Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session D6: ME.1 Particulate/Porous Materials III |
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Chair: Darcie Dennis-Koller, Los Alamos National Laboratory Room: Cascade II |
Monday, July 8, 2013 1:45PM - 2:00PM |
D6.00001: Thermodynamic Work of Adhesion measurements of Polymer Bonded eXplosive constituents via the Wilhelmy Plate technique and their application to Atomic Force Microscope pull-off experiments David Williamson, Neil Hamilton, Stewart Palmer, Andrew Jardine, Claire Leppard There is much evidence that the major strength limiting factor for Polymer Bonded eXplosives above their glass-transition conditions is the magnitude of adhesion that exists between the polymeric matrix binder-system and the filler particles. Experimental measurements of the free surface energies of a number of binders have been made using the Wilhelmy Plate Technique. These data can be combined with equivalent data on the filler particles to calculate the so-called Thermodynamic Work of Adhesion that exits between the matrix and filler particles. This under-pinning quantity can be used to predict the levels of load (stress) required cause debonding in different geometries. A simple geometry of interest is that of spherical-caps of polymers debonding from flat substrates. Experiments using this geometry have been performed with an Atomic Force Microscope pull-off technique to measure the critical loads (stresses) required for debonding. There is good agreement between the predicted values based on the Wilhelmy Plate data, and the measured values from the Atomic Force Microscope. Such understanding and experimental data are required for the development and validation of microstructural models for predicting mechanical behaviour over the whole life cycle. [Preview Abstract] |
Monday, July 8, 2013 2:00PM - 2:15PM |
D6.00002: Mechanisms of fragmentation and microstructure of debris generated during explosive testing of Al-W granular composite rings Po-Hsun Chiu, Karl Olney, Chris Braithwaite, Andrew Jardine, Adam Collins, Gregory Fritz, Adam Stover, David Benson, Vitali Nesterenko Al oxidation has a potential energy release nearly 5 times that of traditional high explosives; however, the oxidation rate scales with the Al particle size. To oxidize on a time scale of $\sim$1ms, Al particle size needs to be on the order of 20 microns. Highly heterogeneous materials with constituents having drastically different densities and shock impedances (e.g., Al and W) may provide additional mesoscale mechanisms to pulverize the material into much smaller fragments. Explosively driven expanding ring experiments were conducted with Al-W granular composite rings with different morphologies (axial/elongated particles of W, bonded/unbonded Al particles processed using cold and hot isostatic pressing). Recovered fragments showed a significantly reduced fragment sizes compared to a homogeneous sample. Examination of the fragments using SEM showed a propensity for fragments to be composed of a cluster of Al and W particles with little plastic deformation in the interior Al. Hydrocode simulations were conducted to gain an insight into this clustering behavior. Understanding of the mesoscale mechanisms may be useful to generate more efficient mesostructures and tailor the size of generated fragments based on the loading conditions. Funding was provided by ONR MURI N00014-07-1-0740 (Program Officer Dr. Clifford Bedford) [Preview Abstract] |
Monday, July 8, 2013 2:15PM - 2:30PM |
D6.00003: Experimentally obtained hugoniot measurements for granular solids Darcie Dennis-Koller, R. Jason Scharff, D. Anthony Fredenburg Porous/granular materials are a class of materials where historical Hugoniot data is frought with difficulty leading to unreliable data or extremely large associated errors. This presentation will present new experimental methods for obtaining reliable experimental Hugoniot data as well as attempt to describe the physical mechanisms responsible for anomalous behavior observed in distended systems. [Preview Abstract] |
Monday, July 8, 2013 2:30PM - 2:45PM |
D6.00004: Explosive formation of coherent particle jets David Frost, Jean-Frederic Ruel, Zouya Zarei, Sam Goroshin, Yann Gregoire, Fan Zhang, Alec Milne, Aaron Longbottom A high-speed jet of solid particles may be formed by detonating an explosive layer lining the outside of a conically-shaped volume of particles. Experiments have been carried out to determine the velocity history and the coherency of a particle jet formed using this shaped-charge arrangement. Important parameters include the cone angle, the ratio of the masses of the explosive and particles, and the particle size and density. Dense particles (e.g., iron) form thin, stable, coherent jets, whereas lighter particles (e.g., glass or Al) lead to more diffuse jets. The jet velocities observed experimentally were close to the predictions from a Gurney velocity formulation for conical geometry. The effects of cone angle and particle density on the jet formation and development were explored with calculations using a multimaterial hydrocode. The simulations indicate that the converging shock and Mach disk within the particle bed have a strong influence on the uniformity of the particle density field. With iron particles, the particle volume remains coherent whereas for glass particles, during the particle acceleration phase, the shock interactions within the particle bed cause the particles to be concentrated in a thin shell surrounding a low density region. [Preview Abstract] |
Monday, July 8, 2013 2:45PM - 3:15PM |
D6.00005: Shock and Release of Duocel$^{\mbox{textregistered}}$ Aluminum Foam {\&} Polyvinylidene Fluoride Composite Up to 20 GPa Invited Speaker: Warren Maines Considerable interest in characterizing the dynamic response of heterogeneous materials under dynamic loading conditions exists because of their energy absorption and dissipation qualities. In the present study,4 pores per centimeter 6101 T-6 aluminum foam, which was initially at 6-8{\%} relative density of solid aluminum, was later compressed longitudinally to 20{\%} relative density, (11 pores per centimeter) and filled with polyvinylidene fluoride (PVDF). The composite was then shocked up to 20GPa using AFRL's 60mm smooth bore powder gun. Results of these experiments will be compared to that of porous aluminum that was not filled. Further, computations at the meso-scale, which tracked well with experiments, highlighted the range of velocity distributions, as well as the damping caused by the addition of plastic. In particular, due to filler that was fairly close in density to the aluminum, the particle velocity variation was relatively low compared to porous foams from previous studies. The behavior of the composite was dominated by the presence of the plastic filled material, which demonstrated dissociation at pressures greater than 8 GPa. [Preview Abstract] |
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