Shear testing and failure modelling of calcium phosphate coated AZ31 magnesium alloys for orthopaedic applications

Magnesium orthopaedic fracture fixation devices can potentially provide significant clinical benefits, such as the elimination of secondary surgeries for device removal due to in-vivo resorption and reduced stress shielding stiffness. However, development, approval, adoption magnesium has been hindered by excessively high rates corrosion that structural integrity be catastrophically before healing occurs. Coating with calcium phosphate coatings shown significantly reduce rates, while enhancing osseointegration. adhesion strength between CaP substrates not previously investigated. Clinical insertion intramedullary nails k-wires will impose shear loading on coated surface implant. If effective coating-device interface is sufficiently high, coating damaged removed during insertion. In current study a bespoke experimental-computational approach developed new understanding relationship thickness, roughness, coating- Mg substrate interface. Nine test cases were created adjusting either deposition time (3 thickness values) or treatment alloy using SiC paper roughness double-lap testing was performed these configurations. Strain development in monitored strain gauges, failure determined each configuration. Test results revealed coating-substrate higher rougher surfaces when compared those smoother surfaces. found influence over range considered this (0.37–1.34 μm). Micro-scale finite element models lap-shear tests constructed experimental profilometry data. Simulations rough interfaces reveal localised compression occurs at regions large asperities. A novel cohesive zone formulation simulate induced hardening, resultant simulations are accurately predict measured experimentally