PSI - Issue 47

J.B.S. Nóbrega et al. / Procedia Structural Integrity 47 (2023) 408–416 Nóbrega et al./ Structural Integrity Procedia 00 (2019) 000–000

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2. Methods 2.1. Materials

The peel strength of the adhesive Araldite® 2015 was estimated using the FRPT under the standard ASTM D3167. Thus, the substrates were cut from aluminium plate and sheet (AW 6082-T651) with thicknesses of 3 mm and 0.6 mm, corresponding to the rigid and flexible adherends. The dimensions of the substrates were 240 mm x 25 mm and 205 mm x 25 mm, corresponding to the rigid and flexible substrates, as recommended by the standard ASTM, 2004). Also, the mechanical properties of this aluminium alloy are shown in Table 1.

Table 1. Mechanical properties of the aluminium AW 6082-T651. Data adapted from (Campilho et al., 2011a). Young’s modulus, E (GPa) Tensile strength, σ r (MPa) Tensile yield stress, σ y (MPa) Tensile failure strain, ε 70 350 305 0.11

As mentioned above, the adhesive tested was Araldite® 2015, an epoxy-based structural adhesive suitable for bonding Sheet Moulding Compounds (SMC) and Glass Fibre Reinforced Polymers (GRP). Tensile, shear, and fracture properties of this adhesive were obtained experimentally in previous work (Campilho et al., 2011b) and are listed in Table 2. however, no previous peel strength tests had been performed on this adhesive. Although the mechanical properties are not required for the experimental testing, they are necessary for the numerical modelling that will be described later in this work (Section 2.3).

Table 2. Mechanical properties of the Araldite® 2015. Data adapted from (Campilho et al., 2011b). Properties Mean value ± std Young’s modulus E (GPa) 1.85 ±0.21 Poisson’s ration ν 0.33a Tensile yield stress σ y (MPa) 12.63±0.61 Tensile failure strength σ f (MPa) 21.63±1.61 Tensile failure strain ε f (%) 4.77±0.15 Shear modulus G (GPa) 0.56±0.21 Shear yield stress τ y (MPa) 14.6±1.3 Shear failure strength τ f (MPa) 17.9±1.8 Shear failure strain  f (%) 43.9±3.4 Toughness in tension G IC (N/mm) 0.43±0.02 Toughness in shear G IIC (N/mm) 4.70±0.34

2.2. Specimen preparation and experimental testing The substrates for a set of four specimens were cut to size using a hydraulic shear and all sharp edges were filed. The substrates’ surfaces were prepared for bonding by sanding the surface in a criss-cross pattern. Afterwards, each surface was thoroughly degreased using acetone. Then, the flexible substrates were placed on a flat surface and held with spring clamps. Shims of 0.2 mm were placed at both ends of the bond area, ensuring the adhesive layer thickness of 0.2 mm; the shims were degreased like the substrates, but an extra layer of a mould releasing agent was applied to them. The adhesive was then applied using an applicator gun. Subsequently, the rigid substrates were placed over the adhesive and aligned and then a slight pressure was applied until contacting the shims. A final alignment check was performed. The specimens were held together with spring clamps over the shimmed areas and were left to cure for a week at room temperature. A detailed description of the specimen preparation, although for