Shock structure and spall behavior of porous aluminum

Abstract

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.

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