Enhancing Sustainability and Functionality with Recycled Materials in Multi-Material Additive Manufacturing

Nida Naveed (), Muhammad Naveed Anwar, Mark Armstrong, Furqan Ahmad, Mir Irfan Ul Haq and Glenn Ridley
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Nida Naveed: Faculty of Technology, University of Sunderland, Sunderland SR1 3SD, UK
Muhammad Naveed Anwar: Faculty of Engineering and Environment, Northumbria University, Newcastle NE1 8ST, UK
Mark Armstrong: Faculty of Technology, University of Sunderland, Sunderland SR1 3SD, UK
Furqan Ahmad: Department of Mechanical and Mechatronics Engineering, Dhofar University, Salalah 211, Oman
Mir Irfan Ul Haq: School of Mechanical Engineering, Shri Mata Vaishno Devi University, Katra 182320, India
Glenn Ridley: Faculty of Technology, University of Sunderland, Sunderland SR1 3SD, UK

Sustainability, 2025, vol. 17, issue 13, 1-25

Abstract: This study presents a novel multi-material additive manufacturing (MMAM) strategy by combining virgin polylactic acid (vPLA) with recycled polylactic acid (rPLA) in a layered configuration to improve both performance and sustainability. Specimens were produced using fused deposition modelling (FDM) with various vPLA: rPLA ratios (33:67, 50:50, and 67:33) and two distinct layering approaches: one with vPLA forming the external layers and rPLA as the core, and a second using the reversed arrangement. Mechanical testing revealed that when vPLA is used as the exterior, printed components exhibit tensile strength and elongation improvements of 10–25% over conventional single-material prints, while the tensile modulus is largely influenced by the distribution of the two materials. Thermal analysis shows that both vPLA and rPLA begin to degrade at approximately 330 °C; however, rPLA demonstrates a higher end-of-degradation temperature (461.7 °C) and increased residue at elevated temperatures, suggesting improved thermal stability due to enhanced crystallinity. Full-field strain mapping, corroborated by digital microscopy (DM) and scanning electron microscopy (SEM), revealed that vPLA-rich regions display more uniform interlayer adhesion with minimal voids or microcracks, whereas rPLA-dominated areas exhibit greater porosity and a higher propensity for brittle failure. These findings highlight the role of optimal material placement in mitigating the inherent deficiencies of recycled polymers. The integrated approach of combining microstructural assessments with full-field strain mapping provides a comprehensive view of interlayer bonding and underlying failure mechanisms. Statistical analysis using analysis of variance (ANOVA) confirmed that both layer placement and material ratio have a significant influence on performance, with high effect sizes highlighting the sensitivity of mechanical properties to these parameters. In addition to demonstrating improvements in mechanical and thermal properties, this work addresses a significant gap in the literature by evaluating the combined effect of vPLA and rPLA in a multi-material configuration. The results emphasise that strategic material distribution can effectively counteract some of the limitations typically associated with recycled polymers, while also contributing to reduced dependence on virgin materials. These outcomes support broader sustainability objectives by enhancing energy efficiency and promoting a circular economy within additive manufacturing (AM). Overall, the study establishes a robust foundation for industrial-scale implementations, paving the way for future innovations in eco-efficient FDM processes.

Keywords: additive manufacturing (AM); fused deposition modelling (FDM); multi-material additive manufacturing (MMAM); polylactic acid (PLA); recycled PLA (rPLA) (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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