To study the effects of nano-additives and nano-indentation variables on viscoplastic behaviour of a polymeric orthopaedic bone cement

PMMA-based orthopaedic cement is an essential medical grade material in the modern healthcare system which has been widely used for the fixation of prostheses in total joint replacement surgeries. A PMMA bone cement is an intrinsically viscoplastic biomaterial, and a review of its constitutive material models seems to be of great importance to design, functionalize and improve the properties of these biomaterials. In this article, using the simultaneous analyses of experimental nano-indentation results and finite element simulation of a well-known two-layer viscoplasticity model, the effect of adding three types of nano-additives including hydroxyapatite (HA), Alumina (Al2O3), and single-walled carbon nanotubes (SWCNTs) on the viscoplastic behaviour of the cement was examined. Additionally, the effect of the experimental conditions such as loading rate, holding time and unloading rate on the viscoplastic behaviour of the cement was investigated. Making an analogy between the numerical and experimental results, the optimal constitutive material model for each case study was obtained. Moreover, by comparing the results with the condition where no nano-additives were added into the cement matrix, the effectiveness of the nano-supplements on the constitutive model was evaluated.