PSI - Issue 41

T.J.S. Oliveira et al. / Procedia Structural Integrity 41 (2022) 72–81 Oliveira et al. / Structural Integrity Procedia 00 (2019) 000 – 000

74

3

This work evaluated the torsional performance of a structural adhesive in aluminum tubular joints (AW6082 T651), considering the variation of the main geometric parameters: L O , and tube thickness. In order to predict the strength, the FEM was used with CZM, whose analysis was based on the analysis of  xy stresses and joint strength, measured by M m . 2. Experimental details 2.1. Materials The material used for the adherends of the tubular joints was an aluminum alloy, namely the high-strength AW6082-T651. It is obtained through artificial aging at a temperature of 180ºC and was carefully chosen for its good mechanical properties, and for allowing a wide range of structural applications in extruded and laminated form. This aluminum alloy belongs to the aluminum-magnesium-silicon family (6000 or 6xxx series), which is one of the most popular alloys (together with alloys 6005, 6061 and 6063) (Avallone et al. 1987). This material was previously characterized by experimentation by the ASTM-E8M-04 standard (Campilho et al. 2011), considering tensile bulk testing. Relevant properties achieved while experimenting were: Young’s modulus ( E ) of 70.07  0.83 GPa, tensile yield stress (  ) of 261.67  7.65 MPa, tensile strength (  f ) of 324  0.16 MPa and tensile failure strain (  f ) of 21.70  4.24%. In order to promote the union between the adherends, the adhesive Araldite ® 2015 (ductile epoxy) was selected (Nunes et al. 2016). This adhesive is expected to produce high transmitted loads in adhesive joints, as it combines reasonable strength with ability to plasticize. In this way, high stresses in the adhesive layer are expected, as well as a marked effect of plasticization without breaking the ends of the adhesive with the progressive loading of the joints (Fernandes et al. 2015) . The adhesive’s mechanical properties were obtained by carrying out dedicated tests in former works (Campilho et al. 2011, Campilho et al. 2013). All the procedure, from fabrication to testing, followed the standard ISO11003-2:2001 (2001). Tensile testing of bulk specimens were carried out, under the indications of the standard NF-T-76-142 (1988), presenting the values of E ,  ,  f and  f . Thick Adherend Shear Tests (TAST) of joints with C45E steel adherends were used in other to establish the shear mechanical properties (Campilho et al. 2013, Faneco et al. 2017). In this work the required fracture properties in tension and shear needed in the simulations ( G IC and G IIC , respectively) were obtained from double-cantilever beam (Campilho et al. 2013) and end-notched flexure testing (Faneco et al. 2017), using a suitable method or theory. It should be mentioned that these tests were made under identical geometry and adherend restraining conditions (namely the same adhesive thickness or t A ), due to the known t A effects in these properties (Ji et al. 2010). The obtained results can be observed in Table 1. Table 1 – Mechanical and fracture properties of the adhesive Araldite ® 2015 (Campilho et al. 2011, Campilho et al. 2013).

Property

2015

Young’s modulus, E [GPa]

1.85±0.21

Poisson’s ratio, 

0.33 a

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

12.63±0.61 21.63±1.61 4.77±0.15 14.6±1.3 17.9±1.8 43.9±3.4 0.43±0.02 4.70±0.34 0.70 b

a manufacturer’s data b estimated from the Hooke’s law using E and 