Experimental characterization and numerical modeling of additive-manufactured composite solid rocket propellant with anisotropic density

Abstract

Additive manufacturing (AM) allows for fabrication of functionally-graded energetic materials such as solid rocket propellant. Significant improvements in grain geometry control and burn rate manipulation may be realizable, but new defects unique to AM processes must be characterized to understand their influence on material performance. The objective of this thesis research is to characterize defects in 3D-printed ammonium perchlorate composite propellant (APCP) related to processing conditions and model their effect on deflagration. X-ray photoelectron spectroscopy (XPS) and x-ray computed tomography (XCT) analysis methods are used to quantify binder photopolymerization and porosity in the build direction, respectively. A model is developed to predict degree of polymerization as a function of depth and experimental data are fit. XCT imaging results indicate that porosity in 3D-printed APCP is attributed to poor inter-layer adhesion and binder phase separation. The slow powder burn equation of state available in ANSYS Autodyn hydrocode software is used to model APCP deflagration as a function of the experimental porosity data, but model results were not compared to experimental closed-bomb data in this research. Results repeatability would be improved in future embodiments of this research that analyze higher-quality 3D-printed APCP samples.