Investigation of the Effect of Printing Orientation and Loading Direction on the Mechanical Properties and Fracture Behavior of Additively Manufactured Polylactic Acid

Document Type : Research Article

Authors

1 Department of Mechanical Engineering, Technical and Vocational University (TVU), Tehran, Iran

2 Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen, 518055, China

3 Moganshan Institute ZJUT, Kangqian District, Deqing 313200, China

4 High-speed Rotating Machinery Laboratory, Zhejiang University, Hangzhou 310027, China

Abstract

The mechanical properties and crack growth resistance of polylactic acid (PLA) specimens produced via additive manufacturing were investigated. The primary objective was to evaluate the influence of printing orientation on the mechanical behavior of specimens under different loading conditions. Specimens were fabricated with three printing orientations: 0°, 90°, and 0°/90°, representing longitudinal, transverse, and bidirectional layer arrangements, respectively. The results revealed that changing the printing orientation from 0° to 90° or 0°/90° significantly increased the maximum tensile stress by approximately 39% and the strain at failure by an average of 30%. To assess crack growth resistance, fracture tests were conducted under tensile (mode-I) and shear (mode-II) loading using butterfly-shaped specimens tested with a modified Arcan fixture. Geometric factors corresponding to different loading orientations were extracted using finite element simulations. The results indicated that the critical strain energy release rate under shear loading was approximately 58% lower than under tensile loading. Additionally, specimens printed at a 90° orientation exhibited lower crack growth resistance compared to those at 0° and 0°/90° due to weaker interlayer bonding. Ultimately, the 0°/90° orientation was identified as optimal, offering a favorable balance between high tensile strength and adequate crack growth resistance.

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References

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Amirkabir Journal of Mechanical Engineering
Volume 57, Issue 3
June 2025
Pages 379-398

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