PSI - Issue 64

Arij Fawaz et al. / Procedia Structural Integrity 64 (2024) 89–96 Arij FAWAZ/ Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 6. Load-displacement curves obtained from ELS tests performed on samples from configurations 1 and 2. The load-displacement curves demonstrate stable crack propagation for all samples. They reveal that once the maximum load is reached, crack propagation starts until the curve reaches its first local minimum thereafter. Consequently, the region between the maximum load and the subsequent first minimum on the curve becomes the zone of interest, with fracture toughness calculations being based upon it. 3.3. Optical fiber results The value of “ap” for each test was retrieved from optical fiber data. For a sample from configuration 1 with an a p /L ratio of 70.1%, the strain profiles obtained from the bonded OF, at different times during the ELS test, are depicted in Fig. 7. According to the beam theory, the maximum strain value corresponds to the crack tip position (Sourisseau et al., 2022). During the first stages of the test, this maximum value increases (times t0 to t5) as the load increases but staying at the same position along the OF. Then, when the crack propagates, the maximum value of the strain shifts to the right (it propagates from point A to B, see Fig. 7).

Fig. 7. (a) The strain profile along the length of the sample at different time t; (b) Load-displacement curve corresponding to the same tested sample. For all the samples from both configurations, the same data analysis was performed. It was noticed that the crack propagates until it reaches a position at least 15 mm away from the fixed support. This 15 mm distance constitutes an area where the effect of the clamping fixture inevitably influences the crack propagation.