PSI - Issue 64

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

93

5

where P is the applied load, b the sample width, and F a correction factor for large displacements (F is usually used in ELS test to account for large deflections). C 0 represents the intercept with the C-axis, and m represents the slope; both C 0 and m are constants. • The Simple Beam Theory (SBT) = 9 2 2 4 2 ℎ 3 1 (5) For further details about the calculation of the correction factor F , please refer to the ISO 15114:2014 standard. 3. Experimental results 3.1. Clamp calibration and E 1 calculation The load-displacement curves at different free lengths for both configurations are illustrated in Fig. 5.

Fig. 5. Load-displacement curves associated with varying free lengths during the clamping calibration procedure.

From these curves, C 1/3 can be plotted against L . The average value of flexural modulus obtained for samples from configuration 1 is approximately 238.85 GPa, whereas for samples from configuration 2, it is equal to 245.17 GPa. In terms of the average value of the calibration correction Δ clamp , it was determined to be 39.41 mm and 38.09 mm for configurations 1 and 2, respectively. The clamp calibration results revealed that for both configurations, the clamping fixture, Δ clamp, is nearly identical. This indicates that the tightening of the clamp is carried out in a very similar manner. Furthermore, the clamp made in this study is not ideal. Achieving a zero value of Δ clamp would imply infinite rigidity, which is not feasible in reality. Some studies showed a small Δ clamp value (Ding et al., 2023; ISO 15114:2014 standard; Tijs et al., 2022). However, unlike these studies, an optical fiber was placed on the top of the specimen in this research. Consequently, a small groove was carved into the upper part of the embedding block to prevent pressure and potential damage to the optical fiber. This difference in setup may account for the higher Δ clamp value obtained in this study compared to those reported in the literature. The flexural modulus E 1 of samples from configuration 1 is slightly lower than that of samples from configuration 2. Moreover, the load-displacement curves indicate that samples from configuration 2 reached failure at both higher displacement and higher load with almost the same initial stiffness. This suggests a difference between the two configurations, which must be accounted for when mechanically testing samples under aging conditions, particularly creep. 3.2. Load-displacement curves for ELS test (configurations 1 and 2) The load-displacement curves for both configurations are presented in Fig. 6. They exhibit closed initial stiffness for both configurations, while a significant difference between the average value of the maximum reached load can be observed between the two configurations (difference of 15%). Higher loads at higher displacement are obtained for samples from configuration 2.