PSI - Issue 41

P.M.D. Carvalho et al. / Procedia Structural Integrity 41 (2022) 24–35 Carvalho et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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3.2.3. Strength prediction Fig. 8 shows the P m vs. t P2 curves for the different joint configurations. The obtained results show that the dual adhesive technique can bring benefits compared to the SAJ, although not for all configurations. The SAJ bonded with the Araldite ® 2015 notoriously provide the worst results for all t P2 and, thus, these are considered as the comparison benchmark to the other joints. Actually, although this adhesive is stronger than the SikaForce ® 7752, as shown in Table 1, the latter adhesive is much more ductile. As a result, and considering the major peak stresses that take place in these peel-dominant joints (Fig. 6 and Fig. 7), a much higher capacity exists from the SikaForce ® 7752 to endure the applied loading before catastrophic failure of the bondline. Table 3 summarizes all data, also including the P m variation over the SAJ bonded with the Araldite ® 2015, defined as  P m . For the SAJ bonded with the SikaForce ® 7752,  P m ranges between 10% ( t P2 =3 mm) and 38% ( t P2 =1 mm). On the other hand, the results clearly show that the advantage in using the dual-adhesive technique is highly dependent on t P2 , and that the overlap extent where the ductile adhesive is used is highly important. For the DAJ 1/8, only for t P2 =3 mm it exists improvement over the best performing SAJ (SikaForce ® 7752), with  P m =20% compared to 10%. For the DAJ 1/3, the maximum  P m were found for all t P2 , although for t P2 =1 mm P m equals that of the SAJ 7752. The maximum  P m was found precisely for this t P2 (38%), while  P m was smaller for the other configurations, although with marked variations to the SAJ 2015 and 7752. Thus, in these configurations, it can be concluded that an advantage exists in using the DAJ concept. Finally, the value of t P2 has important influence on P m for all setups, and the best results correspond to t P2 =3 mm.

2.5

2.0

1.5

P m [kN]

1.0

0.5

0.0

0

1

2

3

4

t P2 [mm] SAJ 2015 SAJ 7752 DAJ 1/3 DAJ 1/8

Fig. 8. P m for the different joint configurations as a function of t P2 .

Table 3. P m and  P m summary for the tested joint configurations.

t P2 (mm)

Setup

1

2

3

4

Araldite ® 2015 SikaForce ® 7752

582.65 N 803.91 N (38%) 796.18 N (37%) 803.94 N (38%)

1437.4 N 1678.74 N (17%) 1636.25 N (14%) 1832.58 N (27%)

1621.86 N 1782.81 N (10%) 1943.46 N (20%) 1968.68 N (21%)

1407.29 N 1712.64 N (22%) 1592.09 N (13%) 1764.87 N (25%)

DA 1/8

DA 1/3

3.2.4. Dissipated energy Fig. 9 presents the U vs. t P2 results for both SAJ and DAJ, in which U was estimated as the area beneath the P -  curves, thus giving an indication on the energy absorption capacity before failure, which acquired relevancy in the damage tolerance of structures, and also damage detection ability. Compared to the former analysis, the improvement potential and consistency of the DAJ technique is not so notorious, and this technique seldom surpasses the SAJ 7752 configuration. Actually, for this calculation, besides P m , the joint compliance and failure displacement also acquire special relevancy.