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Investigation of quasi-static dynamic mechanical properties of functionally graded SiC-particulate reinforced aluminium metal matrix composites
Functionally Graded Material (FGM) systems composing of SiC-particulate reinforced Al Metal Matrix Composites (MMCs) of varying reinforcement volume fractions were prepared using a powder metallurgy route and investigated for mechanical properties under compression at quasi-static and high strain rates. High strain rate tests in the range of 1000-3000s-1 were conducted using a compression type Split Hopkinson Pressure Bar (SHPB) set-up. The compression true stress-strain curves of the tested elastic-plastic FGM systems were satisfactorily approximated using the equal-stress model while the high strain rate testing in SHPB involved complex wave propagation events between the layers of FGM. The samples failed under compression at high strain rates particularly at the interface of the layer of the lowest impedance. This result was also confirmed with LSDYNA3 finite element modeling of a 10 and 20% SiC layered composite material system. The model has shown that higher compressive stress-time history occurred in the layer of the lowest impedance during SHPB testing.Microscopic observation of the failed samples was further shown that the mechanically weakest link of the layered samples was the interfaces between the layers. This was solely due to the formation of a thin oxide layer at the interfaces. The modeling results were further found to be promising in modeling of FGM systems for future investigations.