Investigation of effect of infill structures and density on mechanical, impact energy, degradation and wettability performance of 3D printed PETG specimens

Abstract This paper examines the influence of infill pattern and infill density on the mechanical performance, wettability, and degradation behaviour of fused deposition modelled (FDM) PETG under simulated physiological conditions. Gyroid, tri-hexagon, and octet infill architectures were fabricated at 40%, 60%, and 80% densities and evaluated through tensile, impact, contact angle, and PBS immersion tests. The results demonstrated that gyroid with 80% infill density offered the most balanced performance, achieving the highest tensile strength of 18.42 MPa, impact energy of 11.2 mJ, swelling ratio of 0.00366, contact angle of 95.4°, and smooth surfaces with negligible voids as indicated by the scanning electron microscope. Tri-hexagon structure with 40% density exhibited lowest tensile strength of 14 MPa and at 80% density excelled in impact resistance, absorbing 11.5 mJ without brittle failure. Octet at 80% was the most hydrophilic and showed the fastest swelling rates, but its higher surface porosity and microcracking reduced its mechanical robustness. Thus, internal architecture played a crucial in performance of additively manufactured PETG in applications demanding higher strength, hydrophobic surfaces with lower swelling rates.