فهرست مقالات Scale analysis

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  1 - Multiscale Analysis of Transverse Cracking in Cross-Ply Laminated Beams Using the Layerwise Theory
  W Jin Na J.N Reddy
  A finite element model based on the layerwise theory is developed for the analysis of transverse cracking in cross-ply laminated beams. The numerical model is developed using the layerwise theory of Reddy, and the von Kármán type nonlinear strain field is چکیده کامل

  A finite element model based on the layerwise theory is developed for the analysis of transverse cracking in cross-ply laminated beams. The numerical model is developed using the layerwise theory of Reddy, and the von Kármán type nonlinear strain field is adopted to accommodate the moderately large rotations of the beam. The finite element beam model is verified by comparing the present numerical solutions with the elasticity solutions available in the literature; an excellent agreement is found. The layerwise beam model is then used to investigate the influence of transverse cracks on material properties and the response in cross-ply laminates using a multiscale approach. The multiscale analysis consists of numerical simulations at two different length scales. In the first scale, a mesoscale, a systematic procedure to quantify the stiffness reduction in the cracked ply is proposed exploiting the laminate theory. In the second scale, a macroscale, continuum damage mechanics approach is used to compute homogenized material properties for a unit cell, and the effective material properties of the cracked ply are extracted by the laminate theory. In the macroscale analysis, a beam structure under a bending load is simulated using the homogenized material properties in the layerwise finite element beam model. The stress redistribution in the beam according to the multiplication of transverse cracks is taken into account and a prediction of sequential matrix cracking is presented. پرونده مقاله
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  2 - A New Mathematical Model for Permeability of Composites
  M.M Shahmardan M Nazari M Khaksar M Khatib
  Study of permeability of Fibrous Composites is important in several natural and industrial processes in mechanical engineering. In this study, a comprehensive mathematical model is presented for calculation of normal permeability of ordered elliptical fibrous media. An چکیده کامل

  Study of permeability of Fibrous Composites is important in several natural and industrial processes in mechanical engineering. In this study, a comprehensive mathematical model is presented for calculation of normal permeability of ordered elliptical fibrous media. An innovative scale-analysis technique is employed for determining the normal permeability of elliptical fibrous media. In this technique, the permeability is related to the porosity, elliptical fiber diameters, and tortuosity of the medium. In other word, the normal permeability of the circular fibrous structures, which presented in the literature, is extended to the general case of elliptical fibrous media. The composite material is represented by a “unit cell” which is assumed to be repeated throughout the media. A closed-form relation is obtained for non-dimensional permeability using scale analysis approach. Due to lack of experimental data for permeability of fibrous porous media (composite media), with elliptical cross section, a numerical analysis is also employed. The governing equations are solved numerically in the unit cells using finite volume method. The results obtained by numerical solution are compared with those presented by scale analysis method. The presented relation for normal permeability can suitably cover the case of fibrous media with circular cross section. The results are also compared with those presented in the literature for the case of cylindrical fibers. The developed compact relationships are successfully verified through comparison with the present experimental results and the data reported by others. پرونده مقاله
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  3 - Normal and Parallel Permeability of Preform Composite Materials used in Liquid Molding Processes: Analytical Solution
  M Nazari M.M Shahmardan M Khaksar M Khatib S Mosayebi
  The permeability of the preform composite materials used in liquid molding processes such as resin transfer molding and structural reaction injection molding is a complex function of weave pattern and packing characteristics. The development of tools for predicting perm چکیده کامل

  The permeability of the preform composite materials used in liquid molding processes such as resin transfer molding and structural reaction injection molding is a complex function of weave pattern and packing characteristics. The development of tools for predicting permeability as a function of these parameters is of great industrial importance. Such capability would speed process design and optimization and provide a step towards establishing processing-performance relations. In this study, both normal and parallel permeability of fibrous media comprised of ordered arrays of elliptical cylinders is studied analytically. A novel scale analysis technique is employed for determining the normal permeability of arrays of elliptical fibers. In this technique, the permeability is related to the geometrical parameters such as porosity, elliptical fiber diameters, and the tortuosity of the medium. Following a unit cell approach, compact relationships are proposed for the first time for the normal permeability of the studied geometries. A comprehensive analysis is also performed to determine the permeability of ordered arrays of elliptical fibers over a wide range of porosity and fiber diameters. The developed compact relationship is successfully verified through comparison with the present results. As a result of assuming an elliptical cross section for the fibers in this analytical analysis, an extra parameter comes to play; therefore, the present analytical solution will be more complicated than those developed for circular fiber type in the literature. پرونده مقاله