PSI - Issue 8

A. Pantano et al. / Procedia Structural Integrity 8 (2018) 517–525 A. Pantano, B. Zuccarello / Structural Integrity Procedia 00 (2017) 000–000

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Sheet INH Hardener with Super Sap CLR system), reinforced by optimized agave sisalana fibers, (refer to Zuccarello and Zingales (2017), Zuccarello and Scaffaro (2017)), properly arranged as a sine wave into a “stitched” fabric (see Fig.7a,b).

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b

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Fig. 7. Stitched fabric containing agave sisalana fiber in the form of sinusoidal wave: a) lamina type sen(x) , (b) lamina in phase opposition, type sen(-x) , and (c) specimens obtained.

In particular, as it is shown in Fig.7, two lamine with sinusoidal fiber in phase opposition having amplitude/length ratio a/l =0.05 and specific weight of about 180 g/m 2 , have been manufactured. By means of hand lay-up, a orthotropic biocomposite laminate having V f =0.2 and dimensions equal to 200 x 400 mm, has been manufactured; from it, 4 rectangular specimens having length l =400 mm and width w =50 mm (see Fig.7c), have been obtained. In order to eliminate the effects of other influence parameters, by using the same hand lay-up technique a laminate with rectilinear fibers having the same fiber percentage V f =0.2, has been manufactured (see Fig.8). Such a laminate has been obtained by using an unidirectional fabric properly manufactured in laboratory, by subjecting the fibers to a rigorous “stretching and sewing” process.

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Fig.8. (a) unidirectional biocomposite with rectilinear fibers during the hand lay-up process and (b) specimens obtained for tensile tests.

From each biocomposite laminate 4 rectangular specimens have been extracted (see Fig.7c and 8b), successively reinforced by aluminum tabs; each specimen have been subjected to longitudinal tensile test by using a testing machine of the type MTS 810, equipped with a 25 mm base extensometer. In particular, the longitudinal average strain of the specimens with wavy fibers have been monitored by the displacement of the test machine, whereas the local strain of the central portion of the specimens where the fibers forms the maximum misalignment angle θ max with the longitudinal loading axis, equal to: [ ] [ ] ≈ ± ° = ± = ± = [ ] 9 / 20 [10* (2 / 400)] / 200 π π π θ Cos ArcTan dx Sin x d ArcTan x max The following Fig.9 shows the mean tensile curves relative to the biocomposite with rectilinear fibers and with sinusoidal fibers. As an example, in the same figure the images of two tested specimens after failure, are reported.