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Research in Nondestructive Evaluation

, Volume 8, Issue 2, pp 101–123 | Cite as

Stress-wave displacement polarizations and aftenuation in unidirectional composites: Theory and experiment

  • B. Vandenbossche
  • R. D. Kriz
  • T. Oshima
Article

Abstract

The wave propagation mechanism of changes in displacement polarizations was studied in unidirectional graphite/epoxy composite materials. Change in Displacements can be large enough to cause a transition in the mode or displacement polarizations from longitudinal to transverse. These unusual mode transitions are a result of the peculiar elastic anisotropy observed in only a few crystals and unidirectional graphite/epoxy composities at high-fiber volume fractions Theoretical calculation of these mode transitions were compared with experimental measurements Mode transitions occur when the wave vector orientation is varied from 51.9° to 74.4° in unidirectional samples of T300/5208 graphite/epoxy composite with a 0.6°-fiber volume fraction. Energy flux deviation and particle displacement directions and amplitudes also were compared with theory. To show this mode transition, an attenuation study was performed. The attenuation coefficient, measured in units of reciprocal time, does not appear to depend on the wave vector orientation and the wave type (quasi-transverse and quasi-longitudinal waves) at 5-MHZ frequency. But the attenuation coefficient, expressed in units of reciprocal length, does depend on the wave type and the wave vector orientation because the wave velocity is included in the calculation of this coefficient. Previous studies have focused on how anisotropy and attenuation influence the stress wave speed (eigenvalues), but in this study we focused more on how the same parameters influence the displacement polarizations (eigenvectors) of the same propagating waves. Because eigenvalues and their corresponding eigenvectors are both solutions of the same eigenvalue problem, more attention should be given to measurement of the eigenvectors.

Keywords

Mode Transition Particle Displacement Unidirectional Composite Displacement Polarization Displacement Deviation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of Symbols

Ei

Young’s moduli

Gij

shear moduli

vij

Poisson’s ratios

Cij

elastic-stiffness coefficients

Cijkl

fourth-rank elastic-stiffness tensor

nj

normalized wave vector (vector perpendicular to the plane wave)

p

mass density

δij

Kronecker delta function

v

phase velocity

wi

normalized particle displacement direction

Ji

energy flux vector

σij

stress tensor

Uj

particle displacement velocity

UI

incident wave of particle displacement amplitude

UQL

quasi-longitudinal wave of particle displacement amplitude

UQT

quasi-transverse wave of particle displacement amplitude

UT

pure transverse of particle displacement amplitude

αt

attenuation coefficients ins −1

αl

attenuation coefficients in l−1

A0

maximum amplitude

QLL (θ)

longitudinal component of quais-longitudinal wave at θ

QLT(θ)

transverse component of quasi-longitudinal wave at θ

QTL(θ)

longitudinal component of quasi-transverse wave at θ

QTT(θ)

transverse component of quasi-transverse wave at θ

θmt

wave vector orientation corresponding to mode transition

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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • B. Vandenbossche
    • 1
  • R. D. Kriz
    • 1
  • T. Oshima
    • 2
  1. 1.Department of Engineering Science and MechanicsVirginia Polytechnic Institute and State UniversityBlacksburgUSA
  2. 2.College of EngineeringKitami Institute of TechnologyKitami City, HokkaidoJapan

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