Issue 33

A. Winkler et alii, Frattura ed Integrità Strutturale, 33 (2015) 262-288; DOI: 10.3221/IGF-ESIS.33.32

Experimental observations Beginning with the morphological aspects, the following observations are of vital importance:

When considering a crystalline polymer structure, cracks which have the potential to propagate may initiate as a result of molecular slip. There are also findings that pinpoint the spherulite boundaries as weak areas where cracks can develop following excessive straining. The boundaries may of course also serve as the path of crack propagation. Amorphous structures tend to exhibit cracks developing in voids that form as a result of viscous flow. Crack initiation sites can also manifest in the form of moulding defects 11 (see Fig. 14, Fig. 15 and Fig. 16), filler particles 12 and geometrical discontinuities.

Figure 14. Weld line in a plastic component. [41]

10 High voltage electron microscopy 11 Weld lines, gates, voids, density discontinuities 12 Pigments, stabilisers, flame retardants, lubricants

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