Part II: fracture strength and elastic modulus as a function of porosity for hydroxyapatite and other brittle materials.

Part I of this paper discussed the Weibull modulus m, versus porosity P behavior of brittle materials, including HA. While the Weibull modulus m deals with the scatter in fracture strength data, this paper (Part II) focuses on two additional key mechanical properties of porous materials, namely the average fracture strength <σ(f)>, and Young's modulus E, for P in the interval from P≈ zero to P≈P(G) (the porosity of the unfired compacts). The <σ(f)> versus P data for HA from this study and the literature data for alumina, yttria stabilized zirconia (YSZ) and silicon nitride are described well by functions of ϕ, where ϕ=1-P/P(G)= the degree of densification. A similar function of ϕ applies to the versus P behavior of HA from this study and data from the literature for alumina, titanium and YSZ. All of the data analyzed in this study (Part II) are based on partially and fully sintered powder compacts (excluding green powder compacts), thus the <σ(f)>/σ(0) versus ϕ and /E(0) versus ϕ relationships may apply only to such specimens.