Studies on Measurement of Yield Stress of Propellant Suspensions Using Forced Falling Ball and Slump Test

Abstract

Visco-plasticity characterized by yield stress is an important rheological property of composite propellant suspensions. The yield stress along with viscosity affects various unit operations in propellant processing as well as the quality of final product. The characterization of yield stress of propellant suspensions using direct measurement techniques, such as forced falling ball and slump test is described. The slump test is a simple and quick measurement tool with applicability at processing site whereas forced ball drop is useful for measurement of very high yield stress. The yield stress measurement of propellant suspension of four different compositions with varying particle size and volume fraction using above methods is reported and results are compared with vane geometry of rotational rheometer. Further, the yield stress behavior was studied for the propellant compositions with increasing solid loading. The dependence of yield stress of the studied propellant compositions on the reduced packing fraction f/fm of solids is established and expressed by a mathematical correlation. In addition, effect of vibration on yield stress was also studied using slump test.

Keywords

• composite propellant
• rheology
• yield stress
• forced falling ball
• slump test