Microstructural dependence of Youngʹs and shear moduli of P2O5 glass reinforced hydroxyapatite for biomedical applications

P2O5 glass reinforced hydroxyapatite composite materials were prepared through a liquid-phase sintering process. Secondary phases, β- and α-tricalcium phosphates (β-TCP and α-TCP), were formed in the microstructure of the composites, due to the reaction between the liquid glassy phase and the hydroxyapatite matrix. The dynamic Youngʹs modulus (E) and shear modulus (G) of these composites were determined using an impulse excitation method. By applying the Duckworth–Knudsen equation, the elastic property results were correlated with the relative proportion of β-TCP and α-TCP phases and with the porosity percentage present in the microstructure. Glass reinforced hydroxyapatite composites showed lower Youngʹs and shear moduli than unmodified hydroxyapatite, mainly due to the presence of β-TCP phase. The Duckworth–Knudsen model demonstrated an exponential dependence of E and G modulus with porosity and mathematical equations were derived for composite materials with porosity correction factors (b) of 4.04 and 4.11, respectively, indicating that porosity largely decreased both E and G moduli.