INVESTIGATION ON IMPACT INDUCED ENERGY RELEASE OF PYROPHORIC ALLOY FRAGMENTS USING TIME RESOLVED EMISSION SPECTROSCOPY

Abstract

Technical advancement in material production open new doors in developing reactive material (RM) compounds that combine structural strength with exothermal energetic characteristics. Utilized to exchange inert materials, such as warhead shells, RM enhance the lethal effects. The warhead is initiated, its RM shrapnel accelerated and impact the secondary targets. Upon impact, an impact induced energy release (IIER) occurs in form of exothermal chemical reaction of the RM on the target material. For a repeatable and comparable results, a dedicated experimental set-up has been developed where single cylindrical RM fragments of a diameter D=5 mm and the same length L (L/D=1) represent the shrapnel. They are ballistically driven at initial velocities vi=1500 m/s, using a 7.62 mm powder gun. The RM fragments consists of Ferrocerium, a pyrophoric commercial alloy. Although, Ferrocerium is not primarily a candidate to replace warhead shells, its IIER is academically very suitable for the development of experimental measurement techniques. In order to understand the chemical reaction and quantify the IIER, two parameters are measured, the light emission and the pressure. Time integrated and time-resolved emission spectra, obtained by a Czerny-Turner spectrograph are discussed in this paper. From the investigated wavelength of the oxidation of lanthanum, a predominant compound of the Ferrocerium RM, temperature can be derived between 2300° and 3000° C. In addition, the RM fragment is launched in a closed chamber with pressure sensors and a pressure measurement is taken simultaneously with the light emission. In order to protect against RM enhanced weaponry, the effects of IIER need to be understood.