PSI - Issue 72

L.A.S. Maia et al. / Procedia Structural Integrity 72 (2025) 43–51

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Table 1. DSLJ dimensions.

Parameter

Value [mm]

Overlap length ( L O ) Adherends’ thickness ( t P ) Adhesive thickness ( t A ) Joint total length ( L T )

12.5, 25, 37.5, and 50

2

0.2 215

Width ( B )

25

2.2. Materials The materials used in this work where the steel alloy DIN 55 Si7 for the adherends and the adhesives Araldite ® AV138, Momentive ® RTV106, 3M ® DP-8005 and Nagase Chemtex ® XNR6852E-2. The mechanical properties of the steel alloy DIN 55 Si7 are listed in Table 2. E represents the longitudinal modulus of elasticity, σ y the tensile yield stress, σ f the tensile strength, ε f the tensile failure strain,  the Poisson’s ratio, and ρ the density. Three adhesive combinations were equated in the DSLJ (first adhesive is more ductile, applied at the overlap edges): DP8005+AV138, RTV106+AV138, and DP8005+XNR6852E-2. The properties of the adhesives at different test speeds were determined and are presented in Table 3. The E and tensile cohesive strength ( t n 0 ) values were experimentally estimated by tensile tests, and the shear modulus ( G ) and shear cohesive strength ( t s 0 ) through thick adherend shear tests (TAST). The fracture energies in modes I and II, G IC and G IIC , respectively, were determined using DCB (double-cantilever beam) and ENF (end-notched flexure) tests, respectively. For the test speed of 105000 mm/min, the properties were obtained by logarithmic extrapolation.

Table 2. Mechanical properties of the steel alloy DIN 55 Si7 (Valente et al. 2019). Property Value E [GPa] 210 σ y [MPa] 1078 σ f [MPa] 1600 ε f [%] 6  0.3 ρ [g/cm 3 ] 7.8

Table 3. Mechanical and fracture properties of the adhesives at different test speeds.

Adhesive

Test speed [mm/min]

t n 0 [MPa]

t s 0 [MPa]

G IC [N/mm]

G IIC [N/mm]

1

6.3 13

8.4

1.1

6

DP-8005

100

17.4 36.7 30.2 36.2 51.7 1.97

-

-

105000

27.5

1.1

6

1

41

0.35

0.6

AV138

100

49.9 70.2

-

-

105000

0.35 2.73

0.6

1

2.3

5

RTV106

100

- -

- -

- -

- -

105000

1

42.9

28.7 33.6 45.8

1.68

18

XNR6852E-2

100

46

-

-

105000

53.7

1.68

18

2.3. Impact tests The impact tests carried out were performed using the Rosand ® Instrumented Falling Weight Impact Tester type 5 HV and consisted of a mass falling from a certain height onto the test specimen, which causes the transfer of energy to break the adhesive bond. In the experimental tests, the objective was to apply an energy of 40 J to a mass of 26 kg throughout the test. Therefore, by applying the next equation, a drop height of 15.7 cm can be obtained.