Denture base materials need appropriate mechanical and tribological characteristics to endure different stresses inside the mouth. This study investigates the properties of poly(methyl methacrylate) (PMMA) reinforced with different low loading fractions (0, 0.2, 0.4, 0.6, and 0.8 wt.%) of hydroxyapatite (HA) nanoparticles. HA nanoparticles with different loading fractions are homogenously dispersed in the PMMA matrix through mechanical mixing. The resulting density, Compressive Young’s modulus, compressive yield strength, ductility, fracture toughness, and hardness were evaluated experimentally; the friction coefficient and wear were estimated by rubbing the PMMA/HA nanocomposites against stainless steel and PMMA counterparts. A finite element model was built to determine the wear layer thickness and the stress distribution along the nanocomposite surfaces during the friction process. In addition, the wear mechanisms were elucidated via scanning electron microscopy. The results indicate that increasing the concentration of HA nanoparticles increases the stiffness, compressive yield strength, toughness, ductility, and hardness of the PMMA nanocomposite. Moreover, tribological tests show that increasing the nanoparticle weight fraction considerably decreases the friction coefficient and wear loss.

Aluminum composites are preferred in many kinds of applications such as aviation, space, automotive, and marine, owing to their outstanding properties, high strength, and corrosion resistance. The main objective of the current study is to evaluate the mechanical properties of aluminum alloy 6061/titanium dioxide (micro-TiO₂) microcomposite synthesized using the stir casting method. The effects of changes in stir casting parameters, such as stirring speed and tiring durations, were studied. Al6061 matrix was reinforced with micro-TiO₂ particles with weight fractions of 1, 2, 3, 4, and 5 wt.%. Microstructural and chemical analyses were conducted to explore microstructural transformation resulting from the presence of the TiO₂ microparticles. The mechanical characteristics were evaluated, and the results showed a considerable enhancement in the mechanical strength and hardness resulting from the incorporation of micro-TiO₂ into Al606. The additions of 2 wt.% and 5 wt.% of micro-TiO₂ recorded the highest ultimate tensile strength and hardness, respectively.