Issue 49

D. E. Belhadri et alii, Frattura ed Integrità Strutturale, 49 (2019) 599-613; DOI: 10.3221/IGF-ESIS.49.55 609 D) Effect of composite thickness: Fig. 16 shows the variation of the K I as a function of the thickness of the composite. The crack front describes a nonlinear behavior or one can distinguish four zones, to make out the effect of the thickness is drawn Fig. 17 which shows the variation of the K I for different thickness and for each zone. Figure 16: K I distribution along the front for different composite thickness. Repaired pipe (2c = 45mm, a = 7mm). 5 Figure 17: K I variation versus composite thickness for the four zones It is clear from Fig. 17 that increasing the thickness of the patch leads to the decrease of the K I for internal and external crack positions. A thick patch allows a good absorption of the stresses, this is more marked for zone 3 whereas the K I tends to stabilize for zones 1 and 2, for zone 4 the K I is independent of the thickness of the composite. Fig. 18 (A) shows the K II distribution along the front as a function of the thickness of the composite. For the K II the behavior remains more intensive at the bottom of the crack and takes weak values towards the end of the crack, the effect of the thickness of the composite is significant only for bottom of the crack whereas it is independent of the limit of composite dimension crack. From Fig. 18 (B) it can be seen that in zone 1 the K II reaches its maximum for a thickness of 4 mm from which it decreases. -10 0 10 20 30 40 50 60 70 80 90 100 110 0 4 8 12 16 20 24 28 Zone 4 Zone 3 Zone 2 ep composite =2mm ep composite =4mm ep composite =6mm ep composite =8mm ep composite =10mm Normalized distance K I ( MPa.mm 0,5 ) Zone 1