Issue 33

A. Winkler et alii, Frattura ed Integrità Strutturale, 33 (2015) 262-288; DOI: 10.3221/IGF-ESIS.33.32 274 Figure 15. Void and inhomogeneous melt in a plastic component.[41] Figure 16. Density discontinuity in a plastic component. We will close this section with a few key experimental observations that speak a clear language regarding the damage behaviour and origins of non-reinforced plastics. The first observation (see Fig. 17) is a microtome cut showing the morphology of an injection moulded DIN EN ISO 3167 type A specimen made of PA66. Larger Maltese cross-shaped spherulites dominate the bulk of the structure, their size decreasing with the distance to the surface. The highly oriented skin is also clearly visible, along with the so called trans-crystalline region between the crystallized bulk and the surface layer.