# Material Characterization for Reliable Resin Transfer Molding Process Simulation
## 3 Results and Discussion  
### Material Characterization Tests  
The values of the resin and test oil viscosity measured in the experimental tests are given in Table 3. Clearly, as the room and production temperatures are almost equal, the resin viscosity is almost unaffected by these temperature changes. Table 4 shows the results of the permeability tests, grouped according to their orientation. As visible from the table, the scatter in the data is limited: for every orientation, the results are within a 5% error range. By using Equations (5)-(7), the principal textile permeabilities can be computed. This gives the values collected in Table 5.  
Knowing the values of the principal permeabilities and their corresponding orientation, it is possible to compute the effective permeability \(K_{eff}\) along a general direction \(\theta\), which is defined as  
\[\sqrt{K_{eff}}=\frac{\sqrt{K_{1}K_{2}}}{K_{1}\sin(\theta)K_{2}\cos(\theta)}. \tag{11}\]  
This allows one to visualize the flow distribution in the given layup as a function of the orientation angle \(\theta\). For the tested glass textile layup, the resulting effective permeability is plotted in Figure 3. Effective permeability of the fiberglass textile plotted as a function of the orientation angle \(\theta\). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Permeability** & \(K_{exp}^{0}\) [\(10^{-9}\)\(\mathbf{m}^{2}\)] & \(K_{exp}^{45}\) [\(10^{-9}\)\(\mathbf{m}^{2}\)] & \(K_{exp}^{00}\) [\(10^{-9}\)\(\mathbf{m}^{2}\)] \\ \hline Trial 1 & 2.400 & 2.119 & 2.126 \\ Trial 2 & 2.336 & 2.127 & 2.285 \\ Trial 3 & 2.335 & 2.006 & 2.207 \\
**Mean Value** & **2.357** & **2.084** & **2.206** \\ St. Deviation & 0.030 & 0.055 & 0.065 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Glass textile permeability measured in the tests. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Orth ophthalmic Resin**} & \multicolumn{2}{c}{**Test Oil**} \\ \hline
**Rotational Speed** & \(\mu\) **at 26.6 \({}^{\circ}\)C [cPs]** & \(\mu\) **at 31 \({}^{\circ}\)C** & \(\mu\) **at 26.6 \({}^{\circ}\)C** & \(\mu\) **at 31 \({}^{\circ}\)C** \\
**[rpm]** & \(\mu\) **at 26.6 \({}^{\circ}\)C** [cPs]** & **[cPs]** & **[cPs]** \\ \hline
20 & 196 & 199 & 181 & 152 \\
30 & 200 & 199 & 182 & 151 \\
50 & 209 & 203 & 187 & 154 \\
100 & 233 & 226 & 203 & 175 \\
**Mean Value**\(\mu\) & **210** & **207** & **188** & **158** \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Resin and test oil viscosity as measured in experimental tests. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \(K_{1}\) [\(10^{-9}\)\(\mathbf{m}^{2}\)] & \(K_{2}\) [\(10^{-9}\)\(\mathbf{m}^{2}\)] & \(\beta\) [deg] \\ \hline Principal permeability & 2.530 & 2.074 & –35 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Principal permeabilities of the glass textile. As for the carbon fiber reinforcements, the permeability of the three different carbon fiber reinforcements was tested, i.e., (ply A) unidirectional fiber 12K T700 300 g/m\({}^{2}\), (ply B) triaxial fiber (30/90/\(-\)30) 24K T700 300 g/m\({}^{2}\), and (ply C) Twill 2 \(\times\) 2 fabric 12K T700 630 g/m\({}^{2}\). Three tests were performed for each textile. Data obtained are listed in Tables 6 and 7:  
Data show that the permeabilities of the selected carbon fiber textile styles are at least one order of magnitude lower than those of glass fiber. The achievement was expected as the glass fiber textile comprises a multi-layer of 600 g/m\({}^{2}\) E-glass biaxial fibers [+/-45\({}^{\circ}\) orientation] and a 450 g/m\({}^{2}\) chopped strand mat stitched by means of a 18 g/m\({}^{2}\) PP for enhancing permeability characteristics. In addition, it is shown that anisotropic permeability occurs even in balanced textiles where no apparent preferential direction is expected. Under deeper analysis, the ratio between major and minor in-plane permeability spans between 1.2 for the glass textile and 2.0 for carbon triaxial fiber (ply B) and 1.3 for the carbon 2 \(\times\) 2 will.