On the role of material and optical properties in complete photoelastic analysis

Consideration of the laws of elasticity and optics allows the classification of photoelastic materials into several categories. Two types of photoelastic materials are studied experimentally in compressible and incompressible forms to decide in which category they belong. Two epoxies and three polyurethane rubbers are reported. Both epoxies were calibrated for their response to frozen stress, and one under live load. The rubbers were all calibrated under live load at ambient temperature. The results support an earlier hypothesis that the photoelastic response of incompressible materials is strain sensitive and cannot be used directly in the general three-dimensional case to determine normal stress without additional data.