Issue 47

L. Marsavina et al., Frattura ed Integrità Strutturale, 47 (2019) 266-276; DOI: 10.3221/IGF-ESIS.47.20 273 The mean value of CRDF calculated for maximum loading given in Tabs. 1 and 2, calculated from Pop et al. [19] and Meite et al. [20] developments are resumed in Tabs. 3 and 4. The values of the weighting coefficients associated with opening and shear modes are also summarized in Tabs. 3 and 4. The weighting coefficients were estimated according with the methodology illustrated in Fig. 7. Specimens A 1 1 [m 0.5 ]  10 -3 Mean CRDF Mode I (K I  ) [m 0.5 ]  10 -3 A 2 1 [m 0.5 ]  10 -3 Mean CRDF Mode I (K II  ) [m 0.5 ]  10 -3 (K I  )/(K II  ) (K I )/(K II ) Tab. 1 I.1-6 9.8 0.138 0.07 0.001 125 / I.7-14 7.2 0.102 0.05 0.0008 127 / Table 3 : Single Edge Notch Bend Test– Crack Relative Displacement Factor Specimens A 1 1 [m 0.5 ]  10 -3 CRDF Mode I (K I  ) [m 0.5 ]  10 -3 A 2 1 [m 0.5 ]  10 -3 CRDF Mode II (K II  ) [m 0.5 ]  10 -3 (K I  )/(K II  ) (K I )/(K II ) Tab. 2 II.1-5 0.8 0.012 7.5 0.105 0.11 0.18 II.6-10 2.3 0.032 10 0.142 0.23 0.24 Table 4 : Compact Shear Test– Crack Relative Displacement Factor The data resumed in Tabs. 3 and 4 lead us conclude that the opening and shear modes coexist during the test. The crack path observed after the tests indicated that the crack is not rectilinear. This aspect may be connected with the experimental boundary conditions and the PB fiber orientation. It is also interesting to observe that the relationship between the CRDF corresponding to mode I and II, and the relationship to the SIF show some similarities. Pop et al [19, 20] and Meite et al. [25, 52] show also that the energy may be estimated from the CRDF and SIF values, Eq. (6). ( ) ( ) 8 F K K G       (6) where:   ( ) 1 1 8 K A k       (7) where ఊ ሺఌሻ is the Crack Relative Displacement Factor; ఊ ሺఙሻ is the Stress Intensity Factor and ൌ 1 2 corresponds to mode 1 and mode 2; ଵ௜ , ଶ௜ are the weighting coefficients associated with opening and shear modes. Tab. 5 resumed the values of the energy release rate calculated from the results obtained in the Tab. 1-4. Specimens Energy release rate Mode I [J/m²] Energy release rate Mode II [J/m²] I.1-6 15.3 / I.7-14 9.8 / II.1-5 0.16 8.2 II.6-10 0.73 13.5 Table 5 : Energy values.