Thermomechanical Modeling and Fabrication of Structurally Reinforced Soft Pulse Separation Devices for Dual-Pulse Motors

Abstract

The Structurally Reinforced Soft Pulse Separation Device (SPSD) is a pivotal technology for enabling flexible energy management in Dual-Pulse Solid Rocket Motors (DP-SRMs), yielding significant mass savings and nozzle safety advantages over rigid bulkheads. However, predicting the stochastic rupture behavior of elastomeric membranes under combined thermal and pneumatic loads remains a primary design challenge. This paper proposes a unified Thermomechanical Membrane Rupture Model (TMRM) that integrates Pulse-I thermal ablation history with Pulse-II large-deformation kinematics. Addressing critical gaps in contemporary literature, the model explicitly delineates the phenomenological transition between linear plate theory (applicable to rigid metallic barriers) and non-linear secant-modulus Hencky approximations (essential for soft elastomers). Validated against high-fidelity Fluid-Structure Interaction (FSI) simulations and experimental datasets, the results demonstrate that reliance on classical linear theory for elastomers severely underestimates pressure capacity. Large-deformation geometric stiffening allows Ethylene Propylene Diene Monomer (EPDM) membranes to withstand pressures up to ~ 80% higher than linear predictions. Furthermore, a counter-intuitive thermal hardening phenomenon is quantified, wherein ablation-induced thinning of the bulk membrane paradoxically increases structural compliance, relaxes the radius of curvature, and elevates the rupture threshold, thereby maintaining a robust safety margin during the coast phase. By bridging the gap between elastomeric material science and internal ballistics, this analytic framework establishes a deterministic preliminary sizing protocol for reliable, low-fragmentation petaling in next-generation tactical propulsion systems.