Time-dependent behaviour of demineralised trabecular bone - Experimental investigation and development of a constitutive model.

Abstract

Trabecular bone is a cellular composite material comprising primarily of mineral and organic phases and its mechanical response to loads is time-dependent. The contribution of the organic phase to the time-dependent behaviour of bone is not yet understood. We investigated the time-dependent response of demineralised trabecular bone through tensile multiple-load-creep-unload-recovery experiments. We found that demineralised trabecular bone's time-dependent response is nonlinearly related to the applied stress levels - it stiffens with increased stress levels. Our results also indicated that the time-dependent behaviour is associated with the original bone volume ratio (BV/TV). Irrecoverable strain exists, even at the low strain levels, but are not associated with BV/TV. Furthermore, we found that the nonlinear viscoelastic model can accurately predict the time-dependent behaviour of the trabecular bone's organic phase, which can be incorporated together with the properties of mineral to generate a composite model of bone. This study will help to provide a better understanding of this natural composite material.