Multiscale deformation behavior of polymer bonded explosives subjected to intermediate velocity impact

We present a multiscale experimental investigation of polymer bonded sugar, a mechanical simulant of polymer bonded explosive, subjected to impact loading. The experiments are conducted by shooting a projectile onto the specimen at an impact velocity of 56 m/s using a modified split Hopkinson bar apparatus. Images at two different scales are captured for macroscale and mesoscale deformation measurement during the loading at a rate of 2 million frames/second. The local deformation measurement is conducted using a newly developed high speed-high spatial resolution image based diagnostic technique. Based on the macroscale full-field deformation, the compression wave velocity and the compression wave thickness are calculated. Further, the stress in front and behind the compression front is calculated. It is observed that the compression wave width is not constant, instead, increases as it propagates towards the support end of the specimen. The change in compression wave width could be due to energy dissipation during the propagation of the compression wave. The meso-scale measurement provided much insight into the dissipation mechanism involved during the compression wave propagation. The plastic deformation of a binder and local damage such as grain fracture and relative sliding of crystals have been observed that could have contributed to the energy dissipation in the material.