Microstructural evolution of PETN thin films during thermal aging

Maintaining the microstructure of energetic materials under specific margins is critical to ensure safety and performance. We investigate microstructural evolution of pentaerythritol tetranitrate thin films during thermal aging using phase-field simulations that integrate physical vapor deposition, grain coarsening, porosity evolution, and anisotropic mechanical response. We generate thin films with initial microstructures via physical vapor deposition simulations, followed by aging at two different temperatures. Our results demonstrate three primary stress-driven mechanisms: (1) void elongation along grain boundaries; (2) grain coarsening; and (3) preferential growth of grains with (110) orientations. Additionally, we find that porosity acts as a drag on grain boundary migration, with higher porosity levels reducing grain coarsening rates. These findings reveal the critical role of stresses and elastic anisotropy in controlling long-term microstructural stability of energetic thin films.