Dana Mcgraw Dattelbaum

Accurate modeling and prediction of damage induced by dynamic loading in materials have long proved to be a difficult task. Examination of postmortem recovered samples cannot capture the time-dependent evolution of void nucleation and growth, and attempts at analytical models are hindered by the necessity to make simplifying assumptions, because of the lack of high-resolution, in situ, time-resolved experimental data. We use absorption contrast imaging to directly image the time evolution of spall damage in metals at ∼1.6-μm spatial resolution. We observe a dependence of void distribution and size on time and microstructure. The insights gained from these data can be used to validate and improve dynamic damage prediction models, which have the potential to lead to the design of superior damage-resistant materials. Spall-induced void damage is observed in situ, providing insights into void evolution, which can be used to improve dynamic damage.

We have performed shock compression experiments at the Los Alamos Neutron Science Center (LANSCE) at the proton radiography (pRad) facility on a porous, low-Z material: APO-BMI. APO-BMI is a carbon micro-balloon filled foam that has homogenous pore sizes that measure 20-50 µm. The motivation for these experiments was to advance our understanding of uncertainties inherent in the shock compression of porous materials. We were able to concurrently collect dynamic radiography images with the traditional velocimetry data to directly compare these diagnostics and to, perhaps, better understand experimental uncertainties inherent to shock compression of these low-Z, porous foams.

Trinitrotoluene (TNT) is an explosive of historical importance with a wide variability of reported performance due to the number of ways to prepare it. In this work, we focus on making a consistent data set for an Arrhenius Wescott-Stewart-Davis (AWSD) burn model for pressed TNT at 1.630 g/cm3. We look at a variety of data for the calibration of the reactant and product equations of state (EOS) and produce a Davis form for each EOS. We perform the rate law calibrations based on recent gas gun experiments and historical diameter effect data. We begin to explore several different choices made in the modeling.

Polymer foams are used extensively as structural supports and shock mitigating materials. Under shock wave compression, large compressions result in high temperatures, leading to chemical decomposition at low shock pressures. The high temperature rise is also known to give rise to anomalous compression even at relatively low initial porosities. Furthermore, stochastic porous structures can result in shock wavefront heterogeneities at the microscale. These features make shockwave measurements of highly porous foams plagued with difficulties in diagnostic data return and large experimental errors. Here, we report the results of a series of plate impact experiments on SWIFT silicone-based polymer foams using a shockwave transmission configuration, diagnosed with x-ray phase contrast imaging and photonic Doppler velocimetry. SWIFT foams are produced by a patent-pending Silicon/Water in Familiar Template method, which produces foams by a robust and flexible process, in which variables such as molecular weight, crosslink density, filler, and pore scale can be tightly controlled. We compare the shock properties of SWIFT foams to other polydimethylsiloxane foams, and will comment on the influence of microstructure on reducing error in measurements of the principal Hugoniot over a range of initial densities.