Impact reliability of multilayer stacked-cell thermal batteries using 3D FEM simulation and gas gun test validation

Thermal batteries in guided projectiles must withstand extreme mechanical loading, yet most modeling approaches neglect their multilayered cell architecture. In this study, we developed a 3D finite element framework incorporating actual donut-shaped unit cells, casing, epoxy molding, and terminal pins to analyze internal stress evolution during high-velocity impact. Gas gun experiments at ∼145 m/s against Pb targets were performed for direct validation. The FEM predictions showed strong agreement with experimental deceleration–time curves and penetration depths, confirming the framework's reliability. Mechanistic analysis revealed stress concentration in the lower stacked cells, particularly at the inner rims, but peak values remained below the reference compressive limit (an upper-bound admissible stress) derived from the compaction load and validated by additional compression tests. Though localized stress values varied between simplified and detailed models depending on the inclusion of terminal pins and epoxy molding, the overall deceleration response and penetration behavior remained consistent. These results demonstrate a validated FEM–experiment methodology for evaluating and improving the impact reliability of thermal batteries, offering guidance for material-level design of resilient stacked-cell architectures in defense applications.