Influence of the fiber drawing process on mechanical and vibrational properties of sol-gel silica glass

The influence of fiber drawing on mechanical and vibrational properties of RE-doped sol-gel silica is disclosed by a comparison of bulk silica, before and after the melting process, and fibers. The mechanical characterization is carried out by nanoindentation technique: hardness and elastic modulus are found to be consistent with those of Corning 7980 reference glass, and related to the elasto-plastic behavior of the glassy material. Our results evidence an increase of the resistance of fibers to fracture under an applied load, ascribed to drawing-induced residual stresses. Their impact on sol-gel silica mechanical properties is further disclosed by complementary vibrational characterization by Raman and FTIR spectroscopies, confirming the occurrence of a modification of the structural features after the drawing process and of residual stresses in the fibers. The overall results highlight the role of the fiber drawing in improving the glass mechanical properties, causing a slight rearrangement of the silica structure.