On the compression strength and fluid permeability of LPBF-fabricated Ti6Al4V gyroid structures for spinal implant application
摘要
Porous structures providing proper mechanical performance and biological compatibility are highly demanded for spinal implants. Ti6Al4V gyroid structures with two different unit cell sizes were designed and fabricated by the additive manufacturing laser powder bed fusion. The structures possess pore sizes ranging from 800 to 1500 μm and wall thicknesses ranging from 400 to 700 μm, exhibiting porosity between 67 and 82% and surface-to-volume ratios ranging from 3.16 to 5.54 mm− 1. Mechanical behavior was assessed through finite element analysis, and material model was validated against experiments. Tests revealed that thicker walls and smaller pores significantly enhanced elastic modulus and yield strength. The highest elastic modulus were 1488 MPa and 1810 MPa for 2-cell and 3-cell configurations, respectively. Flow characteristics assessed via computational fluid dynamics and falling head experiments demonstrated a correlation with a correction factor and wall shear stress, with values ranging from 11 to 19 mPa and permeability from 13.9 × 10−9 to 42.8 × 10−9 m2 in the simulation. Two selected designs, including 1200 μm pore size/ 500 μm thickness for 2-cell and 900 μm pore size/ 500 μm thickness for 3-cell structures, provided the best compromise between mechanical strength and S/V ratio. A good agreement was observed for the experimental and simulation results of the compression test and fluid permeability. Energy absorption values obtained from the samples showed that the selected 3-cell structure absorbed up to 46% more energy than the 2-cell variants. These results defined quantitative design windows for additively manufactured spinal implants that target mechanical stiffness and effective fluid transport.