Correlation between the micro-structure and macroscopic mechanical properties of GAP-based propellant during aging

Abstract

The correlation between the macroscopic mechanical properties and micro-structure of glycidyl azide polymer (GAP)-based solid propellants during aging has been studied. A typical 60 °C–180 d high-temperature accelerated aging experiment on propellants was conducted. The changes in micro-structure were analyzed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), scanning electron microscope (SEM), and component analysis of the plasticizer and stabilizer. Changes in the macroscopic properties were analyzed through uniaxial tensile tests. The experimental results indicated that the micro-structure aging mechanisms of the propellants were the chain breakage of crosslinking networks, decomposition of plasticizers, and dissolution of CL-20 particles. The macroscopic mechanical properties were characterized by a gradual decrease in the maximum tensile strength, maximum elongation, dewetting strain, and elastic modulus during the aging process. Through mesoscopic simulation methods and correlation analysis, the relationship between the macroscopic mechanical properties and micro-structure was further established. The macroscopic mechanical properties of propellants are effected by the coupling of microscopic aging mechanisms. Chain breakage of the crosslinking networks and decomposition of the plasticizers lead to a decrease in the elastic modulus of the binder matrix. The elastic modulus of the binder matrix effects the change in the elastic modulus of the propellant. The dissolution of the CL-20 particles results in a decrease in the interface strength. The interface strength mainly causes a decrease in the maximum tensile strength, maximum elongation, and dewetting strain. These results are important for developing reliable predictive aging models for GAP-based propellant.