The effect of geometry on mechanical properties of Ti6Al4V ELI scaffolds manufactured using additive manufacturing technology

Patrycja Szymczyk,Viktoria Hoppe,Grzegorz Ziółkowski,Michał Smolnicki,Marcin Madeja

doi:10.1007/s43452-020-0011-y

Abstract

Owing to the possibility of direct processing of CAD models into three-dimensional objects, additive manufacturing (AM) is widely used in the production of individualized bone scaffolds that can lead to perfect restoration of anatomical structures of missing bone tissues. In this work, one of the AM technologies was applied, referred to as Electron Beam Melting (EBM), using Ti6Al4V ELI alloy to produce open-cell structures. Scaffold architecture influences its mechanical properties and is important from the point of view of biological considerations. To optimize mechanical properties, designed geometries were subjected to Finite Element Method analysis and experimental static compression tests. Also, geometric CT analysis of manufactured scaffolds was carried out (geometry deviations up to ± 300 µm). Obtained results have shown that AM can be used to produce Ti6Al4V ELI alloy scaffolds displaying mechanical parameters similar to those of bone tissue (E = 0.45–2.88 MPa). The EBM process affects the microstructure and macrostructural properties of manufactured parts, e.g., through internal porosities present in the material by to unmelted powder particles (internal porosity in range of 1.25–2.25%). To assess the quality and suitability of additively manufactured implants, a multidimensional verification of the impact of the manufacturing process on the properties of the final product was performed.

Highlights

Scaffold structures have the ability to realize spatially variable material behavior, i.e., stiffness, anisotropy, density, and display attractive properties, such as high stiffness–density ratios [1,2,3,4]
The aim of this work was to determine the structural and mechanical characteristics using X-ray Computed tomography (CT), compression tests and Finite Element Method (FEM) analysis of additively manufactured Ti6Al4V ELI scaffolds intended for the design of modern implants, both in terms of geometric form, and programmed mechanical properties
Particular attention should be paid to the influence of porosity that may occur in the material after manufacturing process

Summary

Introduction

Scaffold structures have the ability to realize spatially variable material behavior, i.e., stiffness, anisotropy, density, and display attractive properties, such as high stiffness–density ratios [1,2,3,4]. They are usually categorized as structures with open or closed cells. Open-cell structures are often the first choice as bone replacement material in orthopedic surgery [4]. This type of structure allows for tailoring the mechanical properties of the material to mimic bone and to avoid the major drawback of bulk metals, i.e., stress shielding generated on the surrounding bone tissue. The ability to control and properly design the shape of the unit cell and surface topography can significantly improve fatigue properties and guarantee long-term use of additively manufactured

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Discussion

Conclusion