Mechanical property extraction through conical indentation of a closed-cell aluminum foam

Deformation and energy absorption characteristics of a closed-cell aluminum foam, ALPORAS, during deep indentation were experimentally investigated by employing frustum of cone shaped indenters with varying cone angles and are compared with those observed in uniaxial compression with an objective of estimating mechanical properties such as shear strength from the indentation experiments. Morphological examination of the indents obtained when the cone angle is 0degrees (a flat-ended cylindrical punch) reveals crushing of the cells beneath the indenter and tearing of the cells at the periphery. No lateral spread in plastic deformation is observed. When the cone angle is greater than 0degrees, shearing of the foam at the periphery takes place in addition to tearing, and the shearing increases with the cone angle. An analytical model that incorporates all the three modes of deformation, crushing, tearing, and shearing, is used to describe the force-displacement and energy absorption data as a function of the cone angle. In turn, it was demonstrated that material properties such as the tear energy and shear strength could be extracted from the conical indentation data. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.