Influence of heat assisted friction stir processing on the mechanical properties and cell viability in PLA/basalt/graphene nanocomposites

Polylactic acid (PLA) composites have been widely used in biomedical implants because of biocompatibility and improved mechanical properties. The aim of this study is to produce the polymer nanocomposite with the graphene nanoparticles as a filler through heat-assisted shoulder less friction stir processing (FSP) and to investigate the effect of the process parameter on the microstructural and mechanical characteristics. Rotational speed of 600 rpm is kept constant, tool feed rate of 10, 15 and 20 mm/min, volume fraction of 5%, 10% and 15% of graphene nanopowder and shoulder temperature of 35, 40 and 45 °C are taken as parameters to conduct the FSP. Response surface methodology (RSM) is performed to identify the process parameters which significantly affect the process. Microstructural observations have been conducted to confirm the presence of graphene nanoparticles along the direction of the FSP. In addition, the tensile and microhardness tests have been carried out to analyze the mechanical properties of the prepared samples. The results of methyl thiazol tetrazolium (MTT) assay analysis conducted on human osteoblastic cell line (MG63) show that the sample fabricated with 10% and 15% of graphene nanoparticles is nontoxic and holds a better survivability after a 48 h of study under in vitro culture conditions for tissue in-growth and confirms that this could be applicable for bone implants. The findings of the ANOVA verify that the temperature is the least important factor for producing a composite with better performance, while the volume percentage and feed rate are the most important factors.

Graphical abstract