Anisotropic properties of 3-D printed Poly Lactic Acid (PLA) and Acrylonitrile Butadiene Styrene (ABS) plastics

Abstract

Research was conducted on the mechanical and anisotropic properties of 3-D printed plastics (PLA and ABS), and the prevailing orientation and deposition of additive layers. Samples were tested in accordance with ASTM D638 - Standard Test Method for Tensile Properties of Plastics. Five print orientations were tested, including 0°, 30°, 45°, 60°, and 90°. Six samples were tested in each orientation, with a total of 30 samples being tested in each iteration of the experiment. An initial, “proof of concept” iteration was conducted with PLA plastic, followed by a second iteration which tested both PLA and ABS.Testing was conducted and based on the hypothesis that the material printed in the 0° orientation (parallel to the direction of applied tension) would be stronger, and that the strength of test specimens would be largely dependent on orientation of the material. In contrast, it was believed that the strength of 90° samples (perpendicular to the direction of applied tension) would be largely dependent on the strength of the bonds formed during the layer by layer deposition of heated material, and comparatively weaker. This was largely proven during testing. Samples printed in the 0° orientation exhibited statistically higher properties of both stress and strain. Conversely, plastics printed in the 90° orientation exhibited statistically weaker properties. It was noted that samples printed in the 30°, 45°, and 60° orientations exhibited some measure of improved ductility, although this was not the focus of the study.

Keywords

• Additive manufacturing
• Stress-strain
• 3-Printing
• Plastics
• Anisotropy
• Strength