Mechanism governing spatiotemporal evolution of confined overpressure induced by PTFE/Al reactive jets

An interfacial-temperature-based ignition model is developed to describe shock-induced reactions in heterogeneous PTFE/Al composites and embedded into a multi-physics Material Point Method–Shock Induced Chemical Reaction (MPM-SICR) framework. A compressible-flow solver is coupled with this framework to resolve reactive jet formation and confined overpressure field evolution. The simulations show good agreement with X-ray and confined chamber overpressure experiments, with deviations below 6.3% and 4%, respectively. The results reveal a characteristic three-stage stepwise evolution of confined overpressure, consisting of an initial deflagration stage near the chamber orifice, a secondary overpressure stage caused by wave focusing and secondary deflagration enhancement at the chamber bottom, and a subsequent venting-dominated quasistatic stage, with representative overpressure peaks of approximately 0.76, 1.68, and 2.21 MPa. Furthermore, by introducing the concept of equivalent reacted mass, a nearly linear scaling relationship between confined overpressure peak and equivalent reacted mass is identified (R² ≈ 0.92). These findings provide a mechanics-based interpretation of reaction driven overpressure evolution in PTFE/Al jets-confined spaces systems.