Microstructural characterisation of a syntactic foam

Stereological sampling procedures were used to characterize the geometry of the cells of a syntactic foam. The foam, formed by, extrusion, consisted o f hollow polymeric microballoons in a low-density, polyethylene matrix. Est imates of cell volume fraction, number density and the mean and standard de viation of volumes of cells were made using design-based methods, which are generally valid without any assumptions about cell shape. Additionally, th e distribution of cell aspect ratio was estimated, assuming ellipsoidal cel ls with the major axis in the direction of extrusion. In addition to descri bing the stereological methods used, this paper illustrates how the results of a pilot study can be used to design an efficient sampling protocol.