Bridge Burst Characteristics of Aluminum and Copper Thin-Film Bridges in Electrical Initiation Devices

Abstract

The optimal design of electrical initiation devices for explosive charges and other high energy materials critically depends on the bridge burst or the electrical explosion of the thin-film metallic bridges. It is therefore quite important to select the right material with suitable explosion properties for the metallic bridge film. However, so far, no dedicated studies, experimental or theoretical, have been carried out to quantify those explosion properties for thin-filmed bridges of various metals. This study employed numerical modeling of the joule heating and bridge plasma expansion by intense electrical energy deposition in aluminum and copper bridges to evaluate and compare the explosion properties such as bridge burst time, bridge burst current density, and threshold charging voltage for the two metallic bridge materials. The prediction model of bridge burst also considered a pulsed electrical input from an RLC initiation circuit as well as plasma property calculations of the aluminum and copper plasma vapor for the state equation of the ionized vapor and the plasma electrical conductivity. The numerical predictions were in excellent agreement with the corresponding measured data of bridge bursts in a series of exploding foil initiator firing tests. The copper bridge was found to possess better explosion properties than the aluminum bridge, showing significantly higher bridge burst current density and threshold charging voltage. These findings confirmed that the copper bridge may provide higher safety and reliability in electrical initiation devices. The theoretical model and results in the present study could be useful for selecting bridge materials and designing electrical initiators or other metallic bridge explosion applications. (Received December 4, 2017; Accepted January 10, 2018)