PSI - Issue 13

Odounga Bernard et al. / Procedia Structural Integrity 13 (2018) 347–352 Odounga Bernard / Structural Integrity Procedia 00 (2018) 000–000

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3.2. Force-displacement curves

Figure 4 represents curves showing the force as a function of the crack opening a . The values of the crack opening along the x axis are negligible compared to those along the y axis. It seems logical since we have here α = 15 0 , an angle close to the α = 0 0 , for which the opening along x is almost null.

Fig. 4. Load-crack opening curves for the thickness b = 20 mm and the angle α = 15 0 .

3.3. Critical energy release rate

In this part, we present the di ff erent results of the energy release rate obtained with the tests carried out on the MMCG wood test specimens. After decoupling of modes 1 and 2, the energy release rates G is given as a function of the length of the crack a . Figures 5 and 6 show the values of G for modes 1 and 2, respectively. The values obtained with both modes are similar. However, the results obtained for the three species show that G I is greater than G II in all cases.

Fig. 5. Critical energy release rate Gc as a function of the crack length for the thickness b = 20 mm and the angle α = 15 0 (mode 1).

Figure 7 shows the mean minimum values G ic with the standard deviation of the energy release rate of the three species (modes 1 and 2). We find that these values are proportional to the density.