Fabrication of bioinspired strucutred hydroxyapatite composites with enhanced fracture toughness

Strength and toughness have been generally deemed as two incompatible properties in many materials . However, balanced toughness and strength have been observe d in bio materials, whose hard and soft phases are arranged into a unique and hierarchical architecture. Therefore, it is essential to develop processing technologies that can mimic the structures observed in biomaterials. In this work , hierarchical structures were achieved in hydroxyapatite (HA) via freeze casting. The suspension solid load changes from 5% to 20% and cooling rate from 1°C/min to 5°C/min were adopted to achieve different microstructures . A ductile phase (PMMA) was also introduced to the HA matrix by in-situ polymerization. In addition, the bonding strength between HA and PMMA was investigated . The fracture toughness was evaluated by a three - point bending test. Based on these , the role of microstructures and interfacial strength in dictating the overall mechanical behaviour were discussed