Experimental Mechanics

, Volume 14, Issue 7, pp 274–280 | Cite as

The use of a high-modulus-inclusion gage in nonlinear viscoelastic materials

The photoelastic rigid-inclusion gage has been developed for measuring stress in composite propellants. The response of the gage is independent of the modulus of the host materials
  • H. J. Buswell
  • D. R. Moore
  • A. Owens
Article
Received:
Revised:

Abstract

The behavior of an inclusion in a host material subjected to a stress system depends primarily on the ratio of the tangent moduli,E inclusion/E host. An inclusion of suitable material used in the form of a gage will give an identifiable photoelastic-fringe pattern. This pattern is related to the applied biaxial stresses in the diametral plane of the gage, and is independent of the actual modulus and strains in the host material provided that the moduli ratio is more than 300.

A program of work has been carried out to verify the use of such an inclusion gage in low-modulus nonlinear viscoelastic materials. The gage geometry used in this work consisted of a hollow cylinder of birefringent material with a ratio of outside diameter to inside diameter of 5 to 1. The host materials were either unfilled or highly filled carboxyl-terminated polybutadiene rubbers. The moduli ratios for both host materials were such that the gages act as rigid inclusions.

A theoretical study has also been conducted to find the optimum measuring points within the gage and the fringe patterns created by selected biaxial-stress ratios. The study also showed that the gage sensitivity is virtually independent of Poisson's ratio but depends on the biaxial ratio of the stresses.

The values of the sensitivity factor obtained experimentally were close to those derived theoretically. The stressfringe order at the optimum measuring points was obtained by Tardy compensation, and the biaxial-stress ratio determined either from fringe-pattern recognition or by measuring points.

Future applications and uses of such a stress-measuring technique will be described.

Keywords

Host Material Fringe Pattern Polybutadiene Tangent Modulus Rigid Inclusion 
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

internal radius of gage

b

external radius of gage

E

tangent modulus

EUFO

equivalent uniaxial fringe order at 45-deg OMP

k

ratio of principal stresses=Q/P

N

gage sensitivity

No

gage sensitivity whenk=0 using 45-deg OMP

OMP

optimum measuring point

P

major principal stress in host in plane of gage

Q

minor principal stress in host in plane of gage

θ

angular measurement in degrees from direction ofP

Sign Convention

-ve

compresion

+ve

tension

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References

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Copyright information

© Society for Experimental Mechanics, Inc. 1974

Authors and Affiliations

  • H. J. Buswell
    • 1
  • D. R. Moore
    • 2
  • A. Owens
    • 2
  1. 1.Rocket Propulsion EstablishmentAylesburyEngland
  2. 2.Stress Engineering Services Ltd.SheffieldEngland

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