Determination of crucial thermomechanical parameters of solid rocket propellants after long-time storage in terms of operational safety

The paper presents experimental research on the thermomechanical properties of solid homogeneous rocket propellant used in anti-tank guided missiles, after long-term storage, with the use of modern analytical tools. A periodic control testing system for munitions and explosives is essential for maintaining the state’s self-defense capabilities. The parameters investigated of the propellant include the thermal decomposition temperature, glass transition, softening temperatures, and the coefficient of thermal linear expansion. These characteristics are essential for the safe operation of rocket motors. The temperature changes to which a rocket motor may be subjected during storage and operation can cause stresses to appear in the rocket propellant grain. This may lead to cracking of the material and, consequently, an uncontrolled increase in the combustion surface, which can result in a sudden increase in pressure in the combustion chamber and, in the worst case, an explosion of the missile during launch. Therefore, conducting comprehensive studies of the thermomechanical properties of stored propellants is necessary, using reliable tools that provide repeatable results. The thermal decomposition of the propellant was determined using the TA Instruments Discovery DSC 250 and Discovery TGA 5500, with a heating rate of 10 K min −1 for both methods. The results of calorimetric and gravimetric analysis provide the upper temperature limit for the mechanical analysis, in which the samples of the propellant are much larger. The mechanical characteristics of the tested propellant were determined using the Netzsch Dynamic Mechanical Analyzer DMA 303 Eplexor device, in the temperature range from − 120 to 100 °C, with a heating rate of 2 K min −1 . The glass transition temperature was determined according to the STANAG 4540 agreement. Thermal linear expansion was studied using the Netzsch Thermomechanical Analyzer TMA 402 F3 Hyperion in the temperature range from − 100 to 80 °C, with a heating rate of 2 K min −1 . Both mechanical analysis techniques show compliance in the results of glass transition and softening temperatures.