The Elastoplastic Behavior of a Class of Two-Phase Composites Containing Rigid Inclusions

1994 ◽  
Vol 47 (1S) ◽  
pp. S45-S65 ◽  
Author(s):  
A. Bhattacharyya ◽  
G. J. Weng
Keyword(s):  
Aspect Ratio ◽  
Transversely Isotropic ◽  
Theoretical Principle ◽  
Transverse Loading ◽  
Random Orientation ◽  
Two Phase ◽  
Elastoplastic Behavior ◽  
Isotropic Composite ◽  
Wide Range

The theoretical principle for the determination of the overall elastoplastic behavior for three types of two-phase composites reinforced with rigid spheroidal inclusions is established. In the first type the inclusions are aligned unidirectionally (1-D) whereas in the second type they are randomly oriented on a plane (2-D), both leading to transversely isotropic composites. The third type of composite involves a 3-D random orientation leading to a globally isotropic material. The theory is based on the energy approach recently proposed by Qiu and Weng (1992) and, while intended only for a modest concentration of inclusions, it can cover a wide range of inclusion shapes, from discs to spheres and all the way to needles (or fibers). It is shown, among others, that the axial response of the 1-D composite is the strongest when reinforced with fibers whereas discs provide the strongest reinforcement under the transverse loading. The outcome is reversed for the 2-D composite. As a consequence of a uniform boundary displacement, the 3-D isotropic composite reinforced with the extreme shapes of rigid needles (aspect ratio → ∞) or discs (aspect ratio → 0) turns out to be also ideally rigid with the entire external stress being carried by the rigid inclusions. For other inclusion shapes, the elastoplastic behavior with prolate inclusions are almost always stiffer as compared to those with oblate shapes with a reciprocal aspect ratio. The asymptotic moduli of the two-phase composites containing the two extreme inclusion shapes are given in terms of the disc and needle density parameters, and the overall elastoplastic behavior for the three different microgeometries are also given as a function of these parameters.

scholarly journals Strength Analysis of Alternative Airframe Layouts of Regional Aircraft on the Basis of Automated Parametrical Models

Aerospace ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 80
Author(s):  
Dmitry V. Vedernikov ◽  
Alexander N. Shanygin ◽  
Yury S. Mirgorodsky ◽  
Mikhail D. Levchenkov
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Performance ◽  
Strength Analysis ◽  
Labor Input ◽  
Aerodynamic Loading ◽  
Aspect Ratios ◽  
Wide Range ◽  
Parametrical Design

This publication presents the results of complex parametrical strength investigations of typical wings for regional aircrafts obtained by means of the new version of the four-level algorithm (FLA) with the modified module responsible for the analysis of aerodynamic loading. This version of FLA, as well as a base one, is focused on significant decreasing time and labor input of a complex strength analysis of airframes by using simultaneously different principles of decomposition. The base version includes four-level decomposition of airframe and decomposition of strength tasks. The new one realizes additional decomposition of alternative variants of load cases during the process of determination of critical load cases. Such an algorithm is very suitable for strength analysis and designing airframes of regional aircrafts having a wide range of aerodynamic concepts. Results of validation of the new version of FLA for a high-aspect-ratio wing obtained in this work confirmed high performance of the algorithm in decreasing time and labor input of strength analysis of airframes at the preliminary stages of designing. During parametrical design investigation, some interesting results for strut-braced wings having high aspect ratios were obtained.

Effective Elastic Moduli of Ribbon-Reinforced Composites

1990 ◽  
Vol 57 (1) ◽  
pp. 158-167 ◽  
Author(s):  
Y. H. Zhao ◽  
G. J. Weng
Keyword(s):  
Aspect Ratio ◽  
Elastic Moduli ◽  
Volume Fraction ◽  
Transversely Isotropic ◽  
Isotropic Case ◽  
Effective Elastic Moduli ◽  
Cross Sectional ◽  
Isotropic Composite ◽  
The Matrix ◽  
The Hill

Based on the Eshelby-Mori-Tanaka theory the nine effective elastic constants of an orthotropic composite reinforced with monotonically aligned elliptic cylinders, and the five elastic moduli of a transversely isotropic composite reinforced with two-dimensional randomly-oriented elliptic cylinders, are derived. These moduli are given in terms of the cross-sectional aspect ratio and the volume fraction of the elliptic cylinders. When the aspect ratio approaches zero, the elliptic cylinders exist as thin ribbons, and these moduli are given in very simple, explicit forms as a function of volume fraction. It turns out that, in the transversely isotropic case, the effective elastic moduli of the composite coincide with Hill’s and Hashin’s upper bounds if ribbons are harder than the matrix, and coincide with their lower bounds if ribbons are softer. These results are in direct contrast to those of circular fibers. Since the width of the Hill-Hashin bounds can be very wide when the constituents have high modular ratios, this analysis suggests that the ribbon reinforcement is far more effective than the traditional fiber reinforcement.

Analytical Determination of Viscous Permeability of Fibrous Porous Media

2008 ◽  
Author(s):  
A. Tamayol ◽  
M. Bahrami
Keyword(s):  
Experimental Data ◽  
Aspect Ratio ◽  
Unit Cell ◽  
Analytical Determination ◽  
Fibrous Media ◽  
Wide Range ◽  
Unit Cells ◽  
The Media ◽  
Micro Structures

In this study, the permeability of ordered fibrous media towards normal and parallel flow is determined analytically. In this approach, porous material is represented by a “unit cell” which is assumed to be repeated throughout the media. Several fiber arrangements including: touching and non-touching arrays are considered. Modeling 1D touching fibers as a combination of Channel-like conduits, a compact relationship is proposed to predict permeability. Employing an integral technique and assuming a parabolic velocity profile within the unit cells, analytical relationships are developed for pressure drop for rectangular arrangements. The developed models are successfully compared with existing experimental data collected by others for square arrangement over a wide range of porosity. Due to the random nature of the porous micro structures, determination of exact permeability of real fibrous media is impossible. However, the analyses developed for ordered unit cells enable one to predict the trends observed in experimental data. Moreover, it is shown that the proposed normal flow permeability of square unit cell serves as a lower bound for the permeability of fibrous media. The effects of unit cell aspect ratio and fibers diameter on the permeability are also investigated. It is noted that with an increase in the aspect ratio the normal permeability decreases while, the parallel permeability remains constant. It is also shown that the permeability of fibrous media is related to the diameter of fibers squared.

Investigation of mixed convection and particle dispersion of nanofluids in a vertical duct

2016 ◽  
Vol 230 (20) ◽  
pp. 3691-3705 ◽  
Author(s):  
Farzad Bazdidi-Tehrani ◽  
Mohammad Sedaghatnejad ◽  
Seyed Iman Vasefi ◽  
Naeem Ekrami Jolandan
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Mixed Convection ◽  
Base Fluid ◽  
Particle Dispersion ◽  
Two Phase ◽  
Wide Range ◽  
Centre Region ◽  
Nanoparticles Concentration ◽  
Number Formula

In the present paper, mixed convection of TiO2-water and CuO-water nanofluids in a laminar flow within a vertical rectangular duct is investigated numerically. The two-phase Euler-Lagrange approach is applied to simulate nanoparticles dispersion in the base fluid. Effects of nanoparticles concentration, aspect ratio, buoyancy and Brownian and Thermophoretic forces in a wide range of Richardson number ([Formula: see text]) on the hydrodynamics and thermal parameters are presented and discussed. It is observed that at [Formula: see text], dispersion of nanoparticles in the base fluid improves heat transfer rate more considerably. Whilst an improvement in convective heat transfer of CuO-water nanofluids is shown to be more than 22% at [Formula: see text], it does not exceed 15% at [Formula: see text]. Moreover, at [Formula: see text], particles disperse in the centre region of duct cross section and variation in aspect ratio does not alter the amount of enhancement of heat transfer significantly.

Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part I: Introduction and Details on the Organization of the Program

1986 ◽  
Vol 14 (4) ◽  
pp. 201-218 ◽  
Author(s):  
A. G. Veith
Keyword(s):  
Aspect Ratio ◽  
Comprehensive Evaluation ◽  
Test Method ◽  
Interactive Effects ◽  
Data Analyses ◽  
Main Effect ◽  
Systematic Determination ◽  
Relationship Of ◽  
The Relationship

Abstract This four-part series of papers addresses the problem of systematic determination of the influence of several tire factors on tire treadwear. Both the main effect of each factor and some of their interactive effects are included. The program was also structured to evaluate the influence of some external-to-tire conditions on the relationship of tire factors to treadwear. Part I describes the experimental design used to evaluate the effects on treadwear of generic tire type, aspect ratio, tread pattern (groove or void level), type of pattern (straight rib or block), and tread compound. Construction procedures and precautions used to obtain a valid and functional test method are included. Two guiding principles to be used in the data analyses of Parts II and III are discussed. These are the fractional groove and void concept, to characterize tread pattern geometry, and a demonstration of the equivalence of wear rate for identical compounds on whole tread or multi-section tread tires.

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