SIMULATION-BASED FINITE ELEMENT MODELING AND CHARACTERIZATION OF CNT REINFORCED Ti-6Al-7Nb NANOCOMPOSITE

Abstract

This paper is aimed to characterize the carbon nanotube (CNT) reinforced Ti-6Al-7Nb nanocomposite, a biocompatible intermetallic for implants, for its effective elastic properties. CNTs are modeled as equivalent solid fibers (ESFs), and a three-dimensional representative volume element (RVE) model containing ESFs in the matrix material is considered. Periodic boundary conditions are applied on the RVE, and finite element (FE) based numerical homogenization, implemented through the commercial FE package ABAQUS, is used to estimate average stresses and strains in an RVE, which are utilized further to evaluate the effective elastic properties of the nanocomposite. Various analytical models are also used to verify the results. The effects of volume fraction, distribution, orientation, and waviness of the ESFs on the effective elastic properties are studied. For a given volume fraction of ESF, different distributions of straight and aligned ESFs result in the same elastic properties of the nanocomposite until agglomeration occurs. Furthermore, the difference between the elastic properties of random and uniform distributions of straight and aligned ESFs is negligible for low values of volume fraction and observable only in transverse tensile modulus (E₂₂) and shear modulus (G₂₃) for higher volume fractions. It is also concluded that the inclusion of wavy reinforcements results in the overall reduction of effective elastic properties of the nanocomposites with random distribution and random orientation of ESFs, but in the case of nanocomposites with aligned wavy ESFs, the value of transverse modulus (E₂₂) and shear modulus (G₁₂) are improved with waviness.