To investigate if this is also of conceptual relevance for the materials investigated in this work, scanning electron microscopy (SEM) images were recorded on the fracture planes of the pellets after they were extracted from the measurement device. Since the PEEK tube showed plastic deformation at the place of the pellet resulting in the pellet indenting the PEEK tube, it was not possible to extract fully intact pellets. However, because the pellets broke in fracture planes at a shallow angle to the pellets surface, it was possible to record images on these fracture planes.