Combustion Reaction Dynamics Modeling of Nano-Aluminum and PVDF Composites

The distribution and size scale of micro- and nano- metallic particles in energetic composites is known to have significant effects on reaction ignition and propagation. Experimental observations of aluminum nanoparticles and polyvinylidene fluoride (PVDF) composites show wide variations in the dependence of critical properties such as burn rate, flame depth, and corrugation to changes in solids loading, clusters, and particle size. We report the creation of a model that uses two size scales to offer physical insights into Al/PVDF combustion. The first model focuses on the nanoscale response of explicitly resolved particles and captures interparticle effects of particles at different solids loadings and sizes, 25 nm – 150 nm, on reaction propagation, such as displacement and agglomeration. The second model is phenomenological and captures response of larger particle clusters, ~ 500 µm, and the effects that varying distributions and densities of particle clusters will have on the material reaction. The bulk model uses reaction kinetics and property insights from the particle model to simulate the effects of particle clusters and size distributions. The peak temperature and flame depth are shown to be dependent on the solids loading of the material and particle size. Burn rate and ignition delay are affected by solids loading, but larger particle sizes can reduce this dependence. These results are compared and are in good agreement with experiments.