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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adhesive, or a combination of both) should be observed and reported. Then, the peel strength is calculated by dividing the peel force by the specimen’s width ( P/b ); however, the peel strength is reported within the displacement interval 25 mm ൑ܽ ൑ 105 mm . The peel strength ( P/b ) within the recommended interval for the tested specimens is shown in Figure 5. Although one of the specimens (2015-2) was slightly stronger than the rest, the results were found comparable. In addition, the observed failure modes were mostly cohesive on all the tested specimens, indicating good specimen preparation.

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0

P/b [N/mm]

0 20 40 60 80 100

a [mm]

2015-1

2015-2

2015-3

2015-4

Figure 5. Experimental peel strength of the Araldite 2015. Four specimens (1 to 4) are shown.

Subsequently, the average peel force ( P avg ) of all the tested specimens was calculated, resulting in a mean peel strength of 1.380 N/mm with a standard deviation of 0.149 N/mm. Although the P/b curves for this adhesive were not found in the literature, the results from Figure 5 present similar trends and behaviour to those reported by de Freitas and Sinke (2014) and Pereira et al. (2022) for two different adhesive types. On the other hand, the manufacturer states that the peel strength of this adhesive is 4 N/mm following the standard ISO 4587 (Huntsman, 2015); this value is significantly higher than the obtained experimentally in this work, even though the testing parameters are similar between standards. Such a difference could be attributed to the difference in testing speed (125 mm/min vs 150 mm/min) and thickness of the adhesive layer, which is not specified in either of the standards. 3.2. Numerical results The numerical estimation of P/b for the chosen adhesive is shown in Figure 6. The curve was obtained from the reaction force at the fulcrum (Figure 2) processed in a similar way as the experimental data, following the ASTM D3167.

0 0,5 1 1,5 2 2,5 3 0 20 40 60 80 100 120 P/b [N/mm] a [mm]

Figure 6. Numerical peel strength of the Araldite 2015.