Abstract
Nano-hydroxyapatite (nHA) based polymer biocomposites have been widely used in biomedical industry because of biocompatibility and improved mechanical properties. The goal of this study was to produce ultra high molecular weight (UHMW) polyethylene/nHA composite via heat-assisted friction stir processing and to investigate the effects of process parameters on composite's microstructure and tensile characteristics. The process parameters include rotational speed (omega), feed rate (f), volume fraction of nHA (v), and shoulder temperature (T). ANOVA was performed to identify the significant process parameters. Moreover, empirical models for tensile properties were developed and validated. Microscopic analysis revealed that the process parameters substantially affect the dispersion of reinforcing particles, formation of defects, and mixing of materials. Low levels of omega and T and high levels of f and v lead to defects (agglomeration of reinforcing particles, voids, and channels). Five percent volume of nHA with medium levels of other process parameters resulted in better material mixing, minimum defects, and better mechanical properties (10% increase in strength with only 1% reduction in percent elongation, relative to the parent material).