A Review of Crack Study Methods in Composite Solid Propellants

Cracking is the breaking of bonds in a part of the propellant polymer due to the existing stresses that change the structure of the propellant polymer and they are classified into two general categories: macrocrack and microcrack. The service life of rocket engines is largely a function of the mechanical properties of the solid rocket propellant, the aging characteristics of the rocket propulsion, the grain design, and the environmental conditions that it undergoes during operation. The mechanical properties of solid rocket propellants are critical to the good performance of rocket engines. Increased combustion of propellant grains due to the presence of undesirable cracks and cavities can cause improper performance. This article reviews the causes of cracks due to heat stress, mechanical fatigue, humidity, temperature, corrosion, light, as well as crack detection methods such as radiography, mechanical waves, microscopy and infrared waves