Modelling and experimental characterization of nanoindentation responses of various biocomposite materials

Abstract

In the past decades, composite materials (which are usually classified into fibre-reinforced composites and particle-reinforced composites, depending on the geometry of the reinforcements) have been widely applied in tissue engineering as implant scaffolds. A lot of work has been done on the bulk mechanical properties of these composites. However, there is lack of nanomechanical characterization of such composites, which is crucial for understanding the cell-material interactions at small scale, and further optimizing the design of scaffold materials to promote the formation of new viable tissue. Nanoindentation has been used for nanomechanical characterization of a wide range of composite materials, but there is lack of comprehensive modelling of these composites. Therefore, this thesis begins with the modelling of the nanomechanics of inclusion-reinforced composite materials. In this part, finite element analysis (FEA) is adopted to study the spatial-dependent mechanical response of fibre/matrix and particle/matrix composites. The effects of various factors (such as inclusion geometry, indenter geometry, inclusion orientation and relative indentation location) on the nanomechanical response are studied. Various indentation-based empirical or semi-analytical models have been examined and novel analytical models are proposed to describe the nanomechanical behaviour of these inclusion-reinforced composites. Towards the end of this thesis, the nanoindentation characterization of typical biocomposite materials is presented, namely extracellular matrix. For these complex composites, the existing analytical models may not be directly applied. However, with the aid of a statistical model and FEA, it has been demonstrated that mechanical properties of each individual component can be determined.