BENDING FATIGUE PROPERTIES OF 3D PRINTED POLYLACTIC ACID VIA DYNAMIC MECHANICAL ANALYSES AND STATISTICAL ANALYSIS USING WEIBULL DISTRIBUTION

Polylactic acid (PLA) is increasingly utilized as a thermoplastic material in fused deposition modeling (FDM) for a wide range of engineering applications since it is a compostable and biodegradable thermoplastic made from renewable sources. Understanding its fatigue behavior and damage mechanisms is crucial for assessing its durability and long-term reliability. Compared to standard testing machines, dynamic mechanical analysis (DMA) applies loads more accurately, especially for small cross- section samples. In this study, flexural strength of PLA samples produced by FDM with three infill patterns (zigzag, lines, and concentric) was measured using 3 bending tests according to ASTM D790. The concentric samples showed the highest strength of 87.3 MPa, followed by zigzag (85.2 MPa) and lines (77.2 MPa). Subsequently, low cycle bending fatigue tests were conducted at 40, 60, and 80% of the corresponding flexural strength values using a DMA equipped with a single cantilever fixture, and stress – cycles of failure (S-N) graphs created. Fatigue properties of samples with concentric infill pattern yielded better results than others at each stress levels. In addition, the failure probabilities were assessed using the two-parameter Weibull distribution.