Effect of tension of a composite propellant on its burning rate

Existing concepts of the effect of tensile strains on the burning rate of propellants are analyzed. It is demonstrated that the basic mechanism of increasing burning rate of composite propellants under tension is spalling of the binder from oxidizer particles, formation of an additional burning surface, and changes in the combustion-zone structure. To describe this effect, a rheological model of a composite solid propellant is developed, which takes into account separation of the binder from disperse particles of the fillers (oxidizers, coolants, metals, etc.). A criterion is found, which describes the difference between the propellant behavior under tension with spalling of the binder from the particles and the tension of the same material without the emergence of internal defects. A method of experimental determination of the number of defects arising in the propellant under tension, based on analyzing the tensile stress-strain diagram of the material, is proposed. A mathematical model of composite propellant combustion is developed, which takes into account separation of the binder from the oxidizer particles and formation of an additional burning surface. A correlation between the change in the burning rate of the propellant under tension and parameters of the propellant tensile diagram is found. A method for predicting the change in the burning rate of the propellant under tension on the basis of the propellant tensile diagram shape is developed.