## 3 Results and Discussion
The fatigue limit, as known, is influenced by the notch geometry, as well as being specific to the material analysed. Therefore, in the case of a smooth specimen, it is correct that the fatigue limit remains unchanged for specimens obtained from the same laminate. This result confirms the reliability of the technique. Figure 8: Identification of the fatigue limit for specimen AA03 for (**a**) hot zone, (**b**) cold zone. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{**Fatigue Limit [N/mm\({}^{2}\)]**} \\ \hline
**Specimen** & \
\begin{tabular}{c} **Hot Area** \\ **(Notched)** \\ \end{tabular} &
\begin{tabular}{c} **Cold Area** \\ **(Smooth)** \\ \end{tabular} & \(\mathbf{k_{f}}\) \\ \hline _AA01_ & 119.2 & 98.1 & 0.823 \\ \hline _AA02_ & 75.8 & 97.7 & 1.289 \\ \hline _AA03_ & 78.4 & 97.9 & 1.249 \\ \hline _A4_ & 46.0 & 51.9 & 1.127 \\ \hline _A11_ & 43.3 & 50.4 & 1.165 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Fatigue limits and \(\mathbf{k_{f}}\) coefficient for different notch geometries. Once the values of the fatigue limit for smooth and notched specimens have been obtained, it is possible to estimate the fatigue notch coefficient for each type of notch by simply carrying out the ratio between the fatigue limits obtained with the thermographic technique. Table 3 shows the k\({}_{\text{f}}\) values for each type of material and notch geometry. These results are comparable with the values obtained in [23] by [PERSON], who studied the fatigue behaviour of composite materials in the presence of a notch for different lay-ups and types of stress, using the traditional Wohler curve technique. It can be noted that in the case of a specimen with a hole, the fatigue behaviour is even improved by the presence of the notch. First of all, it can be observed that the values of the coefficients for the five types of geometry examined are relatively small, despite a non-negligible theoretical notch coefficient in some cases. This indicates low notch sensitivity in the case of a composite subject to fatigue load even in the presence of severe geometries, or in other words, the presence of the notch weakly influences the fatigue behaviour of the composite material. This was also found in [24] in the case of R = 0.05, a value very close to the case examined in the present work. In the case of traction-compression stress (R = \(-1\)), on the other hand, the sensitivity is increased, due to the local microbucklings that feed the damage phenomenon. In the case of the hole specimen, the k\({}_{\text{f}}\) is lower than 1, a result that at first glance could be anomalous but which has a justification in the fact that the evolution of damage at the edge of the hole produces a considerable reduction in the concentration of tension. This is related to the fact that the laminates analysed have a fibre-dominated behaviour [24]. This type of materials, in the case of tensile-tensile loading, have a low sensitivity to the fatigue and present very flat fatigue curves; this is due to the random failure of the fibres, which is similar to that happening in unidirectional composites. However, as affirmed in [25; 26], the notched fatigue strength of the laminates in short-life range is lower than the unnotched fatigue strengths toing a notch-based reduction in static strength. In the long-life range, the notch effect vanishes since its sensitivity in a composite material is reduced by material degradation and plastic deformation in its proximity with consequent stress redistribution at its tips [27]. This behaviour is confirmed in [28; 29] where the authors confirm that the fatigue behaviour of composite material is less affected by the notch effect over \(10^{6}\) cycles, and the stress concentration effect is noted only for lower fatigue lives.