Impact Initiation of Rods of Pressed Polytetrafluoroethylene (PTFE) and Aluminum Powders

ORAL

Abstract

A gas gun has been used to investigate the impact initiation of rods consisting of a mixture of 72 wt{\%} PTFE (28 $\mu $m particle size) and 28 wt{\%} aluminum (95 micron particle size) powders. The rods were 7.6 mm in diameter by 51 mm long, and were fabricated from material that had been pressed and sintered to a full density of 2.27 gm/cm$^{ 3}$. They were sabot-launched into steel anvils at impact velocities ranging from 468 to 970 m/sec. This corresponds to calculated initial impact stresses of 25 to 64 kbar, respectively. A framing camera was used to observe the time sequence of events. These include change in rod shape, fracture, and the initiation and evolution of the reaction phenomena. The time of observation of first light after impact was taken as the initiation time. Initiation occurred at discrete locations in the impacted material. At the lowest impact stress of 25 kbar no light was observed; this value was taken as the initiation threshold stress for this material. Above the initiation threshold, the initiation time dropped abruptly from 74 $\mu $s just above threshold to 14 $\mu $s at the highest impact velocity of 970 m/s. These results are compared with rod impact experiments for a similar material [1] in which the only major difference is a smaller aluminum particle size (9 micron). [1] W. Mock, Jr. and W. H. Holt, in Proc. APS Shock Compression of Condensed Matter--2005, p.1097.

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Authors

  • Willis Mock

    Naval Surface Warfare Center Dahlgren Divison, Naval Surface Warfare Center

  • A. Rajendran

    DE Division, LANL, Chemistry Division, LANL, University of Cambridge, Sandia National Laboratories, Los Alamos National Laboratory, LLNL, UCSD, Institute of Fluid Physics, CAEP, Institute for High Energy Densities, JIHT RAS, Massachusetts Institute of Technology, Lawrence Livermore National Laboratory, DRDC Suffield, Lockheed Martin Corporation, Laboratoire de Combustion et de D\'etonique (UPR du CNRS n9028), ENSMA, B.P. 40109, 86961 Futuroscope Cedex, France, Wash. State Univ., McGill University, Naval Surface Warfare Center, Dahlgren, Air Force Research Laboratory (AFRL/MNME), Harvard University, Fraunhofer, Ernst-Mach-Institut, Materials and Structures Laboratory, Tokyo Institute of Technology, CEA Valduc, LMPM, ENSMA Poitiers, France, LCD, ENSMA Poitiers, France, Applied Research Associates, Seismological Laboratory MS 252-21, California Institute of Technology, Pasadena, CA 91125, Department of Geological Sciences, Brown University, Providence, RI 02912-1846, Lawrence Livermore National Laboratory, University of California, Department of Aeronautics and Astronautics, Faculty of Engineering, Kyushu University, National Institute of Advanced Industrial Science and Technology, Energetic Materials Technology, NSWC Indian Head, AWE, UK, Los Alamos National Laboratory, Materials Science and Technology Division, Seoul National University, University of Duisburg-Essen, Germany, University of Lund, Sweden, University of Oxford, UK, AWE, Aldermaston, UK, LANL, IHED of JIHT RAS, Dorodnicyn Computing Center RAS, Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900, Materials Science and Engineering, OSU, Columbus, OH, RFNC - VNIIEF, Sarov, Russia, School of Materials Engineering, Purdue University, West Lafayette, IN 47907, Applied Physics Division, Los Alamos National Laboratory, Los Alamos, NM 87545, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, University of Manchester, AWE, Aldermaston, HCEI, Russian Federal Nuclear Center - VNIIEF, Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, P.O.Box 919-102, Mianyang 621900, P. 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