Bone Composite Mechanics Related to Collagen Hydration State
Bone is considered in two different composite mechanics frameworks: first as an organic inorganic two phase composite, and second as a fluid-saturated porous solid. Experimental data from previous studies, in which the mechanical responses of bone or collagen were examined following immersion in a range of polar solvents, were used as inputs for both models. The changes in bone elastic modulus with polar solvents could not be predicted by two-phase organic inorganic composites models. A spherical indentation finite element model is generated within the poroelastic framework with the objective of identifying the permeability coefficient. In particular the effect of the ramp rise-time on the identification results is compared with results that assumed a step-load creep experiment. The results confirm that immersion of bone in polar solvents with decreasing polarity results in decreased hydraulic permeability. The developed identification approach based on the normalization of the indentation time-displacement response results shows potential for the efficient analysis of high throughput indentation tests. Further extension of composites models to include all three phases water, collagen and mineral is needed to fully explore the mechanical behavior of bone.