Computer simulations on the mechanical behaviors of biphasic calcium phosphates

Biphasic calcium phosphate (BCP) bioceramics, the mixture of hydroxyapatite (HA) and beta- tricalcium phosphate (β-TCP), are widely used as bone repair materials. Optimization of its composition and mixing pattern is crucial for its design and preparation. A series of BCP structures with a HA/β-TCP mass ratio of 0/100, 30/70, 50/50, 70/30, and 100/0 were constructed and studied with a simulated annealing molecular dynamics method. On the basis of equilibrated BCP structures, their elastic constants and moduli were computed and analyzed. With increasing HA content, the elastic moduli of BCP increase. Under the same mass ratio (50/50), the elastic moduli have no distinct changes for different mixing patterns. Calculations on the uniaxial extension of BCP reveal a sophisticated nonlinear and loading-path dependent behavior. The maximum stress decreases with increasing β-TCP content and mixing level.