:10.1016/j.combustflame.2020.12.025