Abstract
The feasibility for utilizing transparent filament-resin composites for photoelastic stress analysis was investigated. Satisfactory photoelastic stress patterns were demonstrated in simple models with undirectional and bidirectional fiber orientations. A stress-optic law was formulated, based on the concept that the birefringence components contributed by each component of plane stress are combined according to a Mohr circle of birefringence. Applying this concept, the difference of the physical and optical principal directions was accounted for, and a general method of photoelastic solution for the plane-stress problem in orthotropic sheets was developed. The method of analysis is little more complex than the well-known procedures for isotropic materials, but at least three experimental measurements are required to characterize the optical response of the material to plane stress.
Partial confirmation of the proposed stress-optic law was obtained by comparison of the theory to limited experimental data obtained in uniaxial-stress samples. It remains to establish a more positive verification by experiments in a variety of biaxial-stress conditions.
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Abbreviations
- f :
-
stress-fringe value, psi-in./fringe
- h :
-
sheet thickness, in.
- n :
-
fringe order
- N :
-
observed fringe order per unit thickness, fringes/in.
- N x.y,xy :
-
fiber-axis-component birefringence, fringes/in.
- N p,q :
-
principal-axis-component birefringence, fringes in.
- p :
-
major principal stress, psi
- q :
-
minor principal stress, psi
- x :
-
fiber longitudinal axis
- y :
-
fiber lateral axis
- σ:
-
normal stress, psi
- τ:
-
shear stress, psi
- θ:
-
stress isoclinic parameter
- θ′:
-
optical isoclinic parameter
References
Dally, J. W. andRiley, W. F., Experimental Stress Analysis, McGraw-Hill, New York, N. Y., 165–167, (1965).
Timoshenko, S., Theory of Elasticity, McGraw-Hill, New York, N. Y., 16, (1934).
Pih, H. andKnight, C. E., “Photoelastic Analysis of Anisotropic Fiber Reinforced Composites,”Jnl. Compos. Mater. 3 (1),94–107, (1969).
Frocht, M. M., Photoelasticity,1,Chapt. 8,John Wiley & Sons,New York, N. Y. (1941).
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Sampson, R.C. A stress-optic law for photoelastic analysis of orthotropic composites. Experimental Mechanics 10, 210–215 (1970). https://doi.org/10.1007/BF02324034
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DOI: https://doi.org/10.1007/BF02324034