Using a Mathematical Model to Determine the Flame Propagation of Aluminum-Polytetrafluoroethylene Mechanically Activated Composites

Aluminum is being used as the fuel in the combustion of composite energetic materials because of its high energy density and low ignition temperature. Although nano-sized aluminum (nAl) burns faster than micron-sized aluminum (µAl), nAl’s high oxide content causes safety and propellant issues which are not common when burning µAl. Adding polytetrafluoroethylene (PTFE) to the µal material as an oxidizer instead of an oxygen-based oxidizer has shown to have a greater performance. Rather than just mixing, intimately meshing the fuel and oxidizer into one particle by mechanical activation allows for a faster, more efficient combustion. There are multiple applications for energetic materials, but thermites specifically are utilized mostly when an operation calls for a small but intense heat-focused material. In the military, defense operations that use flares to defer heat seeking missiles depend on flares composed of a thermite material, just like Al/PTFE. The concern with Al/PTFE is that its flame propagation is currently slower than nAl, although it is much safer to handle. The main objective of my research was to not only increase the speed of the flame propagation of Al/PTFE, but I planned to make it eventually burn faster than nAl. There were three benchmarks that must have been met in order for me to complete my objective. The first benchmark was to fully understand Al/PTFE by characterizing its combustion in a confined channel. My graduate mentor and I experimented with multiple parameters to try and achieve this. The second benchmark was to devise a mathematical model of Al/PTFE in a confined channel using the thermal properties of the combustion to determine the rate of the flame propagation. Finally, the third benchmark was to utilize the flame propagation model to enhance the combustion of Al/PTFE in a confined channel. After increasing the speed of the flame mathematically, we then wanted to do it experimentally. There is still much to be understood about the thermal and heat properties of the material, so I left Iowa State still in the first benchmark of my project. I am eager and hopeful for the chance to expand on my current research for better future results