PSI - Issue 72

C.F.F. Gomes et al. / Procedia Structural Integrity 72 (2025) 34–42

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The influence of the adherend materials on  xy stresses is shown in Fig. 6 (a). It is possible to observe an upward trend in the stresses at the overlap edges, i.e., x / L O =0 and x / L O =1, similar to the behavior of σ y stresses. The adherend with the highest peak stresses was the aluminum alloy, with  xy / τ avg =2.19 near to x / L O =0. The results for the other adherends were then coherent with the stiffness difference, and the steel adherend exhibited lower  xy stress values, of  xy / τ avg =1.54 near to x / L O =0 and  xy / τ avg =1.26 in the region of x / L O =1. Fig. 6 (b) shows  xy / τ avg stresses as a function of L O for CFRP joints bonded with the 2015, considering L O values of 10, 20, and 40 mm. There is an increasing trend in the peak stresses for higher L O , as it was observed with the σ y stresses. The large bonding areas and the applied loads result in an increase of the stress gradients  xy with greater L O . As a result, the inner overlap loses capability to transfer loads in the elastic regime. The comparison between the adhesives for joints with CFRP adherends and L O =20 mm is presented in Fig. 6 (c). The AV138 achieved the highest peak of  xy / τ avg =2.26 at the overlap edges due to its high stiffness. The 7752 showed a more uniform distribution of  xy stresses and reached a maximum value of only  xy / τ avg =1.33, since it has a lower elastic stiffness. 3.3. Joint strength Fig. 7 P m data was generated from the CZM analysis taking into account variations in L O (10, 20, and 40 mm), different adhesive materials and adherends. Each graph represents an adherend material and includes three curves representing the strength of the different adhesives studied. Fig. 7 (a) shows P m of the different adhesives as function of L O for the CFRP adherends. The P m evolution is linear up to L O =20 mm for three adhesives and the AV138 reveals the highest strength, around 15% higher than the 2015 and 43% higher than the 7752. By increasing the L O from 20 to 40 mm, the increase in P m for the 2015 continues to be linear, while for the AV138 and the 7752 it is possible to observe an inflection point, which means that, if L O increases further, there would be no significant improvement in P m for these two adhesives. In addition, the highest P m value recorded for L O =40 mm, was around 56489.2 N for joints bonded with the 2015. For this L O the P m value of the 2015 is 10% higher than AV138 and 40% higher than the 7752. In Fig. 7 (b), P m is presented for different L O and different adhesives for aluminum AW 6082-T651 bonded tubular joints. When increasing L O from 10 to 20 mm, the increase of P m is practically linear for the three analyzed adhesives, and the AV138 shows higher P m in comparison to the other ones, around 33% higher than the 2015 and 52% higher in relation to the 7752. For an L O of 40 mm and the 2015, which until then presented 14% less strength than the AV138, equals the P m of the AV138. The behavior of the 7752 is the most linear and it shows reduced P m values throughout the L O analyzed. For L O =20 mm, there is a percentile P m difference between the 7752 and 2015 of 33%. On the other hand, for L O =40 mm, the difference between the adhesives is around 23%. Fig. 7 (c) shows the P m results, of the DIN 55Si7 steel joints, as a function of L O for the three adhesives. The results showed no discrepancy in the trends, i.e. the increase of P m is linear for all cases. In the complete range of the L O variation, the AV138 always proved to be the most capable, followed by the 2015 and finally the 7752.

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P m [kN]

P m [kN]

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Araldite AV138

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