Dynamic compression of functionally-graded metal syntactic foams

This study addresses the dynamic compression of functionally-graded (FG) metal syntactic foams (MSF). Cylindrical MSFs are manufactured by combining a ZA27 alloy with equal sized layers of expanded perlite (EP) and activated carbon (AC) particles. For comparison, uniform MSFs containing either particle type are manufactured with different aspect ratios. Samples are tested at the loading velocities 0.2 mm·s-1 (quasi-static) or 284 mm·s-1 (dynamic) to probe for changes of the deformation mechanism and effective mechanical properties. It is shown that uniform MSFs with a lower aspect ratio exhibit an increased overall strength. The underlying mechanism is a change of the shear failure mode, which has been closely studied by combining infrared (IR) imaging with dynamic compression. EP-MSFs exhibit a strength reduction at the higher loading velocity whereas AC-MSFs show no significant change. The dynamic deformation of FG-MSFs originates in the weaker EP layer and thus closely resembles the deformation behavior of the EP-MSFs. At higher strains, the deformation transitions to the AC layer and the stress-strain response changes accordingly.