Isolated and modulated effects of topology and material type on the mechanical properties of additively manufactured porous biomaterials

Authors

R. Hedayati, S.M. Ahmadi, K. Lietaert, B. Pouran, Y. Li, Harrie Weinans, C.D. Rans, A.A. Zadpoor

Abstract

Additive manufacturing (AM) techniques offer the possibility to produce open-cell porous implants with the desired topological design at the micro-scale. The vast majority of previous theoretical and numerical studies carried out on the mechanical properties of AM porous biomaterials had assumed their normalized elastic mechanical properties to be independent from the material type and only dependent on the topological design. In this study, we evaluated this assumption and tried to quantify the isolated and modulated effects of topological design and material type on the mechanical properties of AM porous biomaterials. Towards this aim, we assembled a large dataset comprising the mechanical properties of AM porous with different topological designs (i.e. different unit cell types and relative densities) and material types. Porous structures were additively manufactured from Co-Cr using a selective laser melting (SLM) machine and tested under quasi-static compression. The normalized mechanical properties obtained from those structures were compared with mechanical properties available from our previous studies for porous structures made from Ti-6Al-4V, tantalum, and pure titanium as well as with analytical solutions. The normalized values of elastic modulus and yield stress were found to be relatively close to each other as well as in agreement with analytical solutions regardless of material type. However, the material type was found to systematically affect the mechanical properties of AM porous biomaterials in general and the plateau stress and energy absorption capacity in particular. To put this in perspective, topological design could cause up to 10-fold difference in the mechanical properties of AM porous biomaterials while up to 2-fold difference was observed as a consequence of changing the material type.

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