Mechanical Behavior Of Energetic Materials During High Acceleration
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Mechanical Behavior Of Energetic Materials During High Acceleration Y. Lanzerotti1 and J. Sharma2 1
U. S. Army TACOM ARDEC Picatinny Arsenal, NJ 07806 5000 2 Naval Surface Warfare Center, Carderock Division Silver Spring, MD 20903 ABSTRACT The mechanical behavior of explosives subjected to high acceleration has been studied in an ultracentrifuge at –10oC and 25oC. Melt-cast TNAZ and pressed TNAZ, LX-14, Composition A3 Type II, PAX-2A, and PAX-3 have been studied. Failure occurs when the shear or tensile strength of the explosive is exceeded. The fracture acceleration of melt-cast TNAZ is greater than that of pressed TNAZ at –10oC and 25oC. The fracture acceleration of PAX-3 is greater than that of Composition A3 Type II at –10oC and 25oC. The fracture acceleration of melt-cast TNAZ and pressed TNAZ at –10oC is about 10% less than at 25oC. The fracture acceleration of PAX-3 at –10oC is about 2.6 times that at 25oC. The fracture acceleration of Composition A3 Type II at –10oC is about 1.7 times that at 25oC.
INTRODUCTION We have introduced several new fields of research to study the mechanical behavior of energetic materials during high acceleration by using an ultracentrifuge [1-10]. Energetic materials are of significant interest for scientific and practical reasons in the extraction (mining) industry, structure demolition, space propulsion, and ordnance. In these applications the materials can be subjected to high, fluctuating, and/or sustained acceleration. The nature of the fracture process of such materials under high acceleration is of particular interest, especially in ordnance and propulsion applications. For example, explosives in projectiles are subjected to setback forces as high as 50,000 g during the gun launch process. These high setback forces can cause fracture and premature ignition of explosives. Fundamental understanding of the behavior of energetic materials subjected to high acceleration is a key to better practical ordnance designs that solve the problems of abnormal propellant burning and premature ignition of explosives during gun launch. An energetic material will experience a pressure gradient during acceleration in the gun and under g-loading in the ultracentrifuge. The pressure gradient that is experienced by the explosive during acceleration in the gun and under g-loading in the ultracentrifuge is unique and will produce different kinds of behavior and failure than under other material test conditions. This work is particularly relevant to the future development of insensitive energetic materials to be used in devices with higher acceleration. Previously, [1-10] we have used an ultracentrifuge to study the fracture behavior of TNT (trinitrotoluene), Composition B (59% cyclotrimethylenetrinitramine (RDX), 40% TNT, 1% wax), and four types of Octol (70% cyclotetramethylenetetranitramine (HMX), 30% TNT; 75% HMX, 25% TNT;
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