Influence of ageing conditions on the mechanical properties of Te-As-Se fibres

Mechanical properties of chalcogenide glass fibres from the system Te-As-Se have been investigated as a function of environment (ageing in air, under vacuum and under static stress) through a series of tensile strength measurements. It is shown that the surface quality has a decisive effect on the tensile strength of the fibre. Surface degradation due to air oxidation induces a noticeable decrease in strength. However, a series of mechanical tests performed on fibres preserved in vacuum indicate that structural relaxation of the chalcogenide glass also plays a preponderant role in the loss of mechanical strength. Indeed the trend in mechanical properties correlates well with calorimetric characterizations performed on these glasses. Finally, it is observed that the application of a long-term static stress along the fibre induces a net increase in the tensile strength. These effects are associated with a partial alignment of the chalcogenide chains present in the glass structure. This is consistent with the observation of a longitudinal permanent deformation of these fibres under static stress.