The Effect of Sub-Zero Temperature and High Strain Rate on Mechanical Strength of 9/7 ‘Oak’ Gun Propellant

The article presents the results of compressive strength testing of samples made from 9/7 ‘Oak’ (”Dąb” in Polish) gun propellant under various mechanical and thermal load conditions. The strength tests were conducted in accordance with the split-Hopkinson pressure bar (SHPB) method. The findings indicate that the mechanical behaviour of the tested gun propellant resembles that of some thermoplastic polymers. As the strain rate increases, 9/7 propellant becomes stiffer, and its compressive strength increases, but it maintains good plastic properties, i.e., material samples do not crack under dynamic load. This demonstrates, on one hand, the high sensitivity of the gun propellant to strain, and on the other, its strong resistance to brittle fracture under shock loading conditions. However, it was found that the combined effect of strain rate and lowered temperature (-50C) leads to increased brittleness of the propellant and fracture of the samples.