PSI - Issue 61

Ahmet Çevik et al. / Procedia Structural Integrity 61 (2024) 291–299 Cevik et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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(a) (b) Fig. 8. (a) Crack tip positions with respect to the nucleation point, (b) crack tip speeds calculated by using crack tip positions; the red solid line indicates the upper crack tip, whereas the blue solid line indicates the lower crack tip. Fabric materials have intra-ply interfaces due to their architecture and resin-rich regions exist on the intersection regions between fill and warp yarn. This architecture affects the crack propagation. Damage pattern occurring in the curved region of fabric specimen 1c is shown in Figure 9. The damage propagation on multiple plies is observed. In the close-up micrograph, it is seen that the crack propagates through the intra-ply 0/90 interface. At a region close to the end of the fill yarn, the crack jumps to the intra-ply +45/-45 interface by forming resin and matrix crack. The crack propagation at this interface is interrupted again at a region close to the end of the fill yarn, followed by jumping of the crack to the inter-ply 0/45 interface. The occurrence of damage on more than one ply during one load drop is also reported in Tasdemir and Coker ’ s study (2022) where the fabric specimens are subjected to combined loading.

Fig. 9. Micrograph showing the damage pattern in the curved region of the fabric specimen with a lay-up of [(45/0) 7 /45/45/0/45].