Numerical Analysis on Acceleration Process and Shock Initiation of Parylene C−Cu Flyer in Exploding Foil Initiator

Abstract

AbstractParylene C flyer coated with copper film was often used to shock and initiate insensitive explosives in exploding foil initiator (EFI). However, there were few studies on the acceleration process of parylene C−Cu flyer and the shock initiation induced by parylene C−Cu flyer. In this paper, exploding bridge foil was treated as a kind of special explosive to launch parylene C−Cu flyer, and an instantaneous explosion model was established to describe the acceleration process mathematically. Then, two‐dimensional numerical simulations were carried out using ANSYS/AUTODYN software to analyse the flight history and morphology of parylene C−Cu flyer, as well as the effect of copper film on flyer velocity. Finally, shock initiation of parylene C−Cu flyer impacting ultrafine hexanitrostilbene (HNS‐IV) was also simulated, and the initiation threshold was determined by adjusting the flyer velocity at the collision moment. Compared with previous work, calculated results exhibit good agreement with the experimental data, that is addition of Cu film can indeed improve the shock pressure but leads to lower flyer velocity. For parylene C−Cu flyer with the thickness of 25 μm–3.6 μm, its flyer velocity drops to half of parylene C flyer under same operation conditions, and the initiation threshold that can initiate the HNS‐IV pellet is 2300 m/s. All the results demonstrate that the numerical approach will be useful for the optimization of parylene C−Cu flyer, even any kind of multi‐layer flyer.