scholarly journals Influence of Boundary Conditions on Numerical Homogenization of High Performance Concrete

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1009
Author(s):  
Arkadiusz Denisiewicz ◽  
Mieczysław Kuczma ◽  
Krzysztof Kula ◽  
Tomasz Socha
Keyword(s):  
Experimental Data ◽  
Finite Element Method ◽  
Finite Element ◽  
Boundary Conditions ◽  
Representative Volume Element ◽  
High Performance ◽  
High Performance Concrete ◽  
Volume Element ◽  
Numerical Homogenization ◽  
Representative Volume

Concrete is the most widely used construction material nowadays. We are concerned with the computational modelling and laboratory testing of high-performance concrete (HPC). The idea of HPC is to enhance the functionality and sustainability of normal concrete, especially by its greater ductility as well as higher compressive, tensile, and flexural strengths. In this paper, the influence of three types (linear displacement, uniform traction, and periodic) of boundary conditions used in numerical homogenization on the calculated values of HPC properties is determined and compared with experimental data. We take into account the softening behavior of HPC due to the development of damage (micro-cracks), which finally leads to failure. The results of numerical simulations of the HPC samples were obtained by using the Abaqus package that we supplemented with our in-house finite element method (FEM) computer programs written in Python and the homogenization toolbox Homtools. This has allowed us to better account for the nonlinear response of concrete. In studying the microstructure of HPC, we considered a two-dimensional representative volume element using the finite element method. Because of the random character of the arrangement of concrete’s components, we utilized a stochastic method to generate the representative volume element (RVE) structure. Different constitutive models were used for the components of HPC: quartz sand—linear elastic, steel fibers—ideal elastic-plastic, and cement matrix—concrete damage plasticity. The numerical results obtained are compared with our own experimental data and those from the literature, and a good agreement can be observed.

Three-phase micromechanical analysis of residual stresses in reinforced fiber by carbon nanotubes

2016 ◽  
Vol 51 (12) ◽  
pp. 1783-1794 ◽  
Author(s):  
Ahmad Reza Ghasemi ◽  
Mohammad Mohammadi Fesharaki ◽  
Masood Mohandes
Keyword(s):  
Finite Element Method ◽  
Carbon Nanotubes ◽  
Finite Element ◽  
Carbon Fiber ◽  
Residual Stresses ◽  
Representative Volume Element ◽  
Volume Element ◽  
The Finite Element Method ◽  
Representative Volume ◽  
Element Method

In this study, circular disk model and cylinder theory for two dimension (2D) and three dimension (3D), respectively, have been used to determine residual stresses in three-phase representative volume element. The representative volume element is consisting of three phases: carbon fiber, carbon nanotubes, and polymer matrix, that carbon fiber is reinforced by carbon nanotube using electrophoresis method. Initially, the residual stresses analysis of two-phase representative volume element has been implemented. The two-phase representative volume element has been divided to carbon fiber and matrix phases with different volume fractions. In the three-phase representative volume element, although the volume fraction of carbon fiber is constant and equal to 60%, the volume fractions of carbon nanotubes for various cases are different as 0%, 1%, 2%, 3%, 4%, and 5%. Also, there are two different methods to reinforce the fiber according to different coefficients of thermal expansion of the carbon fiber and carbon nanotube in two longitudinal and transverse directions; carbon nanotubes are placed on carbon fiber either parallel or around it like a ring. Subsequently, finite element method and circular disk model have been used for analyzing micromechanic of the residual stresses for 2D and then the results of stress invariant obtained by the finite element method have been compared with the circular disk model. Moreover, for 3D model, the finite element method and cylinder theory have been utilized for micromechanical analysis of the residual stresses and the results of stress invariant obtained by them, have been compared with each other. Results of the finite element method and analytical model have good agreement in 2D and 3D models.

scholarly journals Design of Reinforcement in Nano- and Microcomposites

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1474 ◽  
Author(s):  
Małgorzata Chwał ◽  
Aleksander Muc
Keyword(s):  
Boundary Conditions ◽  
Representative Volume Element ◽  
Optimization Problems ◽  
Volume Element ◽  
Numerical Homogenization ◽  
Representative Volume ◽  
Material Optimization ◽  
Design Variables ◽  
Element Shape ◽  
Dimensional Optimization

The application of numerical homogenization and optimization in the design of micro- and nanocomposite reinforcement is presented. The influence of boundary conditions, form of a representative volume element, shape and distribution of reinforcement are distinguished as having the crucial influence on a design of the reinforcement. The paper also shows that, in the optimization problems, the distributions of any design variables can be expressed by n-dimensional curves. It applies not only to the tasks of optimizing the shape of the edge of the structure or its mid-surface but also dimensional optimization or topology/material optimization. It is shown that the design of reinforcement may be conducted in different ways and 2D approaches may be expanding to 3D cases.

scholarly journals Micro-CT-based micromechanics and numerical homogenization for effective elastic property of ultra-high performance concrete

2019 ◽  
Vol 29 (1) ◽  
pp. 45-66 ◽  
Author(s):  
Qi Luo ◽  
Dongxu Liu ◽  
Pizhong Qiao ◽  
Zhidong Zhou ◽  
Yanlin Zhao ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Representative Volume Element ◽  
High Performance ◽  
High Performance Concrete ◽  
Volume Element ◽  
Image Resolution ◽  
Micro Ct ◽  
Ultra High Performance Concrete ◽  
Freeze Thaw ◽  
Representative Volume

A computational homogenization model using microstructures obtained from X-ray micro-CT is developed to estimate the porosity-based elastic properties of ultra-high performance concrete under freeze–thaw action. The model is transformed directly from micro-CT which is capable of reflecting realistic distribution of porosity and heterogeneities inside the ultra-high performance concrete. Factors are taken into consideration, including the determination of representative volume element, the position and numbers of representative volume element cubes, fiber orientation, image resolution, applied filter, and pore distribution. The relationship between the material internal structure and freeze–thaw resistance is studied at micro-scale. The volume-averaged homogenization approach is applied to calculate the effective properties of the ultra-high performance concrete which are compared with experimental data. It is demonstrated that the proposed model provides an effective tool to evaluate the elastic properties of the ultra-high performance concrete based on microstructural characterization data.

scholarly journals EFFECT OF INTERPHASE CHARACTERISTIC AND PROPERTY ON AXIAL MODULUS OF CARBON NANOTUBE BASED COMPOSITES

1970 ◽  
Vol 41 (1) ◽  
pp. 15-24 ◽  
Author(s):  
Md. Abdulla Al Masud ◽  
A. K. M. Masud
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
Finite Element ◽  
Carbon Nanotube ◽  
Representative Volume Element ◽  
Volume Element ◽  
Representative Volume ◽  
Tensile Elastic Modulus ◽  
Micrometer Size ◽  
Element Method

In carbon nanotube (CNT) based composite, due to the small (micrometer) size of reinforcements a large amount of interphases is developed during the time of production. It is important to assess whether the interphase is responsible for the poor mechanical properties of CNT-reinforced composite. In this research, the effect of interphase property and characteristics on effective mechanical properties of CNT based composites is evaluated using a 3-D nanoscale representative volume element (RVE). The effect of both soft and stiff interphases on the Tensile Elastic Modulus (TEM) of nanocomposites is investigated using the Finite Element Method (FEM) for the case of both long and short CNTs. With the increase of thickness of stiff interphase, the stiffness of the composite increases significantly for both the short and long CNT cases. On the other hand the increase of thickness of soft interphase reduces the stiffness of the overall composite in a considerable amount.Key Words: Carbon nanotube; Interphase; Representative Volume Element; Finite Element method; TensileElastic Modulus.DOI: 10.3329/jme.v41i1.5358Journal of Mechanical Engineering, Vol. ME 41, No. 1, June 2010 15-24 

Modeling of Cementitious Representative Volume Element with Additives

2017 ◽  
Vol 08 (02) ◽  
pp. 1750003 ◽  
Author(s):  
M. M. Shahzamanian ◽  
W. J. Basirun
Keyword(s):  
Finite Element ◽  
Fly Ash ◽  
Boundary Conditions ◽  
Elastic Properties ◽  
Representative Volume Element ◽  
Volume Element ◽  
Type I ◽  
Element Analysis ◽  
Representative Volume ◽  
Mesh Density

CEMHYD3D has been employed to simulate the representative volume element (RVE) of cementitious systems (Type I cement) containing fly ash (Class F) through a voxel-based finite element analysis (FEA) approach. Three-dimensional microstructures composed of voxels are generated for a heterogeneous cementitious material consisting of various constituent phases. The primary focus is to simulate a cementitious RVE containing fly ash and to present the homogenized macromechanical properties obtained from its analysis. Simple kinematic uniform boundary conditions as well as periodic boundary conditions were imposed on the RVE to obtain the principal and shear moduli. Our current work considers the effect of fly ash percentage on the elastic properties based on the mass and volume replacements. RVEs with lengths of 50, 100 and 200[Formula: see text][Formula: see text] at different degrees of hydration are generated, and the elastic properties are modeled and simulated. In general, the elastic properties of a cementitious RVE with fly ash replacement for cement based on mass and volume differ from each other. Moreover, the finite element (FE) mesh density effect is studied. Results indicate that mechanical properties decrease with increasing mesh density.

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.

scholarly journals Effect of Fiber Geometry and Representative Volume Element on Elastic and Thermal Properties of Unidirectional Fiber-Reinforced Composites

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Siva Bhaskara Rao Devireddy ◽  
Sandhyarani Biswas
Keyword(s):  
Thermal Conductivity ◽  
Finite Element ◽  
Thermal Properties ◽  
Elastic Modulus ◽  
Cross Section ◽  
Representative Volume Element ◽  
Material Properties ◽  
Volume Element ◽  
Unidirectional Fiber ◽  
Representative Volume

The aim of present work is focused on the evaluation of elastic and thermal properties of unidirectional fiber-reinforced polymer composites with different volume fractions of fiber up to 0.7 using micromechanical approach. Two ways for calculating the material properties, that is, analytical and numerical approaches, were presented. In numerical approach, finite element analysis was used to evaluate the elastic modulus and thermal conductivity of composite from the constituent material properties. The finite element model based on three-dimensional micromechanical representative volume element (RVE) with a square and hexagonal packing geometry was implemented by using finite element code ANSYS. Circular cross section of fiber and square cross section of fiber were considered to develop RVE. The periodic boundary conditions are applied to the RVE to calculate elastic modulus of composite. The steady state heat transfer simulations were performed in thermal analysis to calculate thermal conductivity of composite. In analytical approach, the elastic modulus is calculated by rule of mixture, Halpin-Tsai model, and periodic microstructure. Thermal conductivity is calculated analytically by using rule of mixture, the Chawla model, and the Hashin model. The material properties obtained using finite element techniques were compared with different analytical methods and good agreement was achieved. The results are affected by a number of parameters such as volume fraction of the fibers, geometry of fiber, and RVE.

Crystal Plasticity Simulation of the Bauschinger Effect of Polycrystalline AA7075 through a Texture-Based Representative Volume Element Model

2014 ◽  
Vol 553 ◽  
pp. 22-27
Author(s):  
Ling Li ◽  
Lu Ming Shen ◽  
Gwénaëlle Proust
Keyword(s):  
Finite Element ◽  
Representative Volume Element ◽  
Crystal Plasticity ◽  
Bauschinger Effect ◽  
Voronoi Tessellation ◽  
Strain Curve ◽  
Element Model ◽  
Volume Element ◽  
Model Parameters ◽  
Representative Volume

A texture-based representative volume element (TBRVE) model is developed for the three-dimensional crystal plasticity (CP) finite element simulations of the Bauschinger effect (BE) of polycrystalline aluminium alloy 7075 (AA7075). In the simulations, the grain morphology is created using the Voronoi tessellation method with the material texture systematically discretised from experiment. A modified CP constitutive model, which takes into account the backstress, is used to simulate the BE during cyclic loading. The model parameters are calibrated using the first cycle stress-strain curve and used to predict the mechanical response to the cyclic saturation of AA7075. The results indicate that the proposed TBRVE CP finite element model can effectively capture the BE at the grain level.

Sign in / Sign up

Export Citation Format

Share Document