Economical and Consistent Test Methodology for Energy-Absorbing Materials Used for Mitigation of Explosive Effects on Structures

Abstract

This paper discusses the use of an economical ballistic pendulum device to study the effectiveness of energy-absorbing materials to mitigate explosive detonation effects. Besides closing a structure, engineers must develop innovative measures to mitigate the effects of the extreme blast environments expected from very close-in (near-contact) detonations against key structural components. Beyond conventional structural hardening, using energy-absorbing materials to protect structures from blast effects is an option considered but not fully understood. As new materials have evolved in recent years, interest has increased in their potential use as energy absorbers for near-contact blast mitigation. For these new materials, constitutive models are either nonexistent or not well developed for predicting high-pressure and high-strain rate responses. Experiments using the ballistic pendulum were conducted rapidly and with little logistical burden; for one series of tests, over 30 experiments were conducted in 1 week. This fundamental experimental setup produced a wealth of previously nonexistent data on a variety of energy-absorbing materials, such as an elastomer (rubberlike compound), dense foams, a dilatant compound, and liquids. The ballistic pendulum was used to measure the total momentum imparted to the bob from a close-in detonation as a function of absorber materials and distance from the bob. These results provided a comparison of impulse delivered to the bob among the absorber materials with the control measurement of no absorber. Results indicate that, for near-contact detonations, the addition of energy-absorbing materials increased the impulse loading to the pendulum for selected scaled ranges of simulated threats.