Bone is a hierarchical bio-composite, and has a staggered arrangement of soft protein molecules interspaced with hard mineral platelets at the fine ultrastructure level. The investigation into reasons for high fracture toughness of bio-composites such as bone requires consideration of properties at the different levels of hierarchy.In this work, the analysis is done at the continuum level, but the properties used are appropriate to that of the level considered.
In this way, the fine ultrastructure level of bone (refer Figure 1) is considered and the analysis of the stress distribution in platelet 2 adjacent to the broken platelet 1 within a staggered arrangement is undertaken. Results (refer Figure 2) show the influence of overlapping ratio, (OR=L/t) in determining the nature of stress distribution, where t is the width of the platelet.
In this work shear lag theory is used for analysis. The stress is higher at the end of the platelet 2 and lesser at the centre for low OR whereas the stress is higher at the centre and lower at the ends for high OR. Hence it is expected that overlapping ratio may play a role in the fracture toughness of bio-composites.