PSI - Issue 2_A

Fabrizio Moroni et al. / Procedia Structural Integrity 2 (2016) 120–127 Author name / Structural Integrity Procedia 00 (2016) 000 – 000

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specimen dimensions as well as the substrate and adhesive mechanical properties. Adhesive curing was performed at 80°C for 60 minutes. The adhesive thickness was controlled by means of spacer placed at two ends of the joint. The initial crack length was set by mean of a thin Teflon layer placed between the two substrates.

Fig. 2. Sample dimensions.

Table 2. Specimen dimensions. Symbol Dimension

Value

W B H t A a 0

Width [mm] Depth [mm]

120

25

Adherent Thickness [mm] Adhesive Thickness [mm]

6

0.1

Initial crack length (nominal) [mm]

25

Table 3. Material Properties. Symbol

Dimension

Value 70000

E S υ S E A υ A

Substrate Young Modulus [MPa]

Substrate Poisson ratio

0.3

Adhesive Young Modulus [MPa]

1700 0.33

Adhesive Poisson ratio

Fig. 3. Loading set-up and detail of the clip gauge employed to track the crack-opening during testing.

Mode I fatigue tests were carried out using the set-up shown in Fig. 3. The specimens were initially pre-cracked in order to achieve a non-artificial crack tip, and later subjected to fatigue loading. Fatigue tests were conducted at constant load ratio R=P min /P max = 0.1 and at constant load amplitude ΔP=P max -P min . The testing frequency was set to