Pressure-Thresholded Response in Cylindrically Shocked Cyclotrimethylene Trinitramine (RDX)

TL;DR

This study reveals a threshold pressure in cylindrically shocked RDX crystals that triggers a transition from simple deformation to complex chemistry-related dynamics, using advanced imaging and scattering techniques.

Contribution

The paper introduces a novel waveguide geometry for cylindrically shocking RDX and demonstrates a clear pressure threshold for different deformation and chemical response modes.

Findings

Threshold pressure of ~12 GPa separates deformation regimes.

Porous crystal structures form post-shock with size and shape variations.

Preferential deformation directions are identified despite complex stress conditions.

Abstract

We demonstrate a strongly thresholded response in cyclotrimethylene trinitramine (RDX) when it is cylindrically shocked using a novel waveguide geometry. Using ultrafast single-shot multi-frame imaging, we demonstrate that <100-{\mu}m diameter single crystals of RDX embedded in a polymer host deform along preferential planes for >100 ns after the shock first arrives in the crystal. We use in-situ imaging and time-resolved photoemission to demonstrate that short-lived chemistry occurs with complex deformation pathways. Using scanning electron microscopy and ultrasmall-angle X-ray scattering, we demonstrate that the shock-induced dynamics leave behind porous crystals, with pore shapes and sizes that change significantly with shock energy. A threshold pressure of ~ 12 GPa at the center of convergence separated the single-mode planar crystal deformations from the chemistry-coupled multi-plane dynamics at higher pressures. Our observations indicate preferential directions for deformation for our cylindrically shocked system, despite the applied stress along many different crystallographic planes.