Abstract
Polycarbonate resin possesses optical and mechanical properties which make it particularly suitable for certain experimental investigations, including two-and three-dimensional photoelastic analysis. The ductility and transparency of this material might be usefully employed in photomechanical investigations of plastic and viscoelastic response. The similarity of the stress-strain law of polycarbonate to that of mild steel could simplify the similitude problem. In addition, its spectral transmittance in visible and infrared makes polycarbonate useful for studies of material properties and structure.
The optical creep of polycarbonate is respresented by a normalized creep coefficient. The relationship of this factor to the theory of viscoelasticity is discussed, and the conditions for a valid calibration of birefringent materials are reviewed. The wavelength dependence of relative retardation is represented by the normalized retardation, from which the dispersion of birefringence can be deduced.
The stress-birefringence-time-wavelength characteristics of two brands of polycarbonate resin were determined. Because of residual birefringence, it was necessary to heat treat the resin at about 146°C, and properties of both annealed and unannealed resins are presented. Retardation was measured over the visible and near-infrared portions of the electromagnetic spectrum (407 nm to 1900 nm). There exists a definite relationship between dispersion of birefringence, which amounts to 14 percent in visible, and the infrared spectral transmittance, which is indicative of material structure.
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Abbreviations
- m :
-
isochromatic order
- σ:
-
normal stress
- d :
-
thickness of photoelastic model
- λ:
-
wavelength of radiation
- C σ :
-
stress-optic coefficient\(m\lambda /\left( {\sigma _1 - \sigma _2 } \right)d\)
- t :
-
time
- r λ :
-
normalized retardation
- r t :
-
normalized creep
- α(t):
-
stress-birefringence compliance
- R :
-
relative retardation =mλ
References
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Cloud, G.L. Mechanical-optical properties of polycarbonate resin and some relations with material structure. Experimental Mechanics 9, 489–499 (1969). https://doi.org/10.1007/BF02319692
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DOI: https://doi.org/10.1007/BF02319692