PSI - Issue 24

Alessandro Castriota et al. / Procedia Structural Integrity 24 (2019) 279–288 A. Castriota et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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(b)

Fig. 5. Experimental results: (a) comparison of the normalized deformations for some points of the panel for side A vs. side B; (b) normalized load displacement curve and calculation of axial normalized stiffness

In step 3 the load was increased until buckling was achieved. The strain gauge readings at the edges of the cut showed the phenomenon of local buckling, diverging in an important way with respect to the linear behavior (Fig. 6a). Immediately before the final failure, a relevant delamination starting from the tips of the cut was founded (Fig. 6b).

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Fig. 6. Experimental results: (a) Normalized load – strain curves of strain gauge strip; (b) damage near the tip of the notch at the maximum load before failure

5.2. Numerical and experimental comparison

Experimental and numerical results for the panel with saw-cut are critically compared. In this way, it possible to experimentally validate the numerical model. In accordance with the experimental evidence, considerable deformations were calculated close to the cut tips (Fig. 7), which justified the local delamination and the high out of-plane displacements of the surface lamina of the skin.