PSI - Issue 41

Karolina Głowacka et al. / Procedia Structural Integrity 41 (2022) 232 – 240 Głowacka K., Łagoda T./ Structural Integrity Procedia 00 ( 2019) 000 – 000

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4

3. Laminate fatigue tests The study analyzed the fatigue tests of GFRP laminates [0/(±45) 2 /0] T of specimens cut at different angles = (0°, 30°, 45°, 60°, 90°) in relation to the axis 0 presented by Philippidis and Vassilopoulos (2002a, 2002b). Figure 1 shows a diagram of the analyzed composite laminate, along with the 0 ° direction, with respect to which the angle θ was marked, and it was also the tension direction.

Fig. 1. Diagram of the analyzed composite laminate, including the angle 0 ° , with respect to which the test specimens were cut out.

The stress in each direction can be recorded depending on the angle of cutting out the specimens: 1 = 2 ( )

(6)

2 = 2 ( ) and 6 = 0.5 (2 ) .

(7)

(8) Based on the results of fatigue tests taken from the works of Philippidis and Vassilopoulos (2002a, 2002b), for the cycle asymmetry coefficient R = -1, the fatigue characteristics were determined in accordance with Basquin's proposal in a double logarithmic system in the general form of = ′ (9) for different specimen cut angles with respect to the on-axis direction. Set of the coefficients in equation (4) is summarized in Table 1. The procedure for determining the above-mentioned parameters is in accordance with the ASTM standard (2015). Table 1. Summary of coefficients in Basquin's equation (9) for different angles. , ° ′ , MPa b (10 5 ) , MPa 0 162.95 -0.052 89.55 30 102.85 -0.059 52.14 45 100.10 -0.048 57.60 60 107.74 -0.079 43.39 90 82.63 -0.062 40.47