PSI - Issue 61

Jose Beltra Mira et al. / Procedia Structural Integrity 61 (2024) 156–163 Author name / Structural Integrity Procedia 00 (2024) 000–000

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7

(b)

(a) Sensitivity Analysis – Thickness, W = 30 mm

6

5

4

0.5 )

3

2 K Q (MPa ·m

1

0

B = 6 mm (ABS)

B = 3 mm (ABS)

B = 6 mm (PC)

B = 3 mm (PC)

B = 6 mm (PLA)

B = 3 mm (PLA)

Fig. 7. (a) Means data from the sensitivity analysis and (b) plane stress to plane strain transition curve [19]. Panel (b) reproduced under the terms of the CC-BY license.

5. Conclusions and Future Work

This project explored the e ff ect of sample size on the repeatability and reliability of ASTM D5045 tests for FFF processed thermoplastic materials. While some di ff erences based on sample size were observed for the materials and geometries studied, the statistical analysis suggested that these di ff erences are likely noise in the data due to printing defects seen in all AM materials and therefore do not indicate a strong size e ff ect. This result was further validated using three di ff erent methods, namely a statistical analysis, a material property comparison, and a sensitivity analysis. All cases agreed with the initial analysis and did not show any statistically-significant di ff erence in fracture load or fracture toughness based on the specimen size, with special attention to the thickness in the sensitivity analysis. It was concluded from the results, replicated several times, that the sample size did not have a strong e ff ect on the tests even though the samples did not meet the requirements for plane strain according to ASTM D5045. While a true K IC value cannot be produced, the results show that this standard is useful and produces valid design and fracture mechanics data for FFF-processed materials. Future work on this problem will focus on larger studies, bending and mixed-mode loading, more materials, di ff erent printing layouts, hybrid and composite materials, and on more extreme variances in sample dimensions. It is very likely that future studies will show some sample size e ff ect for specific materials and printing combinations, which needs to be considered when planning and conducting research in this area in the future.

RawData

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

Acknowledgements

The authors thank Iwona Jasiuk and Charul Chadha for feedback and advice on an early iteration of the current study and for proving some of the equipment used to collect a portion of the raw data.

References

[1] ASTM, “D5045 - 14: Standard Test Methods for Plane-Strain Fracture Toughness and Strain Energy Release Rate of Plastic Materials,” standard, ASTM International, West Conshohocken, PA, 2014. [2] F. Arbeiter, M. Spoerk, J. Wiener, A. Gosch, and G. Pinter, “Fracture mechanical characterization and lifetime estimation of near-homogeneous components produced by fused filament fabrication,” Polymer Testing , vol. 66, pp. 105–113, Apr. 2018. [3] E. A. Papon and A. Haque, “Fracture toughness of additively manufactured carbon fiber reinforced composites,” Additive Manufacturing , vol. 26, pp. 41–52, Mar. 2019.