## 3 Results
### Validation of Process Simulation  
During the simulation, we used the same parameters as for the injection moulding (melt temperature: 280 \({}^{\circ}\)C; mould temperature: 80 \({}^{\circ}\)C; injection speed: 50 cm\({}^{3}\)/s; holding: 800 bar for 20 s; residual cooling time: 20 s). The first step of validation was the comparison of the filling time and the injection pressure in the simulation (Figures S3 and S4) and in reality (0.574 s and 0.58 s; 310 bar and 325 bar, respectively), which showed a match. The second step of the validation was the comparison of volumetric shrinkage in the simulation and in reality (Figure 4). The surface of the door handle was measured with GOM and the deviation was generated between it and the mould cavity. The shape of the shrinkage did not match perfectly, but in the areas important from the point of view of the load, in the middle of the handle stem, there was a match; the biggest deviation was generated where the shrinkage was high, so we could state that the simulation was a good representation of reality. The third step of validation was the comparison of the fibre orientation tensor. The global conformation of the flow direction part of the fibre orientation tensor (A\({}_{11}\)) along the longitudinal section of the door handle is presented in Figure 5, based on the Autodesk Moldflow Insight 2011 injection moulding simulation software. The simulation was calculated in accordance with the previously mentioned Folgar-Tucker model. The visualisation was quite spectacular, because the 3D solver in AMI was based on the Navier-Stokes model; it can be seen that the fibre orientation in the core and the shell differed from each other (A\({}_{11}\) was 0.75 and 0.9, respectively). However, due to the large wall thickness, the shear rate was more evenly distributed in the cross-section; therefore, the difference was smaller than expected. However, this representation was incapable of comparing the results to the real fibre orientation. Instead, the diagonals of the fibre orientation tensor were applied in a specific cross-section and were presented as a function of distance from the midplane. During the experimental investigation, sections were prepared from the injection-moulded door handle and, on the 8 \(\times\) 15 mm slices, the elliptic projection of the GF sections was examined with optical microscopy, and the minor (m) and major (M) axes and the angle of the major axis (\(\varphi\)) (Figure 6) [16] were measured. With the help of these results, the orientation was determined with Equation (1) in the flow direction (A\({}_{11}\)), with Equation (2) in the width direction (A\({}_{22}\)) and with Equation (3) in the height direction (A\({}_{33}\)) [31]. A\({}_{11}\) showed the oriented fibres' ratios in the direction of axis 1, A\({}_{22}\) showed the oriented fibres' ratios in the direction of axis 2 and A\({}_{33}\) showed the oriented fibres' ratios in the direction of axis three. The sum of these variables (A\({}_{11}\), A\({}_{22}\) and A\({}_{33}\)) had to be one. \[A_{11}=\left(\frac{m}{M}\right)^{2} \tag{1}\]  
\[A_{22}=\left(\sin\varphi\sin\cos^{-1}\frac{m}{M}\right)^{2} \tag{2}\]  
\[A_{33}=\left(\cos\varphi\sin\cos^{-1}\frac{m}{M}\right)^{2} \tag{3}\]  
Figure 4: The simulated volumetric shrinkage (**a**) and the deviation between injected door handle and mould cavity according to GOM measurements (**b**). Figure 5: The simulated fibre orientation tensor component in direction 1 (A\({}_{11}\)) in the longitudinal section. During validation, more sections of the injection-moulded part were checked, and we found that the orientation in the middle of the door handle stem (from 10 to 55 mm from the end of the product) was similar. The measured and simulated fibre orientations in a specific section (10 mm from the end of the product) are presented in Figure 7 as a function of distance from the midplane. The effect of shear rate could be clearly seen from the results, although obvious core and s hell layers could not be determined.