The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
R. J. Young - One of the best experts on this subject based on the ideXlab platform.
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Deformation Micromechanics of natural cellulose fibre networks and composites
Composites Science and Technology, 2003Co-Authors: Stephen J. Eichhorn, R. J. YoungAbstract:Abstract The deformation Micromechanics of cotton and flax single natural cellulose fibres in relation to their use in cellulose-based networks and composite materials is reported. The deformation of such fibres induces a shift in the 1095 cm −1 Raman band, corresponding to the ring structure of the particular polymorph, which can be calibrated against strain. It is shown that this band shift can be used to monitor the deformation Micromechanics of fibrous networks (cotton paper) and the composite Micromechanics of single natural cellulose fibre unidirectional composites. The shear lag approach of Cox [Br. J. Appl. Phys. 3 (1952) 72] is investigated for the fibrous network and composite materials. For the network it is demonstrated that this theory does not apply since bonding across the end modifies the stress transfer by ‘shear-lag’. For the natural fibre composites it is thought that bonding occurs across the ends, also modifying this effect, but other possibilities are discussed in detail.
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Analysis of composite test methods using Raman spectroscopy
Plastics Rubber and Composites Processing and Applications, 1995Co-Authors: R. J. Young, Y.-l. Huang, Richard J. DayAbstract:The three main test methods that are generally used for the analysis of Micromechanics in polymer-based composites systems are the fragmentation, pullout and microbond tests. Although the techniques are used widely, there are problems with their interpretation, particularly in the determination of the interfacial shear stress. This present paper is concerned with both the use of the test methods to analyse the Micromechanics for carbon-filter/epoxy composites and the application of Raman spectroscopy to determine the variation of fibre strain with position along a carbon fibre in a resin
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Raman microscopy of fibres and composites
Journal of Microscopy, 1993Co-Authors: R. J. YoungAbstract:SUMMARY Some of the progress made in using Raman microscopy to examine the structure and Micromechanics of polymer and inorganic fibres is reviewed. Examples of how the technique has been used to verify some of the theories of composite reinforcement are then given. Finally, a specific example of how Raman microscopy has been used, in conjuction with other approaches, to understand the Micromechanics of the microbond test, which is often used to measure interfacial shear strength in composite systems, is presented.
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Raman microscopy of fibres and composites
Journal of Microscopy, 1993Co-Authors: R. J. YoungAbstract:SUMMARY Some of the progress made in using Raman microscopy to examine the structure and Micromechanics of polymer and inorganic fibres is reviewed. Examples of how the technique has been used to verify some of the theories of composite reinforcement are then given. Finally, a specific example of how Raman microscopy has been used, in conjuction with other approaches, to understand the Micromechanics of the microbond test, which is often used to measure interfacial shear strength in composite systems, is presented.
Qing Ping Sun - One of the best experts on this subject based on the ideXlab platform.
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Micromechanics modelling for the constitutive behavior of polycrystalline shape memory alloys-I. Derivation of general relations
Journal of the Mechanics and Physics of Solids, 1993Co-Authors: Qing Ping SunAbstract:A Micromechanics constitutive model has been proposed in this paper to describe the pseudoelastic and shape memory behavior of polycrystalline shape memory alloys under various temperatures. The derivation of the model is based on the thermodynamics, Micromechanics and microstructural physical mechanism analysis of the material during deformation and it is shown that the inelastic deformation of the material in the mechanical and/or thermal loading processes is associated with some temperature, stress state and loading history dependent yielding surfaces which microscopically correspond to the forward and reverse transformation (or reorientation) processes, respectively. © 1992.
Yao Koutsawa - One of the best experts on this subject based on the ideXlab platform.
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New Micromechanics approaches for the effective properties of multiferroics composites with spring-type imperfect interfaces
Composite Structures, 2019Co-Authors: Yao KoutsawaAbstract:Abstract This study proposed two new Micromechanics models to predict the effective properties of multiferroics composites with spring-type imperfect interfaces. The first model is a full field Micromechanics scheme based on the mechanics of structure genome, a multiscale constitutive modeling framework, recently discovered to unify the Micromechanics and the structural mechanics. The second model is a mean field Micromechanics approach that extends the Mori-Tanaka scheme using the concept of the interior and exterior-point Eshelby tensors to multiferroics composites. The imperfect interface model assumes that the normal components of the fluxes (stress, electric displacement and magnetic flux) are continuous across the interface, whereas the potential fields (displacement, electric potential and magnetic potential) suffer interfacial jumps proportional to the normal components of the fluxes. In contrast to multiferroics composites with perfect contact conditions, the effective properties formulations show the dependence on the size of the reinforcements. Numerical examples of fibrous multiferroics composites are used to demonstrate the robustness and accuracy of the proposed Micromechanics theories. The size-dependency of the overall properties shows the importance of imperfect interfaces in predicting the effective properties of multiferroics composites.
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Multi-site Micromechanics of composite materials with temperature-dependent constituents under small strain and finite thermal perturbation assumptions
Composite Structures, 2014Co-Authors: Yao KoutsawaAbstract:Abstract This study presents mean-field based Micromechanics models to predict the effective thermoelastic properties, namely, elasticities, thermal expansions and heat capacity, of thermoelastic composite materials with temperature-dependent constituents under finite temperature changes and small strain assumptions. First, the Helmholtz potential density for small strain finite thermoelasticity has been presented. The fundamental solution based on Green’s function of elasticity problem has been used to derive the general expressions for the elastic and thermal strains concentration tensors with temperature-dependent material properties. A family of mean-field based Micromechanics models (multi-site Eshelby dilute model, Mori–Tanaka model and self-consistent model) has been presented. The models are general enough to account for the morphology and topology textures of the microstructure of a thermoelastic composite. Numerical examples based on the multi-site Mori–Tanaka model are used to quantify the differences of the effective properties based on the small strain finite thermoelasticity in comparison to the linear thermoelasticity. The predictions of the multi-site Mori–Tanaka Micromechanics model are also compared to those of the VAMUCH, a finite element based Micromechanics model.
Tian Tang - One of the best experts on this subject based on the ideXlab platform.
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TMS2015 Supplemental Proceedings - A Micromechanical Model for Hygrothermoelastic Heterogeneous Materials
TMS 2015 144th Annual Meeting & Exhibition, 2015Co-Authors: Tian Tang, Sergio D. FelicelliAbstract:A Micromechanics model has been developed for predicting effective hygrothermoelastic properties of composite materials and recovering the local fields within the unit cell. Starting from the functional of free energy, a variational statement governing the Micromechanics model was formulated through an asymptotic expansion of the functional of free energy. Finite element method was employed to solve the fluctuation functions, which in turn were used to obtain the effective material properties and to recover the distributions of the local fields. Numerical examples were used to validate the theory and the code.
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Micromechanical modeling of the multiphysical behavior of smart materials using the variational asymptotic method
Smart Materials and Structures, 2009Co-Authors: Tian Tang, Wenbin YuAbstract:A multiphysics Micromechanics model is developed to predict the effective properties as well as the local fields of periodic smart materials responsive to fully coupled electric, magnetic, thermal and mechanical fields. This work is based on the framework of the variational asymptotic method for unit cell homogenization (VAMUCH), a recently developed Micromechanics modeling scheme. To treat the general microstructure of smart materials, we implemented this model using the finite element technique. Several examples of smart materials are used to demonstrate the application of the proposed model for prediction of multiphysical behavior.
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Variational Asymptotic Method for Unit Cell Homogenization
Solid Mechanics and Its Applications, 2009Co-Authors: Wenbin Yu, Tian TangAbstract:This article presents an overview of a recently developed Micromechanics theory, namely, the variational asymptotic method for unit cell homogenization along with its companion code VAMUCH. It is emerging as a general-purpose Micromechanics tool for predicting not only the effective properties of heterogeneous materials but also the local fields within the microstructure. The differences between VAMUCH and other Micromechanics approaches are articulated. A simple realistic example is used to demonstrate it application in practical situations.
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Variational asymptotic Micromechanics modeling of heterogeneous piezoelectric materials
Mechanics of Materials, 2008Co-Authors: Tian Tang, Wenbin YuAbstract:Abstract In this paper, a new Micromechanics model is developed to predict the effective properties and local fields of heterogeneous piezoelectric materials using the variational asymptotic method for unit cell homogenization (VAMUCH), a recently developed Micromechanics modeling technique. Starting from the total electric enthalpy of the heterogenous continuum, we formulate the Micromechanics model as a constrained minimization problem using the variational asymptotic method. To handle realistic microstructures in engineering applications, we implement this new model using the finite element method. For validation, a few examples are used to demonstrate the application and accuracy of this theory and the companion computer program – VAMUCH.
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Micromechanics Modeling of the Nonlinear Behavior of Electrostrictive Multiphase Composites
Smart Materials Adaptive Structures and Intelligent Systems Volume 1, 2008Co-Authors: Tian Tang, Wenbin YuAbstract:The Micromechanics modeling of the nonlinear behavior of the electrostrictive multiphase composites is developed using an incremental formulation based on the variational asymptotic method for unit cell homogenization (VAMUCH), a recently developed Micromechanics modeling scheme. The microstructure of composites is assumed to be periodic. Taking advantage of the small size of the microstructure, we formulate a variational statement of energy change of the unit cell through an asymptotic analysis of the functional by invoking only two essential assumptions within the concept of Micromechanics. Finally, the expression of the effective instantaneous tangential electromechanical matrix of the composites are established. Several numerical examples will be used to demonstrate the capability of the present theory.Copyright © 2008 by ASME
Qing-hua Qin - One of the best experts on this subject based on the ideXlab platform.
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Micromechanics-BEM analysis for piezoelectric composites
Tsinghua Science and Technology, 2005Co-Authors: Qing-hua QinAbstract:Abstract The effective material properties of piezoelectric composites are predicted using Micromechanics models of the composite structure combined with a boundary element method (BEM) solution of the governing equation. The composites consist of inclusion and matrix phases. The Micromechanics method gives formulae for the overall material constants as functions of the concentration matrix, while the boundary element simulation gives numerical solutions of the boundary displacement and electric potential equations for inclusion or hole problems. Numerical results for a piezoelectric plate with circular inclusions are presented to illustrate applications of the proposed Micromechanics-BEM formulation.
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Micromechanics-BE solution for properties of piezoelectric materials with defects
Engineering Analysis with Boundary Elements, 2004Co-Authors: Qing-hua QinAbstract:Abstract A Micromechanics boundary element (BE) algorithm is developed to predict the overall properties of a piezoelectric material with defects such as cracks or holes. The algorithm is based on Micromechanics models and boundary element formulation for piezoelectric materials with cracks or holes. In particular, the self-consistent and Mori–Tanaka methods are considered. A representative volume model for materials with defects is employed and introduced into a BE formulation to provide an effective means for estimating overall material constants of the defected materials. The Micromechanics method produces formulas for overall material constants as functions of the concentration matrix A 2 , and A 2 is in turn related to the boundary displacement. The boundary element simulation presents numerical solutions of boundary displacement and electric potential for crack or hole problems. In the Micromechanics-BE model, the volume (or area) average stress and strain is calculated by the boundary tractions and displacements of the RVE. Thus BEM is suitable for performing calculations on average stress and strain fields of such defected materials. An iterative scheme is introduced for the self-consistent-BE method. Numerical results for a piezoelectric plate with elliptic holes are presented to illustrate the application of the proposed Micromechanics BE formulation.
