Issue 46

L. Sorrentino et alii, Frattura ed Integrità Strutturale, 46 (2018) 285-294; DOI: 10.3221/IGF-ESIS.46.26 289 Process to prepare the sample with Fibrelam ® and AF163-2k adhesive Three marble tiles and three granite tiles, whose dimensions were 200 mm x 200 mm x 10 mm, were brushed on the raw side by means of an abrasive paper and, then, they were cleaned by a cloth soaked in ethylic alcohol. The same operations were repeated on the Hexcel Fibrelam ® panels, once cut through a band-saw at 205 mm x 205 mm. Now, a film of adhesive was taken out the freezer and kept at room temperature for two hours. Then, it was cut at the dimensions of the tile and it was applied on the stone surface; then the Fibrelam ® panel was put on the other side of the adhesive film (see Fig. 3). The obtained samples were put into a vacuum bag (see Fig. 4), previously lined with breather in order to support the vacuum distribution around the samples. The bag was sealed and the air was inhaled up to a pressure of 0.50 bar. Now, the bag was put into the oven and the temperature was increased of 4.95 °C per minute for twenty minutes, up to arrive at 135 °C; then, the temperature was kept constant for 1 hour. Finally, the oven was off and the bag was kept in pressure till the temperature reached 65 °C. Figure 3 : Sample with core Hexcel Fibrelam ® and AF163-2k adhesive. Figure 4 : Process scheme for the manufacturing of sandwich structure with core Fibrelam ® and AF163-2k adhesive. R ESULTS DISCUSSION n Instron ® machine was used to perform 3-point bending test on the specimens manufactured as described above, see Fig. 5. The samples were tested in an unconditioned state at room temperature. Results from the 3- point bending tests are presented in Tab. 2. Figs. 6-8 show an example of load trend vs displacement in 3-point bend test of samples with a stone tile of 3 mm thickness. Three points bending tests results show that the samples with the core DIAB P60 reached an average maximum load higher than that of samples with the core Hexcel Fibrelam®. Moreover, in Figs. 6-8 deflection before failure of the sample with the core Hexcel Fibrelam ® is higher than that of the samples reinforced with the core DIAB P60, that makes more rigid the sample. If AF163-2k adhesive is used instead of EC-2216, the samples reinforced with the core DIAB P60 show an average maximum load higher of about 0.2-0.5 kN, once fixed the stone type and thickness; this is probably due to, in addition to the best mechanical performances of the adhesive, also and above all to its uniform thickness. A