Intercrossed Microstructures of Hydroxyapatite Sheets of Tibia Bone

The observation of Scanning Electron Microscope (SEM) shows that a tibia bone is a kind of bioceramic composite consisting of hydroxyapatite layers and collagen protein matrix. All the hydroxyapatite layers are parallel with the surface of the bone and consist of numerous hydroxyapatite sheets. The observation also shows that there is a kind of intercrossed microstructure of the hydroxyapatite sheets. In this kind of microstructure, the hydroxyapatite sheets in an arbitrary hydroxyapatite layer make a large intercrossed angle with the hydroxyapatite sheets in their adjacent hydroxyapatite layers. The maximum pullout force of the intercrossed microstructure, which is closely related to the fracture toughness of the bone, is investigated and compared with that of the parallel microstructure of the sheets through their representative models. The result of the investigation indicates that the maximum pullout force of the intercrossed microstructure is markedly larger than that of the parallel microstructure, which is experimentally verified.