MECHANICAL CHARACTERIZATION AND DAMAGE TOLERANCE IMPLICATIONS OF SOLID AND TRUSS NACA 6412 WING RIB CONFIGURATIONS FABRICATED WITH PETG USING FUSED DEPOSITION MODELING

The structural use of Fused Deposition Modeling (FDM) printed thermoplastic components in aerospace design requires mechanical performance data at the component level, which is presently limited in the available literature. This study presents an experimental mechanical characterization of two additively manufactured NACA 6412 airfoil wing rib configurations fabricated from Polyethylene Terephthalate Glycol (PETG), carried out to assess the implications of the results for the fatigue resistance and damage tolerance of FDM printed aerospace structures. A Solid Rib with a chord length of 200.20 mm and a uniform extrusion depth of 10 mm, incorporating three circular lightening apertures, and a Truss Rib with a chord length of 180.00 mm and an extrusion depth of 3 mm, incorporating an open diagonal bracing pattern, were designed and fabricated on a Bambu Lab A1 printer from the same PETG filament stock. Five mechanical tests were carried out: static tensile testing of the PETG filament, three points flexural testing of the filament and the Solid Rib, Leeb rebound hardness testing of the Solid Rib, pendulum impact testing of the Solid Rib, and sliding wear testing of both rib configurations. Tensile testing returned a mean ultimate tensile strength of 25.24 MPa and a mean elastic modulus of 563.46 MPa for the raw filament. Three points flexural testing of the Solid Rib produced a maximum flexural stress of 19.01 MPa, a flexural elastic modulus of 210.87 MPa, a strain at maximum stress of 15.07 percent, and a fracture energy of 2.978 J. The 62.6 percent reduction in elastic modulus between the raw filament and the fabricated rib is attributed to insufficient polymer chain interdiffusion at the print parameters used rather than to a limitation of PETG as a material. Leeb hardness measurements returned a mean of 46.04 HL across three locations, with a narrow range of 2.606 HL indicating uniform surface consolidation. Pendulum impact testing returned a mean absorbed energy of 9.737 J/mm². Sliding wear testing showed that the Solid Rib achieved a wear resistance of 70.175 N·m/mm³, outperforming the Truss Rib specimens at 48.001 and 41.678 N·m/mm³. The combined results confirm that PETG retains a ductile, progressive failure mode even at sub optimal print parameters, satisfying the fundamental precondition for damage tolerance methodology to apply at the component level. Fatigue crack propagation testing and fractographic analysis were outside the scope of this study, so the damage tolerance conclusions drawn here are qualitative rather than quantitative. The study established a component level experimental baseline for FDM printed PETG wing ribs.