PSI - Issue 83

Wong Kam Chee et al. / Procedia Structural Integrity 83 (2026) 14–27

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The characteristics of H1 and H2 are shown in Table 5 . Both the surface area and volume of H2 increase from 1086.2224mm 2 to 1089.1846mm 2 and 129.8836mm 3 to 183.5518mm 3 , respectively, which leads to a decrease in the surface-to-volume ratio from 8.363 to 5.9334. Mass and relative density of H2 also increase from 0.5754g to 0.8131g and 12.9884 to 18.3552, respectively, due to the increase of lattice volume. The lattice has a higher density, which leads to better strength at the trade-off of a heavier lattice. The decrease in surface area-to-volume ratio is also a critical issue to take note especially for some surface area-critical applications such as thermal management and biomedical.

Table 5. Characteristics of H1 and H2 Aspects

H1

H2

Surface Area (mm 2 ) Volume (mm 3 )

1086.2224 129.8836

1089.1846 183.5518

Surface area-to-volume ratio

8.363 0.5754 12.9884

5.9334 0.8131 18.3552

Mass (g)

Relative Density

The simulation result of H1 and H2 are shown in Table 6 . The slight increase in lattice mass, surface area and volume of H2 has a tremendous effect on the simulation result. H2 has a displacement of 1.7782 x 10 -2 mm, which is decreased by 36.18% compared to H1. Von Mises stress of H2 shows the largest difference of 104.31% compared to H1, which decreases from 1126.269 MPa to 354.151 MPa, due to the elimination of the stress-concentrating sharp points. Strain of H2 also decreased by 4.12%, from 3.69041 x 10 -3 to 3.54151 x 10 -3 . The decrease in displacement, Von Mises stress, and strain proves that the load is distributed throughout the lattice without concentrating at certain points, which prevents structural weakness. These improvements show that the modification to the hybrid lattice with the objective of removing the critical stress-concentration points was a success.

Table 6. Simulation results of H1 and H2 Aspects

H1

H2

Difference

Displacement (x 10 -2 mm) Von Mises Stress (MPa)

2.56355 1126.269 3.69041

1.77820 354.151 3.54151

0.78535 (36.18%) 772.118 (104.31%)

Strain (x 10 -3 )

0.1489 (4.12%)

From the von Mises stress of Schwarz P (552.741MPa), Gyroid (433.081MPa), and H2 (354.151MPa), the H2 has the lowest von Mises stress. This indicates the stress distribution of the H2 is better than Gyroid and Schwarz P as it can distribute the stress along the lattice rather than concentrate the stress at localised regions. Thus, H2 has a high potential as an alternative to traditional strut-based lattice hip implant which are often prone to stress concentrations at the strut junctions. By promoting even stress distribution, H2 also reduces stress shielding effect in hip implants, thereby enhancing load transfer to the surrounding bine and finally prolong the service life of the hip implant. 3.3 Homogenization Figure 7 shows the homogenisation of the lattice unit cells. Homogenisation is done to extract directional mechanical properties of the lattices. Table 7 shows the maximum and minimum directional stiffness of the unit cells. Gyroids show a small difference between maximum and minimum of 12.65%, which indicates near-isotropic behaviour. Schwarz P shows the highest percentage difference between maximum and minimum of 60.28%, which will have some slight directional preference and perform in a certain direction, but is poor in others. H1 and H2 show a moderately anisotropic property as the difference between maximum and minimum is 27.39% and 36.68%, respectively.