PSI - Issue 72

P.D.A. da Silva et al. / Procedia Structural Integrity 72 (2025) 52–60

58

L O =10 mm (  E a ) was recorded with the AV138, of over 1000%. Smaller values were obtained with the DP8005 (570.7%) and XNR6852 E-2 (726.9%). It is confirmed that L O has a major role in E a . Between adhesives, the AV138 generally provided the best E a , except for L O =10 mm, in which case the DP8005 gave the best results.

Table 3. E a comparison between adhesives.

AV138

DP8005

XNR6852 E-2

L O (mm)

E a (J)

∆ E a (%)

E a (J)

∆ E a (%)

E a (J)

∆ E a (%)

10 20 40

3.9

-

4.3

-

3.8

-

11.3 48.3

+193.6% +1149.7%

10.3 28.9

+139%

10.3 31.8

+169.4 +726.9

+570.7%

3.2.2. Tube thickness

The t p variation was applied simultaneously on both adherends. The t p values were 1, 2, 3 and 4 mm, and all specimens had a base L O of 10 mm.  y and  xy stress plots are only shown for the tubular joints bonded with the adhesive AV138 (Fig. 8). All analysis conditions, such as stress normalization procure, also apply to this analysis. Fig. 8 (a) shows that t p has a significant influence on peak  y stresses. At the left end ( x / L O =0), there is a higher concentration of stresses, due to the smaller cross-sectional area of the inner tube, the opposite happening at the opposite end ( x / L O =1). The behavior was identical for the specimens bonded with the DP8005 and XNR6852 E-2. For the DP8005, however, the differences between the four tested t p were very low, not reaching a 25% difference between t p =1 and 4 mm. In the case of the XNR6852 E-2 these differences were around 40%. Fig. 8 (b) shows τ xy stresses along L O for the AV138. The highest peak τ xy stresses occur for t p =1 mm, while the joint with t p =4 mm recorded the lowest stress peak. With the DP8005, τ xy stresses were much more uniform for each tested t p , and with stress concentration peaks with lower absolute values, since the DP8005 has lower stiffness compared to the others. Middle values were expected with the XNR6852 E-2 and so it was recorded, despite between the joints with t p =2 mm and 3 mm the difference was none.

2

2

1.5

1

1

 xy /  avg

 y /  avg

0

0.5

-1

0

0

0.2

0.4

0.6

0.8

1

0

0.2

0.4

0.6

0.8

1

x / L O 1 mm 2 mm 3 mm 4 mm

x / L O 1 mm 2 mm 3 mm 4 mm

a)

b)

Fig. 8.  y (a) and  xy (b) stresses at the adhesive layer midline vs. t p .

Fig. 9 (a) shows the P-  curves for the joints bonded with the AV138 and t p =2 mm. The highest value of P allowed by the joint before failure was found for the AV138, followed by the XNR6852 E-2, and finally the DP8005. The δ before failure for each joint is smaller for higher t p , due to the increased stiffness of the adherends. Fig. 9 (b) graphically shows the P m values achieved by the three adhesives. As expected, the AV138 achieved a higher absolute P m , followed by the XNR6852 E-2 and the DP8005. Using the AV138 results, the P m values increase with t p , but  xy stresses decrease, showing that a higher stiffness of the adherends minimizes those stresses.