Enhancing mechanical properties of 3D-printed PETG-CF composites through HGRA optimization and annealing heat treatment

3D printing has recently emerged as a rapidly evolving manufacturing technique that enables the production of intricate geometries with ease. This investigation delves into the development of a virgin PETG-CF composite filament that incorporates 20% short carbon fibres in order to improve the mechanical performance of printed parts. The DOE framework was employed in conjunction with a hybrid Grey Relational Analysis method to optimise five critical printing parameters: layer thickness, infill density, printing temperature, raster angle, and printing speed. The optimisation was done using an L27 orthogonal array. Components that were printed with the most optimal process parameters were subjected to an annealing heat treatment to improve crystallinity and increase molecular chain mobility. This step was taken to further enhance the properties. Optimal parameters were determined to be 0.2 mm layer thickness and 75% infill density, as optimisation revealed that infill density and layer thickness were the most noteworthy variables. As opposed to the least effective parameter combinations, the tensile strength (TS) increased by 108.36%, the impact strength by 200%, and the surface roughness decreased by 81.94% under these conditions. Following optimisation, annealing at 90°C for 200 min results in a 21.8% increase in tensile strength (TS), a 33.3% increase in impact strength (IS), and a marginal reduction in surface roughness (SR) (3.11%). These findings verify that thermal annealing substantially enhances mechanical performance, albeit with only a modest enhancement in surface quality.