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<p>Fused deposition modeling (FDM) enables economical fabrication of polymer components; however, insufficient interlayer fusion and internal porosity limit the tensile performance of printed polylactic acid (PLA). This study investigated the effects of nozzle temperature, infill ratio, thermal annealing, and ultraviolet (UV) irradiation on the tensile response of unmodified commercial FDM-printed PLA. ASTM D638 Type I specimens were printed with the primary raster direction aligned with the tensile axis (0°) using nozzle temperatures of 205, 215, and 225&#xa0;°C and infill ratios of 10%, 33%, 50%, and 100%. The specimens were evaluated in the as-printed condition, after UV irradiation, after annealing at 50, 70, or 90&#xa0;°C, and after annealing followed by UV irradiation. Young’s modulus, <i>E</i>, and ultimate tensile strength, 𝜎<sub>𝑢</sub>, varied with structural density and thermal history. At 100% infill, annealing at 90&#xa0;°C increased <i>E</i> by approximately 8.2% for specimens printed at 225&#xa0;°C and increased 𝜎<sub>𝑢</sub> by approximately 23.9% for specimens printed at 205&#xa0;°C. These different responses indicate that annealing provides a larger mechanical benefit when the as-printed bonding state is less fully developed. Because 70 and 90&#xa0;°C exceed the nominal glass-transition temperature of the PLA filament, these gains must be balanced against dimensional distortion, warpage, shrinkage, and surface-texture changes. UV irradiation reduced <i>E</i> and 𝜎<sub>𝑢</sub> under most conditions; more importantly, it partially offset annealing-induced gains rather than providing an additive strengthening effect. These results position annealing as a condition-dependent post-processing option and clarify how UV exposure affects thermally strengthened FDM-printed PLA.</p>

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Competing effects of thermal annealing and UV irradiation on the tensile performance of unmodified FDM-printed PLA

  • 期刊论文

  • 发表日期：

    2026年7月23日

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  • Wei-Ting Chen,
  • Ming-Hsien Hsueh,
  • Chao-Jung Lai,
  • Ping-Tong Lu,
  • Feng-Ting Wu,
  • Meng-Gang Han

摘要

Fused deposition modeling (FDM) enables economical fabrication of polymer components; however, insufficient interlayer fusion and internal porosity limit the tensile performance of printed polylactic acid (PLA). This study investigated the effects of nozzle temperature, infill ratio, thermal annealing, and ultraviolet (UV) irradiation on the tensile response of unmodified commercial FDM-printed PLA. ASTM D638 Type I specimens were printed with the primary raster direction aligned with the tensile axis (0°) using nozzle temperatures of 205, 215, and 225 °C and infill ratios of 10%, 33%, 50%, and 100%. The specimens were evaluated in the as-printed condition, after UV irradiation, after annealing at 50, 70, or 90 °C, and after annealing followed by UV irradiation. Young’s modulus, E, and ultimate tensile strength, 𝜎𝑢, varied with structural density and thermal history. At 100% infill, annealing at 90 °C increased E by approximately 8.2% for specimens printed at 225 °C and increased 𝜎𝑢 by approximately 23.9% for specimens printed at 205 °C. These different responses indicate that annealing provides a larger mechanical benefit when the as-printed bonding state is less fully developed. Because 70 and 90 °C exceed the nominal glass-transition temperature of the PLA filament, these gains must be balanced against dimensional distortion, warpage, shrinkage, and surface-texture changes. UV irradiation reduced E and 𝜎𝑢 under most conditions; more importantly, it partially offset annealing-induced gains rather than providing an additive strengthening effect. These results position annealing as a condition-dependent post-processing option and clarify how UV exposure affects thermally strengthened FDM-printed PLA.