Study on strength criterion of composite solid propellants under complex loading

A solid rocket motor is the power source of the missile. In order to accurately evaluate its structural integrity and improve the reliability of the power system, it is mandatory to construct an accurate strength criterion for the composite solid propellant. For investigating the strength criterion of the composite solid propellant, a series of experiments were carried out, including solid propellant uniaxial/biaxial stretch and compress strength experiments, stretch–compress experiments, and uniaxial stretch experiments under confining pressure. Several stress–strain curves were obtained based on observing and analyzing the propellant deformation under different stress conditions. In addition, the strength and elongation rate envelope curve of a composite propellant under a biaxial stress state was obtained. Furthermore, based on the unified strength theory of uniaxial, biaxial, confining pressure, and double shear, the biaxial strength and confining pressure strength criteria of the composite solid propellant were established.