Fracture Surface Roughness of Ti-Scaffold Filaments with Different Microporosity

Abstract

implants. The previous research has shown that the titanium scaffolds with porous filaments (14% microporosity) exhibited better fatigue resistance than those with compact filaments (6% microporosity). This was primarily attributed to fatigue crack growth shielding mechanisms induced by crack-pore interactions and by an extension of fatigue crack path in the porous filaments. A quantification of these effects demands a determination of fracture surface roughness parameters of both types of filaments, which is the main aim of this article. Selected roughness parameters Sa (arithmetical mean height), Sv (maximum valley depth) and Sdr (developed interfacial area ratio) of fracture surfaces of scaffold filaments after cyclic three-point bending tests were determined using the confocal laser microscope Olympus LEXT™ OLS5100 according to ISO 25178. Each sample was subjected to 7 measurements on small surfaces of size 4500 m2 spread over the fatigue fracture surface and the average value with the standard deviation was computed. All the average values of roughness parameters for the porous samples were found to be higher than those for the compound fibers. These parameters decreased with an increasing number of cycles to fracture Nf in the range Nf (102, 105). The statistical analysis of fracture surface roughness will serve as a benchmark for a currently developed model of the fatigue crack growth in metallic materials of variable porosity which will improve our understanding the mechanistic response of scaffolds and enable the optimization of their microporosity.