Research Of Multi-scale Mechanics Behavior In Hierarchical Porous Bio-ceramics

As good substitute in the bone tissue engineering, hydroxyapatite bio-ceramics with hierarchical microporous/macroporous subjected to complex loads when in use. It is important to study on its mechanical behavior and it will greatly improved the security of use and extended the range of application. At the mesoscopic level, porous bio-ceramics presented in different magnitude of porous structure in different scales. From the biological point of view, this structure amplified the function greatly. But its mechanical property affected by factors of hierarchical pore structure in different scales. And in the preparation process, defect such as crack is easy to be introduced. Hierarchical porous bio-ceramics' carrying capacity greatly influenced by the interaction of cracks and holes. Therefore, study the effective property of hierarchical porous bio-ceramics at the mesoscopic level and do researches on its fracture behavior have both theoretical and practical significance. In this paper, the contents of chief studies are as follows:1. At the mesoscopic level, based on the theory of homogenization method, the finite element method was combined with two-scale asymptotic expansion technology. Detailed discussions of periodical boundary conditions were presented. By calculating the effective properties of fiber reinforced composites, good results proved the effectiveness of this method.2. Study on Micro-structure of hierarchical porous bio-ceramics, established different representative volume element(RVE) of mesoscopic channel with different porosity and arrangement. Then do research on the results of effective modulus and sum up the relevant patterns. Evaluate and guide the design of micro-structure based on the need of mechanical property and porosity.3. Research on porous bio-ceramics with different porosity which contains growing cracks. Based on the fracture mechanics and set finite element software ABAQUS as a platform. According to the principle of extended finite element method the crack growing behavior was studied. Select maximum principal stress as crack initiation criterion and energy release rate as damage evolution criterion, the crack path and critical load was predicted. When hierarchical porous bio-ceramics implanted into human body, interaction between implant and humoral or bone cells appears. Study on the influence of pore pressure and predict the crack path. Then considered the toughness of bio-ceramics and investigated the material bearing capacity. The results show that as the fracture toughness increased the bearing capacity of materials significantly improved and it indicated that ranges of hierarchical porous bio-ceramics in use have been greatly expanded.In this paper, hierarchical porous bio-ceramics were studied separately in both micro and macro scales. Then the link was established between the two scales. Through this modeling method, the simulations of mechanical behavior of hierarchical porous bio-ceramics in different scales were more appropriately modeled consistent with the real material. In turn, when study on hierarchical porous bio-ceramics, better structure can be designed in the overall level.