## 5 Results and Discussions
### Beam Specim  
The work reported in [PERSON] et al. [7] focused on applying the optimized deposition method on the Single Edge Notched Bending SENB specimen. It reproduces the principal stress direction in the V notch tip vicinity and keeps a classical deposition \(\pm 45^{\circ}\) elsewhere. The printing trajectories from the G code are shown in Figure 10.  
Figure 8: Numerical models of the CT specimen. (**1**) Corresponds to the classical deposition with \(\pm 45^{\circ}\) layers alternation. (**2**) For the optimized deposition; (**a**) denotes the first principal direction while (**b**) is for the second principal direction. Figure 10: Deposition trajectories from the G code of the SENB specimen after applying the optimization method on the V notch vicinity. (**a**) First principal direction and (**b**) second principal direction. Figure 9: Load-displacement curves of CT test. Numerical model response is compared to experimental results. (**a**) Classical samples are printed with \(\pm\) 45\({}^{\circ}\) and (**b**) Optimized samples; the filament is oriented according to the principal direction of the stress. The SENB specimen dimensions and the boundary conditions used for the simulations are shown in Figure 11. A mesh size of 0.56 mm was used in the V notch area to better capture the deposition trajectories. This value is equal to the thread width used during the printing. A bigger mesh size can still capture the trajectories elsewhere since they have unidirectional orientations. This will also allow a reduction in computational time. The first vectors representing the deposition trajectories of all the local references are showcased in all the integration points in Figure 12.  
Interestingly, the numerical response seems to be practically the same for both models (classical and optimized). The mesh elements' orientations have almost no effect on the global numerical response. A numerical stiffness equal to 253.15 N/mm was calculated for both models. Although, the classical specimen has an average stiffness of 174.3 \(\pm\) 11.8 N/mm, the stiffness of the optimized sample is 224.3 \(\pm\) 12.7 N/mm. This is related to the quasi-isotropic stiffness of the material since no large difference in the elastic modulus was found between the longitudinal and the transversal directions (16%). Figure 11: SENB specimen geometry’s definition and the boundary conditions for the numerical model. Figure 12: Numerical models of the SENB specimen. (**1**) Corresponds to the classical deposition with \(\pm\)45° layers alternation. (**2**) For the optimized deposition with principal stress reproduction in the V notch tip vicinity; (**a**) denotes the first principal direction while (**b**) is for the second principal direction. Moreover, the modification of the raster orientation is only carried out locally in the notch tip vicinity. The remaining domain is built by \(\pm 45^{\circ}\) stacked layers. Although this local modification leads to the improvement of the sample fracture toughness, however, no substantial difference was found in the elastic response of the model. The model assumes the material continuum. This assumption omits any potential effect of the air gaps, weld lines, and even the anisotropy of the filament itself. This partially interprets the difference found between the sample stiffness measured experimentally and numerically. On the other hand, the simulation results show that the influence of the local modification of filament orientation in the notch tip vicinity is vanishingly small so that the model cannot capture it. The model uses a stiffness matrix and materials constants from tensile tests printed so that the filaments are stacked in the same direction. This is supposed to maximize the bonding conditions between layers, and can therefore explain why the model overestimates the experimental stiffness. The biggest area of the specimen is printed using stacking layers at \(\pm 45^{\circ}\).