Fracture Behaviour Investigation into a Polymer‐Bonded Explosive

Abstract

Polymer-bonded explosive (PBX) is used widely in weapon systems. Failure of PBX caused by mechanical damage is one of the sources of accidental ignitions. A brittle crack of PBX produces local heating, creating a 'hot spot' finally. Investigation into the tensile fracture behaviour of PBX is one of the main works to determine the failure mechanism. Although many researchers have carried out the quasi-static Brazilian test to understand the damage evolution of PBX, the fracture feature of PBX under dynamic impact is rarely reported. In this article, dynamic Brazilian tests were conducted. A single-pulse loading apparatus was used to ensure that specimen was loaded only once during a dynamic Brazilian test. High-speed camera, digital image correlation and micro-observation techniques were adopted for strain measurement and microfracture observation. All the dynamic tensile crack exhibits transgranular fracture, which indicates more heat would released by the propagation of crack and more friction between fractured crystal surfaces. On the basis of the theories of interface debonding and transgranular fracture, larger crystals are more prone to crack, whereas smaller crystals simply debond with neighbouring binders. Discrete element method simulation results show that specimen with interface debonding microcracks was able to sustain additional load until transgranular fracture begins.

Modeling impact‐induced damage and debonding using level sets in a sharp interface Eulerian framework

“…The PBX materials are composed of a large volume fraction of energetic crystals (HMX) embedded in a polymeric (viscoelastic) binder matrix. Experiments under quasi‐static tensile loading show that the main damage mode appears at the particle/matrix interfaces due to debonding of the binder from the crystals. At higher loading rates, the fracture of the crystals can also occur .…”

High speed X-ray phase contrast imaging of energetic composites under dynamic compression

“…The fracture behavior of the PBX specimens has also been studied with uniaxial compression, [13][14][15][16][17][18][19] nanoindentation, 20 and Brazilian experiments [21][22][23] at various strain rates. The de-bonding between the energetic crystals and the binder was the main fracture mode observed in the quasistatic experiments.…”

“…14,21,22 As the loading rate was increased, the stiffness of the PBX samples increased 14,15,19 and higher number of crystals were observed to fracture. 14,15,23 The main fracture mechanism for the energetic crystals was the trans-granular fracture caused by the tensile stress generated due to particle-particle contacts. 15 The mechanical responses and the fracture behaviors of the PBX depend significantly on the loading rate.…”

X‐Ray Phase Contrast Imaging of the Impact of a Single HMX Particle in a Polymeric Matrix

“…Other dynamic processes include impact, chemical reaction or ignition, and growth of hot spots. Despite extensive literature on this topic a complete understanding of all the processes and dynamics does not yet exist, especially at the particle or microstructure level [2][3][4][5][6][7][8][9][10][11][12][13]. Studies have examined a variety of sample geometries, materials, and loading conditions.…”

“…Both single and multiple particles were tested, and it was determined that initiation sensitivity is partially dependent on particle-particle interactions. Jun-Ling et al studied the fracture behavior of PBXs by experimentation and simulation [8]. Two conclusions were made, there was a low critical stress for debonding and transgranular cracks lead to global failure.…”