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Porous materials under shock and impact loading present significant potential for energy absorption and shock mitigation in various applications. Furthermore, additively manufactured materials which feature inherent levels of porosity due to the manufacturing process are increasingly used in shock applications. In this work, we have investigated porous 6061 aluminum samples with different levels of porosity, which were manufactured using a modified process of 3D printing. To achieve pores smaller than the 3D printing resolution (<50 µm), the printing parameters were altered to control the pore sizes, resulting in porosities between 2%-10%. Plate impact experiments were conducted on these materials at pressures in the range of 2 to11 GPa, for which the free surface velocity was measured using a photonic Doppler velocimeter (PDV). The experiments were designed to extract both the shock structure properties and spall behavior. The structure of the steady shock was characterized as a function of porosity and shown to confirm trends revealed by the analytical approach (Czarnota et al, 2017), highlighting the importance of micro-inertia effects. The spall behavior was found to change significantly for the porous materials with respect to what was observed in dense materials. Mesoscale modeling has been carried out, to reveal the possible mechanisms underlying the observed phenomena.

Recent modifications of a powder gun facility at Caltech have enabled pressure shear plate impact (PSPI) experiments on materials at very high strain rates (>10⁷ s⁻¹) and pressures (>20 GPa), that have not been reached before. The high strain rate/pressure regime expands significantly the advantages of this well-studied technique. However, it requires overcoming several challenges including requiring a new approach for analysis of the experimental measurements, to extract the material’s strength. At high pressures, standard anvils such as steel and tungsten carbide (WC) do not remain elastic, and their inelastic behavior needs to be accounted for in the analysis. The methodology presented here extracts the strength of the material using a hybrid method, combining numerical simulations to simultaneously match both the normal and transverse free surface velocity measurements. First, the inelastic response of the anvils is measured using symmetric PSPI experiments and a material model is calibrated to best match the experimental measurements. Then, measuring the response including the material of interest in a sandwich PSPI configuration, the anvil's material model is used for the analysis and the extraction of the strength of the material of interest. The methodology is demonstrated for soda-lime glass with WC anvils and pure magnesium with steel anvils. The proposed methodology has the potential to expand the PSPI experiments to higher pressures and strain rates.

Magnesium and its alloys are widely used in the aerospace, automotive and defense industries, taking advantage of its high strength to weight ratio. However, these materials show strong anisotropy with its hexagonal close packed structure and texture. The experimental investigations probing the behavior of these materials at high pressures and strain rates are limited. In this study, experiments are conducted on extruded commercially pure magnesium using pressure shear plate impact (PSPI) experiments. The strength and the behavior of the materials are measured at pressures up to 10.5 GPa and strain rates of 105 s−1. The PSPI experiments measure the materials under unique conditions, loading the material simultaneously in two directions. Experiments are conducted at two different pressures where the normal compressive stresses are aligned in one direction and the shear stresses, probing the material strength, are aligned perpendicular to the direction of the normal stress. The effect of pressure on the behavior of these materials under high pressures and strain rates are discussed. It was seen that magnesium exhibit higher strength at higher pressures due to the pressure hardening.