Glass-reinforced hydroxyapatite composites: fracture toughness and hardness dependence on microstructural characteristics

Fracture toughness and hardness properties of CaO-P2O5 glass-reinforced hyd roxyapatite composites have been assessed using indentation techniques and results calculated according to Laugier and Evans' equations. Both properti es showed to be dependent upon several microstructural characteristics, nam ely residual porosity and the percentage of secondary beta and alpha trical cium phosphate phases in the structure of the composites. Composites presen ted a Palmqvist-type indentation crack system, which is the specific crack system addressed by Laugier's approach. Fracture toughness determinations a ccording to Evan's equation, which is a universal one and adapted to both m edian and Palmqvist crack systems, did not correlate well with Laugier dete rminations. (C) 1999 Elsevier Science Ltd. All rights reserved.