Mechanical behavior of FDM-printed PETG under temperature–speed coupling and sequential annealing/UV: Implications for process design

Additive manufacturing of structural polymers for reinforced plastics and composite systems demands process‐aware rules that couple printing, post-processing, and mechanical response. This study establishes an engineering processing–structure–property relation for FDM-printed polyethylene terephthalate glycol used as a matrix material. ASTM D638 Type I specimens with 0.20 mm layers and a 0.40 mm nozzle were produced under a two-factor full-factorial design with nozzle temperature set at 225, 235, and 245°C and print speed set at 15, 20, and 25 mm/s. Post-processing comprised annealing at 75, 85, and 95°C for 60 min, with and without subsequent ultraviolet exposure. Tensile modulus and ultimate tensile strength were measured using a clip-on extensometer. Results show a robust temperature–speed coupling: higher temperature and lower speed consistently increased both modulus and strength, while speed increases degraded performance through insufficient interlayer fusion. Annealing exhibited a single-peak response: 75°C yielded the largest gains, 85°C provided moderate improvement, and 95°C caused partial deterioration consistent with stress relaxation near the glass transition. Ultraviolet exposure generally reduced stiffness by a few percent and often reduced strength, with limited recovery after 95°C annealing. A practical process window is recommended for load-bearing PETG parts: nozzle temperature between 235 and 245°C, print speed at or below 20 mm/s, and annealing at 75 to 85°C for 60 min while avoiding or tightly controlling ultraviolet exposure. The relation and methodology provide actionable baselines for tailoring PETG matrices and for translation to fiber-reinforced PETG and related composite architectures.