Mechanical behavior of additively manufactured porous biomaterials made from truncated cuboctahedron unit cells

Fueled by continuous improvements in the additive manufacturing and 3D printing technologies, additively manufactured porous biomaterials have been receiving increasing attention during the last few years particularly for application in orthopedics. The mechanical properties of porous biomaterials are of paramount importance for any such application, as both osseointegration and implant performance are dependent on the spatial distribution of mechanical properties within the implant. In this paper, we studied the mechanical properties of porous biomaterials based on a relatively new type of repeating unit cell, namely truncated cuboctahedron. Analytical relationships were obtained to estimate the elastic modulus, Poisson׳s ratio, and yield stress of the above-mentioned porous biomaterials given the dimensions of their repeating unit cell. The analytically predicted mechanical properties were compared with computational results obtained in the current study and with experimental observations from one of our recent studies on selective laser melted porous titanium (Ti-6Al-4V) biomaterials. Both the Euler-Bernoulli and Timoshenko beam theories were used for the analytical study. The analytically calculated and computationally predicted elastic moduli and Poisson׳s ratios were found to be in good agreement, provided that the analytical solution was based on Timoshenko beam theory. The analytical yield stress based on both the Euler-Bernoulli and Timoshenko beam theories were close to each other and to the numerical results. The elastic moduli predicted using both analytical and computational approaches based on Timoshenko beam theory were in good agreement with experimental observation for smaller values of the relative density, but both approaches somewhat over-predicted the elastic moduli for larger values of the relative density (i.e. >0.3). As for the yield stress, the experimental values were between the two lines corresponding to the yield stresses predicted for the two most critical points of the porous structures, indicting good agreement between experimental, analytical, and computational values of yield stress.