# Mechanical and Tribological Performance of Carbon Fiber-Reinforced PETG for FFF Applications
## 4 Conclusions  
According to the results of the tensile tests, the incorporation of carbon fiber reinforcement has a detrimental effect, leading to a decrease in the maximum stress (834.052 N compared to 956.6 N for conventional PETG) and a reduction in the material's strength (39.23 N/mm\({}^{2}\) vs. 48.41 N/mm\({}^{2}\) for the conventional material). As expected, due to the nature of the reinforcement (short fibers), the deformation of the material also decreases (2.13% compared to 2.9%). Therefore, it may not be suitable for applications requiring high ductility in tensile strength.  
Conversely, conventional PETG appears to be a more attractive option for applications involving tensile stresses. It demonstrates improved performance at higher temperatures, and the best results are obtained at medium layer thicknesses (0.25 mm), despite the potential expectation of increased layer cohesion at lower thicknesses.  
The compression tests reveal distinct behaviors in both materials, with the reinforced material outperforming the non-reinforced material, as anticipated. In the case of the standard material, increasing the layer thickness leads to better results across all relevant variables. In contrast, for the reinforced material, improved results are achieved as layer thickness decreases due to increased layer cohesion.  
In the context of the compressive tests, it is evident that the displacement and the deformation are considerably lower with the minimum layer thickness used for conventional PETG. This could be attributed to the absence of internal voids that may have been introduced by the reinforcement in the PETG matrix.  
Considering the dimensional deviations calculated for the specimens, a clear trend emerges where the material stabilizes at medium layer thicknesses. In terms of tensile strength, the positive deviation benefits the conventional material, but not the reinforced one. Additionally, it is observed that thinner layer thicknesses result in a more fragile rupture due to the increased cohesion between layers, especially in the case of the conventional material. However, this is not the case for the reinforced material, where the tensile results are most favorable for the thinner layer thickness. Even though there is a negative deviation in both measured dimensions, it yields the highest mechanical performance.  
In conclusion, the incorporation of CF reinforcement into the PETG matrix is beneficial for applications involving compressive strength but not tensile strength, where conventional PETG is the preferred material. The results confirm that, as reported by several authors, layer thickness is the most critical parameter influencing the material's behavior in both test cases.  
Conceptualization, J.M.L., J.M.V.-M. and M.B.; project administration, M.R.-P.; experimental methodology, J.M.L.; investigation, J.M.V.-M. and M.B.; data processing, J.M.L.; formal analysis, J.M.L., J.M.V.-M. and M.B.; project review, M.R.-P.; writing--original draft preparation, J.M.L. and M.B.; writing--review and editing, J.M.V.-M.; final review, M.R.-P. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Data Availability Statement: Data are contained within the article.  
This work has been developed under the support of the Mechanical Engineering and Industrial Design department and the Vice-Rector's Office for Scientific Policy of the University of Cadiz.  
The authors declare no conflict of interest.