PSI - Issue 41

P.M.D. Carvalho et al. / Procedia Structural Integrity 41 (2022) 24–35 Carvalho et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Table 1. Properties of the adhesives Araldite ® 2015 (Campilho et al. 2013), and SikaForce ® 7752 (Faneco et al. 2017).

Property

2015

7752

Young’s modulus, E (GPa)

1.85±0.21

0.493±0.089

0.33 a

0.33 a

Poisson’s ratio, 

3.24±0.5 11.49±0.25 19.18±1.4 5.16±1.1 10.17±0.6 54.82±6.4 2.36±0.2 5.41±0.5 0.188

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

Tensile yield strength,  y (MPa) Tensile failure strength,  f (MPa) Tensile failure strain,  f (%) Shear modulus, G (GPa) Shear yield strength,  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)

a: values provided by the adhesives’ manufacturers.

2.2. Joint geometry and dual-adhesive concept The architecture of the T-joint is depicted in Fig. 1. The dimensional parameters (in mm) applied in this work are: width B =25, flat adherend thickness t P1 =3, curved adherend thickness t P2 =1, 2, 3 and 4, adhesive thickness t A =0.2, curved element free length L A = 60, L O =25, specimen length L T =100 and curved adherend radius R =5, 5.5 and 7.5.

Fig. 1. Joint geometry and respective dimensions.

In addition, to compare SAJ and DAJ performance, the design used on simulations is similar to the one presented in Fig. 1. However, different DAJ configurations were considered for evaluation, expressed as % of L O , namely 12.5 75/12.5 (DAJ 1/8) and 33.3/33.3/33.3 (DAJ 1/3). As formerly described in the introductory part of this work, a stiffer and more brittle adhesive is used in the middle (Araldite ® 2015) and a compliant and more ductile adhesive is placed at the edges (SikaForce ® 7752). 2.3. Fabrication and testing The adherends were cut to size from aluminum sheets and plates with thickness from 1 mm to 4 mm on increments of 1 mm. The aluminum alloy was AW 6082-T651, as previously mentioned. The value of t P1 was always 3 mm, whilst different t P2 were used ( t P2 =1, 2, 3, and 4 mm). Furthermore, the upper adherend was bent to 90°, with a radius of 5 mm, in a manual press brake. The areas where the adhesive was going to be applied were prepared by grit blasting and subsequently degreased with acetone. Afterwards, the lower adherends were placed on a flat surface and the