3D Reconstruction of Cracks in Polymers-New Insight into the Fracture Behaviour?

The fracture behaviour of ethylene-propylene rubber (EPR) and linear low-density polyethylene (PE-LLD)-modified polypropylene was investigated. Most interpretations of the fracture behaviour of such polymers are based on results gained from completely fractured samples. To gain deeper insight into the fracture mechanisms the focus was put on the very early stages of the fracturing process. For this purpose tensile tests of the samples were stopped at predefined forces far below the yield. Subsequently 3D reconstructions of the already damaged regions were performed, using serial block-face scanning electron microscopy to get the image stacks. In a comprehensive discussion of the sample preparation the limitations of this method are disclosed. The EPR-and PE-LLD-modified samples showed completely different fracture behaviour, at least at the crack initiation and at low stresses. The results also seem to prove that the interparticle distance is a decisive parameter in the interpretation of the results.