Experimental and numerical investigation on dynamic deformation and ignition response of NEPE-based propellants

An experimental and numerical study has been conducted to investigate the effects of strain rates on the mechanical responses and ignition mechanism of NEPE-based propellants (Nitrate Ester Plasticized Polyether). The modified split Hopkinson pressure bar (SHPB) equipped with a high-speed camera was used to capture the mechanical-chemical feature images during the whole impact process. The macro-mesoscopic thermomechanical model was employed to describe the viscous shear flow hotspot formation at the mesoscale. The results showed that the mechanical and ignition responses of the NEPE-based propellants are heavily dependent on strain rates. It is observed that the impact processes can be summarized into four stages: homogeneous deformation, shear flowing, initiation of local shear region and ultimate fracture (or ignition). Selected image sequence and SEM images indicate that viscous shear flow is important to the ignition of propellants. The calculated axial stress-strain curves indicate that propellant exhibits a remarkable rate-dependence and viscous effect. The predicted features of hot spot-ignition evolution are consistent with the experimental phenomenon and prove the critical strain rate of ignition is 4500 s⁻¹.