Elsevier

Materials & Design

Volume 67, 15 February 2015, Pages 501-508
Materials & Design

Failure modes in high strength and stiffness to weight scaffolds produced by Selective Laser Melting

https://doi.org/10.1016/j.matdes.2014.10.063Get rights and content
Under a Creative Commons license
open access

Highlights

  • Selective Laser Melting was used to produce high strength scaffold structures.

  • In situ X-Ray Micro Tomography was used to study their failure under compression.

  • Finite Element Modelling revealed that surface roughness caused high stress areas.

  • Failure first occurred in areas of high tensile stress predicted by the modelling.

  • The failure mode was very different to the classic foam materials.

Abstract

The production of porous scaffold structures using additive manufacturing is becoming widespread, however a detailed understanding of the scaffold failure mechanisms is lacking. In this research, Selective Laser Melting (SLM) is used to produce Ti–6Al–4V scaffold structures consisting of a regular array of unit cells previously designed using topology optimisation. Interrupted compression testing and subsequent X-Ray Micro Tomography (XMT) characterisation is used to study the deformation and failure of the scaffolds for a range of solid fractions. Further, the XMT data of the unloaded scaffolds is used to generate meshes for finite element analysis which allowed direct comparison of desired and as built behaviour. Likely failure sites predicted from the finite element analysis compare favourably with the experimentally observed ones. Failure is initiated in areas that exhibit the greatest tensile stress, while the onset of the commonly observed layered failure occurs afterwards. The XMT of the unloaded scaffolds also highlights the inaccuracies in the SLM build process, which contributes to stress concentrations in the horizontal arms within the scaffolds. The results indicate that although the strength of the topology optimised structures is very high, further refinement in both the unit cell design and build quality would further increase the strength.

Keywords

Selective Laser Melting
X-ray computed tomography
Titanium alloys
Porous material
Finite-element analysis

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Present address: Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW 2109, Australia.