Strain-rate dependency and impact dynamics of closed-cell aluminium foams

Strain rate sensitivity and deformation mechanisms of closed-cell aluminium foams under low-velocity impact loadings are investigated in this study. Instrumented drop-weight impact experiments and Finite Element (FE) modelling were conducted to explore the deformation rate dependency of aluminium foams (manufactured by CYMAT^TM corporation). An X-ray micro-Computed Tomography (XCT) reconstructed foam geometry was used in the FE modelling approach to explore actual deformation mechanisms and strain rate sensitivity of foams. The deformation and pore collapse mechanisms were explored through investigating the stress and plastic strain contours. Our results show that the FE modelling with rate-dependent material properties agreed with the dynamic experimental results. The foam showed significant rate sensitivity within the examined range of strain rates. Our modelling and experimental results collectively indicate that the rate sensitivity of the base material is the primarily responsible for enhancing strength during impacts. Furthermore, the FE modelling with rate-independent material properties and unique foam topology confirms the negligible inertia effect at low velocity impacts.