Combustion Reaction Dynamics of Nano-Aluminum and Polyvinylidene Fluoride Composites. Part II: Multiscale Computational Simulations

In Part I ( J. Phys. Chem. C 2026, 10.1021/acs.jpcc.6c00579 ) of this two-part series, experiments were conducted to characterize the reaction propagation in aluminum and polyvinylidene fluoride (Al/PVDF) composites. Here, we report the development of integrated models at two size scales to gain insights into the experimental observations. The two models have different but mutually reinforcing spatial resolutions: the mesoscale model provides explicit resolution of the particle–polymer heterogeneous microstructure and focuses on the material response at the particle level (∼5 μm), and the coarse-grained model phenomenologically captures the effects of particle agglomeration and density fluctuations at higher length scales (∼1500 μm). The coarse-grained model is informed by and calibrated using results from the lower-scale model in terms of reaction kinetics. The mesoscale model is used to show how particle size, interparticle distance, and solids loading influence the burn rate. It is found that heat flux, temperature distribution, and burn rate at the interparticle level are strongly affected by particle size and interparticle distance. On the other hand, the coarse-grained model allows large-scale temperature distribution fluctuations and flame front corrugation observed in experiments to be quantitatively assessed. The results agree with the experimental observations in terms of statistical variations in the temperature field, local burn rate, and burn front morphology. Overall, heterogeneities at both the micro interparticle scale and in the form of higher-scale particle clustering are found to significantly affect the material response and act to obscure the dependence of burn rate on solids loading.