Effective Mechanical Properties Of Nanocomposites Research Articles

Equivalent inclusions in micromechanics with interface energy effect

In order to apply classical micromechanics in predicting the effective prop-erties of nanocomposites incorporating interface energy, a concept of equivalent inclusion (EI) is usually adopted. The properties of EI are obtained by embedding a single inclusion with the interface into an infinite matrix. However, whether such an EI is universal for different micromechanics-based methods is rarely discussed in the literature. In this pa-per, the interface energy theory is used to study the applicability of the above mentioned EI. It is found that some elastic properties of the EI are related only to the properties of the inclusion and the interface, whereas others are also related to the properties of the matrix. The former properties of the EI can be applied to both the classical Mori-Tanaka method (MTM) and the generalized self-consistent method (GSCM). However, the latter can be applied only to the MTM. Two kinds of new EIs are proposed for the GSCM and used to estimate the effective mechanical properties of nanocomposites.

Effects of carbon nanotubes’ dispersion on effective mechanical properties of nanocomposites: A finite element study

Effects of volume fraction and random dispersion of carbon nanotubes on effective mechanical properties of carbon nanotube-reinforced nanocomposites are studied at continuum level using finite element methods. Utilizing a continuum model of tubes with specific pairing of elastic properties and wall thickness for describing carbon nanotubes, representative volume elements with non-uniform distribution of uniaxial nanotubes within a base matrix are generated. Furthermore, a dispersion quantification technique is employed to quantify nanotubes’ dispersion degree. Finite element simulations are carried out in six independent loading conditions, while applying periodic boundary conditions to the models. Homogenizing the models and using the formulations of linear elasticity, equivalent mechanical properties of the models are computed and the effects of the aforementioned influential parameters as well as the modeling volume size are investigated. The results demonstrate that in volume fractions higher than 5%, the effects of carbon nanotubes’ dispersion become more significant and if increasing the volume fraction leads to bigger agglomerations and subsequently worse dispersion, the effective properties of the composite as a whole will decrease. Moreover, the pre- and post-processing procedures implemented are verified by analyzing previously studied models available in the literature and comparing the corresponding results.

Modeling and Analysis the Effect of Helical Carbon Nanotube Morphology on the Mechanical Properties of Nanocomposites Using Hexagonal Representative Volume Element

Carbon nanotubes (CNTs) are the ultimate reinforcing materials for the development of an entirely new class of composites. However, they have the complicated shapes and do not usually appear as straight reinforcements when introduced in polymer matrices. This decreases nanotube’s effectiveness in enhancing the matrix mechanical properties. In this paper, nanostructure having hexagonal representative volume element (RVE), theory of elasticity of anisotropic materials and finite element method (FEM) are used to investigate the effect of helical CNT morphology on effective mechanical properties of nanocomposites. CNT with different helical angles are modeled to estimate the nanocomposite mechanical properties. The results of helical nanotube models are compared with the effective mechanical properties of nanocomposites reinforced with straight nanotubes.

Evaluation of effective mechanical properties of nanocomposites reinforced with multiwalled carbon nanotube

Effective mechanical properties of nanocomposites reinforced with multiwalled carbon nanotubes (MWCNTs) have been determined using Finite Element Analysis (FEA). The effects of several parameters on nanocomposite effective mechanical properties are investigated. First, FEA models are created consisting of MWCNTs with different spring constants to investigate the effects of the interlayer van der Waals forces. Next, the reinforcing efficiency of MWCNTs in different matrices is investigated using models consisting of matrices with different moduli of elasticity. In addition, the effects of MWCNT volume fraction are investigated. Finally, models were created to determine effective mechanical properties of nanocomposites reinforced with Single-Walled Carbon Nanotubes (SWCNTs). Comparison of the results suggests that SWCNTs are more efficient in strengthening the matrix than MWCNTs. Also, Young’s modulus prediction for multiwalled carbon nanotube in a propylene matrix is compared to experimental data investigated by Andrews et al. (2002), and good agreement is observed.

Mechanical property characterization of carbon nanotube modified polymeric nanocomposites by computer modeling

This paper reports a two-step modeling approach for predicting the effective mechanical properties of polymeric nanocomposites modified with single walled carbon nanotube (SWNT). In step one, the nano-heterostructures of the nanocomposites were represented by 3-D nanoscale cylindrical, square, or hexagonal prismatic representative volume elements (RVEs). Each RVE contained a long or a short carbon nanotube (CNT) and consisted of three phases, i.e., CNT, matrix, and interphase. The mechanical properties of each RVE were extracted from the modeling results of the RVE undergone three load tests, i.e., uniaxial tensile test, lateral expansion test, and axial torsional test, using appropriately derived formulae. The effects of the volume fraction of CNTs on the mechanical properties of the RVEs were studied. The equivalent mechanical properties of the nano-heterostructures were obtained by averaging the mechanical properties extracted from each RVE. In step two, micro/macroscale nanocomposites were represented by a 3-D microscale unit cell which was discretized into cubic elements. Using Monte Carlo method, each element was assigned the averaged mechanical properties of the RVEs with random CNT orientation and length type. The overall effective mechanical properties of the nanocomposites were predicted by a tensile test on the unit cell. The modeling results by this proposed approach was compared with and validated by the experimental data of the SWNT modified epoxy nanocomposites.

Effective mechanical properties of nanocomposites reinforced with wavy carbon nanotubes

Carbon nanotubes (CNTs) possess exceptional mechanical properties and are therefore suitable reinforcements for composite materials. Nanotube efficiency in reinforcing the matrix depends on the CNT alignment, volume fraction and configuration, as well as matrix properties. In this investigation, finite element method (FEM) is used to investigate the effects of nanotube waviness ratio, volume fraction, and matrix modulus on properties of CNT based polymer nanocomposites. Nanocomposite mechanical properties are evaluated using a 3D nanoscale representative volume element. Models consisting of CNTs with different waviness ratios are created to investigate the effects of nanotube configuration on nanocomposite mechanical properties. Next, the effect of nanotube volume fraction on nanocomposite moduli of elasticity is investigated. Finally, the effects of matrix modulus are investigated by analysing models consisting of matrices with different moduli. The results of this investigation are compared with those found in the literature and good agreement is observed.

The Influence of Debonding Interface on the Effective Mechanical Properties for Nano-Composites

Combining the contact elements into the two-scale homogenization method, the effective mechanical properties of nano-composites with a debonding interface are analyzed. A periodic microscopic representative volume element (RVE) is modeled by using a four-phase composite composed of matrix, nano-tube, bonded, and debonding interfaces. The initial stress and coulomb's friction are considered within debonding interface, which is applied to transfer the shear stress produced by the relative slip between nano-tube and matrix, and a simple elastic–plastic constitutive model is established to study the effective mechanical properties of nano-composites. The predicted results show a strong non-linear dependence of the effective mechanical properties on the elastic modulus, volume fraction, debonding length and the ratio of length with thickness of interface.

Effects of nanotube helical angle on mechanical properties of carbon nanotube reinforced polymer composites

Carbon nanotubes (CNTs) possess exceptional mechanical properties and are therefore suitable candidates for use as reinforcements in composite materials. The CNTs, however, form complicated shapes and do not usually appear as straight reinforcements when introduced in polymer matrices. This results in a decrease in nanotube effectiveness in enhancing the matrix mechanical properties. In this paper, theory of elasticity of anisotropic materials and finite element method (FEM) are used to investigate the effects of CNT helical angle on effective mechanical properties of nanocomposites. Helical nanotubes with different helical angles are modeled to investigate the effects of nanotube helical angle on nanocomposite effective mechanical properties. In addition, the results of models consisting of helical nanotubes are compared with the effective mechanical properties of nanocomposites reinforced with straight nanotubes. Ultimately, the effects of helical CNT volume fraction on nanocomposite longitudinal modulus are investigated.

Homogenization Analysis of Effective Mechanical Properties of Nano-Composites with Non-Linear Material Components

Combining the cohesive zone model into the homogenization method, the effective mechanical properties of nano-composites with debonding interface and the non-linear matrix phase are analyzed. The matrix phase is considered as bilinear material satisfying the von Mises conditions in the presented algorithm, and a simple elastic–plastic constitutive model is established for a periodic microscopic representative volume element (RVE) to study the longitudinal Young’s modulus and shear modulus of nano-composites. The results show that the non-linearity of material components can degenerate the effective materials properties, and the shear modulus is more sensitive to the debonding length of interface and the change of yield stress of matrix phase.

Two-Scale Analysis for the Mechanical Properties of Nano-Composites with Non-Linear Interface

Combining the cohesive zone elements into the two-scale homogenization method, the effective mechanical properties of nano-composites with a non-linear interface are analyzed. A periodic microscopic representative volume element (RVE) is modeled using a four-phase composite composed of matrix, nano-tube, bonded, and debonded interfaces. The debonded interface is simultaneously considered as bilinear plastic material satisfying the von Mises conditions in the presented algorithm, and a simple elastic–plastic constitutive model is established to study the non-linear effective elastic properties of nano-composites and equivalent stress for interface and nano-tube. The predicted results show a strong non-linear dependence of the effective mechanical properties on the interfacial modulus and yield stress.