Analysis of rheological properties of solid propellant based on a solid content-modified herschel-bulkley model

To clarify how solid content regulates the rheological properties of solid propellant and support rheological prediction and process optimization for broad solid content formulations, this study investigated the steady-state shear properties and dynamic viscoelasticity of solid propellant with 0%–80% solid content via steady-state shear and dynamic frequency sweep tests. A modified Herschel-Bulkley constitutive model incorporating solid content was established through multi-model comparative analysis. Results reveal that solid content exerts a distinctly segmented effect on propellant rheology, dividing into three intervals (0%, 20%–40%, 60%–80%) with divergent shear and viscoelastic behaviors. As solid content rises, the propellant transitions from a storage modulus-dominated viscoelastic matrix to a loss modulus-dominated particle-matrix composite, with a modulus crossover in 20%–40% reflecting frequency-dependent elastic-to-viscous shift. The modified model shows excellent fitting performance across intervals, achieving a 0.997 R ² in 60%–80% high solid content range, and outperforms Power-Law and Bingham models in parameter flexibility and mechanistic interpretability. This segmentation behavior and modified model provide a quantitative tool for NEPE formulation design, rheological prediction and molding process optimization, holding substantial engineering value.