In research carried out by [PERSON] and colleagues [17], fibre orientation determined with Moldex3D simulation software was compared to values measured with micro-CT on short-GF-reinforced composites, on long-GF-reinforced composites [18; 19] and also on long carbon-fibre-reinforced composites [20; 21]. It was stated that by using an integrated simulation in modelling components composed of fibre-reinforced thermoplastics, an accurate prediction of fibre orientation has become available for the industry. Figure 1: Explanation of fibre orientation tensor, based on [14; 15]**(a)** oriented in direction 1, (**b**) planar isotropy in plane 1-2, (c) isotropic. Another research project carried out by [PERSON] and colleagues [22] examined a 3 mm thick, rectangular plaque with a fan gate produced from 50 wt% short- and long-GF-reinforced polyamide 6.6. The plaques were manufactured with injection moulding; then, the two components, the flow direction and perpendicular, of the fibre orientation tensor were measured with micro-CT, and were compared to predictions of the Moldex3D software (Taiyuan St. Zhubei City, Taiwan) using the same injection moulding parameters. The results showed a qualitative agreement between the measured and the simulated values for both materials. The exact results for both long- and short-fibre-reinforced composites were within the 15% relative margin of error, which was the qualitative criteria (\(-3.5\%\) and \(8.5\%\), respectively). At both fibre lengths, the shell-core-shell structure was clearly identified, which was the result of the fountain flow of the melt. It was revealed that compared to the short-fibre-reinforced composite, the thickness of the core was greater in the long-fibre-reinforced system. After that, the material model (including the inhomogeneity caused by the fibre orientation) from Moldex3D was imported into the Digimat MF software (Cobham, UK), where the tensile flexural modulus of the composites was calculated. Values of the simulation were compared to the measured results, and it was found that in both cases, the simulation underestimated the real values, but the difference was acceptable. In conclusion, the fibre orientation in sizing injection-moulded parts is crucial. Numerous analytical and numerical methods are available in the literature for examining the structure of composites from the perspective of either stress, dislocation, oscillation or stability [23]. Of these methods, the finite element method (FEM) is an extremely efficient way of calculating approximate solutions of complex problems. The FEM is typically divided into two main categories based on the applied principles. Classic or displacement-type finite elements [24; 25] are classified into the first category, while hybrid or mixed-type finite elements [26; 27] are sorted into the second one. In the case of displacement-type finite elements, the variables are geometric quantities from which forces and torques can be derived, while in the case of hybrid finite elements, apart from geometric quantities, force and torque-type quantities can also contain variables under certain conditions. The advantages of both types are undoubted, but in the case of solving static problems, engineering calculations can be executed using fewer elements with the hybrid FEM. [PERSON] et al. [28] examined hybrid injection-moulded short- and continuous-fibre-reinforced thermoplastic composites using a numerical simulation with experimental validation. For injection moulding, simulation Moldex3D software was used, while for the numerical simulation of the flexural test, Ansys software (Canonsburg, PA, USA) was used. In the hybrid FEM analysis, the Mori-Tanaka analytical model was used, which was necessary for the simulation of the complex microstructure. During the simulation, they used mechanical properties from the supplier and Ansys database, the fibre volume content from pyrolysis, fibre aspect ratio from the fibre length analysis and fibre orientation tensor from the CT analysis.