Compressive and energy absorption characteristics of directional graded Ti6Al4V Split-P lattices for biomedical applications

Purpose – This study aims to investigate the mechanical properties of graded triply periodic minimal surface Split-P lattices fabricated via laser powder bed fusion (L-PBF) and examine how grading direction affects energy absorption.

Design/methodology/approach – This work established a design approach for graded Split-P with various grading directions referred as 1-D (one-directional), 2-D (bidirectional) and 3-D (three-directional). The graded samples were fabricated using Ti6Al4V ELI powder and L-PBF technology. This study then focuses on analysing the quasi-static behaviours to identify the failure mechanism of these Ti6Al4V Split-P lattices. Furthermore, the stress–strain behaviour was explored to evaluate the three Split-P lattice’s energy absorption. The unit cell homogenization method was used to predict the isotropy behaviour of the Split-P lattices.

Findings – Compression test results showed that the 1-D-graded Split-P lattice exhibited higher elastic modulus (4.97 ± 0.13 GPa) and yield strength (132.47 ± 1.56 MPa) compared to other lattices, with an elastic modulus lattice closer to that of cancellous bone, potentially reducing the stress-shielding effect. The 3-D-graded Split-P lattice demonstrated a lower elastic modulus (2.95 ± 0.15 GPa) and yield strength (44.15 ± 3.26 MPa). However, the 3-D-graded lattice had a high energy absorption capacity (75.85 MJ/m3) compared to other lattices. Furthermore, the as-designed 3-D-graded Split-P lattice shows greater anisotropy compared to other lattices. Three power-law models were developed to predict the mechanical properties of graded Ti6Al4V Split-P lattices with different grading directions. This study also highlights the design of graded Ti6Al4V Split-P lattices for biomedical applications.

Originality/value – This work provides the design method for creating Split-P lattices with varying grading directions to control the mechanical properties and energy absorption for advanced biomedical implants. The homogenization method used in this study enables the prediction and control of isotropic properties in as-designed lattices.