Issue 48

J.P.S.M.B. Ribeiro et alii, Frattura ed Integrità Strutturale, 48 (2019) 332-347; DOI: 10.3221/IGF-ESIS.48.32 335 process took 1 hour to accomplished and was carried out in a hot-plates press under a temperature and pressure of 130ºC and 2 bar, respectively. Tab. 1 describes the elastic-orthotropic properties of an CFRP unidirectional layer fabricated under similar conditions [24]. The SLJ and DLJ tested in this work for validation purposes were fabricated from an aluminium alloy sheet metal with reference AW6082-T651. This alloy is produced using a method of artificial ageing, carried at a temperature of 180ºC. This material presents several important features, which were relevant during the material selection, such as the good mechanical properties and the wide field of structural applications in the laminated form. This alloy was characterized in a previous study [25], on bulk specimens, from which the results depicted in Tab. 2 were obtained. E x =1.09E+05 MPa  xy =0.342 G xy =4315 MPa E y =8819 MPa  xz =0.342 G xz =4315 MPa E z =8819 MPa  yz =0.380 G yz =3200 MPa Table 1: Elastic orthotropic properties of a unidirectional carbon-epoxy ply aligned in the fibres direction ( x -direction; y and z are the transverse and through-thickness directions, respectively) [24]. Properties Aluminium alloy AW6082 T651 Young’s modulus, E [GPa] 70.07±0.83 Poisson ratio,  0.3 Tensile yield stress,  y [MPa] 261.67±7.65 Tensile failure stress,  f [MPa] 324.00±0.16 Tensile failure strain,  f [%] 21.70±4.24 Vickers hardness, [HV] 100 Table 2: Properties for the aluminium alloy AW6082 T651 [25]. Three adhesives were tested, in order of increasing ductility: Araldite ® AV138, Araldite ® 2015 and Sikaforce ® 7752. The use of these adhesives allowed testing different materials behaviours. Their tensile mechanical properties, such as the Young’s modulus ( E ), tensile yield stress (  y ), tensile strength (  f ) and tensile failure strain (  f ), were defined in previous studies [26- 28]. This was accomplished by tensile testing bulk specimens with a dogbone shape, produced in accordance with the French Standard NF T 76-142, in a servo-hydraulic machine. Example tensile stress-tensile strain curves (  -  ) are represented in Fig. 1. Figure 1: Example of  -  curves of the adhesives Araldite ® AV138, Araldite ® 2015 and Sikaforce ® 7752. To characterize the adhesives’ shear properties, the Thick Adherend Shear Test (TAST) was used in former studies [26-28]. To estimate G IC and G IIC , DCB and ENF tests were performed, respectively. The specimens were fabricated and tested as described in reference [28]. The gathered adhesives’ properties are described in Tab. 3. 0 10 20 30 40 50 0 0.05 0.1 0.15 0.2  [MPa]  Araldite® AV138 Araldite® 2015 Sikaforce® 7752