Computational studies of collagen fibril biominerals using a virtual internal bond model with extrinsic length scale

Mineralized type-I collagen fibrils are made up of mineral hydroxyapatite and type-I collagen and are known to have good mechanical properties. Hydroxyapatite by itself is stiffer and collagen is relatively weaker. The development of a multiscale virtual internal bond model (VIB) used to model the material behavior and failure of such biocomposites was described in an earlier paper by the authors. An explicit finite element based framework using a two parameter fracture-constitutive VIB model, with an extrinsic length scale, was used in this study. The model used in this study is a nano sized dahlite mineral crystal commonly found in collagen fibrils. Two important computational implementation characteristics are presented here; namely the effect of a material parameter used in the VIB model and the effect of thickness of the material at the nanoscale on the failure behavior. The effect of the thickness is studied in order to demonstrate the extrinsic length scale capability of the VIB model at nano length scales. 1.