engleski

Study of mechanical properties of rocket db propellant during natural ageing

Various chemical reactions and physical processes (such as stabilizer consumption, migration and evaporation of NG, decomposition of NG and NC, etc.) take place in rocket propellant grains over the time, even under ambient storage conditions. The overall effect of these reactions and processes are the change of physical, chemical, thermal, ballistic and mechanical properties of rocket propellants with storage time, i.e. the reduction of propellants performances and safe service life. The aim of this work was to evaluate mechanical changes of rocket propellant – sustainer, as a part of in-service ATGM system, induced by “ natural” ageing after many years of storage. The results of the mechanical properties testing of double base rocket propellants in some selected antitank guided missiles (ATG), stored under ambient conditions up to 35 years, are presented in this paper. The mechanical properties are tested using dynamic mechanical analysis (DMA), uniaxial tensile and compression tests, and notch toughness test. It has been found out that the trend of changes of the mechanical properties during the storage time is evident, although in some cases the results of the tests are rather scattered (as a consequence of measuring uncertainty) and changes of some mechanical properties are not too pronounced. For example, after 15 years of storage at ambient conditions the glass transition temperature increases for about 5 oC, tan in the glass transition region decreases for about 5%, storage and loss modulus at 25 oC increase for about 15%, Young modulus at 23 oC increases up to 30%, notch toughness at -30 oC decreases up to 15 % etc. Other mechanical characteristics showed small but not significant trend of changes. Along with those tests, the stabilizer content and prooving ground test were also done.

mechanical properties; rocket propellant; natural ageing; dynamic mechanical analysis; tensile test

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