PSI - Issue 33

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

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shown in Fig. 2a. A flat steel base is placed on the lower grip of testing machine to support the various specimens, while the impactor is gripped on upper grip. As shown in Figure 2b, the static three points bending tests of AFS samples are carried out using another universal servo-hydraulic testing machine INSTRON 8516 with a load cell of ± 250 kN. The maximum load applied was 5 kN, using a test speed of 2 mm / min. The cylindrical supports have diameter of 10 mm for two lower supports and 15 mm for central support. No specific regulations are followed to perform the test of simulated impact damage, while the indications of ASTM C 393 - 00 Standard Test Method for Flexural Properties of Sandwich Constructions are followed for the bending tests. a b c

Fig. 2. (a) Experimental set-up for impact damage; (b) three-point bending setup; (c) example of impact damages on AFS-20 (upper) and AFS-30 (lower).

2.3. NDT techniques

All the specimens were checked in advance by ultrasound and thermographic techniques. As seen in Figure 3a, an Olympus OmniScan MX was used to perform Phased Array (PA) ultrasound analysis. It is equipped with an innovative 64-element probe (2.25L64-A2) and has a frequency of 2.25 MHz. The probe is fixed on a plexiglass wedge. A Mini-wheel absolute encoder with a resolution of 12 steps / mm connected to the probe was used to perform the C-scan to acquire data in a synchronized manner with the one-way movement of the probe. a b

Fig. 3. (a) PA ultrasonic set-up with probe and encoder movement system and (b) pulsed thermographic set-up with thermal source array.