PSI - Issue 77

C.F.F. Gomes et al. / Procedia Structural Integrity 77 (2026) 95–102 Gomes et al. / Structural Integrity Procedia 00 (2026) 000–000

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degradation recorded was 0.77 for L O =40 mm at x / L O =0, while the minimum was 0.36 for L O =10 mm at x / L O =1. The highest ΔSDEG (31%) was observed in the L O =20 mm joint, confirming that the increase in P m is not proportional to L O due to the asymmetric damage distribution. The adherend material analysis utilizes the 2015, L O =20 mm, and all adherends (Fig. 4 b). Although CFRP exhibited the highest SDEG value at the overlap edges (0.55), aluminum adherends experienced the most degradation along the bond length. This occurred because CFRP’s E 2 property is lower than E 1 , leading to increased stiffness at the adhesive edges. The central area showed no damage in all three cases. Steel DIN 55Si7 had the largest undamaged region, covering 25% of the total L O , followed by CFRP with 15% and aluminum with only 11%. Steel also recorded the highest ΔSDEG (66%), as SDEG dropped from 0.19 at x / L O =0 to 0.07 at x / L O =1. The comparison between adhesives was performed using CFRP joints with L O =20 mm (Fig. 4 c). The AV138 experienced failure in the adhesive up to x / L O =0.13, which was expected given its higher τ xy and σ y peak stresses. As the most brittle adhesive with greater stiffness, it suffered a catastrophic failure with minimal plastic deformation. The 7752 did not fail at the moment P m was reached due to its ductility. The 2015, while exhibiting significant plastic deformation along x/ L O , did not fail at any point at P m . This adhesive experienced more overall damage than the 7752, resulting in a lower undamaged percentage (17%). In contrast, the AV138 maintained 82% of its L O undamaged, while the 7752 increased this length to 95% of L O . The highest ΔSDEG (90%) was recorded for the 7752, highlighting its superior resistance to progressive degradation. 3.3. Maximum load Fig. 5 shows P m originating from the CZM analyses. Each chart corresponds to a particular adherend material and shows three curves, each representing the strength characteristics of one of the studied adhesives.

(a)

(b)

(c)

Fig. 5. P m as a function of L O and different adhesives for a) AW 6082-T651 aluminum; b) CFRP, and c) DIN 55Si7 steel adherends.

Fig. 5 (a) relates to the aluminum alloy. Between L O values of 10 mm and 20 mm, P m increases in a near-linear fashion for all adhesives. The AV138 displays superior P m , registering 33% higher strength compared to the 2015 and 52% higher than the 7752. At L O =40 mm, the 2015, which had previously shown 14% lower strength than AV138, reaches an equivalent P m level. The 7752 maintains the most consistent linear trend, exhibiting lower P m for all L O . The percentile P m difference between the 7752 and the 2015 at L O =20 mm is 33%, while at L O =40 mm, this difference reduces to 23%. In Fig. 5 (b), the P m values relate to the CFRP adherends. Up to L O =20 mm, the progression of P m