Multiscale analysis and constitutive modeling of the creep behavior of composite solid propellants under solid content control

The creep behavior of composite solid propellants directly affects the long-term storage reliability of solid rocket motors, with solid content (particle volume fraction) acting as a key controlling parameter. A meso–macro cross-scale simulation approach was employed to elucidate the regulation mechanism of solid content on creep behavior and to establish a coupled constitutive model. First, particle-reinforced elastic and viscous elements were introduced, and a parameterized constitutive equation was constructed in which the elastic modulus and viscosity coefficient vary explicitly with solid content. Second, based on the real mesostructure reconstructed via high-resolution micro-CT, particle-reinforced mesoscale models with solid contents ranging from 10.48% to 50.42% were generated using a Monte Carlo algorithm, and cross-scale creep simulations were carried out under constant stresses of 0.02~0.1 MPa. The results show that with increasing solid content, the initial elastic modulus and effective viscosity coefficient exhibit a pronounced nonlinear increase, which is further intensified by interfacial stress concentration. Moreover, the increase in solid content effectively suppresses the strain rate in the decelerating creep stage, confirming that particle filling improves creep resistance by enhancing the viscoelastic damping of the matrix. The constitutive parameters are identified from the simulation data, and the prediction error is below 7.5%, enabling accurate prediction of creep behavior over a wide range of solid contents.