Selective laser melted Ti6Al4V split-P TPMS lattices for bone tissue engineering

This study investigates Ti6Al4V Split-P triply periodic minimal surface (TPMS) structures produced by selective laser melting for the first time. The designs include two different cell morphologies (CM) with five different relative densities (RD). Scanning electron microscopy is utilized to assess the manufacturability and accuracy of the 3D printed Split-P lattice structures. The quasi-static mechanical responses are then studied to identify the failure mechanisms of each lattice type. Afterward, the stress-strain behavior and plateau stress responses are explored to evaluate the load-bearing capacity and energy absorption of five Split-P lattices. Furthermore, finite element analysis is performed to gain insight into the elasto-plastic behavior of the Split-P structures, and unit cell homogenization is employed to determine the equivalent stiffness tensor. The results demonstrate that the elastic modulus, yield strength, and ultimate strength of the 3D printed Split-P lattices range from 1.50 to 3.50 GPa, 57.95 to 152.74 MPa, and 93 to 170 MPa, respectively. Depending on RD and CM, load-bearing capacity range from 0.04 to 0.17. The energy absorption capacity and plateau stress of lattices vary from 22 to 61 MJ/m³ and 30 to 63 MPa, respectively. Gibson-Ashby power law represents the elastic modulus and yield stress of the Split-P lattices as a function of RD and reveals a stretch-dominated deformation behavior. Unit cell homogenization on Split-P structures with zero isovalue shows isotropy in mechanical properties and anisotropy for lattices with non-zero isovalue. Ti6Al4V Split-P lattices with the highest surface area and surface area-to-volume ratio, among other TPMS, can achieve mechanical properties close to those of trabecular and cortical bones, making them suitable for bone implants in load-bearing applications.