Process-structure co-optimization of CF/PETG auxetic structures fabricated by FDM for enhanced dimensional accuracy and impact resistance

This study investigates the optimization of dimensional accuracy and impact performance for carbon fiber-reinforced polyethylene terephthalate glycol (CF/PETG) structures with negative Poisson’s ratios fabricated via fused deposition modeling. Box–Behnken design response surface methodology is utilized with printing speed, nozzle temperature, bed temperature, and layer height as variables. An optimized parameter set (233 mm/s, 220 °C, 45 °C, 216 µm) is found to reduce the comprehensive dimensional error of specimens to ±0.05 mm. Multi-objective optimization of re-entrant hexagonal unit cell parameters (P1 = 9.74 mm, P2 = 7.07 mm, P3 = 108.37°, P4 = 1.89 mm) is also performed using a genetic algorithm. Under high-velocity impact loading at 16 m/s, the optimized structure achieves a specific energy absorption of 1799.6 J kg−1, up to 25.5% over the initial design, while reducing peak stress and displacement by 4.1% and 5.9%, respectively. Experimental and simulation analyses demonstrate the reliability of the finite element model, where this synergistic process-structure optimization strategy for CF/PETG materials enhances both fabrication accuracy and impact resistance in auxetic structures.