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The high pressure dynamic response of polymers is important to a wide variety of applications. The details of compressibility and reactivity can have a large effect on overall behaviors of dynamic systems even when polymers are used in small amounts. Polyethylene is of broad interest for a variety of applications, as an ingredient and as a pure material. It is also of significant interest as a model system to understand the correlating effects of polymer dynamics in a material with a relatively simple chemical composition that can have highly varied properties through the alteration of molecular weight and associated crystallinity of the material. Although a variety of Hugoniot and dynamic information is available for polyethylene, it is a challenge to obtain information on the product equation of state at pressures high enough to achieve decomposition. Following recent successes in producing deep release states in compressed epoxy material, a series of plate impact experiments was performed in the same configuration on high density and ultra-high molecular weight polyethylene at pressures where there is only limited Hugoniot data. The experimental wave profiles are presented and the Hugoniot states are compared to previous results. In ongoing work, the release profiles are intended to calibrate a product equation of state. [ABSTRACT FROM AUTHOR]

Gas-gun driven plate impact experiments were performed on High Performance Propellant (HPP) to measure the shock compression behavior and Hugoniot. HPP is a proprietary blend of ammonium-perchlorate (AP), aluminum, and plastic binder. A small amount of FeO2 gives the propellant a rust color. The primary diagnostic was embedded magnetic particle velocity gauges. The Hugoniot was determined by performing multiple experiments using different impactors and a range of impact velocities. Impact stresses ranged from 0.3 GPa to 15 GPa. Even at the highest stress no reaction was observed; none was expected. At low stress HPP exhibits viscoelastic behavior with rounded wave profiles. Hugoniot data can be described using a model based on a Murnaghan isotherm with a small amount of porosity. [ABSTRACT FROM AUTHOR]

The shock to detonation transition was evaluated in the HMX based explosive PBXN-9 by a series of light-gas gun experiments. PBXN-9 consists of 92 wt% HMX, 2wt% Hycar 4054 & 6 wt% dioctyl adipate with a density of 1.75 g/cm3 and 0.8&% voids. The experiments were designed to understand the specifics of wave evolution and the run distance to detonation as a function of input shock pressure. These experiments were conducted on gas guns in order to vary the input shock pressure accurately. The primary diagnostics were embedded magnetic gauges, which are based on Faraday’s law of induction, and Photon Doppler Velocimetry (PDV). The run distance to detonation vs. shock pressure, or “Pop plot,” was redefined as log(X) = 2.14–1.82 log (P), which is substantially different than previous data. The Hugoniot was refined as Us = 2.32+2.211 Up. This data will be useful for the development of predictive models for the safety and performance of PBXN-9 along with providing increased understanding of HMX based explosives in varying formulations. [ABSTRACT FROM AUTHOR]

Several HMX-based explosive samples were subjected to shockless compression using Sandia’s Z magnetic compression accelerator. A multi-panel ICE configuration containing various thicknesses of energetic composites PBX9501, PBXN9, LX-10 was subjected to ramp loading up to 320 Kbar over 500 ns. A Velocity Interferometer System for Any Reflector (VISAR) was used to measure transmitted wave profile data of particle velocity and forward and backward procedures were used with an optimization method to determine appropriate EOS data. [ABSTRACT FROM AUTHOR]

To further understand the deformation mechanisms associated with the dynamic yield point and shock initiation of single crystals of explosives, shock wave loading experiments were performed on oriented crystals of RDX at impact stresses of approximately 1 GPa. Defect content in the crystals and the surface polishing technique were varied and the resulting materials were characterized by optical microscopy. In previous experiments on (100) oriented crystals, multiple loading inflections in the proximity of the dynamic yield point were thought to be due to cracks introduced during experiment assembly. Experiments were performed to try to reproduce these features on other crystal orientations by deliberately inducing cracks and/or choosing crystals with voids. Previously observed inflections in the proximity of the dynamic yield point can be interpreted as discrete yielding events potentially caused by one or more defects that eventually lead to a disperse elastic-plastic transition as observed in randomly oriented powders or perhaps sufficiently defective single crystals. The intent of this effort is to understand the effects of orientation dependent crystal plasticity and large defects, such as surface finish, cracks, and voids, on dynamic deformation separately so that the efficiencies and importance of deformation mechanisms in the initiation process can begin to be delineated for energetic molecular single crystals. [ABSTRACT FROM AUTHOR]

A series of quasi-isentropic magnetic pulse compression experiments using the Sandia Z accelerator and DICE small pulser have provided new insights to the material behavior of various constituents typically used in energetic composites. In this study, a combination of forward and backward procedures with optimization methods is used to determine appropriate constitutive and EOS property data. Sensitivity analysis is performed to assess the uncertainties of the experimental measurements and the subsequent influences in determining material response. The data interrogation technique has been applied to a series of tests with ramp loading condition to 50 Kbar over duration of ∼500 ns for panel configurations containing explosive crystals (HMX and RDX), binders (Estane, C7-Teflon, Kel-F and THV) and composites (PBS9501, PBX9502, and Al/Teflon). [ABSTRACT FROM AUTHOR]

New experimental diagnostics and computational modeling provide an unprecedented means for improving the understanding of energetic material behavior at the mesoscale (grain or crystal ensemble levels). This study focuses on the determination of appropriate constitutive and EOS property data of the constituents of an energetic composite at high stress and moderate strain-rate states. The Sandia Z accelerator is used to determine the mechanical response of energetic composites via isentropic ramp wave compression loading. In this paper we describe an energy source method in CTH that models ramp loading for the analysis of ICE experiments. This approach is applied to design experimental configurations to probe the constituent response of PBX 9501 subjected to ∼40 Kbar ramp load over 300 ns duration. Multiple VISAR are used to determine the averaged response of the composite material in comparison to the individual constituents including the effects of anisotropy of HMX crystals and the interactions of fine crystallites with binder material. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This work applies a ramped, quasi-isentropic compression loading technique (ICE) to investigate the mechanical behavior of polymers that are often used in energetic composites. The focus of this effort is the determination of appropriate constitutive and EOS property data at high stress states and moderate strain rates that is needed for detailed mesoscale modeling. Several thicknesses of samples were subjected to a ramp load of ∼45 Kbar over 500 ns duration using the Sandia Z-machine. Profiles of transmitted ramp waves were measured at window interfaces using conventional VISAR. Shock physics analysis is then used to determine the nonlinear material response of the binder materials. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Nitroplasticized Estane (hereafter NP-Estane) is the plastic binder used to hold HMX grains together in the plastic bonded explosive PBX 9501. It is a mixture of 49 wt. % Estane®5703 (BF Goodrich), 49 wt. % Nitroplasticizer (a 50/50 eutectic mixture of bis(2,2-dinitropropyl)formal and bis(2,2 dinitropropyl)acetal), and 2 wt. % Irganox® 1010 stabilizer. NP-Estane samples 0.1 – 2 mm thick were prepared by compression molding at 110°C. Hydrostatic compression to 2 kbar was measured at 34, 43, and 53°C. CP was measured at ambient conditions. NP-Estane was also isentropically compressed to ≈ 35 kbar in experiment Z1251 on the Sandia Z-Machine. Profiles of ramp waves transmitted through NP-Estane were measured and compared with a free surface reference profile using Hayes’s “Backward” analysis and repeated forward analysis with the CTH hydrocode. The following thermodynamic quantities have been obtained; volume coefficient of thermal expansion α = 7.2(10-4)/C, CP = 1.76 J/g C, CV = 1.41 J/g C, isentropic and isothermal bulk moduli, BS = 36.4 kbar, BT = 29.3 kbar, Grüneisen constant Γ = 1.45. The Z1251 experiment is well fit using a Mie-Grüneisen equation of state with the quadratic US - uP relation, US = 1.69 + 2.7uP - (0.7/1.69)uP2 km/s. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Experiments were performed with in-material ytterbium piezoresistive gauges in PBX 9501. Impact stresses were below 2 GPa. Experiments were performed in a few different target geometries, with gauges placed with varying depths, lateral distances, and adhesive environments. The gauge placement in the different geometries resulted in some differences in the data acquired. The most important discrepancies in the data resulted from the use of machined grooves for gauge placement. The variations in experimental design will be presented along with a comparison of the data acquired for these variations. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

An increasing interest in the properties of single crystals of high explosives necessitates a continuing supply of these crystal samples. An overview of our capabilities for single crystal sample preparation and characterization will be discussed. Large single crystals are grown, then cut along specific Miller planes and polished. Perfection and orientation are confirmed through optical techniques and transmission Laue X-ray diffraction. Gas-gun impact experiments were performed on three orientations of HMX crystals. The experiments measured decay of the elastic precursor shock along the (110), (011), and (010) planes. The results show that the (010) plane has higher strength and lower decay rates, by a factor of almost 2, than the other two. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have studied the effects of damage caused by compressive loading on the shock sensitivity of the plastic bonded explosive PBX 9501. PBX 9501 consists of 95 wt. % HMX and 5 wt. % nitroplasticized Estane binder. The binder is a mixture of 49 wt. % Estane® 5703 (BF Goodrich), 49 wt. % Nitroplasticizer (a eutectic mixture of bis(2,2-dinitropropyl)formal and bis(2,2 dinitropropyl)acetal), and 2 wt. % Irganox® 1010 stabilizer. PBX 9501 cubes, 25.4 mm on a side, were compressed to various uniaxial loads in an Instron machine. After loading, 10×10 mm cross-sections, 3.5 mm thick, were taken from the center of each cube. These slices were then subjected to nearly identical 35 kbar shocks. Transmitted shock wave profiles were measured using interface velocimetry (VISAR). Comparison of shock wave growth is a measure of shock sensitivity. Results on four samples indicate little change in sensitivity caused by compressive loading. [ABSTRACT FROM AUTHOR]