13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- voids which contributed to the first crack was plotted as a function of the void fraction. The normalized length in the tensile direction represents the local displacement field within the vicinity of a void. The results are shown in Figure 3. Figure 3: Normalized void length vs. void fraction. The data does not show a strong correlation between the void lengths at failure and void fraction. This is different from what has been observed in isotropic materials. The variability of the data for a given void fraction suggests that the voids do not grow uniformly. The effects of void orientation on failure were examined by testing samples with the holes oriented at various angles from the tensile axis. The center to center spacing of the holes was held constant in these experiments at 40 µm. The results are shown in Figure 4. Figure 4: Normalized void length vs. void orientation.
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