PSI - Issue 8

Giuseppe Pitarresi et al. / Procedia Structural Integrity 8 (2018) 474–485 Author name / Structural Integrity Procedia 00 (2017) 000–000

483

10

et al. have only a similar longitudinal Young’s modulus, but probably a different internal fabric architecture, which likely has a marked influence on the fatigue behavior. With GFRP and extensometer was also used, which allowed the evaluation of d ε max /d N in Eq. (2), and hence the prediction of d a /d N . Table 1 shows that the extensometer prediction (column 7) is rather close to that obtained from the TSA data.

0.1

150

0.09

0.3

0.08

100

0.25

0.07

50

0.06

0.2

0

0.05

0.15

0.04

-50

0.03

0.1

-100

0.02

0.05

0.01

-150

(a) (c) Figure 7. Maps of thermoelastic signal amplitude (a), phase (b), and second harmonic signal (c) from the edge face of a GFRP sample under cyclic loading. 0 0 (b)

p [ ]

N. cygles from left to right: 170, 2000, 4000, 6000, 8000, 10000, 10500 (back face), 11500 (back face)

[°C]

0

20

0.5

40

0.4

60

0.3

mm

80

0.2

100

0.1

120

0

250

150

200

100

50

0

mm

Figure 8. Maps of thermoelastic signal amplitude from the front faces of a GFRP sample at various steps of fatigue cycling.

6. Conclusions

Thermoelastic Stress Analysis has been implemented to evaluate the Mode II crack growth behavior of Transverse Crack Tensile modified with insert films and subject to cyclic loading fatigue. TSA has allowed a full field and non contact monitoring of the stress field at the delamination fronts, on both edge and front faces of samples. To obtain the thermoelastic signal, time intervals of ten seconds, spread throughout the fatigue testing history, have been selected