Sensitivity effects of void density and arrangement in a REBO high explosive

TL;DR

This study investigates how void density and arrangement in high explosives influence shock response and detonation timing, revealing that void size, porosity, and arrangement significantly affect ignition and detonation behavior.

Contribution

It provides new insights into how void configurations affect shock sensitivity and detonation timing in high explosives using molecular dynamics simulations.

Findings

Smaller voids and higher porosity lead to faster ignition and earlier detonation.

Square lattice void arrangements cause quicker detonation than random arrangements.

Hotspot development and pressure wave merging drive the transition from deflagration to detonation.

Abstract

The shock response of two-dimensional model high explosive crystals with various arrangements of circular voids is explored. We simulate a piston impact using molecular dynamics simulations with a Reactive Empirical Bond Order (REBO) model potential for a sub-micron, sub-ns exothermic reaction in a diatomic molecular solid. In square lattices of voids (of equal size), reducing the size of the voids or increasing the porosity while holding the other parameter fixed causes the hotspots to consume the material more quickly and detonation to occur sooner and at lower piston velocities. The early time behavior is seen to follow a very simple ignition and growth model. The hotspots are seen to collectively develop a broad pressure wave (a sonic, diffuse deflagration front) that, upon merging with the lead shock, transforms it into a detonation. The reaction yields produced by triangular lattices are not significantly different. With random void arrangements, the mean time to detonation is 15.5\% larger than with the square lattice; the standard deviation of detonation delays is just 5.1%.