John Lang

Shockwave compression of Ar gas at several initial densities

Experimental data of the principal Hugoniot locus of variable density gas-phase noble and molecular gases are rare. The majority of shock Hugoniot data is either from shock tube experiments on low-pressure gases or from plate impact experiments on cryogenic, liquefied gases. In both cases, physics regarding shock compressibility, thresholds for the on-set of shock-driven ionization, and even dissociation chemistry are difficult to infer for gases at intermediate densities. We have developed an experimental target design for gas gun-driven plate impact experiments on noble gases at initial pressures between 200-1000 psi. Using optical velocimetry, we are able to directly determine both the shock and particle velocities of the gas on the principal Hugoniot locus, as well as clearly differentiate ionization thresholds. The target design also results in multiply shocking the gas in a quasi-isentropic fashion yielding off-Hugoniot compression data. We describe the results of a series of plate impact experiment...

Systematics of Compaction for Porous Metal and Metal-Oxide Systems

The effects of particle morphology and initial density is examined with respect to the shock densification response of initially porous metal (Cu) and metal-oxide (CeO2) materials. Specifically, the ability of a continuum-level compaction model to capture the measured densification trends as a function of initial density and particle morphology are investigated. Particle morphology is observed to have little effect on the densification response of both Cu and CeO2, while initial density appears to have a stronger effect. In terms of continuum-level compaction strength, Cu and CeO2 exhibit dissimilar trends.

High pressure deep-release impact experiments on high density and ultra-high molecular weight polyethylene

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.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 c...

Deep-release of Epon 828 epoxy from the shock-driven reaction product phase

A series of gas-gun experiments was conducted to obtain product isentropes for 70/30 weight percent Epon 828 epoxy resin/Jeffamine T-403 curing agent. Thin epoxy flyers backed by a low-density syntactic foam impacted lithium fluoride (LiF) windows at velocities up to 6.3 km/s, creating stresses in excess of those required for reaction (∼25 GPa). Following this, a rarefaction fan from the back of the thin flyer reduced the pressure in the epoxy products. VISAR and PDV were used to measure the velocity of the epoxy/LiF interface. Numerical simulations using several different treatments for the reactant-to-product transformation were conducted and the results compared with measured wave profiles. The best agreement with experiment was obtained using separate tabular equations of state for the reactants and products and an irreversible transformation to products.A series of gas-gun experiments was conducted to obtain product isentropes for 70/30 weight percent Epon 828 epoxy resin/Jeffamine T-403 curing agent. Thin epoxy flyers backed by a low-density syntactic foam impacted lithium fluoride (LiF) windows at velocities up to 6.3 km/s, creating stresses in excess of those required for reaction (∼25 GPa). Following this, a rarefaction fan from the back of the thin flyer reduced the pressure in the epoxy products. VISAR and PDV were used to measure the velocity of the epoxy/LiF interface. Numerical simulations using several different treatments for the reactant-to-product transformation were conducted and the results compared with measured wave profiles. The best agreement with experiment was obtained using separate tabular equations of state for the reactants and products and an irreversible transformation to products.

Shock and Release Response of Unreacted Epon 828: Shot 2s-905

This document summarizes the shock and release response of Epon 828 measured in the dynamic impact experiment 2s-905. Experimentally, a thin Kel-F impactor backed by a low impedance foam impacted an Epon 828 target with embedded electromagnetic gauges. Computationally, a one dimensional simulation of the impact event was performed, and tracer particles were located at the corresponding electromagnetic gauge locations. The experimental configuration was such that the Epon 828 target was initially shocked, and then allowed to release from the high-pressure state. Comparisons of the experimental gauge and computational tracer data were made to assess the performance of equation of state (EOS) 7603, a SESAME EOS for Epon 828, on and off the principal shock Hugoniot. Results indicate that while EOS 7603 can capture the Hugoniot response to better that 1%, while the sound speeds at pressure are under-predicted by 6 - 7%.

U) Design Considerations for Obtaining Deep Release in Reacted Epon 828

Our document summarizes results from one-dimensional calculations performed to investigate the release behavior of reacted Epon 828. Two design goals were set, (1) the product phase had to be achieved upon the initial shock loading, and (2) a deep release state could be achieved. Both transmission and front surface impact geometry were investigated. Moreover, the two design criteria were met with the front surface impact design employing a modi ed projectile.

(U) Implementation and demonstration of a time-resolved pyrometry/spectroscopy capability in shock compression experiments on metal oxide powders

Temperature is notably the most difficult quantity to measure in shock compression experiments; however, it is critical for accurately constraining theoretical or tabular equations of state. Until now, the temperature achieved during the shock loading of porous materials could only be calculated. The technique presented in this report measures, for the first time, the shocked temperature of porous systems.