Comparative study on mechanical properties and combustion characteristics of additive manufacturing/casting composite solid propellants

Compared to casting process, the advantages of additive manufacturing (AM) technology, such as the elimination of mold requirements, and enhanced adaptability to complex geometries, render it highly promising for applications involving the configuration of energy release gradients, and regulation of combustion processes. To explore the disparities in mechanical performance and combustion characteristics of printed and casted propellants, a computed tomographic scanner and a universal testing machine were employed to characterize the pore structure and tensile strength. A visual online detection experimental system was established to investigate the combustion characteristics under 1–9 atm, with the condensed combustion products (CCPs) being diagnosed. Results indicate that the printed sample exhibits a lower porosity, a higher density, and a greater tensile strength. Under identical pressure, the radial flame diffusion of printed strand is weaker, whereas the axial diffusion is stronger. The burning rates and combustion temperatures of the printed strand consistently exceed those of the casted strands, with this disparity progressively widening during pressure increasing. Moreover, the printed strand exhibits enhanced combustion stability. The diagnostic results indicate that the CCPs can be categorized into smoke oxide particles (SOPs), spherical agglomerates (SAGs) and irregular agglomerates (IAGs), and the particle size of the printed strand is smaller than that of the casted strand under high pressures. The printed strand exhibits characteristic of complete combustion at lower pressures, as evidenced by the obvious high XRD peak of Al2O3 and the higher combustion efficiency. The AM process reduces the porosity of propellant, thereby intensifying the consumption rate of reactants, and increasing the combustion intensity. This study contributes to a deeper understanding of the application of AM on the solid propellants.