Effect of layer angle and ambient temperature on the mechanical and fracture characteristics of unidirectional 3D printed PLA material

This study aims to investigate the mechanical properties and crack resistance of unidirectional polylactic acid-based 3D printed components. In this regard, the effects of three printing angles (e.g., 0°, 45°, and 90°) and four ambient temperatures (e.g., −20, 0, 20, and 40 °C) on the tensile, flexural, and mode-I fracture characteristics were investigated. Additionally, utilizing theoretical theories appropriate for 3D printed samples as transversely isotropic samples, the results were assessed and expanded. Using the concepts of inlayer and interlayer failure modes in layered samples, the critical printing angle that separates the failure modes were evaluated. Also, failure patterns and the behavior of load-displacement curves were observed and assessed. The results show that an increase in temperature from − 20–40 °C caused tensile strength to decrease by 55–75%. Considering the samples isotropically, the strengths and energies were compared, then considering the anisotropy, inlayer, and interlayer tensile and shear strengths were reviewed. The results show that perpendicularly and transitively printed specimens have tensile strengths that are 4.4 and 2.5 times lower than parallel to loading direction printed specimens. Also, the critical printing angle is calculated as 23–31° based on the test temperature (respecting the load direction).