- Jeddah, Makkah Province, Saudi Arabia
With the recent great progress made in flexible and wearable electronic materials, the upcoming next generation of skin-mountable and implantable smart devices holds extensive potential applications for the lifestyle modifying, including... more
With the recent great progress made in flexible and wearable electronic materials, the upcoming next generation of skin-mountable and implantable smart devices holds extensive potential applications for the lifestyle modifying, including personalized health monitoring, human-machine interfaces, soft robots, and implantable biomedical devices. As a core member within the wearable electronics family, flexible strain sensors play an essential role in the structure design and functional optimization. To further enhance the stretchability, flexibility, sensitivity, and electricity performances of the flexible strain sensors, enormous efforts have been done covering the materials design, manufacturing approaches and various applications. Thus, this review summarizes the latest advances in flexible strain sensors over recent years from the material, application, and manufacturing strategies. Firstly, the critical parameters measuring the performances of flexible strain sensors and material...
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提出了一种统计的二阶双尺度分析方法预测颗粒非一致随机分布复合材料结构的热传导性能。首先给出了非一致随机分布复合材料的表征方法;接着针对这种材料的稳态热传导问题用构造性方法给出了温度解的双尺度渐近展开公式,提出了预测热传导参数的方法。最后给出了数值算例,通过与试验结果的比较和对数据的合理性分析,验证了本文方法的可行性。
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A Statistical two-order and Two-Scale computational Method (STSM) based on two-scale homogenization approach is developed and successfully applied to predicting the strength parameters of random particle reinforced composites. Firstly,... more
A Statistical two-order and Two-Scale computational Method (STSM) based on two-scale homogenization approach is developed and successfully applied to predicting the strength parameters of random particle reinforced composites. Firstly, the probability distribution model of composites with random distribution of a great number of particles in any ε - size statistic screen, as ε- size cell, is described. And then, the stochastic two-order and two-scale computational expressions for the strain tensor in the structure, which is made from the composites with random distribution model of ε - size cell, are formulated in detail. And the effective expected strength and the minimum strength for the composites with random distribution are expressed, and the computational formulas of them and the algorithm procedure for strength parameter prediction are shown. Finally, some numerical results of its application to the random particle reinforced composites, the concrete with random distribution of a great number of particles in any ε- size statistic screen, are demonstrated, and the comparisons with physical experimental data are given. They show that STSM is validated and efficient for predicting the strength of random particle reinforced composites.
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We introduce a framework that adapts local and non-local continuum models to simulate static fracture problems. Non-local models based on the peridynamic theory are promising for the simulation of fracture, as they allow discontinuities... more
We introduce a framework that adapts local and non-local continuum models to simulate static fracture problems. Non-local models based on the peridynamic theory are promising for the simulation of fracture, as they allow discontinuities in the displacement field. However, they remain computationally expensive. As an alternative, we develop an adaptive coupling technique based on the morphing method to restrict the non-local model adaptively during the evolution of the fracture. The rest of the structure is described by local continuum mechanics. We conduct all simulations in three dimensions, using the relevant discretization scheme in each domain, i.e., the discontinuous Galerkin finite element method in the peridynamic domain and the continuous finite element method in the local continuum mechanics domain.
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A statistical second-order two-scale (SSOTS) method is established in a constructive way for predicting the thermomechanical properties of statistically inhomogeneous materials. For this kind of composite materials, the complicated... more
A statistical second-order two-scale (SSOTS) method is established in a constructive way for predicting the thermomechanical properties of statistically inhomogeneous materials. For this kind of composite materials, the complicated micro-characteristics of inclusions, including their shape, size, orientation, spatial distribution, volume fraction and/or material properties and so on, lead to changes of the macroscopic thermomechanical properties, such as stiffness, coefficient of thermal expansion and strength of material. In this paper, a statistical model at an arbitrary position of the composite material is defined to represent the microstructure of the statistically inhomogeneous media at first. And then, the statistical second-order two-scale analysis formulation is derived. Finally, the numerical results for some statistically inhomogeneous composites are calculated by SSOTS algorithm, and compared with the data by experimental and theoretical methods.
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The statistical two-order and two-scale method is developed for predicting the mechanics parameters, such as stiffness and strength of core-shell particle-filled polymer composites. The representation and simulation on meso-configuration... more
The statistical two-order and two-scale method is developed for predicting the mechanics parameters, such as stiffness and strength of core-shell particle-filled polymer composites. The representation and simulation on meso-configuration of random particle-filled polymers are stated. And the major statistical two-order and two-scale analysis formulation is briefly given. The two-order and two-scale expressions for the strains and stresses of conventionally strength experimental components, including the tensional or compressive column, the twist bar and the bending beam, are developed by means of their classical solutions with orthogonal-anisotropic coefficients. Then a new effective mesh generation algorithm is presented. The mechanics parameters of core-shell particle-filled polymer composites, including the expected stiffness parameters, minimum stiffness parameters, and the expected elasticity limit strength and the minimum elasticity limit strength, are defined by means of the stiffness coefficients and elasticity strength criterions for core, shell and matrix. Finally, the numerical results for predicting both stiffness and elasticity limit strength parameters are compared with the experimental data.
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In this paper, a statistical second-order two-scale (SSOTS) method is presented for predicting heat conduction performances of the structures of composite materials with inconsistent random distribution. Firstly, the meso-scopic... more
In this paper, a statistical second-order two-scale (SSOTS) method is presented for predicting heat conduction performances of the structures of composite materials with inconsistent random distribution. Firstly, the meso-scopic configuration for the structure with inconsistent random distribution is characterized. Secondly, the SSOTS asymptotic formulation for predicting the heat conduction parameters and the temperature fields of the heat conduction problems of the structure is given by means of construction way. Then the heat conduction properties for the functional gradient materials (FGM) with varying volume fraction are predicted by the SSOTS method. The numerical results are compared with experimental data and theoretical results. Finally, macroscopic heat conduction properties for the structures with varying probability distribution models including size, location and orientation distributions of grains are calculated. The numerical results show that the SSOTS method in this paper is valid to predict heat conduction performances of composite structures with inconsistent random distribution.
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In this article, we develop a method to couple anisotropic local continua with anisotropic non-local continua with central long-range forces. First, we describe anisotropic non-local models based on spherical harmonic descriptions. We... more
In this article, we develop a method to couple anisotropic local continua with anisotropic non-local continua with central long-range forces. First, we describe anisotropic non-local models based on spherical harmonic descriptions. We then derive compatible classic continuum models. Finally, we apply the morphing method to these anisotropic non-local models and present three-dimensional numerical examples to validate the efficiency of the technique.
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A class of random composite materials with statistically inhomogeneous microstructure, for example, functionally graded materials is considered in this paper. The microstructures inside a component are gradually varying in the statistical... more
A class of random composite materials with statistically inhomogeneous microstructure, for example, functionally graded materials is considered in this paper. The microstructures inside a component are gradually varying in the statistical sense. In view of this particularity, a novel statistical second-order two-scale (SSOTS) method is presented to predict the mechanical properties, including stiffness, and elastic limit. To develop this method, the microstructures of statistically homogeneous, and inhomogeneous materials are represented. In addition the SSOTS formulas are derived based on normalized cell depending on the position variables by a constructing way, and the algorithm procedure is described. The mechanical properties of the different inhomogeneous materials are evaluated. The numerical results are compared with the experimental findings. It shows that the SSTOS method is effective.
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A method for coupling non-local continuum models with long-range central forces to local continuum models is proposed. First, a single unified model that encompasses both local and non-local continuum representations is introduced. This... more
A method for coupling non-local continuum models with long-range central forces to local continuum models is proposed. First, a single unified model that encompasses both local and non-local continuum representations is introduced. This model can be purely non-local, purely local or a hybrid depending on the constitutive parameters. Then, the coupling between the non-local and local descriptions is performed through a transition (morphing) affecting only the constitutive parameters. An important feature is the definition of the morphing functions, which relies on energy equivalence. This approach is useful in large-scale modeling of materials that exhibit strong non-local effects. The computational cost can be reduced while maintaining a reasonable level of accuracy. Efficiency, robustness and basic properties of the approach are discussed using one- and two-dimensional examples.
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The objective of this work is to develop and apply the Arlequin framework to couple nonlocal and local continuum mechanical models. A mechanically-based model of nonlocal elasticity, which involves both contact and long-range forces, is... more
The objective of this work is to develop and apply the Arlequin framework to couple nonlocal and local continuum mechanical models. A mechanically-based model of nonlocal elasticity, which involves both contact and long-range forces, is used for the ‘fine scale’ description in which nonlocal interactions are considered to have non-negligible effects. Classical continuum mechanics only involving local contact forces is introduced for the rest of the structure where these nonlocal effects can be neglected. Both models overlap in a coupling subdomain called the ‘gluing area’ in which the total energy is separated into nonlocal and local contributions by complementary weight functions. A weak compatibility is ensured between kinematics of both models using Lagrange multipliers over the gluing area. The discrete formulation of this specific Arlequin coupling framework is derived and fully described. The validity and limits of the technique are demonstrated through two-dimensional numerical applications and results are compared against those of the fully nonlocal elasticity method.
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An effective computer generation method is presented in this paper to more perfectly and rapidly generate the random distribution domains with large numbers of grains (pores). At first, the geometries of heterogeneous grains and the... more
An effective computer generation method is presented in this paper to more perfectly and rapidly generate the random distribution domains with large numbers of grains (pores). At first, the geometries of heterogeneous grains and the stationary random distribution model with large numbers of grains are defined. Second, the effective computer generation method, including compactness algorithm and selection algorithm, is described in detail. Then the effectiveness of the generation method and the comparison with the take-and-place method are given, and some examples with different geometries of grains in 2- and 3-dimension cases are illustrated. The computer generation method in this paper has been applied to the computation of effective heat transfer behavior for the composites of the random distribution with large numbers of grains, and some numerical results are demonstrated. The generation method in this paper is able to make the generated samples hold better stochastic property, and it is also suitable to generating samples subjected to non-uniform probability model.
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We present two modeling approaches for predicting the macroscopic elastic properties of carbon nanotubes/polymer composites with thick interphase regions at the nanotube/matrix frontier. The first model is based on local continuum... more
We present two modeling approaches for predicting the macroscopic elastic properties of carbon nanotubes/polymer composites with thick interphase regions at the nanotube/matrix frontier. The first model is based on local continuum mechanics; the second one is based on hybrid local/non-local continuum mechanics. The key computational issues, including the peculiar homogenization technique and treatment of periodical boundary conditions in the non-local continuum model, are clarified. Both models are implemented through a three-dimensional geometric representation of the carbon nanotubes network, which has been detailed in Part I. Numerical results are shown and compared for both models in order to test convergence and sensitivity toward input parameters. It is found that both approaches provide similar results in terms of homogenized quantities but locally can lead to very different microscopic fields.