Time-dependent optical characterization in the photoviscoelastic study of stress-wave propagation

Dynamic photoviscoelastic analysis requires the time and temperature dependency of the material to be taken into account. Mechanical relaxation processes have generally been incorporated in dynamic analysis, but there has been no widespread application of optical relaxation or creep functions over the complete time spectrum in photomechanics of birefringent polymers. Using material characterizations previously developed, this study compares a theoretical viscoelastic solution and its predicted fringe pattern for stresswave propagation in a thin rod of polyurethan material (Solithane 113) with the photoviscoelastic data from a similar experimental arrangement. The agreement demonstrates both the validity and general necessity of such an approach for the time-domain characteristic of wave-propagation phenomena in low-modulus polymers.