CHARACTERIZATION OF MECHANICAL AND OPTICAL PROPERTIES OF RHEO-OPTICALLY SIMPLE MATERIALS.

Classical photoelasticity can be extended to analyze the stress-strain fields in viscoelastic materials. In this photoviscoelastic analysis, it is necessary to record and approximate with mathematical formulae a complete time history of the mechanical and optical characteristic properties of the viscoelastic materials. A new procedure, where the nonlinear minimization technique ″SUMT″ was utilized, was proposed to approximate those properties with Prony series representations. This procedure has been proved to be very rigorous and effective by applying it to two polymers, polyurethane elastomer and epoxy resin. Furthermore, it was considered appropriate to regard these two polymers as rheo-optically simple materials. Thus, their mechanical and optical behaviors were linear and the principle of reduced time (or time-temperature superposition principle) could be applied well.