Fracture toughness of titanium foams for medical applications

The fracture behavior of titanium open foam is characterized and the R-curves of crack propagation from pre-cracks are measured. The crack growth has been optically observed, the measured initiation toughness, JIC, has been analyzed and the effect of material morphology on the JIC is discussed. The fracture toughness was found to be dependent on the expanding crack bridging zone at the back of the crack tip. The compact tension specimens also have some plastic collapse along the ligaments and it has shown that the titanium foam with a higher relative density is tougher. The non-uniform stressing within the plastic zone at the crack tip and the plastic collapse of cell topology behind the tip was found to be the primary cause of the R-curve behavior in low relative density titanium foams.

Research highlights▶ The Ti foam with higher ρ¯ is tougher than the Ti foam with lower ρ¯. ▶ The plane strain fracture toughness increases with relative density. ▶ The fracture toughness was dependent on the expanding crack bridging zone. ▶ Ti foams with 0.30<ρ¯<0.40 seem to be appropriate as implant material.