PSI - Issue 72

Božica Bojović et al. / Procedia Structural Integrity 72 (2025) 491–498

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In the specimens tested immediately and after one month (Fig. 4b and 4d), the fracture surfaces exhibit a stepped morphology, while the two-month-old specimen (Fig. 4f) shows a clean, straight fracture line. A detailed examination of the fracture surfaces of the DLP-LCD specimens shows two different zones:  A brittle zone characterized by flat, smooth and shiny surfaces, which are prevalent in all specimens, especially in Fig. 4b, 4d and 4f.  A ductile zone characterized by striation patterns, which can be seen in Fig. 4d and 4f, indicating localized plastic deformation prior to final failure. These two fracture zones are shown in Fig. 4b, 4d and 4f. It is important to notice that the ductile zone is absent in the specimens tested immediately after compression, which exhibit rough and irregular fracture surfaces, indicating abrupt, brittle failure. In contrast, the DLP-LCD specimen aged for two months shows a uniform and clean fracture surface, indicating a gradual transition to a more brittle behavior as a result of material aging. 4. Conclusion This study compared how 3D-printed specimens made from PLA filament and PLA-like resin change over a two month period of natural aging. Through mechanical testing and microscopic analysis, the goal was to better understand how time and environmental exposure affect the performance of printed parts, and also to help guide material and technology choices for more durable applications. Results showed that specimens printed with FDM using PLA filament maintained stable mechanical properties over time. The flexural modulus changed very little, strength decreased slightly (by up to 9%), and strain at failure increased moderately (up to 17%), suggesting the material became slightly more ductile but remained tough and elastic. On the other hand, specimens printed with DLP-LCD from PLA-like resin showed significant degradation. Flexural modulus and strength dropped to about 45% and 43% of their original values, while strain increased by a similar amount. These changes point to a noticeable loss of stiffness and strength, and a shift toward a more flexible — but less structurally reliable — behavior. Overall, the findings underline how much material and printing method matter when long-term performance is important. FDM-printed PLA appears more stable and reliable over time, while resin-printed parts may require additional protection or improved formulations to prevent early degradation. Aging is an important factor in the design and use of 3D-printed components, especially for real-world applications where time, humidity, and routine handling are important to be considered. Acknowledgements This research was financially supported by the Ministry of Science, Technological Development, and Innovation of the Republic of Serbia under Contracts No. 451-03-136/2025-03/200105 and 451-03-137/2025-03/200105 dated February 4, 2025. References Ngo, T.D., Kashani, A., Imbalzano, G., Nguyen, K.T.Q., Hui, D., 2018. Additive manufacturing (3D printing): A review of materials, methods, applications and challenges. Composites Part B: Engineering 143, 172 – 196. doi:10.1016/j.compositesb.2018.02.012 Gross, B.C., Erkal, J.L., Lockwood, S.Y., Chen, C., Spence, D.M., 2014. Evaluation of 3D printing and its potential impact on biotechnology and the chemical sciences. Analytical Chemistry 86(7), 3240 – 3253. https://doi.org/10.1021/ac403397r Gebisa, A. W., Lemu, H.G., 2018. Investigating Effects of Fused-Deposition Modeling (FDM) Processing Parameters on Flexural Properties of ULTEM 9085 using Designed Experiment. Materials 11(4), 500. https://doi.org/10.3390/ma11040500 Rankouhi, B., Javadpour, S., Delfanian, F., Letcher, T., 2016. Failure Analysis and Mechanical Characterization of 3D Printed ABS With Respect to Layer Thickness and Orientation. Journal of Failure Analysis and Prevention 16(3), 467 – 481. https://doi.org/10.1007/s11668 016-0113-2 Tymrak, B.M., Kreiger, M., Pearce, J.M., 2014. Mechanical properties of components fabricated with open-source 3-D printers under realistic environmental conditions. Materials & Design 58, 242 – 246. https://doi.org/10.1016/j.matdes.2014.02.038