## 4 Conclusions  
This study investigates the influence of process parameters on the tensile strength of FDM manufactured CFRP composite parts. Besides RSM, also ANN methods were introduced as a useful tool for predicting the tensile strength of FDM fabricated CFRP composite parts. A significant difference between ANN and RSM was found based on the paired t-test for the presented data. There should also be stressed that there is a fundamental difference between RSM and ANN test outputs since RMS adopts all the data in model building and ANN does not (the ANN success rate is tested on unseen data via the LOSO k-fold cross-validation technique).  
The following conclusions were drawn:  
1. Analyzed process parameters have a significant influence on the mechanical behavior of CFRP composite parts. The tensile strength can be significantly increased and improved by the selection of the optimal process parameters.
2. Presence of carbon fibers in polyamide decreased the ductility of polyamide and improved the tensile strength.
3. Carbon fibers have a significant effect on the tensile strength only in the case that the load direction was in the direction of deposition of the material (at raster angle of 90 degrees).
4. The layer thickness has the most significant influence on the tensile strength. The value of tensile strength increases with decreasing layer thickness, it can be explained by the increase in air gap between individual layers and rasters.
5. The raster angle also has a significant effect on tensile strength, it can be explained by different mechanisms that cause the fracture material.
6. The wall thickness and printing speed have a secondary effect on the tensile strength. Nevertheless, a slight increase in tensile strength can be achieved with an increase in wall thickness and with a decrease in printing speed;
7. Among the nine different tested ANN topologies, the ANN 6 model was recognized as the most appropriate.
8. The average percentage error between the predicted tensile strength values and the experimental values was assessed.  
Figure 13: Experimental tensile strength vs. predicted tensile strength of the training data.  
The main benefits of the introduced methods also include the future reduction in experimentation time, especially since CFRP belongs to the new and insufficiently researched FDM materials.  
The future research is to investigate the influence of process parameters on the compressive and flexural properties of FDM fabricated CFRP composite parts, as well as the effect of the percentage of carbon fibers on the properties of the printed parts.  
Conceptualization, M.F. and D.B.-H.; methodology, M.C.H., D.B.-H., K.M. and L.B.; software, D.P. and K.M.; validation, M.F., A.C. and M.C.H.; formal analysis, D.B.-H., M.F. and A.C.; investigation, K.M., L.B. and D.P.; resources, M.F., M.C.H. and D.B.-H.; data curation, A.C.; writing--original draft, D.B.-H., L.B., K.M., and D.P.; writing--review and editing, M.F.; visualization, D.B.-H., D.P. and L.B.; supervision, M.C.H. and M.F.; project administration, M.F. and D.B.-H.; funding acquisition, M.C.H. All authors have read and agreed to the published version of the manuscript.  
This research was funded by UNDP, Norwegian Embassy, University of Sarajevo and Federal Ministry of Education and Science, B&H (Grant Number 0101-8745/21).  
Not applicable.  
The data that support the findings of this study are available from the corresponding author, upon reasonable request.  
The authors declare no conflict of interest.