Mesoscale study on the shock response and initiation behavior of Al-PTFE granular composites

A combination of mesoscale simulations and explosive loading experiments is used to investigate the shock response and shock-induced initiation behavior of aluminum-polytetrafluoroethylene (Al-PTFE) granular composites. A two-dimensional model following the random distribution of real Al particle sizes is developed and validated against experiments. The model is employed to investigate the effect of Al mass fractions on shock characterizes as well as Hugoniot relationships, and noticeable differences are visualized at the grain-level in the pressure, temperature, and strain response. Systematic shock structures in metals have been identified, and the underlying mechanisms of deformation and energy dissipation are discussed respectively. Results demonstrate that the high pressure is concentrated in the wave front, but a much greater heat and larger strain exhibit along grain/matrix interfaces that enable the friction dissipation the main mechanism of hot-spots formation. Specific quantities of critical temperature to initiate are obtained based on basic microstructure attributes to analyze the influence on hot-spots distribution by mass fractions. The interaction of shock wave with mesoscale heterogeneities accounts for the stochastic nature of the initiation process.