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Thermal and mechanical damage of PBX's

The TNO Prins Maurits Laboratory, has conducted research in energetic material response to several Insensitive Munition (IM) stimuli like cook-off, bulletfragment impact and shaped charge impact. In addition to the development of highly instrumented test set-ups, predictive computer codes are also in development. The response of energetic materials to these stimuli, depend strongly on the properties of these materials at onset and during an event. To understand the mechanisms and the parameters influencing the response, these materials have been tested in laboratory scale experiments. The mechanical properties have been measured as a function of the strain rate (0.001 m/s-5m/s,) in the temperature range from −60 up to 60°C. In addition to tensile-strength testing, relaxation testing for the same temperature range, has been performed. These experiments determine the Poisson ratio and time-temperature dependence of the mechanical properties of the explosive at intermediate and high strain rates impact, at ambient temperatures (rates that can be found in experiments like the gas gun and bullet/fragment impact experiments). Optical microscopy as well as scanning electron microscopy has been used to examine the samples after impact. The information is then used in the erosion/damage models for Autodyn calculations. To assess thermal damage, mechanical properties have been measured as a function of the temperature (up to 160°C) and as a function of the degree of decomposition. These parameters will be used in cook-off computer models, to couple the thermal-chemical behaviour to the mechanical response. Also, laboratory scale experiments, shock initiation and fragment impact tests have been performed with damaged material. An overview of the research is presented in this paper.