Cyclic Fatigue Failure of Perforated 3D-Printed Polylactide (PLA) Specimens by Inserted Pin Loading

Area of Science:

• Materials Science
• Mechanical Engineering
• Additive Manufacturing

Background:

• 3D printing, specifically fused deposition modeling (FDM), is increasingly used for functional components.
• Polylactide (PLA) is a common FDM material, but its mechanical properties, especially under complex loading conditions, require thorough investigation.
• Perforated components are critical in many engineering applications, and their failure mechanisms in additively manufactured materials are not fully understood.

Purpose of the Study:

• To analyze the tensile and cyclic loading failure behavior of 3D-printed Polylactide (PLA) specimens with circular holes.
• To investigate the influence of varying print angles on the failure modes and mechanical performance of PLA.
• To develop and validate predictive models for failure stresses and fatigue life.

Main Methods:

• Experimental testing of 3D-printed PLA specimens with circular holes under tensile and cyclic loading.
• Systematic variation of print angles (0° to 90°, [0°/90°]s, [0°/±45°/90°]s) and hole locations.
• Application of a failure criterion based on stress and stress gradient conditions for prediction.
• Development of a mathematical interpolation equation for estimating failure stresses and S-N curves.

Main Results:

• Two distinct failure modes were observed: through-print lines and between-print lines.
• Tensile failure stress was sensitive to print angle.
• Normalized S-N data for cyclic loading showed similar trends for through-print line failures but separated for between-print line failures.
• The predictive failure criterion accurately estimated tensile failure stresses, locations, and orientations.
• The interpolation equation effectively estimated tensile failure stresses and S-N curves.

Conclusions:

• Print angle is a critical parameter influencing the mechanical failure of 3D-printed PLA under pin loading.
• Failure mode significantly affects fatigue behavior, necessitating distinct analysis for each.
• A combined stress and stress gradient failure criterion provides reliable predictions for tensile failure.
• Mathematical modeling offers a viable approach for estimating mechanical performance across different print angles.