# Material Characterization for Reliable Resin Transfer Molding Process Simulation
## 3 Results and Discussion
### Numerical Models and Experimental Comparison  
The average filling time measured in the carbon textiles permeability tests is reported in Table 8, together with values computed by the numerical model. Comparison between the experimental and numerical results shows a limited difference within experimental data scatter. For better visualization of the numerical data, they are also plotted in Figure 4. as a contour map. Clearly, the points located further from the injection valve, i.e., the right-most point in the figure, have the highest filling time.  
For the fiberglass component, the filling time calculated in the simulation is equal to 304.3 s and the resin flow is uniform in the entire component. Figure 5 shows the position of the flow front at four time instants, while a contour plot of the filling time is given in Figure 6.  
As visible in Figure 5, the resin flows through all the empty borders in less than 1 s. After that, the flow front uniformly follows the vertical faces and the flow eventually forms a circular shape around the vacuum valve.  
Therefore, the analysis of the flow pattern in the numerical simulation shows that the injection and vent valves are in good positions to assure an adequate filling path of this simple component.  
The filling time of the real component was measured to be 303 s. A comparison of this value to that predicted by the numerical model shows an error of 0.44%.  
Moreover, by analyzing the component pulled out of the mold after resin polymerization (Figure 7), there was an absence of holes, bubbles, or other defects. This shows that, also in the real condition, valve locations and pressure settings are adequate in order to obtain a good structure.  
Therefore, comparing the numerical and experimental results shows a good correspondence in all analyzed cases. This highlights the reliability of the methodology discussed in this paper. In fact, it has been proved that the RTM process simulation, by means of the PAM-RTM software, could give reliable results for optimization of the injection strategy in complex components, provided that realistic values are input to the model. To this end, accurate material characterization is needed, which must take into account the dependence of the material properties on the specific experimental conditions  
Figure 4: Contour map of the filling time computed numerically: example of case Ply C 0\({}^{\circ}\) (color scale in s).  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & **Ply A 0\({}^{\circ}\)** & **Ply A 90\({}^{\circ}\)** & **Ply B 0\({}^{\circ}\)** & **Ply B 90\({}^{\circ}\)** & **Ply C 0\({}^{\circ}\)** & **Ply C 90\({}^{\circ}\)** \\ \hline
**Exp. [s]** & Mean value & 2.5 & 6.9 & 2.7 & 5.0 & 3.0 & 11.0 \\  & St. Dev. & 0.2 & 0.7 & 0.5 & 0.9 & 0.3 & 1.6 \\
**Num. [s]** & 2.7 & 7.5 & 2.9 & 5.4 & 3.1 & 9.5 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Carbon textile reinforcement permeability experimental and numerical filling time results.  
(e.g., temperature). Moreover, the results presented are in good accordance with other studies where good correspondence between RTM (as well as VARI and C-RTM) modelling and experimental results was obtained [1; 27; 3; 28; 27]. In summary, a workflow explaining the phases and procedures for the characterization of the materials and then to simulate the RTM process, as followed in this paper, is reported in Figure 8.  
Figure 5: Visualization of the flow front calculated by the numerical model.  
Figure 6: Contour plot of the filling time computed by the numerical model.