Study on Delayed Extrusion Behavior in Additive Manufacturing Process of Solid Propellants

In this study, the delayed extrusion behavior during the additive manufacturing of solid propellants and its adverse effect on the forming quality were discovered. Targeting this phenomenon, rheological studies were conducted on propellants with different filler gradations to analyze the viscoelastic characteristics of the propellant slurries and compare the differences in their creep behaviors. The results show that in the linear viscoelastic region, the propellant slurry completes the phase transition from decelerated creep to steady-state creep within 5 minutes of testing. A decrease in the content of coarse-grained ammonium perchlorate (AP) leads to a significant reduction in the relaxation time of the slurry, weakened elastic performance, decreased structural strength, increased susceptibility to deformation, and thus larger creep strain. During the creep recovery stage, the recovery strains of slurries with different filler gradations are similar, indicating that the elastic strain is mainly affected by the binder matrix. Without changing the propellant performance, further optimizing the nozzle structure and reducing the cavity volume is the optimal approach to solve the delayed extrusion behavior.