PSI - Issue 33

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R. Nobile et al. / Procedia Structural Integrity 33 (2021) 685–694 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Finally, on the binarized C-scan and thermal maps, the routine automatically calculates the areas in pixels of the impacts, which are then converted into mm 2 on the basis of a conversion factor evaluated with respect to the known length of one side of the specimen. The same procedure was applied in all other cases to estimate the impact areas, the results of which were reported in Table 2. From a geometric point of view, the base of the spherical cap of the impactor with a diameter of 23 mm which penetrates the specimen up to 4 mm is 238.76 mm 2 . From the results it is evident that the areas differ a lot even between specimens belonging to the same lot; however, if only the technique is analysed, it is observed that each thermography seems to underestimate the size of the impactor's impression, except for two AFS-30 specimens. This could be motivated by the fact that the direct heat flow from the lamps to the surface of the specimen does not invest in the same way the deformed surface towards the inside of impact, as observed in Figures 5a and 5b. a b

Fig. 7. (a) Comparison of thermal and binarized maps of AFS-20_P5 and (b) AFS-30_P5 specimens.

a

b

Fig. 8. (a) S-scan, (b) C-scan (top) and binarized C-scan (bottom) maps of AFS-30_P5 specimen.

3.2. Experimental results of bending tests Twelve specimens were tested in three-point bending and half of the batch had impact damage, with the impacted side facing the side of the stretched GFRP laminate. Figures 9a and 9b show the load / displacement curves obtained