| Popis: |
Because of their viscoelastic nature, double based rocket propellants may undergo the degradation of their mechanical properties, which can significantly influence their stability. Because of safety reasons, it is necessary to establish an appropriate method for the prediction of the propellants behaviour over a long-term period of time under defined temperature conditions. Applying accelerated temperature measurements and time-temperature superposition (TTS) treatment of the data, limited lab testings (creep or stress relaxation) is sufficient to project long-term properties under different conditions. Dynamic mechanical analysis, which measures the modulus and damping properties of material, is one of the most convenient thermal analysis techniques that can be applied for time-temperature superposition approach. The goal of this work was to investigate the applicability of the TTS principle to the prediction of the mechanical properties of double based rocket propellants during the ageing. The master curve was generated on the basis of the creep measurements in the temperature region from -71 to +20 °C, by a dynamic mechanical analyser. The generated master curve was mathematically described by Williams-Lander-Ferry (WLF) and Arrhenious models. Material constants in the WLF equation were determined to be C1=44.43 and C2=308.4, and the viscoelastic activation energy from the Arrhenious equation was determined to be E_a= 152.7 kJ/mol. The results have shown that the TTS principle is applicable to the prediction of the propellants behaviour during a long-term period of time at defined temperature conditions. |
