PSI - Issue 47

J.P.M. Lopes et al. / Procedia Structural Integrity 47 (2023) 48–55 Lopes et al. / Structural Integrity Procedia 00 (2019) 000 – 000

50

3

Fig. 1. T -joint geometry and dimensions.

2.2. Adherend and adhesive materials

The selected adherend material is the AW 6082-T651 alloy, a structural aluminum alloy with the highest strength of the 6000 series alloys and excellent corrosion resistance. Mechanical characterization campaign was previously performed in the work of Moreira and Campilho (2015), giving : Young’s modulus ( E ) of 70.07±0.83 GPa, tensile yield stress (  y ) of 261.67±7.65 MPa, tensile strength (  f ) of 324±0.16 MPa and tensile failure strain (  f ) of 21.70±4.24%. Three adhesives with distinct ductility were used: the brittle epoxy Araldite ® AV138, the ductile epoxy Araldite ® 2015, and the polyurethane-based adhesive with high ductility, the SikaForce ® 7752. Tensile properties ( E , σ y , σ f and ε f ) were determined by bulk tests on dog bone shaped specimens. Shear properties were assessed by thick adherend shear tests. Double-Cantilever Beam and End-Notched Flexure tests were conducted to extract G IC and G IIC , respectively. The adhesives’ properties and respective reference to previous research works can be found in Table 1. Table 1 - Properties of the adhesives Araldite ® AV138 (Campilho et al. 2011c), Araldite ® 2015 (Campilho et al. 2013) and SikaForce ® 7752 (Faneco et al. 2017)

Property

AV138

2015

7752

Young’s modulus, E [GPa]

4.89 ± 0.81

1.85 ± 0.21

0.49 ± 0.09

0.35 a

0.33 a

0.30 a

Poisson’s ratio, 

36.49 ± 2.47 39.45 ± 3.18 1.21 ± 0.10 1.56 ± 0.01 25.1 ± 0.33 30.2 ± 0.40

12.63 ± 0.61 21.63 ± 1.61 4.77 ± 0.15 0.56 ± 0.21 14.6 ± 1.3 17.9 ± 1.8 43.9 ± 3.4 0.43 ± 0.02 4.70 ± 0.34

3.24 ± 0.48 11.48 ± 0.25 19.18 ± 1.40 0.19 ± 0.01 5.16 ± 1.14 10.17 ± 0.64 54.82 ± 6.38 2.36 ± 0.17 5.41 ± 0.47

Tensile yield stress,  y [MPa] Tensile failure strength,  f [MPa] Tensile failure strain,  f [%] Shear modulus, G [GPa] Shear yield stress,  y [MPa] Shear failure strength,  f [MPa] Shear failure strain,  f [%] Toughness in tension, G IC [N/mm] Toughness in shear, G IIC [N/mm]

7.8 ± 0.7

0.20 0.38

b b

a manufacturer’s data

2.3. Model pre-processing The bonded T -joints and the adhesive type effect were numerically analyzed by CZM using the Abaqus ® software. To take advantage of the models’ geometrical and loading symmetry , and save on computational resources, only half model was considered with the respective symmetry conditions. The models were constructed in two-dimensions (2D) to take advantage of plane-strain conditions, which accurately represent the geometry of Fig. 1. After dividing the base geometry into geometrically-simpler partitions, four-node plane-strain solid elements were assigned to the aluminum adherends (CPE4 elements), and four-node cohesive elements were assigned to the adhesive layer (COH2D4 elements), with the height equal to t A , to fully represent the adhesive layer by a single row of elements (Campilho et al. 2011a). Two refinements were produced: a coarser mesh for strength prediction and a refined mesh for elastic stress extraction. The refined mesh was derived from the former mesh by dividing all element spacings by 10, enabling to accurately capture the stress variations, and the respective peak stresses at the singular regions (Fig. 2).