Macro-microscopic study on the damage threshold strain of particle-filled polymer composites

Abstract

During the loading process, particle-filled polymer composites will soften due to damage to their internal microstructure, resulting in a decrease in stiffness, toughness, and strength. This study proposes a damage threshold strain prediction model for typical particle filled polymer composites (composite solid propellants) based on the theory of particle inclusion micromechanics. Firstly, uniaxial tensile tests were conducted on three sizes of bone shaped hydroxyl terminated polybutadiene (HTPB) propellant specimens at different loading speeds, and the damage threshold strain during the tensile process was determined based on the stress-strain curve and pseudo strain calculation method; Then, micro computed tomography was applied to test and statistically analyze the size and morphology of the HTPB propellant filling particles. Based on the statistical results of filling particles, a mathematical model was constructed to predict the damage threshold strain of solid propellants during uniaxial loading using micromechanics methods and Weibull damage statistics theory. Subsequently, optimization algorithms were used to determine the parameter values in the model, and the effectiveness of the model was compared and verified. The parameters in the model were analyzed, and the influence of each parameter on the damage threshold strain was elucidated, laying the foundation for the quantitative design of the mechanical properties of propellants in the future. The results indicate that the established model can predict the damage threshold of HTPB propellants with different loading rates and specimen sizes at the specimen level, demonstrating the potential of macro-microscopic methods in analyzing damage in viscoelastic particle reinforced composite materials.