Modelling and characterization of a porosity graded lattice structure for additively manufactured biomaterials

A novel approach has been proposed for the design of porosity-graded lattice structures suitable for bone replacement applications. A MATLAB routine was developed in order to model a lattice structure and generate an STL file for additive manufacturing. With this routine, geometric properties, such as the pore size and strut thickness, can be controlled to provide the desired porosity distribution and mechanical properties of the structure. The stiffness and yield stress of three titanium structures with densities of 20, 42 and 60% were evaluated by finite element analysis and tensile testing. The experimental results diverged by up to 50% from those predicted by the finite element analysis. The geometrical deviations between the modelled and fabricated structures and the approximations made for the material modelling were considered to be at the root of these discrepancies. The experimentally evaluated Young's modulus ranged from 1.6 to 20.3 GPa for the 20 and 60% dense structures, respectively, while the yield stress ranged from 23 to 181 MPa for the same structures. These results are comparable to those for cortical and trabecular bone. Scaling relations for the stiffness and yield stress of porous structures were developed to allow the computer-assisted design of porosity-graded load-bearing implants. (C) 2017 Elsevier Ltd. All rights reserved.