# PSI - Issue 49

Nataliya Elenskaya et al. / Procedia Structural Integrity 49 (2023) 43–50 Author name / Structural Integrity Procedia 00 (2023) 000–000

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For the VD models, as expected, a proportional decrease in the effective modulus was observed, whereas for the SD models the decrease in the effective properties was non-linear (Figs. 2 a, c, e). There is a significant difference in the effective properties of the structure for the same extent of degradation (Fig. 2 b, d, e). The divergence of the effective properties for the final degradation step considered in this study between the SD and VD techniques was minimal for the D cell, at 28.2%, and maximal for the I-WP cell, at 53.4%. The inverse problem of finding the percentage of volumetric degradation corresponding to the surface degradation calculated in terms of the effective properties of the structure was also solved; the results are presented in Table 3.

Table 3 Comparison of SD and VD for same effective modules

Structure

Effective Young’s Modulus, MPa

SD, %

VD, %

732.8 598.1 452.7 331.8 637.5 480.5 367.6 257.0 697.7 502.0 340.6 213.3

12.5 25.0 37.5 50.0 12.5 25.0 37.5 50.0 12.5 25.0 37.5 50.0

20.7 35.3 51.0 64.1 23.9 42.6 56.1 69.3 23.8 45.1 62.8 76.7

D

G

I-WP

These data allow a comparison of resulting elastic properties of the scaffold after degradation of its surface and volumetric degradation calculated with the same degradation level. The surface degradation of the scaffold had a more rapid effect on the effective properties than the volumetric one. For instance, the same effective modulus for the type D unit cell can be obtained with 12.5% surface shrinkage of the structure and 20.7% reduction of volumetric elastic properties without the change in geometry. This difference grew further – to 50% and 64.1%. For the type G and I-WP unit cells, 12.5% surface degradation corresponded to approximately 24% volumetric degradation, while further discrepancy reaches 19.3% and 26.7%. The dependence between the effective properties of the studied unit cells and experimentally obtained data on volume degradation of PLA is shown in Fig. 3 for all studied types of TPMS unit cell.

Fig. 3 Decrease in effective elastic properties of scaffold according to data on PLA degradation

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