Fiber-reinforced Medium Research Articles

Dynamic response of normal moving load on an irregular fiber-reinforced half-space

Studying the problem of a moving load causing fracture is used in the interpretation analysis of geophysical fracture. This paper aims to study the stress produced in an irregular fiber-reinforced half-space due to a normal moving load on a free surface. The stress produced in this case has been obtained in a closed form. Three different cases of irregularity, viz. rectangular, parabolic and no irregularity, have been discussed and compared. The effects of depth, irregularity factor and maximum irregularity depth on stress have been investigated. Also, the stress produced from a normal moving load in an irregular isotropic half-space has been deduced as a special case of the problem and comparative study has been made with that of fiber-reinforced medium. Moreover, some important peculiarities have been depicted with the use of graphs.

Effect of Heterogeneity and Reinforcement on Propagation of a Crack due to Shear Waves

This paper investigates the effect of reinforcement and nonhomogeneity on the propagation of cracks caused by horizontally polarized shear waves in a heterogeneous fiber-reinforced medium. The effects of reinforcement and heterogeneity on the propagation of the crack are highlighted in this study. The stress intensity factor at the crack tip for a concentrated force of a constant intensity has been calculated and depicted by means of graphs for various cases. It is observed that fiber reinforcement and heterogeneity parameters decrease the stress intensity factor. Remarkably, the stress intensity factor decreases with the increase in the length and speed of the crack. Also, a comparative study was made for the stress intensity factor in reinforced medium over reinforced-free medium and heterogeneous medium over the homogeneous medium. Moreover, some important peculiarities were observed in graphs.

2D problem of magneto-thermoelasticity fiber-reinforced medium under temperature dependent properties with three-phase-lag model

The aim of the present work is to investigate the influence of magnetic field on wave propagation within a fiber-reinforced medium under the three-phase-lag theory and Green–Naghdi theory without energy dissipation. The modulus of the elasticity is given as a linear function of the reference temperature. The exact expression for the displacement components, temperature, and stress components are obtained by using normal mode analysis. Numerical results for the field quantities are given in the physical domain and illustrated graphically in the absence and presence of magnetic field. Comparisons are made between the results for the two different theories with and without temperature dependent properties as well as reinforcement. The results are a valuable contribution to the problem of practical design of such structures, for example to design stiffness, damping and so on into the right place of a structure by selecting the appropriate material properties.

English

The objective of this paper is to investigate the surface waves in fibre-reinforced anisotropic elastic medium subjected to gravity field. The theory of generalized surface waves has firstly developed and then it has been employed to investigate particular cases of waves, viz., Stoneley waves, Rayleigh waves and Love waves. The analytical expressions for waves velocity and attenuation coefficient are obtained in the physical domain by using the harmonic vibrations. The wave velocity equations have been obtained in different cases. The numerical results are given and presented graphically. Comparison was made with the results obtained in the presence and absence of gravity and parameters for fibre-reinforced of the material medium. The results indicate that the effect of gravity and parameters of fibre-reinforced of the material medium are very pronounced. Key words: Fibre-reinforced media, surface waves, Stoneley waves, Rayleigh waves, Love waves, gravity.

Two-dimensional problem of a fibre-reinforced anisotropic thermoelastic medium. Comparison with the Green–Naghdi theory

The propagation of plane waves in fibre-reinforced, anisotropic, elastic media is discussed. The theory of generalized thermoelasticity proposed by Green and Naghdi is used to solve the problem. Normal mode analysis is used to obtain analytical expressions of the displacement components, stresses, and temperature distribution. Numerical results for the temperature distribution, displacement components, and thermal stress are given and illustrated graphically. Comparisons are made with the results predicted by the Green–Naghdi theory, types II and III, in the presence and absence of fibre-reinforced media.

Homogenization of high-contrast two-phase conductivities perturbed by a magnetic field. Comparison between dimension two and dimension three

Homogenized laws for sequences of high-contrast two-phase non-symmetric conductivities perturbed by a parameter h are derived in two and three dimensions. The parameter h characterizes the antisymmetric part of the conductivity for an idealized model of a conductor in the presence of a magnetic field. In dimension two an extension of the Dykhne transformation to non-periodic high conductivities permits to prove that the homogenized conductivity depends on h through some homogenized matrix-valued function obtained in the absence of a magnetic field. This result is improved in the periodic framework thanks to an alternative approach, and illustrated by a cross-like thin structure. Using other tools, a fiber-reinforced medium in dimension three provides a quite different homogenized conductivity.

Reflection of quasi-P and quasi-SV waves at the free and rigid boundaries of a fibre-reinforced medium

The propagation of plane waves in fibre-reinforced media is discussed. The expressions of phase velocities of quasi-P (qP) and quasi-SV (qSV) waves propagating in plane symmetry are obtained in terms of propagation vectors. We have established a relation from which the displacement vector can be obtained in terms of the propagation vector. Expressions for the reflection coefficients of qP and qSV waves are obtained. Numerical results of reflection coefficients are obtained and presented graphically. The partition of energy between qP and qSV waves reflected on free and rigid boundaries due to incident qP and qSV waves are also obtained and presented graphically.

Homogenization¶of Non-Uniformly Bounded Operators:¶Critical Barrier for Nonlocal Effects

This paper deals with the homogenization of a class of highly oscillating monotonic operators which are uniformly elliptic but non-uniformly bounded. We determine an asymptotic barrier below which we obtain a classical behaviour and above which nonlocal effects appear. We also prove that this condition is optimal in the case of a fibre-reinforced medium.

Non-local effective relations for fibre-reinforced composites loaded by configuration-dependent body forces

In this paper, fibre-reinforced media are analysed. The distribution of the fibres is assumed random. A combination of deterministic and configuration-dependent body forces is considered. In this case, several non-local effective constitutive operators must be taken into account in order to define the mean response of the material. For two phase composites, expressions for all these operators have been obtained and in the case of fibre-reinforced materials Hashin–Shtrikman type bounds are explicitly developed in the real and the Fourier space. Finally, a periodic distribution of fibres is studied as an example.

A study of wave motion in fiber-reinforced medium

Measurements, both macroscopic and microscopic, of longitudinal wave motions propagating in the direction of reinforcing fibers were made on laboratory fabricated fiber-reinforced composites. Two waves with different propagation speeds and amplitudes were observed. Results are in good agreement with the predictions based on the mixture theory and the effective stiffness theory.

Wave Propagation and Parametric Instability in Materials Reinforced by Fibers With Periodically Varying Directions

This paper concerns the propagation of plane harmonic waves in an infinite fiber-reinforced elastic medium. The composite material is represented by an equivalent homogeneous transversely isotropic matter whose preferred directions coincide with the orientations of the fibers. The fibers are assumed to wobble periodically about a dominant direction, all fibers being parallel to each other. This wobbliness endows the material with a structural periodicity which generates dispersion at all frequencies and instability for various frequency bands. The zones of instability are analyzed in some detail.

A superimposed mixture theory for wave propagation in a biaxially fiber-reinforced composite

A superimposed mixture theory is constructed for a biaxially fiber-reinforced medium composed of fiber-reinforced materials in alternating layers in which the angle of reinforcement alternates from layer to layer. In this theory every one of the two constituents of each layer has its own motion but is allowed to interact with the other. In addition, the layering microstructure is taken into account by allowing interactions between the layers via the interface shear stresses. For the resulting system, the eight coupled equations of motion for every constituent in each layer are derived and then used to investigate the response of the composite material under time-dependent loadings.

Dynamic Equivalence of Composite Material and Eigenstrain Problems

The variational method is employed for determining the displacement mode shapes and dispersion relations for the problem of plane time-harmonic waves propagating through an infinitely extended, periodically arranged composite material. Numerical results are obtained for the special cases of laminated and fiber-reinforced media. Using variational formulation, the composite problem is compared with the problem of a homogeneous material subjected to eigenstrain and body forces. Necessary conditions are developed for the dynamic equivalency of the two problems. Distributions of eigenstrain are shown which yield the same displacement solutions as the problem of a transverse wave propagating normal to the layers of a laminated media.