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

522

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concentration of the fibers, similar to the case of straight fibers for which, as is well known, the rule of mixture applies. Fig. 6 shows the trend of the same ratio between Young's modules as function of the ratio a/l , between the wave length and the amplitude, for V f = 0.2. An exponential decrease of the longitudinal Young's modulus of the biocomposite is observed as waviness increases. The same chart shows the trend of the percentage deviation (in modulus) of the longitudinal Young's modulus of the biocomposite as function of a/l . In fact, we observe how the fiber waviness produces a negligible deviation, less than about 2% for a/l <0.05, while it becomes significant, above 10%, for a/l > 0.125.

6

E L / E m

5

4

3

2

1

V f

0

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Fig. 5. Relationship between the longitudinal modulus E L of the biocomposite and the modulus of the polymeric matrix E m as function of the volume fraction V f .

3.9

E L / E m

14

12

3.8

10

3.7

Scostamento Devi tion

8

3.6

6

3.5

4

3.4

2

a/ l

3.3

0

0.000

0.025

0.050

0.075

0.100

0.125

0.150

Fig. 6. Effect of the a/l ratio on the stiffness of the biocomposite (in blue), and relative trend of the percentage deviation (in red) for V f = 0.2.

3. Experimental results In order to assess experimentally the results predicted by the numerical analysis above exposed, proper experimental tests have been carried out by considering a biocomposite laminate made with a green epoxy, type SUPERSAP CNR with IHN hardner (produced by the Entropy Resins, Inc. CA - USA), (refer to Technical Data