PSI - Issue 14

Robert Brandt et al. / Procedia Structural Integrity 14 (2019) 891–899 Robert Brandt/ Structural Integrity Procedia 00 (2018) 000 – 000

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4.3. Cyclic Shear Strength

is according to Eq. (3)

The nominal maximum cyclic stress

(4)

Since no increase of the displacement happens before failure, the failure criterion is the loss of integrity of the specimen. A stress-cycle-diagram (s. Fig. 5) shows the cyclic shear strengths of the GFRP reference at room temperature and at an elevated temperature . The inclination of a Wöhler-Type curve at room temperature is and the fatigue strength at cycles is . For the elevated temperature of the inclination is and the cyclic shear strength . Fig. 6 exhibits the stress cycle-

40

T = RT T = 80 ° C

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10 Cyclic Shear Strength s,cyclic [MPa] #GFRP 15 20 25 30

10 % Probability of Survival 50 % Probability of Survival 90 % Probability of Survival

1E+01 1E+02 1E+03 1E+04 1E+05 1E+06 1E+07

Cycles N [-]

Fig. 5. Fatigue strength of the GFRP reference determined by the EST

40

40

a)

b)

10 % Probability of Survival 50 % Probability of Survival 90 % Probability of Survival

10 % Probability of Survival 50 % Probability of Survival 90 % Probability of Survival

35

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10 1E+02 1E+03 1E+04 1E+05 1E+06 1E+07 Cyclic Shear Strength s,cyclic [MPa] Cycles N [-] T = RT T = 80 ° C #Ti 15 20 25 30

10 Cyclic Shear Strength s,cyclic [MPa] T = RT T = 80 ° C 15 20 25 30

#Si

1E+02 1E+03 1E+04 1E+05 1E+06 1E+07

Cycles N [-]

Fig. 6. Fatigue strength of a) the silane treated and b) the titanium dioxide treated specimens determined by the EST