PSI - Issue 68

Aleksa Milovanović et al. / Procedia Structural Integrity 68 (2025) 922 – 928 A. Milovanović et al. / Structural Integrity Procedia 00 (2025) 000–000

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As suggested by Milovanović et al. (2022c), the so-called ‘’candle shape’’ curves show that the highest strain values in the ligament are located at places of the expected crack path, i.e., the crack follows the correct straight path. Worth pointing out is that all SENBs here (i.e., all ten infill groups on all layer height configurations) have these ‘’candle shape’’ curves (see some examples from Fig. 7), proving the test validity regarding the crack path direction. 4. Conclusions The plane-strain fracture toughness assessment tests were performed on FDM-grade PLA material with different infill percentages. The comprehensive research includes ten infill cases in three different layer height configurations (i.e., 0.3; 0.2; 0.1 mm), giving a total of 30 specimen groups. This conference paper includes only four infill cases (100%; 70%; 40%; 10%) from one layer height (0.1 mm). The results show that the lower infills have an inherent plasticity in their response. Namely, the plane-strain condition was met for all the tested specimens and all of them had a correct straight crack path. However, due to the apparent presence of plasticity in the load-deflection response from the tests, the P max / P Q ratio was over the 1.1 limit for lower infill cases. The EPFM approach was thus employed, and the resulting values were compared. For this short paper, the J max values were prepared for the comparison between infill groups, and the extended paper will include the J-R curves for all infill cases and other J-integral values (such as J IC ), for better result comparison. Acknowledgments The authors would like to thank the support from the Ministry of Science, Technological Development and Innovation of the Republic of Serbia, under contract No. 451-03-66/2024-03/200213 (from February 5th, 2024.). References Alami, A.H., Olabi, A.G., Alashkar, A., Alasad, S., Aljaghoub, H., Rezk, H., Abdelkareem, M.A., 2023. Additive manufacturing in the aerospace and automotive industries: Recent trends and role in achieving sustainable development goals. Ain Shams Engineering Journal 14(11), 102516: pp. 1-18. DeStefano, V., Khan, S., Tabada, A., 2020. Applications of PLA in modern medicine. Engineered Regeneration 1, pp. 76-87. Farah, S., Anderson, D.G., Langer, R., 2016. Physical and mechanical properties of PLA, and their functions in widespread applications — A comprehensive review. Advanced Drug Delivery Reviews 107, pp. 367-392. Milovanović, A., Golubović, Z., Babinský, T., Šulák, I., Mitrović, A., 2022a. Tensile properties of polypropylene additively manufactured by FDM. Structural Integrity and Life 22(3), pp. 305-308. Milovanović, A., Golubović, Z., Kirin, S., Babinský, T., Šulák, I., Milošević, M., Sedmak, A., 2023. Manufacturing parameter influence on FDM polypropylene tensile properties. Journal of Mechanical Science and Technology 37, pp. 5541-5547. Pandžić, A., Hodžić, D., Milovanović, A., 2019. Effect of infill type and density on tensile properties of PLA material for FDM process. The 30 th DAAAM International Symposium on Intelligent Manufacturing and Automation, Vienna, Austria; Paper #074: pp. 545-554. Linul, E., Marsavina, L, Stoia, D.I., 2020. Mode I and II fracture toughness investigation of Laser-Sintered Polyamide. Theoretical and Applied Fracture Mechanics 106, 102497: pp. 1-12. Stoia, D.I., Marsavina, L., Linul, E., 2020. Mode I Fracture Toughness of Polyamide and Alumide Samples obtained by Selective Laser Sintering Additive Process. Polymers 12, 650: pp. 1-12. Marsavina, L., Valean, C., Marghitas, M., Linul, E., Razavi, N., Berto, F., Brighenti, R., 2022. Effect of the manufacturing parameters on the tensile and fracture properties of FDM 3D-printed PLA specimens. Engineering Fracture Mechanics 274, 108766: pp. 1-15. Valean, C., Marsavina, L., Marghitas, M., Linul, E., Razavi, J., Berto, F., Brighenti, R., 2020b. The effect of crack insertion for FDM printed PLA materials on Mode I and Mode II fracture toughness. Procedia Structural Integrity 28, pp. 1134-1139. Milovanović, A., Golubović, Z., Trajković, I., Sedmak, A., Milošević, M., Valean, E., Marsavina, L., 2022b. Influence of printing parameters on the eligibility of plane-strain fracture toughness results for PLA polymer. Procedia Structural Integrity 41, pp. 290-297. Ayatollahi, M.R., Nabavi-Kivi, A., Bahrami, B., Yahya, M.Y., Khosravani, M.R., 2020. The influence of in-plane raster angle on tensile and fracture strengths of 3D-printed PLA specimens. Engineering Fracture Mechanics 237, 107225: pp. 1-13. Arbeiter, F., Spoerk, M., Wiener, J., Gosch, A., Pinter, G., 2018. Fracture mechanical characterization and lifetime estimation of near-homogeneous components produced by fused filament fabrication. Polymer Testing 66: pp. 105-113. Milovanović, A., Sedmak, A., Paunić, M., Mitrović, A., Popović, M., Milošević, M., 2024. Tensile properties of pure PLA polymer dedicated for additive manufacturing. Structural Integrity and Life Vol.24, No.3. Milovanović, A., Milošević, M., Trajković, I., Sedmak, A., Razavi, M.J., Berto, F., 2022c. Crack path direction in plane-strain fracture toughness assessment tests of quasi-brittle PLA polymer and ductile PLA-X composite. Procedia Structural Integrity 42, pp. 1376-1381.