SIF Prediction of Nanocomposite With Interfacial Debonding

2014 ◽  
Author(s):  
Waleed K. Ahmed
Keyword(s):  
Representative Volume Element ◽  
Volume Element ◽  
Uniaxial Tensile ◽  
Element Analysis ◽  
Linear Elastic ◽  
Composite Failure ◽  
Representative Volume ◽  
Uniaxial Tensile Stress ◽  
Composite Stiffness ◽  
The Impact

Local debonding in nanofiber/matrix interface of a nanofiber reinforced composite has been considered as one of the most important factors that can significantly reduce the composite stiffness as well as increases the interfacial stresses levels which eventually causes composite failure. In the present study, the debonded zone is considered as an interfacial defect and modeled to be a circumferential crack. Linear Elastic Fracture Mechanic (LEFM) was used to investigate the impact of a nanofiber/matrix debonded interface in a nanocomposite through estimating Stress Intensity Factor (SIF). Finite element analysis (FEA) has been carried out to investigate SIF along the debonded edge using 3D-axisymmetric method, and this was done through modeling half of the representative volume element (RVE). A representative volume element of the nanocomposite was modeled and analyzed to explore SIF. Mainly, RVE consists of a nanofiber confined by a matrix and subjected to uniaxial tensile stress. A longitudinal debonding is proposed along the interfacial nanofiber/matrix. It has been shown that FE results indicates a significant impact of the debonding on the SIF of the nanocomposite.

An Introduction to Micromechanics

2016 ◽  
Vol 828 ◽  
pp. 3-24 ◽  
Author(s):  
Wenbin Yu
Keyword(s):  
Representative Volume Element ◽  
Volume Element ◽  
Local Fields ◽  
Homogenization Theory ◽  
Element Analysis ◽  
Full Field ◽  
Linear Elastic ◽  
Representative Volume ◽  
Complete Set ◽  
Periodic Materials

This article provides a brief introduction to micromechanics using linear elastic materials as an example. The fundamental micromechanics concepts including homogenization and dehomogenization, representative volume element (RVE), unit cell, average stress and strain theories, effective stiffness and compliance, Hill-Mandel macrohomogeneity condition. This chapter also describes the detailed derivations of the rules of mixtures, and three full field micromechanics theories including finite element analysis of a representative volume element (RVE analysis), mathematical homogenization theory (MHT), and mechanics of structure genome (MSG). Theoretical connections among the three full field micromechanics theories are clearly shown. Particularly, it is shown that RVE analysis, MHT and MSG are governed by the same set of equations for 3D RVEs with periodic boundary conditions. RVE analysis and MSG can also handle aperiodic or partially periodic materials for which MHT is not applicable. MSG has the unique capability to obtain the complete set of 3D properties and local fields for heterogeneous materials featuring 1D or 2D heterogeneities.

LEFM to Investigate the Impact of Deteriorated Particles in Composite Material

2015 ◽  
Author(s):  
Waleed K. Ahmed ◽  
Wail Al-Rifaie ◽  
Y. Al-Douri ◽  
Mostefa Bourchak
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Representative Volume Element ◽  
Particulate Composite ◽  
Volume Element ◽  
Element Analysis ◽  
Representative Volume ◽  
Reinforced Composite ◽  
The Impact ◽  
Particulate Reinforced

Due to its distinguished properties especially being isotropic, particulate reinforced composite is considered as one of the attractive material for wide range of applications, where the relatively low manufacturing cost is a desirable advantage. In the present analysis, deteriorated particles embedded in particulate reinforced composite have been investigated. The impact of the fractured particles is studied through the principles of fracture mechanics using finite element method. Mainly the stiffness variation of the composite due to the presence of the fractured particles is mainly predicted, since it is considered as an important factor especially from the view point of the damage-tolerant design of composite structures. A representative volume element (RVE) has been selected to represent the particulate composite with different particle volume fractions. It is important to point out that based on a previous investigation and comparison between two and three dimensional finite element analysis for a particulate reinforced composite, two-dimensional, plane strain finite element analysis is used to estimate the stresses and deformation that taken place. Uniaxial tensile stress perpendicular to the crack face of the fractured particle has been applied to the representative volume element. Due to symmetry of the studied geometries, quarter of the representative volume element is modeled via finite element method with a consistent mesh as possible to maintain reliable results. Linear elastic fracture mechanics (LEFM) is adopted through estimating stress intensity factor (SIF) of the cracked particles. Basically, the investigation covers the assessment of fractured particles with different crack lengths, where the particle’s stiffness is considered as a substantial parameter in the analysis in combination with others. Moreover, various particles volume fractions are taken into account to figure out their influence on the effective Young’s modulus of the representative volume element chosen for the studied cases. Multiple point constraints (MPC) technique is adopted in the finite element model to calculate the effective stiffness of the fractured particle. In general, it has been shown that there is a considerable influence of the deteriorated particles on increasing stress intensity factor levels at the crack tip as long as the crack length increases with respect to the particle size, and this basically depends on the stiffness ratio of the matrix/particle considered in the analysis. In the other hand, it has been noticed that a significant reduction in the effective stiffness of the particulate composite which is calculated based on the modeled representative volume element as a function of the crack length.

Localization simulation of forming-induced residual stresses of composite using prescribed boundary

2021 ◽  
pp. 073168442094118
Author(s):  
Qi Wu ◽  
Hongzhou Zhai ◽  
Nobuhiro Yoshikawa ◽  
Tomotaka Ogasawara ◽  
Naoki Morita
Keyword(s):  
Residual Stresses ◽  
Representative Volume Element ◽  
Computational Cost ◽  
Volume Element ◽  
Thermoplastic Composite ◽  
Structural Deformation ◽  
Element Analysis ◽  
Micro Scale ◽  
Representative Volume ◽  
Localization Approach

A novel localization approach that seamlessly bridges the macro- and micro-scale models is proposed and used to model the forming-induced residual stresses within a representative volume element of a fiber reinforced composite. The approach uses a prescribed boundary that is theoretically deduced by integrating the asymptotic expansion of a composite and the equal strain transfer, thus rendering the simulation setting to be easier than conventional approaches. When the localization approach is used for the finite element analysis, the temperature and residual stresses within an ideal cubic representative volume element are precisely simulated, given a sandwiched thermoplastic composite is formed under one-side cooling condition. The simulation results, after being validated, show that the temperature gradient has an impact on the local residual stresses, especially on the in-plane normal stress transverse to the fiber, and consequently, influences the structural deformation. This newly designed localization approach demonstrates the advantages of enhanced precision and reduced computational cost owing to the fast modeling of the finely meshed representative volume element. This is beneficial for a detailed understanding of the actual residual stresses at the micro-scale.

Representative Volume Element for Mechanical Properties of Carbon Nanotube Nanocomposites Using Stochastic Finite Element Analysis

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Seyed Hamid Reza Sanei ◽  
Randall Doles
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Representative Volume Element ◽  
Volume Element ◽  
Length Scale ◽  
Stochastic Finite Element ◽  
Element Analysis ◽  
Representative Volume ◽  
Element Approach ◽  
Stochastic Finite Element Analysis

Abstract The aim of this study is to present a representative volume element (RVE) for nanocomposites with different microstructural features using a stochastic finite element approach. To that end, computer-simulated microstructures of nanocomposites were generated to include a variety of uncertainty present in geometry, orientation, and distribution of carbon nanotubes. Microstructures were converted into finite element models based on an image-based approach for the determination of elastic properties. For each microstructure type, 50 realizations of synthetic microstructures were generated to capture the variability as well as the average values. Computer-simulated microstructures were generated at different length scales to determine the change in mechanical properties as a function of length scale. A representative volume element is defined at a length scale beyond which no change in variability is observed. The results show that there is no universal RVE applicable to all properties and microstructures; however, the RVE size is highly dependent on microstructural features. Microstructures with agglomeration tend to require larger RVE. Similarly, random microstructures require larger RVE when compared with aligned microstructures.

scholarly journals Influence of crystallographic orientation on the void growth at the grain boundaries in bi-crystals

2020 ◽  
Author(s):  
GUADALUPE VADILLO
Keyword(s):  
Grain Boundary ◽  
Representative Volume Element ◽  
Void Growth ◽  
Crystallographic Orientation ◽  
Stress Triaxiality ◽  
Volume Element ◽  
Lattice Rotation ◽  
Lode Parameter ◽  
Representative Volume ◽  
The Impact

Void growth and morphology evolution in fcc bi-crystals are investigated using crystal plasticity fi?nite element method. For that purpose, representative volume element of bi-crystals with a void at the grain boundary are considered in the analysis. Grain boundary is assumed initially perpendicular/coaxial with the straight sides of the cell. Fully periodic boundary conditions are prescribed in the representative volume element and macroscopic stress triaxiality and Lode parameter are kept constant during the whole deformation process. Three di?erent pairs of crystal orientations characterized as hard-hard, soft-soft and soft-hard has been employed for modellingthe mechanical response of the bi-crystal. Simulations are performed to study the implications of triaxiality, Lode parameter and crystallographic orientation on slip mechanism, hardening and hence void evolution. The impact of void presence and its growth on the heterogeneity of lattice rotation and resulting grain fragmentation in neighbouring areas is also analysed and discussed.

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