PSI - Issue 53

C.T. Duarte et al. / Procedia Structural Integrity 53 (2024) 299–308 Duarte et al./ Structural Integrity Procedia 00 (2023) 000–000

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only the A5P5A5 configuration showed a significant decrease of approximately 26%. Comparing the control and aged cases, it was observed that aging in seawater did not significantly alter the Young's modulus. This might be attributed to the duration of exposure, as (Menezes, O. et al. 2022) noted that the effects of aging become more pronounced after 8 weeks of immersion. Flexural properties Figure 10 presents the quantitative data for the flexural tests for both general cases, unaged and aged. From Fig. 10a, it was observed that after aging, the only configuration that significantly varied compared to ABS was A1P13A1, an approximate 18% enhancement. This suggests that a single ABS layer presented enough barrier properties to protect the lower PLA layers, while more layers may have their barrier properties negated by water uptake in the interlaminar space. Among the multi-materials, a plateau-like trend was observed between the A5P5A5 and A3P9A3 configurations, as well as between the A3P9A3 and A1P13A1. However, A5P5A5 exhibited a decrease in flexural strength of approximately 13% when compared to the A1P13A1 specimens. Comparing the two general cases, control and aged, ABS showed no significant variation, while the pure PLA experienced a decrease of approximately 22% in maximum flexural strength. Fig. 10b presents the quantitative data of the flexural modulus for the two general cases. Similar to the flexural strength, the only configuration that showed significant variation compared to ABS was the one with the highest number of PLA layers (A1P13A1), with an increase of approximately 18%. Once again, suggesting that this case, which presented the highest results in all aged specimen properties, afforded the material a balance between barrier properties and lowest interlaminar space water uptake. In comparison with the PLA, the configuration with the lowest number of PLA layers (A5P5A5) exhibited a variation of approximately 18%. This is due to the decreased number of PLA layers. Among the multi-materials, the A5P5A5 and A3P9A3 cases did not show significant variation compared to each other, but they exhibited variations of approximately 26% and 16%, respectively, compared to the A1P13A1 specimens. Comparing all the aged cases with their respective unaged control groups, except for ABS, which retained its properties, all others were influenced by aging in seawater. The aged PLA exhibited a decrease of approximately 16% in stiffness compared to the unaged PLA, and all multi-materials showed a significant increase in stiffness. For example, the A5P5A5 configuration had a variation of approx. 26%, and the A3P9A3 and A1P13A1 configurations exhibited a variation of approx. 31%. This may be due to the remaining water between the layers of the aged specimens since they were tested immediately after surfacing. This will be further discussed in the failure modes.

Fig. 9. Quantitative data of unaged and aged specimens: (a) tensile strength; (b) modulus.