Room temperature viscosity and delayed elasticity in infrared glass fiber

Infrared transparent optical fibers from the Te–As–Se system (TAS) exhibit a viscoelastic behavior at room temperature. The study of the change of the radius of curvature of fibers, once the fibers are unrolled from the mandrel onto which they were rolled just after fiber-drawing, allows the determination of constitutive laws both for the stress relaxation kinetics and for the delayed elasticity process. Whereas, a linear Burger's model provides a good modelling of the stress relaxation stage, a stretched exponential function gives a better description for the delayed elasticity behavior. The room temperature viscosity of the fibers ranges from 3 × 1016 to 2 × 1017 Pa s and the time constant of the anelastic strain recovery process is from 4 to 15 days.