The influence of fabrication parameters on the durability of material extrusion (MEX) thermoplastics (PLA, ABS, PETG, PC, and PP): a review of impact, hardness, and creep behavior

Abstract As additive manufacturing (AM) transitions from rapid prototyping toward the production of functional, load-bearing components, characterizing long-term mechanical reliability is paramount. Material Extrusion (MEX) has emerged as a leading modality for industrial applications, yet its inherent mesostructural anisotropy and interlayer porosity present distinct challenges for predicting structural integrity. This paper provides a systematic review of current research regarding the impact performance, surface hardness, and creep behavior of 3D-printed thermoplastics. While the existing literature relies heavily on polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS), this work identifies a critical research gap regarding the comparative performance of polyethylene terephthalate glycol (PETG), engineering-grade polycarbonate (PC), polypropylene (PP), and their recycled counterparts under identical processing conditions. The analysis evaluates the influence of critical fabrication settings, including infill architecture, layer height, thermal processing, and raster orientation, on the resulting mechanical performance. A synthesis of the empirical data indicates that while increasing infill density consistently correlates with improved surface hardness and creep resistance, the response of impact toughness is highly variable. Specifically, while several studies report maximum toughness at a 100% infill, others observe peak energy absorption at lower densities ranging from 70% to 85%, suggesting a complex relationship between material volume, internal porosity, and fracture propagation modes. This review assesses the mechanical durability of recycled polymers in the context of sustainable manufacturing. The study concludes by identifying a major research gap in creep-impact interactions and discussing the limitations of current standardized testing protocols for characterizing the unique failure modes of 3D-printed mesostructures. This work establishes a rigorous technical framework for optimizing MEX parameters in safety-critical industrial applications.