Advancing Sustainable Manufacturing through Multi-Material Additive Manufacturing

Background: Sustainable engineering focuses on designing and manufacturing products that meet current needs without compromising future generations or the environment, emphasizing waste reduction, resource conservation, and ecological balance. Additive Manufacturing (AM), particularly Multi-Material Additive Manufacturing (MMAM), offers significant potential for sustainability through material efficiency and functional integration. However, MMAM faces challenges including material compatibility, bonding issues, residual stress, and process control complexities. Objective: This study aims to present a novel MMAM strategy combining virgin polylactic acid (vPLA) with recycled polylactic acid (rPLA) in a layered configuration to simultaneously improve mechanical performance and enhance sustainability in 3D printed components. Methods: Components were fabricated using vPLA and rPLA in layered configurations. Mechanical testing (tensile strength, elongation, tensile modulus) was performed. Thermal analysis assessed degradation temperatures and residue. Full-field strain mapping, digital microscopy (DM), and scanning electron microscopy (SEM) were employed to investigate microstructural characteristics, interlayer adhesion, and failure mechanisms. Results: Mechanical testing revealed that vPLA as the exterior material significantly improved tensile strength and elongation (10–25%) over single-material prints, while tensile modulus depended on material distribution. Thermal analysis indicated both vPLA and rPLA degrade around 330∘C, with rPLA showing higher end-of-degradation temperatures (461.7∘C) and increased residue, suggesting improved thermal stability. Strain mapping, DM, and SEM confirmed that vPLA-rich regions exhibited superior interlayer adhesion with fewer defects, whereas rPLA-dominated areas showed higher porosity and brittle failure. Conclusion: These findings underscore that strategic material placement in MMAM can effectively mitigate the inherent deficiencies of recycled polymers, reducing reliance on virgin materials. This work contributes to broader sustainability objectives by enhancing energy efficiency and promoting a circular economy within AM, establishing a robust foundation for industrial implementations and future eco-efficient FDM processes.