PSI - Issue 83

Manuel A.R.V. Esteves et al. / Procedia Structural Integrity 83 (2026) 146–153

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Following impact testing, the fractured halves of all specimens were visually inspected to identify dominant fracture mechanisms. Representative fracture surfaces are presented in Fig. 4.

Fig. 4. Fracture surfaces of Charpy specimens: virgin PLA at 24.1 °C (a) and -30.9 °C (b); recycled PLA printed at 220 °C at 24.1 °C (c) and - 30.9 °C (d); recycled PLA printed at 237 °C at 24.1 °C (e) and -30.9 °C (f); recycled PLA printed at 255 °C at 24.1 °C (g) and -30.9 °C (h). Visual analysis reveals that virgin PLA specimens exhibit more irregular and rough fracture surfaces, characteristic of ductile failure associated with higher plastic deformation and energy absorption. In contrast, recycled PLA specimens display smoother and more planar fracture surfaces, indicating a predominantly brittle fracture mode. This transition towards brittle behavior becomes more pronounced with increasing extrusion temperature and decreasing testing temperature, explaining the observed reductions in absorbed impact energy. 4. Conclusions This study evaluated the suitability of recycled PLA for FDM by analyzing its impact behavior under controlled processing and testing conditions. At room temperature, recycled PLA printed at 220 °C exhibited the highest absorbed impact energy among the recycled configurations, although its performance remained inferior to that of virgin PLA. In contrast, low-temperature testing revealed a change in material ranking, with recycled PLA printed at 237 °C providing the best impact response and the lowest result dispersion. These results indicate that an extrusion temperature near 237 °C offers an effective compromise for recycled PLA, balancing interlayer bonding quality and impact energy absorption in different service temperatures. Overall, the findings demonstrate that recycled PLA can be reliably employed in FDM processes, particularly for applications in which stiffness and dimensional stability are more critical than high ductility or impact toughness. From a sustainability perspective, recycled PLA represents a viable and economically attractive alternative to virgin filament, enabling material reuse and waste reduction without severely compromising functional performance. Although increased brittleness remains an inherent limitation, appropriate optimization of processing parameters, namely the extrusion temperature, can partially alleviate this drawback and enhance the practical applicability of recycled PLA in engineering-oriented AM. References Acierno, D., Patti, A., 2023. Fused deposition modelling (FDM) of thermoplastic-based filaments: process and rheological properties—an overview. Materials 16(24): 7664. Ahn, S. H., Montero, M., Odell, D., Roundy, S., Wright, P. K., 2002. Anisotropic material properties of fused deposition modeling ABS. Rapid prototyping journal 8(4): 248-257. Almansoori, K., Pervaiz, S., 2023. Effect of layer height, print speed and cell geometry on mechanical properties of marble PLA based 3D printed parts. Smart Materials in Manufacturing 1: 100023. Badia, J., Strömberg, E., Karlsson, S., Ribes-Greus, A., 2012. Material valorisation of amorphous polylactide. Influence of thermo-mechanical degradation on the morphology, segmental dynamics, thermal and mechanical performance. Polymer degradation and stability 97(4): 670 678.