Mechanical and Thermal Optimization of Fused Deposition Modeling of PETG and PETG–Carbon-Fiber Composites

This study presents process optimization of fused deposition modeling (FDM) to enhance the physio-mechanical performance of polyethylene terephthalate glycol (PETG) and polyethylene terephthalate glycol - carbon fiber (PETG-CF) for automotive applications. A Central Composite Design (CCD) is implemented using Response Surface Methodology (RSM) to examine the combination of infill density, print speed, and layer height. Mechanical properties (tensile, flexural, impact, and compression), density, solvent absorption, UV-A resistance, thermal analysis (DSC and TGA), contact angle, and SEM fractography were evaluated. Results show that infill density has the most significant effect on all mechanical properties, while print speed and layer height enhance interlayer adhesion. PETG exhibits warpage at low print speed, but optimized parameters achieve a tensile strength of 40.2 MPa, flexural strength of 75.7 MPa, impact strength of 19.5 kJ/m 2 , and compressive strength of 44.5 MPa. PETG-CF samples exhibit lower strength due to poor fiber-matrix adhesion. However, the optimized parameter improved mechanical strength, achieving a tensile strength of 46.4 MPa, flexural strength of 81.9 MPa, impact strength of 33.9 kJ/m 2 , and compressive strength of 49.7 MPa. Water and acetone absorption and UV-A degradation tests confirm structural stability for outdoor applications. This study provides insight into interaction and optimized parameters for durable, lightweight automotive parts with demonstrated chemical resistance from solvent-absorption tests.