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The effect of environmental-loading history on longitudinal strength of glass-fiber reinforced plastics

  • O. Ishai
  • A. Mazor

Abstract

The main difficulty in dealing with the present subject lies in formulating and classifying the variables. Most cases of a structural element exposed to an external environment involve at least three simultaneous time varying factors — temperature, humidity and load — which, in view of the coupling between them and their interactive effect on the material, do not lend themselves to simple isolation or superposition.

List of symbols and abbreviations

a

Water content.

c

Crack or flaw dimension, perpendicular to tensile stress direction.

Cm, Cf

Matrix and fiber volume contents respectively.

α

Coefficient of thermal expansion.

αi

Ratio of initial failure stress to the ultimate reference one.

γ

Specific surface energy.

γd

Specific surface energy of dry glass surface.

γw

Specific surface energy of wet glass surface (by water adsorbtion).

E

Tensile Youngs modulus.

Ef

Fiber Youngs modulus.

Em

Matrix Youngs modulus.

m

Modular ratio.

l, Δl

Length and change of length respectively.

W, ΔW

Weight and change of weight respectively.

t

Time.

T

Temperature.

σ

Tensile stress.

σu

Ultimate tensile stress.

σ0u

Ultimate tensile stress of specimens stored and tested at reference environmental conditions (22 °C, 50% R.H.).

σH

Tensile stress applied during environmental-loading history.

σHu

Current tensile strength of specimens tested at their E.L.H. conditions.

σHu

Initial failure tensile stress, determined by onset of R.L.S. reduction.

σdu

Tensile strength of specimens at dry environment.

σwu

Tensile strength of specimens at humid, environment.

σuc

Composite strength.

σuf, σum

Fiber and matrix strength respectively.

ϱ

Density.

L

Loading condition.

W

Cold water environment (R.T.)

T

Dry hot environment (80 °C).

W+ T.

Hot water environment (80 °C).

W+L

Loading at cold water environment (R.T.).

W + L+ T

Loading at hot water environment (80 °C).

E.L.H.

Environmental loading history.

G.R.P.

Glass reinforced plastics.

C.L.S.

Current longitudinal strength.

R.L.S.

Residual longitudinal strength.

U.D.F.

Unidirectional fabric laminate.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1975

Authors and Affiliations

  • O. Ishai
    • 1
  • A. Mazor
    • 1
    • 2
  1. 1.Abteilung für Technische MechanikTechnion HaifaIsrael
  2. 2.Dept. of MechanicsTechnion HaifaIsrael

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