X-ray tomography and three-dimensional image analysis of epoxy-glass syntactic foams

Syntactic foams (glass hollow spheres embedded in an epoxy matrix) were produced on purpose to be used as test materials for the present study. Two kinds of spheres (MS1 and MS2) were adjoined to a same polymer matrix, MS1 with a volume fraction of 55 and MS2 with 30 and 55%. The samples were analysed by X-ray tomography using synchrotron radiation. The three-dimensional images were used to observe the qualitative differences between the three samples. Three-dimensional image processing was then carried out to quantify the differences. The images were used to retrieve the fraction of the different phases which was in fairly good agreement with the expected values. The external and internal diameter of the spheres and their thickness were also measured. The MS1 spheres are smaller, thicker and their size distribution is less homogeneous compared to the MS2. The size distribution of the spheres before blowing was retrieved and evidenced to be similar for the two kinds of spheres. The thickness depends only weakly on the diameter of the spheres.