Experimental Investigation of the Tensile and Fatigue Behaviour of 3D-Printed Recycled PLA Parts

The growing emphasis on sustainable manufacturing has driven significant interest in recycled polylactic acid (rPLA) for fused deposition modelling (FDM), yet its mechanical performance particularly under cyclic loading remains underexplored. This study investigates the influence of key 3D printing parameters (print temperature: 190–220°C, layer height: 0.1–0.2 mm, print speed: 40–60 mm/s) on the mechanical properties of rPLA using a Taguchi L9 experimental design. Results reveal that print temperature is the most critical parameter, with optimal performance achieved at 220°C, 0.1 mm layer height, and 40 mm/s print speed, yielding a peak ultimate tensile strength of 47.82 ± 0.30 MPa. Microhardness improved by 18% at higher temperatures due to enhanced layer adhesion, while fatigue performance improved under high-cycle loading conditions for samples printed under optimised conditions. Fractography analysis via scanning electron microscopy confirmed that lower temperatures (190°C) introduced voids and weak interlayer bonding, whereas higher temperatures promoted denser microstructures. This study offers practical recommendations for enhancing rPLA in load-bearing applications, connecting sustainability with performance in additive manufacturing. The results support the implementation of high-temperature, low-speed printing to address the fundamental limitations of recycled polymers, promoting the objectives of a circular economy in 3D printing.