In-situ investigation of damage evolution and mechanism in composite propellants under monochromatic X-ray irradiation

Synchrotron radiation monochromatic X-ray computed tomography (CT) is a powerful tool for in-situ characterization of the internal microstructure evolution in composite materials. However, prolonged X-ray irradiation during long-term in-situ studies may affect the structure and properties of material. While the effects of white beam irradiation have been widely investigated, the specific damage mechanisms and material sensitivity to monochromatic X-ray irradiation, particularly in composite materials like propellants, are not well understood. In this study, we identify the threshold irradiation time that triggers radiation damage in PBT propellant and observe the accumulation and worsening of damage over time, primarilyinitiated by ether bond cleavage, leading to radiation-induced decomposition and increased internal porosity. This resulted in a significant reduction in the mechanical strength of PBT propellant, particularly under prolonged exposure to synchrotron radiation. In contrast, the inert binder system HTPB propellant exhibited better radiation stability. Our study highlights the importance of considering both radiation-induced damage and material X-ray sensitivity when designing in-situ synchrotron radiation CT experiments for composite materials, and suggests that the development of dynamic experimental methods to further reduce the risk of radiation damage for high-reliability in-situ assessment of material properties, as well as the need for careful consideration of radiation effects in the design and safety evaluation of solid propellant systems working in extreme circumstance.