The tension-shear fracture behavior of polymeric bone cement modified with hydroxyapatite nano-particles

Polymethylmethacrylate (PMMA)-based bone cement is a well-known polymer in the medicine, especially orthopedic. However it has some drawbacks like lack of enough biocompatibility and poor mechanical properties. These problems can be addressed by incorporation of nano-materials. Hydroxyapatite has been proved to enhance biocompatibility of acrylic bone cements. This bioceramic can affect the mechanical properties of polymeric cements as well. In this study, a number of fracture tests were carried out to investigate the influence of nano-hydroxyapatite (HA) on the fracture behavior of acrylic bone cement under combined tension-shear (mixed mode) loading conditions. Semi-circular specimens were prepared by incorporating different amounts of HA powder into the cement matrix. It was found that adding up to 10 wt% HA into the cement causes an increase in the fracture toughness of PMMA/HA nano-composite in all modes. However, pure cement exhibited the greatest fracture resistance among all samples. Moreover, the comparison between the experimental and theoretical results showed that the generalized maximum tangential stress criterion could estimate the experimental data satisfactorily.