Multiscale investigation of the microstructural mechanisms driving ratchet growth in PBX 9502

ABSTRACT

The high explosive PBX 9502 undergoes irreversible expansion during thermal cycling (“ratchet growth”). Recent innovations in thermomechanical modeling via homogenization strategies are beginning to incorporate mesoscale information such as grain size, total porosity, and spatial distribution of voids and cracks. To generate a complete experimental data set to challenge and inform these models, PBX 9502 pellets were thermally cycled, cross-sectioned using ion polishing, and imaged in high resolution with scanning electron microscopy. Ratchet growth was found to drive expansion through microcracking. Microcracks were affected by agglomeration of crystals within the PBX. Virgin material showed greater ratchet growth than recycled material.

KEYWORDS:

• Plastic-bonded explosive
• triaminotrinitrobenzene
• scanning electron microscopy
• ratchet growth
• microcracking
• thermal stability
• microstructure
• insensitive explosive

Acknowledgments

The authors would like to thank Darla Thompson and Racci DeLuca for assistance with the thermal cycling measurements. Barry Ritchey and Adam Pimentel collected the SEM images. Daniel Trujillo provided direction and facilitated LANL-Sandia collaboration.Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of U.S. Department of Energy (Contract No. 89233218CNA000001). This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Funding for this work was provided by the System Engineering Group at Los Alamos National Laboratory. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of U.S. Department of Energy (Contract No.89233218CNA000001)