## 3 Experimental Results and Discussion
### Flexural Experimental Results
#### 3.2.2 Woven 3D TRC  
Three specimens were tested in bending for each orientation of the woven 3D TRC layup. Figure 15 summarizes the experimental curves along both orientations. Similarly to tension, the uncracked stage yielded comparable results for both orientations, and the post-cracking stage showed a preference in the x-direction because the in-plane weft yarns in the x-direction were straightened while the warped yarns in the y-direction were not. All the experimental flexural parameters are given in Table 9.  
Comparing the woven 3D layup in bending (respectively 218 N/mm and 143 N/mm in x and y) with the knitted 3D layup (92 N/mm in both directions) and the equivalent 2D layup (72 N/mm) (Figure 14 and Table 8), showed a strong increase of the flexural post-cracking stiffness. This was in contrast with the tensile experimental results, where all the layups yielded the same post-cracking stiffness in the x-direction. Since all flexural experiments had the same anchorage length (175 mm) and both layups had the same flexural lever arm, as well as in-plane fiber volume fraction, this post-cracking  
Figure 15: All flexural experimental curves in x- and y-direction for the woven 3D TRC layup, as well as averaged curves.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Knitted 3D AVG** & \begin{tabular}{c} **Woven 3D AVG** \\ **x** \\ \end{tabular} & \
\begin{tabular}{c} **Woven 3D AVG** \\ **y** \\ \end{tabular} &
\begin{tabular}{c} **2D-EQ AVG** \\ \end{tabular} \\ \hline K\({}_{1}\) (N/mm) & 551 & 536 & 558 & 552 \\ K\({}_{2}\) (N/mm) & 70 & 166 & 103 & 68 \\ K\({}_{3}\) (N/mm) & 92 & 218 & 143 & 72 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Averaged stiffness in three stages in bending for all layups.  
stiffness increase can be attributed to the continuously woven transversal connections providing a better flexural anchorage of the in-plane textiles than their discretely knitted counterpart.  
The difference in post-cracking stiffness in tension and bending between the x- and y-direction of the woven 3D layup was a further suggestion towards the anchorage efficiency of these transversal connections.  
Failure of the specimens happened by means of fiber pull-out, at 1598 N and 1401 N in x and y, respectively (compared to 1503 N for the knitted 3D layup).  
Finally, when comparing the relative failure stress and force of all layups in Figures 11 and 14, the positive influence of the transversal connections was again highlighted. The pull-out stress of the woven 3D layup in tension (respectively 4.96 MPa and 4.82 MPa along x and y) was considerably lower than the knitted 3D and equivalent 2D layups (respectively 7.02 MPa and 7.52 MPa). In bending, however, the average pull-out force of the woven 3D layup (respectively 1598 N and 1401 N) was similar or even higher than the knitted 3D and equivalent 2D layups (respectively 1503 N and 1456 N). This shows that in the loading condition where the transversal connections were activated, the woven 3D transversal connections achieved a superior anchorage of the in-plane textiles than their knitted 3D counterpart.  
A hypothesis for the activation of the transversal connections in bending and not in tension can be linked to the different loading conditions of the individual textile layers in both alternatives. In tension, both the top and the bottom textile layer were subjected to equal tensile forces, while in bending the top layer was subjected to compression and the bottom layer to tension. At the level of the transversal connections, this translates to a zero stress-value gradient over their length (in the composite's thickness direction) in tension and a constant stress gradient in bending. This stress gradient is believed to activate their anchoring effects, leading to the observed mechanical improvement in bending rather than tension.