Dynamic compressive behaviour of aluminium foams fabricated from rejected precursor materials

The work aims to study the deformation and failure mechanisms of rectangular aluminium foam blocks prepared from rejected precursors using dynamic uniaxial compressive tests supported by middle-wave infrared thermography. The dynamic compressive behavior of these foams was compared to the behavior of the foam blocks prepared from a traditional single precursor. The results indicate that the foams from rejected precursors begin to deform at lower strain with local deformation dispersed at the foam surface leading to the formation of many deformation bands, while the reference samples (fabricated from a single precursor) present only few deformation bands which are mainly located at their lower and upper ends. The bands occur at the weakest points of the samples, which in case of the samples made of rejected precursors correspond to the joining regions formed within the foam by the different precursors used during the foaming process. In these joining regions imperfections and structural defects are developed, i. e. micropores promoting a stress concentration for crack initiation. The results also indicate that the plateau region of the compressive stressstrain curves (the stress gradually increases with increasing strain) is much more inclined in case of the foams from rejected precursor pieces compared to the reference ones. (C) 2016 Portuguese Society of Materials (SPM). Published by Elsevier Espana, S.L.U. All rights reserved.