Issue 43

D. Gentile, Frattura ed Integrità Strutturale, 43 (2018) 155-170; DOI: 10.3221/IGF-ESIS.43.12 163 has been calculated with the three methods previously discussed and a crack resistance curve has been recorded. In some cases, only a single estimation of G was possible due to problems in the propagation such as extensive fiber bridging and loss of planarity of the running crack. Figure 8: Detail of the three point bending fixture for ENF mode II tests. The experimental results relative to DCB tests have been analyzed in order to derive statistical trends. Firstly, the data have been analyzed grouping all the crack resistance measurements by specimen sets, which is by different lamina type. Successively, the same data have been grouped based on the thickness of the samples independently on the material. Only the samples for which more than three crack advance data points have been collected are considered in the following analysis. The G values are those obtained with the compliance calibration method (CC). Since the occurrence of fiber bridging phenomenon characterizes crack propagation in most of the tested samples, all the data points have been considered in the following statistics since it is opinion of the author that this may contribute in evaluating the effective material data scatter expected. For each graph, the following quantities are given in the summary table: A: Intercept value and its standard error. B: Slope value and its standard error. R: Correlation coefficient. P: value - Probability (that R is zero). N: Number of data points. SD: Standard deviation of the fit In Fig. 9 e in Tab. 2 are reported the results for material designed TA1. Figure 9: TA-1 Summary of crack resistance data.