Mixed mode fracture characterization of hydroxylapatite–titanium alloy interface

Publisher Website
Google Scholar
Abstract
Cantilever beam and four‐point bend specimen geometries were used to experimentally determine the critical energy release rates for a plasma sprayed hydroxylapatite‐titanium alloy (HA–Ti alloy) interface. A locus of energy release rates as a function of crack tip phase angle was determined where a 0° phase angle represented tensile opening (mode I) loading and a 90° phase angle represented in‐plane shear (mode II) loading. Energy release rates were found to increase substantially with an increase in phase angle. An energy release rate of 0.108 N/mm was determined for a phase angle of 0° (mode I). Energy release rates of 0.221, 0.686, and 1.212 N/mm were determined for phase angles of 66°, 69°, and 72°, respectively. The experimental data was matched to a phenomenological model for which crack propagation depended on mode I loading alone indicating that crack propagation at the Ha‐Ti alloy interface is dominated by the mode I loading alone indicating that crack propagation at the Ha–Ti alloy interface is dominated by the mode I loading component. Therefore, regions of HA coated implants that experience compressive or shear loading across the HA–Ti alloy interface may be much less likely to debond than regions that experience tensile loading. © 1994 John Wiley & Sons, Inc.