Investigating the influence of annealing and nozzle diameter on tensile strength of polyethylene terephthalate glycol composites

Additive Manufacturing (AM) techniques, particularly Fused Filament Fabrication (FFF), have revolutionized prototyping and low-volume production. Improving the tensile properties of FFF-printed parts is a primary objective to elevate their functional utility. This study aimed to investigate the effects of annealing time (ATM), annealing temperature (ATP), and nozzle diameter (ND) on the tensile strength (TS) of two commonly used printing materials: Polyethylene Terephthalate Glycol (PETG) and PETG reinforced with carbon fibre (PETG-CF). Samples with varying ND (0.4 mm, 0.6 mm, and 0.8 mm) underwent annealing at ATP of 80°C and 100°C for ATM of 60 min and 120 min, respectively. Subsequent tensile tests were meticulously conducted, and regression models were employed to comprehensively analyse the influence of these control factors on TS. The findings from the tensile tests on annealed specimens revealed substantial improvements in TS for both PETG and PETG-CF materials. Statistical analysis, Taguchi method (TM), and response surface methodology (RSM) indicated that ND exerted a more pronounced impact on TS compared to ATM and ATP. By identifying the optimal control factor combinations for each material, the study pinpointed that the best TS was achieved at 0.8 mm ND, 120 minutes ATM, and 100°C ATP for PETG-CF. The remarkable enhancement in tensile properties for annealed FFF-printed parts underscores the potential of PETG-CF to replace structural metallic components in critical applications within the automotive and aeronautical industries.