Jonathan Zucker

Frictional heating and ignition of energetic materials

For many years, powder friction tests have been an integral part of explosives sensitivity and safety testing. More recently, oblique impact tests have been used in the hazard assessment of monolithic charges. However, these tests are simply threshold tests for reaction, and relatively little work has been done to try to examine the processes that lead to frictional heating and ignition of energetic materials. We report the results from a series of experiments in which energetic materials are subjected to frictional heating under closely‐controlled conditions (normal load, sliding speed, grit quantity and composition, substrate). The response of the energetic material and grit, if present, is observed by optical and infrared high‐speed photography to determine the nature of the interactions between the test material, grit and substrate, and the mechanisms by which the energetic material may be heated to ignition.

Interplay of explosive thermal reaction dynamics and structural confinement

Explosives play a significant role in human affairs; however, their behavior in circumstances other than intentional detonation is poorly understood. Accidents may have catastrophic consequences, especially if additional hazardous materials are involved. Abnormal ignition stimuli, such as impact, spark, friction, and heat may lead to a very violent outcome, potentially including detonation. An important factor influencing the behavior subsequent to abnormal ignition is the strength and inertia of the vessel confining the explosive, i.e., the near-field structural/mechanical environment, also known as confinement (inertial or mechanical). However, a comprehensive and quantified understanding of how confinement affects reaction violence does not yet exist. In the research discussed here, we have investigated a wide range of confinement conditions and related the explosive response to the fundamentals of the combustion process in the explosive. In our experiments, a charge of an octahydrotetranitrotetrazine-...

Molten Composition B Viscosity at Elevated Temperature

A shear-thinning viscosity model is developed for molten Composition B at elevated temperature from analysis of falling ball viscometer data. Results are reported with the system held at 85, 110, and 135°C. Balls of densities of 2.7, 8.0, and 15.6 g/cm3 are dropped to generate a range of strain rates in the material. Analysis of video recordings gives the speed at which the balls fall. Computer simulation of the viscometer is used to determine parameters for a non-Newtonian model calibrated to measured speeds. For the first time, viscosity is shown to be a function of temperature and strain rate–dependent maximum RDX (cyclotrimethylenetrinitramine) particle volume fraction.

Thermal Decomposition Models for High Explosive Compositions

As interest in the cook‐off response of high explosives expands to include commercially‐available compositions, the need has arisen for a broad spectrum of predictive capabilities to describe the untoward thermal decomposition of these explosives. Empirical models for several compositions, including PETN, Semtex and Comp B, have been developed and tested against existing experimental data. Models for Semtex 1A and RDX are presented and discussed.

Cookoff of non-traditional detonators

Significant work has gone into understanding the cookoff behavior of a variety of explosives, primarily for safety and surety reasons. However, current times require similar knowledge on a new suite of explosives that are readily attainable or made, and are easily initiated without expensive firesets or controlled materials. Homemade explosives (HMEs) are simple to synthesize from readily available precursor materials. Two of these HMEs, triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) are not only simple to prepare, but have sufficient output and sensitivity to act as primary explosives in an initiation train. Previous work has shown that detonators may be an integral vulnerability in a cookoff scenario. This poster contains the results of cookoff experiments performed on detonators made with TATP and HMTD. We found that the less chemically stable TATP decomposed during heating, while the more chemically stable HMTD acted like a traditional primary explosive, namely reaction vio...

THERMAL IGNITION OF DETONABLE HYDROGEN PEROXIDE COMPOSITIONS

Hydrogen peroxide can be mixed with a variety of fuels to produce detonable compositions. These compositions can be thermally unstable and their behavior can be difficult to predict. Furthermore, the addition of some acids to the mixture could increase its sensitivity. Presented here are the outcomes of cookoff experiments performed on hydrogen peroxide and fuels compositions, as well as an acid‐sensitized mixture. Soak temperatures of 88° C, 84° C and 82° C were used, with reaction times of 3010 seconds, 3560 seconds and 3230 seconds, accordingly. The acid‐sensitized experiment, when soaked at 82° C, reacted after just 2450 seconds.