Manufacturing and failure mechanisms of syntactic foam under compression

Failure mechanisms of syntactic foams under compression were studied. The syntactic foams produced with a new manufacturing method involving buoyancy were made of glass hollow microspheres and epoxy resin. The foam density was varied from 0.09 to 0.15 g/cc, which resulted from variation of resin concentration. Two different failure modes were identified and these were attributed to different failure initiation processes. One was initiated by longitudinal splitting and the other by layered crushing. The former occurred in the lowest foam density and the latter in higher densities used in the study. The failure sequence associated with the former mode was: (a) formation of multiple longitudinal cracks along the circumference of the compression specimen, (b) widening of longitudinal cracks and then (c) failure at one end of the specimen resulting in further lateral expansion. The sequence for the latter failure mode was deduced on the basis of the proposed schematic mode-1: (a) the first failure initiation occurrence at a weakest microsphere, (b) failure of adjacent microspheres due to stress concentration resulting in propagation of microsphere failure laterally until it reaches the end of specimen wall, and (c) thickening of the crushed layer. The thickening of the crushed layer is due to accumulation of broken microspheres. 2004 Elsevier Ltd. All rights reserved.