Multiscale Analysis of Mechanical Properties in Carbon Nanotube-Reinforced Solid Propellants Using the PPR Cohesive Model

• A three-level equivalent multiscale representative volume element framework was established to predict the tensile elastic modulus and strength of carbon-nanotube-reinforced composite solid propellants. • A potential-based Park-Paulino-Roesler cohesive zone formulation was implemented via a user-defined element to capture interfacial debonding, progressive damage evolution, and multiscale load-transfer behavior. • Simulations and constant-rate tensile tests identify 0.3 wt.% carbon nanotubes (aligned with the tensile direction) as optimal, achieving 63% modulus and 24% strength increases with only 3.97% simulation and experiment deviation. The relatively low strength and modulus of composite solid propellants often limit the structural integrity of solid rocket motors. While the incorporation of carbon nanotubes (CNTs) offers a promising pathway for mechanical enhancement, the factors and mechanisms governing the effectiveness of CNT reinforcement are not yet fully elucidated. To address this gap, a multiscale simulation approach incorporating the Park–Paulino–Roesler (PPR) cohesive zone model is presented to elucidate the mechanisms governing CNT-induced strengthening in composite solid propellants. Three-level multiscale models incorporating diverse particulate architectures are constructed. The PPR model is employed to accurately capture interfacial dewetting and progressive damage evolution. Through systematic simulations, the effects of CNT content and orientation on macroscopic mechanical properties are quantified. Results predict an optimal CNT content of 0.3 wt.% when the nanotubes are aligned with the tensile direction. Under this condition, the elastic modulus increases by 63% and the tensile strength improves by 24%. Macroscale tensile tests were designed and conducted to validate the proposed framework. The discrepancy between simulated and experimental results is a mere 3.97% at the optimal loading. Thus, the proposed multiscale framework which employs the PPR cohesive zone model provides a robust basis for predictive design and mechanical optimization of composite solid propellants.