PSI - Issue 5

Marcin Wachowski et al. / Procedia Structural Integrity 5 (2017) 422–429 Author name / Structural Integrity Procedia 00 (2017) 000 – 000

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b)

Fig. 2. Sample dimensions for high cycle tests; (a) flat specimen with a central hole, (b) smooth specimen

The fatigue tests of samples were conducted at room temperature on a computer-controlled 250 kN Instron 8802 closed-loop servo-hydraulic test machine. Load applied during the tests was oscillating sinusoidal with the stress ratio R = 0,1 and constant load frequency equal to 20 Hz. The tests were performed at five levels of stress amplitude dependent on shape of samples. Assumed as the criterion for the end was the number of cycles at specimen failure or when number of cycles was equal to 5 x 10 6 . The fatigue limit (endurance limit) was determined by taking the average of the stress levels in a staircase test for each type of samples. 3. Results and discussion The monotonic stress – strain curves obtained for laminate before and after heat treatment are shown in Fig. 3.

Fig. 3. Stress – strain diagram for AA2519/AA1050/TI6AL4V composite laminate before and after the heat treatment.