PSI - Issue 18

Costanzo Bellini et al. / Procedia Structural Integrity 18 (2019) 373–378 Author name / Structural Integrity Procedia 00 (2019) 000–000

376

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3. Results and discussion In the following paragraphs there is the presentation and the discussion of the results obtained from the experimental tests, keeping in mind the effect of both the single factor and their combination, and adopting statistical

analysis to confirm a significant difference among different kinds of laminate. The subsequent relation was considered for the calculation of the ILSS: ���� � 3 � 4

(1)

This formula is reported in the ASTM D2344 and it is generally employed in the literature; P represents the load applied on the specimen centre, h the specimen thickness and b the specimen width. Indeed, the full factorial plan was not entirely explored; since the load of the specimens with two metal sheets bonded with the resin was very low, the relevant values were not taken into consideration. Table 2 and Fig. 3 report the results registered from the ILSS test carried out on the different CARALL types. The highest ILSS value was obtained for the type A laminate, that was the laminate with only one metal sheet bonded with structural adhesive, and it was equal to 47.49 MPa, while the lowest one was achieved for the type B laminate, that was the laminate with one metal sheet bonded only with prepreg resin, and it was equal to 40.64 MPa. The type C specimen, that was the laminate with two aluminium sheets bonded with structural adhesive, presented an intermediate value of 45.57 MPa. The CoV (Coefficient of Variation) obtained from the experimental tests carried out in this work was quite low, in fact it ranged between 3.6% and 3.7% for all the specimen types.

Table 2. ILSS [MPa] for the tested specimen. Specimen Type A

Type B

Type C

1 2 3 4

47.94 49.03 47.95 45.05

41.82 39.62 39.08 42.05

44.34 46.84 47.14 43.94

Fig. 3. Short beam bending test on FML specimens.