Issue 47

F. Moroni et alii, Frattura ed Integrità Strutturale, 47 (2019) 294-302; DOI: 10.3221/IGF-ESIS.47.22 300 The Force vs. opening behavior and fracture surface of co-cured ENF are shown in Fig. 12. Only one test was available at the time of writing this article. An example of Force vs. opening behavior and fracture surface of co-bonded DCB tests is shown instead in Fig.13. The examination of the fracture surface shows that the propagation of the defect starts in the adhesive and then jumps between composite plies, possibly with multiple delaminations. By comparing the image of the fracture surface and the G I vs crack length diagram, it is therefore possible to distinguish the fracture toughness values relative to propagation inside the adhesive from those related to propagation inside the composite material, see Fig. 14. The value of G Ic and, in general the trend of the R-curve, are lower than those of co-cured CFRP specimens. Figure 10 : Example of force vs. opening behavior and fracture surface of massive CFRP DCB tests. Figure 11 : Mode I R-curve of co-cured CFRP tests. Figure 12 : Example of force vs. opening behavior and fracture surface of co-cured CFRP ENF tests. fatigue precrack multiple delaminations fatigue precrack