Stress relaxation of 3D printed PLA of various infill orientations under tensile and bending loadings

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Abstract In recent years, the widespread use of 3D printing technology in various industries has highlighted the crucial issue of how 3D printed polymers behave mechanically when subjected to stress relaxation. The time‐independent mechanical properties of these polymers, as well as their stress relaxation behavior, are both affected by the 3D printing parameters used. Therefore, this study examines the stress‐relaxation behavior of PLA under tensile and bending loading modes, specifically investigating how different raster orientations affect this behavior. The findings indicate that the ±45° infill orientation had the least amount of relaxation in both tensile and bending modes compared to the other orientations. Additionally, there was higher stress relaxation in the bending loading mode across all infill orientations. The findings indicate that the experimental duration should exceed 750 s to achieve an accurate model, as both Maxwell‐Weichert elements contribute to stress relaxation during this period. On the other hand, extending the test beyond 20,000 s is not necessary since neither of the elements contributes significantly to stress relaxation.