PSI - Issue 41

A.E.S. Pinheiro et al. / Procedia Structural Integrity 41 (2022) 60–71 Pinheiro et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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between the FEM stress distributions and analytical methods. The review work of He (2011) emphasized that the initial FEM-based strength predictions methods were performed either by continuum or fracture mechanics approaches. In the present days, one of the most used and accepted methods is CZM (Woelke et al. 2013, Rocha and Campilho 2018). CZM makes possible to model complex structural adhesive joints and also accurately predict their strength. However, the CZM accuracy depends on the proper estimation of the cohesive strengths in tension ( t n 0 ) and in shear ( t s 0 ), and the fracture toughness in tension or mode I ( G IC ) and shear or mode II ( G IIC ) (Campilho et al. 2012). This work compares the tensile performance of three adhesives in aluminum tubular joints (AW6082-T651), as a function of different L O . An analytical analysis is carried out, whose results are compared with a numerical analysis using CZM and with the experimentally obtained P m . The analytical analysis was carried out using two analytical methods, from a simpler and more direct formulation, in which σ y and τ xy stresses were analyzed, and subsequently, continuum mechanics criteria were used to infer P m . 2. Materials and methods 2.1. Tubular geometry This section presents the geometry of the tubular adhesive joints analyzed in this work. Fig. 1 shows the geometry and characteristic dimensions of the tubular joints, while Table 1 lists the dimensions (in mm) of the joints.

Fig. 1. Geometry and characteristic dimensions of the tubular adhesive joints.

Table 1. Designation of the dimensions and respective values (in mm). Overlap length, L O 20

40 60 80

Adherends’ free length, L S

50 80

Joint free length, L T

Outer diameter of the inner tube, d SI Outer diameter of the outer tube, d SE Thickness of the inner tube, t SI Thickness of the outer tube, t SE

20.0 24.4

20.0 24.4

2 2

2 2

Adhesive thickness, t A

0.2

0.2

The specimens used have cylindrical shape because the tubes and aluminum used in the joints have circular section. The adhesive thickness ( t A ) is the same for all specimens (0.20 mm), as are the thicknesses of the inner ( t SI ) and outer ( t SE ) adherend (2 mm). The same applies to the external diameter of the pipes: inner ( d SI ) 20 mm and outer ( d SE ) 24.40 mm. The adherends’ free length ( L S ) is 50 or 60 mm up to the testing machine clamping fixtures. For each of the three adhesives under study, ten samples were manufactures, five of them with an L O of 20 mm and the remaining with 40 mm. The value of the joint free length ( L T =80 mm) does not depend on L O . 2.2. Materials The aluminum alloy AW6082-T651 was selected for the adherends. This is an alloy obtained through artificial ageing at a temperature of 180˚C. Its selection was due not only to its good mechanical properties, but also to its wide field of structural applications in extruded and laminated form. This aluminum alloy has been characterized in previous works (Campilho et al. 2011) , where the following properties were obtained: Young’s modulus of 70.07±0.83 GPa,