PSI - Issue 61

Albert E. Patterson et al. / Procedia Structural Integrity 61 (2024) 148–155 Author name / Structural Integrity Procedia 00 (2024) 000–000

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materials and layout patterns. Future layout work on these materials must consider this possibility and specifically check designs for such weak spots.

5. Conclusions and Future Work

In this study, the impact of the notching technique on the fracture load for three common FFF-processed ther moplastic materials was studied. The results showed that the notching method had a large e ff ect on the outcome of the experiment, which contradicts studies such as [21–23] which concluded that printed and machined notches were equally good for various mechanical tests. This di ff erence is likely due to the use of careful pre-cracking of the specimens, the use of a static testing process, and di ff erent material selection, as shown in other works such as [24]. After it was concluded that CT samples need to use pre-cracked notches with either machined or printed notches, this information was used to prepare a larger set of samples to test the impact of element layout. Using basic linear elastic fracture mechanics theory, it was expected that the layouts would have a large impact as they presented di ff erent possible crack paths. This e ff ect was clearly observed in the final results and crack analysis. Therefore, it is possible to toughen FFF-processed materials simply using basic existing layout methods without needing to use a specific patterned design, such as the methods presented by [7–11, 18, 19]. While those methods are excellent, they can be computationally expensive and not easily translate into useful g-code for printing. The only major exception to the expected outcomes was the concentric PC specimens, but it was concluded that this issue was likely due to a fundamental printing defect specifically for the 0.6mm nozzle, an issue that was not expected but will be watched for in the future. It is recommended that all layout / nozzle size combinations be checked manually for gaps and unusually large voids before printing, with the layout pattern and print settings adjusted to account for these issues when they are encountered. Of the three materials studied in this paper, it appears that more brittle materials are more a ff ected by this issue and so more care should be given to them. Future work will focus on testing other materials, studying the e ff ect of sample thickness, exploring methods for detecting and eliminating potential printing defects in brittle materials such as PC, and in using the lessons learned to drive new layout design methods and standard techniques for testing these materials.

RawData

All the raw data is available from the corresponding author upon request.

Acknowledgements

This work did not receive any external funding. Opinions and conclusions are solely those of the authors.

References

[1] A. E. Patterson, C. Chadha, and I. M. Jasiuk, “Identification and mapping of manufacturability constraints for extrusion-based additive manufac turing,” Journal of Manufacturing and Materials Processing , vol. 5, p. 33, Apr. 2021. [2] A. E. Patterson, C. Chadha, and I. M. Jasiuk, “Manufacturing process-driven structured materials (MPDSMs): design and fabrication for extrusion based additive manufacturing,” Rapid Prototyping Journal , vol. 28, pp. 716–731, Oct. 2021. [3] A. E. Patterson, C. Chadha, I. M. Jasiuk, and J. T. Allison, “Tensile behavior of individual fibers and films made via material extrusion additive manufacturing,” Next Materials , vol. 1, p. 100002, Mar. 2023. [4] N. Guo and M. C. Leu, “Additive manufacturing: technology, applications and research needs,” Frontiers of Mechanical Engineering , vol. 8, no. 3, pp. 215–243, 2013. [5] J. Allum, A. Gleadall, and V. V. Silberschmidt, “Fracture of 3D-printed polymers: Crucial role of filament-scale geometric features,” Engineering Fracture Mechanics , vol. 224, p. 106818, Feb. 2020. [6] F. Peng, Z. Zhao, X. Xia, M. Cakmak, and B. D. Vogt, “Enhanced impact resistance of three-dimensional-printed parts with structured filaments,” ACS Applied Materials & Interfaces , vol. 10, pp. 16087–16094, Apr. 2018. [7] A. Lenti, “Fracture toughness assessment using digital image correlation in additive manufacturing,” Master’s thesis, Polytechnic of Turin, Turin, Italy, 2019. Masters Thesis - Mechanical Engineering. [8] J. Gardan, A. Makke, and N. Recho, “A method to improve the fracture toughness using 3D printing by extrusion deposition,” Procedia Structural Integrity , vol. 2, pp. 144–151, 2016.