## 4 Results and Discussion
Subsequent investigation consisted of the evaluation of the influence of the T-shaped channel aspect ratios \(L_{\rm I}\)/\(H_{1}\), \(L_{0}\)/\(H_{0}\), and \(H_{0}\)/\(H_{1}\) on the filling time for resin impregnation in the rectangular  
Figure 8: Resin volume fraction for \(\phi=0.1\) and two different ratios of \(L_{0}\)/\(H_{0}\): \((L_{0}\)/\(H_{0})_{\rm o}=0.11\) (optimal), \(L_{0}\)/\(H_{0}=7.0\) (worst scenario) as a function of time: (**a**) \(t=20.0\) s, (**b**) \(t=40.0\) s, (**c**) \(t=60.0\) s.  
porous plate. For this configuration, the optimization process was performed only for \(\phi=0.05\) due to the high number of simulations needed. Firstly, the effect of the ratio \(L_{\text{I}}/H_{1}\) on resin infusion time along the mold was evaluated for different values of the ratio \(L_{0}/H_{0}\), keeping \(H_{0}/H_{1}\) fixed. Figure 9a-d present the effect of the ratio \(L_{\text{I}}/H_{1}\) over the filling time for various constant ratios of \(L_{0}/H_{0}\) and four different magnitudes of \(H_{0}/H_{1}\) = 10.0, 20.0, 30.0 and 40.0, respectively. It should be noted that for \(H_{0}/H_{1}\) = 30.0 and \(H_{0}/H_{1}\) = 40.0, the \(L_{0}/H_{0}\) search space becomes more restricted due to the generation of very thin channels. For example, when \(H_{0}/H_{1}\) = 40.0, the variation is viable only in the range \(0.05\leq L_{0}/H_{0}\leq 0.1\) because for higher magnitudes of \(L_{\text{I}}/H_{1}\), the thickness of the bifurcated channel would become insignificant, which disfigures the T-shaped geometry of the channel and leads to the generation of permanent voids. In Figure 9a-d, the continuous curves represent valid geometries, i.e., those geometries with no permanent void inside the porous plate or empty channel. The dashed curves represent cases where permanent voids are generated, even if the monitoring line indicates complete impregnation of the mold (with \(f=1.0\) along the whole measurement line). In this sense, these results are disregarded for optimization evaluation, since void formations are a critical problem in manufacturing. It is to be noted that some cases in the dashed region of the curves achieved lower filling times, indicating that the resin has a higher impregnation in the porous plate. However, the mold was not completely filled. Results in Figure 9a-d also show that the higher magnitudes of \(L_{\text{I}}/H_{1}\) for all investigated ratios of \(L_{0}/H_{0}\) lead to the best performance, i.e., there is a reduction in resin filling time (\(t\)) when the bifurcated channel has higher penetration into the mold toward its lateral surfaces. However, some T-shaped channels with higher ratios of \(L_{1}\)/\(H_{1}\) and lower magnitudes of \(L_{0}\)/\(H_{0}\) lead to the formation of permanent voids, mainly when the geometry is composed of skinny channels. Therefore, the results recommend the building of elongated channels, since this does not lead to skinny channels. The generation of permanent voids occur, in general, in the corner that connects the single stem to the bifurcated branches. One possible reason for this behavior is the detachment of resin flow in the channel corner with not enough resin flow coming from the inlet to degenerate the void. Therefore, the permanent void remains during all the simulations in the area mentioned above. To illustrate the influence of ratio \(L_{1}\)/\(H_{1}\) on mold filling time, Figure 10 shows the advancement of resin for two different ratios of \(L_{1}\)/\(H_{1}\), \(L_{1}\)/\(H_{1}\) = 6.0 and \((L_{1}\)/\(H_{1})_{\rm o}\) = 35.0, which represents the worst and best shapes when the constant ratios of \(H_{0}\)/\(H_{1}\) = 40.0 and \(L_{0}\)/\(H_{0}\) = 0.1 are assumed. For both cases, the volume fraction fields for three different instants of time--\(t\) = 10.0 s, 30.0 s, and 60.0 s--are presented in Figure 10a--c, respectively.