Investigation of flexural fatigue behavior of functionally graded hybrid nanocomposite

Abstract

In this paper, functionally graded polymer hybrid nanocomposites have been produced by the Silica (SiO₂) nanoparticles and Alumina (Al₂O₃) nanoparticles distribution in a matrix of epoxy during the ultrasonication via hand layup method. The variation in nanoparticles volume fraction (Vf.) was given in the thickness direction for reaching the gradation. Each layers having a thickness of 1.2 mm through various concentrations of nanoparticles were sequentially cast in acrylic molds for fabricating the graded composite sheet with a 6 mm thickness.

This study includes two parts. First is the experimental part which includes studying the structural properties and fatigue behavior of FGM hybrid and their isotropic hybrid nanocomposite. While, the second part comprises the preparation of numerical models to simulate the fatigue test of FGM hybrid and their isotropic hybrid nanocomposite by using Finite Element Method (FEM) through ANSYS release 2020 R2.

For fabricating the functionally graded layers, various nanoparticles concentrations with different nanoparticles have been taken (1.5% SiO₂, 1% SiO₂, epoxy, 2% Al₂O₃ and 3% Al₂O₃) and tested by flexural fatigue test for each isotropic layers of functionally graded material (FGM). The flexural fatigue properties performed at the zero mean stress (stress ratio) (R = -1) of the FGM hybrid, isotropic hybrid nanocomposite (1% SiO₂ + 2% Al₂O₃) and pristine epoxy, for evaluating their fatigue properties, including stress- strain curve, have been determined and compared with numerical results.

Design modeler (ANSYS - 2020 R2 workbench) was employed for verifying the investigational outcomes of the fatigue tests. The results of experiments were confirmed via building a detailed 3D FE model. This was done by constructing five layers for each model of FGMs which being dealt as 3D structural composites. The results manifested that varying the FGM kind possesses a higher effect upon the measured characteristics. Good agreement between experimental and theoretical results, where the percentage error was less than 7.53% for fatigue test.

The structural test by SEM was utilized for evincing the region of fracture and the agglomerations of maximum bending moment of fatigue test after failure and a good desperation of nanoparticles in epoxy matrix.