Fatigue characterization of functionally graded ZA27 alloy syntactic foams

In this study, the fatigue properties of functionally graded metal syntactic foams (FG-MSF) are investigated under cyclic loading. The functionally graded foams are produced by controlling the spatial distribution of weak expanded perlite and stronger activated carbon particles within a ZA27 alloy matrix. As a reference, uniform metal syntactic foams containing only expanded perlite particles are tested alongside the functionally graded foams. These uniform foams are referred to as expanded perlite metal syntactic foam (EP-MSF). All samples are fatigue tested at three load levels in a compressive-compressive mode. The fatigue limits are evaluated using the staircase method and show similar values for both uniform and functionally graded foams. The Wöhler curves at the failure criterion ecrit=2% indicate almost identical numbers of fatigue cycles for FG-MSF and EP-MSF. The analysis of the deformation mechanism showed that the weaker EP layer controls the deformation mode of FG-MSFs. Similar to EP-MSF, the samples deform in a brittle manner with the propagation of shear bands.