PSI - Issue 77

P.D.A. da Silva et al. / Procedia Structural Integrity 77 (2026) 103–110 Silva et al. / Structural Integrity Procedia 00 (2026) 000–000

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6

3.2.2. Inner chamfer The introduction of inner chamfers in the adherends aims to reduce the peak stresses at the overlap ends. Fig. 6 shows σ y and τ xy stresses for the AV138 as a function of θ . Peak stresses take place at the ends of the adhesive joint. As shown in Fig. 6 (a), the highest σ y / τ avg peak stresses occur for θ =15º, due to the smaller cross-sectional area of the adherend. In general, higher θ increase stress concentrations at the inner bevel regions. This increase of θ results in a decrease in the amount of adhesive at the end of the joint, making it more susceptible to high stresses. The variations achieved between θ =90º and 15º were 171.3% (AV138), 392.8% (DP8005), and 200.7% (XNR6852 E-2). Fig. 6 (b) shows τ xy stresses for the AV138 with variation of θ . τ xy peak stresses appear at the ends of the adhesive layer, at x / L O =0 and 1. A second peak occurs at the geometric variation induced by the inner chamfer. The excess adhesive at the ends, at x / L O =0 and 1, reduces τ xy stresses due to the difference in stiffness in the adhesive-adherend zone. These variations achieved between θ =90º and 15º were -0.7% (AV138), -18.0% (DP8005), and 13.5% (XNR6852 E-2).

2

3.25

2.5

1.5

1.75

1

τ xy / τ avg

σ y / τ avg

1

0.5

0.25

-0.5

0

0

0.25

0.5

0.75

1

0

0.25

0.5

0.75

1

x / L O

x / L O

a)

b)

90

15

30

45

60

15º

30º

45º

60º

90º

Fig. 6. σ y and τ xy stresses at the AV138 adhesive layer midline with inner chamfer.

40

30

30

P m [kN]

P [kN]

15

20

0

10

0

0.1

0.2

0

20

40

60

80

100

δ [mm]

β [º] AV138 DP8005 XNR6852 E-2

a)

b)

15º

30º

45º

60º

90

Fig. 7. P- δ curves for the AV138 joint with inner chamfer (a) and evolution of P m for all adhesives (b).

Fig. 7 (a) shows the P- δ curves for the AV138 with changes in θ . For θ =45° and θ =60°, there was an almost perfect overlap. For θ =15º, δ at failure was similar to θ =45º and θ =60º, despite the P m difference. The greatest variation of δ was for θ =30º. The variations from θ =90º to θ =15º were -26.1%, -46.3%, and -22% for the adhesives AV138, DP8005, and XNR6852 E-2, respectively. As shown in Fig. 7 (b), the joint without chamfer has the highest P m .

Table 4. E a comparison between adhesives.

AV138

DP8005

XNR6852 E-2

θ ( ο )

E a (J)

∆ E a (J) −50.7% −53.2% −31.6% −30.1%

E a (J)

∆ E a (J) -48.4% -35.4% -26.3% -21.2%

E a (J)

∆ E a (J) -36.3% -56.1% -29.7% -26.9%

15 o 30 o 45 o 60 o 90 o

2.2 2.8 3.2 3.4 4.3

2.4 1.7 2.7 2.8 3.8

1.9 1.8 2.6 2.7 3.9

-

-

−