Aluminum agglomeration and combustion characteristics of PET-based solid propellants: Additive manufacturing vs. casting

The print sample exhibits superior combustion performance over the casted sample. • A linear correlation is observed between combustion temperature and burning rate. • The impulse exhibits a linear correlation with pressure for the printed sample. • Secondary merging mechanism of agglomerates is elucidated. Additive manufacturing (AM) provides a superior alternative to casting for solid propellants, enabling complex geometries alongside safer and more efficient manufacturing. This study compares the thermal decomposition behavior of binder systems for these two different processing methods, as well as combustion properties and aluminum agglomeration of the two different solid propellants. The results indicate significant distinctions between casted and printed samples in terms of combustion and aluminum agglomeration characteristics. Although the combustion temperature, burning rate, and impulse of both samples increase with rising pressure, the values for the printed sample are consistently higher than those of the casted sample. Furthermore, strong linear correlations are observed between the combustion temperature and burning rate of both samples, as well as between the impulse of the printed sample and pressure. Despite differences in the degree of aluminum agglomeration between the two samples, the evolutionary trends of their agglomeration behaviors exhibit high consistency. Under identical pressure, the number of agglomerates detaching from the burning surface is significantly greater for casted sample compared to printed sample. At lower pressures, larger or even irregular agglomerates are prone to form during combustion. The secondary merging location of agglomerates is determined by the competition between aerodynamic force and adhesive force. When aerodynamic force dominates, secondary merging tends to occur in the gas-phase flame zone. However, when adhesive force prevails, secondary merging is more likely to happen on the burning surface. The findings provide scientific support for the application of AM technology in the field of solid propellants. This study compares the combustion characteristics and aluminum agglomeration behavior of solid propellants prepared by additive manufacturing and casting, utilizing a visual online monitoring system. Download: Download high-res image (177KB) Download: Download full-size image