Influence of porosity on the mechanical behaviour of single phase β-TCP ceramics

Processing and mechanical behaviour of fine grained (diameter ≈0.5-3 µm) and pure β-TCP materials with different levels of porosity (up to 19%) is described. Pores with diameters, d50 ≈13-14 µm were formed fromcorn starch during sintering. Comprehensive mechanical characterisation -Young´s modulus, strength and toughness- has been done paying special attention to toughness determined in stable fracture tests. The dependence of Young´s modulus and strength with porosity was well fitted to the minimum solid area models while toughness values did not. The competitive processes occurring during fracture impede the degradation of toughness associated to the decrease in Young´s modulus as porosity increases. Materials present similar values of the critical energy release rate GIC, which describes crack initiation. A maximum of the specific fracture energy, GF, which averages crack propagation, has been obtained for the material with the highest porosity.