Topology-Regulated BGAP Binder Networks and Debonding-Based Constitutive Modeling for Solid Propellants

Composite solid propellants face mechanical limitations due to microstructural defects in energetic binders, primarily caused by side-group steric hindrance. To address this, we propose four binder network design strategies: reactive activation, segmental densification, node reinforcement, and topological balancing. Systematically optimizing the formulation (via stoichiometric adjustments, short-chain copolyethers, multifunctional cross-linkers, and gradient curing agents) transforms the binder into a topologically dense network. This structural regulation improves the balance between strength and deformability under the present formulation design, increasing the propellant’s tensile strength to 1.04 MPa and elongation at break to 44.4%. For practical structural integrity evaluation, we developed a nonlinear viscoelastic-damage coupled constitutive model based on a Prony series and interfacial debonding geometry. Implemented via a finite element user subroutine, the model reasonably captures the macroscopic mechanical response and modulus softening of the optimized propellant across a wide temperature range (−40 to 70 °C). This integrated approach of network regulation and constitutive modeling bridges theoretical material design with computational evaluation for actual engineering applications.