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Experimental Mechanics

, Volume 19, Issue 2, pp 41–49 | Cite as

Elastic moduli of transversely isotropic graphite fibers and their composites

Equations used to calculate the complete set of elastic transversely isotropic properties for unidirectional fiber-reinforced materials having transversely isotropic fibers are experimentally verified by using improved ultrasonic techniques
  • R. D. Kriz
  • W. W. Stinchcomb
Article

Abstract

This paper demonstrates that it is possible to calculate the complete set of elastic mechanical properties for graphite-epoxy fiber-reinforced materials at any fiber-volume fraction by modifying equations previously developed to include transversely isotropic graphite-fiber properties. Experimental verification of the modified equations is demonstrated by using these equations to curve fit elastic-property data obtained ultrasonically over a range of fiber-volume fractions. Material systems under consideration are T300/5208, AS-3501 and Modomor II/LY558 graphite epoxy. Using the modified equations it is possible to extrapolate for fiber properties. From Modomor II/LY558 ultrasonic data, it is shown that five out of seven extrapolated graphite-fiber properties are consistent with the assumption that graphite fibers are transversely isotropic. Elastic properties for T300/5208 and AS-3501 are ultrasonically evaluated by propagating stress waves through six individual specimens but at various angles from a block of unidirectional material. Particular attention is devoted to specimen dimensions. To demonstrate the need for accurately calculating or experimentally measuring all lamina elastic properties, a brief discussion is included on the effect that variations in lamina elastic properties have on calculating interlaminar stresses.

Keywords

Epoxy Fluid Dynamics Elastic Property Stress Wave Experimental Verification 
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

A

unidirectional block dimensions, m

Cij

material stiffnesses, contracted notation (i,j=1,2,3,4,5,6), Pa

ci

wave-phase speeds (i=1,2,3), m/s

D

transducer diameter, m

Ei

Young's moduli along lamina coordinates (i=1,2,3), Pa

Eb

matrix Young's modulus, Pa

EfL

fiber longitudinal Young's modulus, Pa

EfT

fiber Young's modulus in the transverse plane, Pa

Gij

shear moduli in the laminai-j plane (i,j=1,2,3), Pa

Gb

matrix shear modulus, Pa

GfLT

fiber shear modulus in the longitudinal-transverse plane, Pa

GfTT

fiber shear modulus in the transverse plane, Pa

Kb

matrix plane-strain bulk modulus, Pa

KfTT

fiber plane-strain bulk modulus, Pa

L

specimen length, m

M

margin, m

QL

quasi-longitudinal wave

QT

quasi-transverse wave

S

time separatingQL andQT waves, s

Tmax

specimen thickness necessary to separateQL andQT waves, m

Tmin

specimen thickness satisfying energy-flux requirements, m

b

matrix-volume fraction

Vf

fiber-volume fraction

W

transmitted pulse width, s

θ

angular deviation of energy flow from the wave normal, deg

νb

matrix Poisson's ratio

νfLT

fiber Poisson's ratio in the longitudinal-transverse plane

νfTT

fiber Poisson's ratio in the transverse plane

ϱ

lamina mass density, kg/m3 (N-sec2/m4)

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References

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Copyright information

© Society for Experimental Mechanics, Inc. 1979

Authors and Affiliations

  • R. D. Kriz
    • 1
  • W. W. Stinchcomb
    • 1
  1. 1.Department of Engineering Science and MechanicsVirginia Polytechnic Institute and State UniversityBlacksburg

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