Issue 47

F. Cucinotta et alii, Frattura ed Integrità Strutturale, 47 (2019) 367-382; DOI: 10.3221/IGF-ESIS.47.27 378 (a) (b) Figure 12 : A sandwich (a) and B sandwich (b) : FEA and Experimental comparison of the 4 point flexural test. Concerning the impact tests, the load-displacement curves were used again to derive the considered quantities: absorbed energy, stiffness, peak force and maximum displacement of the striker. The ratio between the Impact Energy and Absorbed Energy (damage degree), as shown by Belingardi [16], helps to understand if there is rebound (value less than 1) or perforation and then failure (equal to 1) during the test. The impact tests have been carried out on three specimens for each sandwich typology and each impact energy (i.e. 18 tests in total). The mean values of the considered quantities are reported in Tab. 11 and Tab. 12 for A sandwich and B sandwich respectively. A sandwich Impact Energy [J] 20.0 40.0 60.0 Absorbed Energy [J] 17.6 35.3 56.1 Ratio Impact/absorbed Energies 0.9 0.9 0.9 Stiffness [N/mm] 1170.3 2015.3 2011.0 Peak Force [N] 6736.2 7854.0 7693.0 Maximum displacement [mm] 5.57 6.86 10.09 Table 11 : Mean values for specimens of A sandwich. B sandwich Impact Energy [J] 20.0 40.0 60.0 Absorbed Energy [J] 16.1 38.1 60.0 Ratio Impact/absorbed Energies 0.8 0.9 1.0 Stiffness [N/mm] 2429.1 1362.1 1394.6 Peak Force [N] 7154.6 6212.4 6499.1 Maximum displacement [mm] 4.08 10.20 19.78 Table 12 : Mean values for specimens of B sandwich. Load, kN Load, kN