Exploring the chemistry of lightweight microstructural architectures through structure-property correlations in 3D-printed PETG-carbon fiber composites

Abstract This study examines the effect of infill structure topology on the tensile and flexural performance of lightweight components fabricated by fused deposition modeling using carbon fiber–reinforced PETG (PETG–CF). Seven infill architectures—gyroid, octet, triangle, solid cross, cubic, tri-hexagon, and grid—were systematically evaluated to establish structure–property correlations relevant to load-bearing applications. Standard specimens were fabricated under controlled conditions and characterized through mechanical testing, hardness measurements, scanning electron microscopy, compositional analysis, and finite element simulations. The gyroid infill exhibited the highest tensile strength (45.2 MPa) and Young’s modulus (2.6 GPa), followed by the tri-hexagon structure (43.5 MPa). In contrast, the grid infill showed superior flexural strength (88.5 MPa) and flexural modulus (4.1 GPa), while the cubic structure displayed comparable flexural performance. Stress–strain behavior revealed infill-dependent stiffness–ductility trade-offs, supported by microstructural observations and numerical stress distribution trends. The results demonstrate that infill topology plays a critical role in governing the mechanical response and failure behavior of FDM-printed PETG–CF components, providing practical guidance for the design of lightweight and mechanically reliable additively manufactured polymer composites.