Papers by Keyword: Homogenization

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Authors: L. Li, M.H. Ferri Aliabadi
Abstract: This paper presents homogenization of twill woven composites. It includes presenting formulated geometrical unit cell models, establishing meshfree micromechanical and CDM models for twill woven composites. The results cover meshfree nodal distributions, meshfree yarn geometries, predicted mechanical properties, effectiveness of yarn waviness, non-linear stress-strain relation of unit cell, stress distributions inside unit cell volume, and necessary comparisons with existing literatures.
Authors: Makoto Imura, Tetsusei Kurashiki, Hiroaki Nakai, Masaru Zako
Abstract: Fiber reinforced composite materials have been applied widely to many structures, because they have some advantages like easy handling, high specific strength, etc. The numerical method like finite element method has been applied to design and to evaluate the material properties and behavior as the development of Computer Aided Engineering. It is very difficult to calculate with accuracy not only in structural scale but also in detail material scale (for example, the order of fiber diameter) by the traditional FEM, becausecompositematerials like woven fabric composites have the geometrical complexityand the large difference between above mentioned scales. The development of multi-scale analysis method is one of the major topics in computational mechanics. Mesh superpositionis one of multi-scale analysis methods and is an effective method to solve the problems which have the large difference between the structure scale and the reinforcement scale. We have expanded the finite element mesh superposition method with 3 scales and have defined as M3 (Macro-Meso-Micro) method. In this paper, we have proposed a new approach method combined with M3 method and homogenized method to obtain the mechanical properties and to simulate the behavior of woven fabric composites. In addition, the elastic-plastic mechanics and the damage mechanics have been introduced into M3 method to investigate the effects of matrix-crack on the structural and material properties. From the numerical results, it is revealed that it is very useful for the evaluation of mechanical properties of composite materials.
Authors: Andrea Bacigalupo, Andrea Cavicchi, Luigi Gambarotta
Abstract: The influence of the bond pattern on the in-plane limit strength of masonry is analyzed through a simplified procedure based on the application of the safe theorem of limit analysis to the unit cell that generates the whole masonry by periodic repetition. The limit strength domains of running bond, English bond and herringbone bond masonry are obtained with different orientations of the mortar bed joints with respect to the principal directions of the average stress. The effects of different brick geometries are analyzed and comparisons between strength properties of different masonry patterns are made.
Authors: Manfred Schneider, Günter Gottstein, L. Löchte, Jürgen Hirsch
Authors: Jürgen Hirsch, Kai F. Karhausen, L. Löchte
Authors: Takayuki Koda, Tetsuya Matsuda
Abstract: In this study, the elastic-viscoplastic properties of aluminum honeycomb sandwich panels are investigated using a homogenization theory for free edge analysis. For this, the mathematical homogenization theory is reconstructed for elastic-viscoplastic analysis of honeycomb sandwich panels by introducing a traction free boundary condition. Moreover, the domain of analysis is reduced to a quarter using point-symmetry of internal structures of honeycomb sandwich panels. The present method is then applied to the analysis of macroscopic elastic-viscoplastic behavior and microscopic stress distribution of an aluminum honeycomb sandwich panel subjected to in-plane uniaxial compression. It is shown that the stress concentration arises at face/core interfaces, especially at intersections of core walls.
Authors: Bahattin Kimence, Samed Demirkan, Hale Ergun
Abstract: The aim of this study is to investigate the effect of mortar/unit thickness ratio and unit configuration on the masonry wall behaviour and on masonry structure modelling. Firstly, five wall models with different mortar/unit thickness ratios and with different sizes of units are micro-modelled by using SAP2000 software. The results of these walls are used to obtain the material properties of anisotropic macro-models in vertical and horizontal directions. Secondly, a sample unreinforced masonry structure is simulated by the same software using anisotropic material properties. Earthquake loading is applied following the Turkish seismic code. Responses of these five structure models are compared with each other and also with their isotropic modelled counterparts. It is observed that isotropic modelling overestimates the rigidity of the structure around 3-5% for low mortar/unit thickness ratios, but underestimates the rigidity around 5-7% for high mortar/unit thickness ratios
Authors: Vit Šmilauer, František Škvára, Jiří Němeček, Lubomír Kopecký, Petr Hlaváček
Abstract: Research of alkali-activated materials has been a traditional domain of chemists. This paper exploits contribution of micromechanics to the subject. A new model for volumetric evolution of chemical phases is formulated. The first homogenization level identifies elasticity on the scale of N-A-S-H gel. Nanoindentation sensing technique yielded the intrinsic Young's modulus of N-A-S-H gel as ~18 GPa, which was further downscaled to the solid gel particles. Percolation theory had to be introduced to match an early-age elasticity. The second homogenization level takes into account an unreacted fly ash. Homogenization models match well the experimental elasticity and demonstrate stiffening of N-A-S-H gel, induced by increasing packing density of the solid gel particles. The percolation model explains a long setting time of alkali-activated materials.
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