PSI - Issue 38

242 Hamza Abbad El Andaloussi et al. / Procedia Structural Integrity 38 (2022) 238–250 Hamza Abbad El Andaloussi, Luc Mouton, Firas Sayed Ahmad, Xabier Errotabehere, Stéphanie Mahérault-Mougin, Stéphane Paboeuf/ Structural Integrity Procedia 00 (2021) 000 – 000 5

Figure 2 Experimental test set-up

The steel substrate of each specimen is placed between the upper and the lower jaws of the testing machine. The lower jaw is fixed while the upper jaw applies a controlled tensile load to the single-strap specimen. The specimens are tested under tensile loading only. The compressive loading is not studied in this experimental campaign due to the buckling of the specimens under such loading, which is not supported by stiffeners as a real structure. I t can be noted that a tensile load in the steel substrate produces shear and peel stress at the interface (concerned by the failure), whereas a compressive load produces a shear stress combined with compressive stress. As peel stress is known as very damaging for bonded assembly, hypothesis was made that the tensile approach is the most severe. The tensile fatigue tests are performed at room temperature (around 23°C). First, a quasi-static tensile test is performed with a displacement speed of 600 mm/min in order to define the ultimate capacity of the specimen under monotonic loading (707 kN on average with a COV of 12%). Fatigue tests are performed for different tensile load ranges as presented in the Table 1 (four load levels are tested and presented in terms of % of the average ultimate tensile capacity given above). The frequency of the test is adjusted so that all the fatigue tests are done with a constant average strain rate. The test frequency is kept under 4 Hz as recommended by Erreur ! Source du renvoi introuvable. in order to avoid any pollution coming from potential viscoelastic effect of polymeric materials. Table 1 Load levels for the fatigue tests campaign

Frequency (Hz)

Number of specimens

Load level

Load range (kN)

75.0%

10 kN to 540 kN

1.6 Hz

9

62.5%

10 kN to 450 kN

2.0 Hz

10

56.5%

10 kN to 405 kN

2.1 Hz

5

50.0%

10 kN to 360 kN

2.4 Hz

1*