Finite element analysis based design of biomimetic functionally graded Ti-6Al-4V alloy scaffolds for human cortical bone applications

Abstract

Bone defects may impede the functionality of a bone as an organ. The bone defects can be repaired using osteogenic cells, growth factors, and bone scaffolds. Functionally graded scaffolds ideally meet the purpose of repair of these damaged bones as they have mechanical and biological properties similar to the surrounding tissues. The properties of these biomaterial structures can be mimicked to that of the human bone for improved osseointegration and bone regeneration without causing any stress shielding effect. Triply Periodic Minimal Surface (TPMS) lattices have geometric properties similar to human bones, making them suitable for orthopaedic implant applications. In this study, the implicit modelling approach was adopted to create a TPMS gyroid unit cell using nTopology software. Thereafter, the gyroid TPMS lattice was used to parametrically design a functionally graded scaffold with radial grading, mimicking the topology of human bone. Here, the scaffold porosity and pore size were varied from 62 to 82% and 236–320 µm, respectively, from the outer to the inner layer. The mechanical responses and compression behaviour of the Ti-6Al-4V alloy scaffold were studied by employing Abaqus the commercial Finite Element Analysis (FEA) software. Capitalizing on the cyclic symmetry, only 1/24th of the geometric model was considered for Dynamic Explicit FEA, yielding a computationally efficient solution. The obtained Young's modulus of 22.1 GPa and compressive strength of 205 MPa of the designed scaffold closely matches with those of human cortical bone, confirming their ability to meet its structural requirements. The objective of this work is to develop a robust numerical framework to parametrically design functionally graded metallic bone scaffolds.