Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session Y6: SMGPB: Soft Materials I |
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Chair: Peter Gould, Qinetiq Room: Galleria South |
Friday, June 21, 2019 9:15AM - 9:45AM |
Y6.00001: Dynamic Strength Measurements in Polymethylmethacrylate (PMMA) Invited Speaker: Jennifer Jordan In a 1996 paper by Bat'kov and co-workers, the dynamic strength in several polymer systems was shown to increase with longitudinal stress to some critical stress and subsequently fall off to zero. The authors attributed this to the increased temperature in polymers at high pressures resulting in decreased strength. In this study, the dynamic strength of PMMA was determined using longitudinal and lateral manganin gauges across a wide range of pressure inputs. The dynamic strength as a function of input pressure will be presented.\\ \\In collaboration with: Daniel Casem, Nicholas Lorenzo, U.S. Army Research Laboratory; Blake Sturtevant, Los Alamos National Laboratory [Preview Abstract] |
Friday, June 21, 2019 9:45AM - 10:00AM |
Y6.00002: ABSTRACT WITHDRAWN |
Friday, June 21, 2019 10:00AM - 10:15AM |
Y6.00003: Dynamic Strength and Friction Behavior of Thermosetting Polyurethane and Epoxy Peter Sable, Christopher Neel, John Borg Flyer-plate impact experiments were performed on fully-dense polyurethane and epoxy to characterize and model the dynamic material response. Uniaxial and oblique impact configurations were employed to specifically isolate yield strength and friction phenomena at high strain-rate, with impact velocities ranging from less than 50 to 1200 m/s. Oblique impact tests utilized a slotted-barrel gas gun to maintain the orientation of a keyed projectile with an angled face. Upon impact, pressure and shear stress waves were generated creating a combined, off-Hugoniot, stress state within the target. States were then inferred from particle velocity measurements using Photon Doppler Velocimetry. Measured Hugoniots resemble others in literature; including nonlinear effects seen below particle velocities of 150 m/s attributed to viscoelasticity. Oblique impact results show a pressure-dependence of yield strength for both polymers, up to maximum pressure ``cap''. Strain-rate dependent strengthening was also apparent when compared alongside low-rate data. Friction coefficients taken for polymer-aluminum tribo-pairs were found to be inversely proportional to pressure. Drucker-Prager yield surfaces were fit from data and implemented into CTH, with experiment-based Mie Gruneisen equations-of-state. The resulting simulations were able to adequately recreate the polymer response. [Preview Abstract] |
Friday, June 21, 2019 10:15AM - 10:30AM |
Y6.00004: Extension of the window correction for Kel-F 800: a near-impedance matched window for high explosives Lloyd Gibson, Dana Dattelbaum, John Lang, Justin Jones, Andrew Houlton, Brian Bartram The chemical reaction zone (CRZ) of detonating explosives is defined by the leading, inert shock front, which compresses the explosive to the von Neumann (vN) spike condition on the unreacted Hugoniot, and the Chapman-Jouget (CJ) sonic locus condition according to the Zel'dovich/von Neumann/Doering (ZND) 1-dimensional theory of detonation. The CRZ is often measured using optical velocimetry techniques at a windowed interface; the window affects the reaction zone dynamics due to wave interactions at the interface. Fluoropolymer windows are attractive as they provide a near-impedance match to most common explosives, with initial densities $\rho $ \textgreater 2.0 g/cm$^{\mathrm{3}}$. Poly(chlorotrifluoroethylene-\textit{co}-vinylidene fluoride) (Kel-F 800, Lot 30013) was purchased from 3M, Inc. St. Paul, Minnesota. Small (150 mm\texttimes 150 mm\texttimes 50mm) billets were prepared by compression molding (Afton Plastics) the polymer at 90 $^{\mathrm{o}}$C and \textasciitilde 50,000 psi. This method resulted in a semi-transparent, golden-colored billet from which window samples were machined, and polished to an optical clarity for experiments. To extend the window correction for Kel-F 800 (see D. M. Dattelbaum \textit{et al.} Proceedings of the 14$^{\mathrm{th}}$ International Detonation Symposium), a series of symmetric gas gun driven plate impact experiments were performed using both VISAR (532 nm) and PDV (1550 nm) velocimetry methods to extend the window correction to a larger range of initial shocked pressures and densities. [Preview Abstract] |
Friday, June 21, 2019 10:30AM - 10:45AM |
Y6.00005: Mechanical and optical response of polymethylpentene under dynamic compression L. M. Barmore, M. D. Knudson Polymethylpentene, commonly referred to by its trade name TPX, is a thermoplastic polymer that has the potential to be a useful window material for x-ray measurements in dynamic compression experiments. An optically transparent or low x-ray absorptive window is often used to maintain stress within the sample during compression. TPX can be used as a low-impedance optical and x-ray window due to its good transmittance in most parts of the electromagnetic spectrum, very low density, and low x-ray absorption. In such experiments, laser interferometry can be used to determine the particle velocity at the interface between the sample and window. Because velocimetry measures the rate of change of the optical path length, commonly referred to as the apparent particle velocity, an experimentally determined window correction factor is needed to ascertain the actual particle velocity. Here we present the results of a series of dynamic compression experiments designed to characterize the mechanical and optical response of TPX, determine the range of stresses over which TPX is transparent, and determine the window correction factor. The index of refraction was found to be essentially linear in density, resulting in a simple constant correction factor. [Preview Abstract] |
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