Mesoscale Reactive Burn Modeling of Shock Initiation in Vapor-Deposited PETN Films*

We have developed a mesoscale model of vapor-deposited PETN that predicts initiation sensitivity as a function of age-related microstructural changes.  Recent experiments [1] have shown growth to detonation occurring in PETN films of 67 – 125 µm thickness.  Shifts in initiation threshold were observed after ageing [2], along with corresponding observations of grain coarsening due to the accelerated ageing conditions.  Most continuum hydrocode reactive burn models do not account for microstructure properties and are thus unable to account for shifts in performance as a function of grain-scale changes. In our model we conduct direct numerical simulations of flyer impact and shock propagation in porous films consisting of solid grains and voids/defects reproduced from scanning electron microscope cross-section images.  In the model, shock wave energy is localized at voids and defects creating hotspots which trigger the release of chemical energy due to global reaction kinetics based on local temperature in the solid.  Simulations were conducted for various flyer velocities impacting films of various thickness.  The agreement or discrepancy between the model and experimental data will be discussed, as well as next steps for improving model accuracy.

 

Ref.

[1] Knepper, et al., J. Appl. Phys. 131, 155901 (2022)

[2] Knepper, et al., this conference