Evaluation of the mechanical properties of hydroxyapatite-silica aerogel/epoxy nanocomposites: Optimizing by response surface approach

Abstract

This study attempted to investigate the effects of adding hydroxyapatite and silica aerogel nanoparticles on the density, tensile, Izod impact, and morphological properties of epoxy using the Response Surface Methodology (RSM). RSM relied on Box–Behnken Design (BBD) was used to design the mechanical tests. The concurrent effects of two parameters including hydroxyapatite content and silica aerogels content on the mechanical properties have been evaluated. Finally, by using the equations obtained from regression for each of the responses, their optimal states were obtained using both the desirability approach and the Multi-Objective Particle Swarm Optimization (MOPSO) method. The results from tensile, and Izod impact tests indicated the combination of hydroxyapatite and silica aerogel nanoparticles led to an improvement in the tensile properties and energy absorption of epoxy matrix. The findings related to density test demonstrated that with addition of silica aerogel to the hydroxyapatite/epoxy nanocomposites, density of these samples was decreased. The maximum tensile strength of 86.9 MPa was obtained with hydroxyapatite content of 2.38 wt% and silica aerogels content of 4 wt%. Also, the maximum impact strength of 18.14 kJ/m2 was obtained with hydroxyapatite content of 1.11 wt% and silica aerogels content of 3.51 wt%. The field emission scanning electron microscope images showed the homogeneous distribution of combined hydroxyapatite and silica aerogel nanoparticles in epoxy matrix, except in 5 wt% of hydroxyapatite nanoparticles.