Issue 46

L. Sorrentino et alii, Frattura ed Integrità Strutturale, 46 (2018) 285-294; DOI: 10.3221/IGF-ESIS.46.26 290 The mechanical performances of the samples increase slightly as the thickness of the stone increases, once fixed the type of stone and adhesive; this is probably due to the fact that stone is as more rigid as greater is its thickness, stiffness that limits the deflection to failure of the samples. Among the samples with core DIAB P60 and adhesive AF163-2k that with the highest value of the average maximum load has a marble or granite thickness of 6 mm; it presents a load to bend of about 3.9 kN or 4.8 kN for marble and granite respectively that is 150% or 60% more than the corresponding sample in marble or granite only (see Tab. 2). Figs. 6-8 show how the deflection before failure of the samples with granite is higher than those with marble, that is due to the greater resistance and homogeneity of the granite compared to the marble. a) b) Figure 5 : Example of 3-point bend test: a) granite with Diab ® core; b) marble with Fibrelam ® core. Tab. 3 reports the weights, with the same total thickness, of the sandwich structure samples compared to the same ones in marble or granite. As can be seen from the table, the lightest samples have a core of Hexcel Fibrelam ® , since this panel has a weight of 2.5 kg/m 2 compared to 9.5 kg/m 2 of the sandwich structure constituted by the DIAB P60 core and the two glass fiber laminates. The lightest sample, that has a marble tile of 3 mm thickness and a Hexcel Fibrelam ® core, has a weight of 11.12 kg/m 2 that is about 3 times lower than that of the same sample of marble. The heaviest panel, that has a granite tile of 6 mm thickness and a DIAB P60 core, weights 28.14 kg/m 2 compared to 54.54 kg/m 2 of the same sample in granite only. Therefore, considering the ratio between flexural load and weight, that is called Performance Index PI, it can be seen that the sandwich structures have a PI from 2 to 5 times higher than that of the stone sample with the same thickness; in particular, the sandwich structure with Hexcel Fibrelam ® panel and a marble tile of 3 mm thickness has a PI equal to 138.35 N*m 2 /kg compared to 30.64 N*m 2 /kg of marble sample with the same thickness. Figure 6 : Trend of load vs displacement in 3-point bending test: Stone 3mm+Adhesive AF163-2k+ core Hexcel Fibrelam ® core.