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 of hollow polymeric microballoons in a low-density, polyethylene matrix. Estimates of cell volume fraction, number density and the mean and standard deviation of volumes of cells were made using design-based methods, which are generally valid without any assumptions about cell shape. Additionally, the distribution of cell aspect ratio was estimated, assuming ellipsoidal cells with the major axis in the direction of extrusion. In addition to describing the stereological methods used, this paper illustrates how the results of a pilot study can be used to design an efficient sampling protocol.