Elastic moduli of glass fibers drawn under various conditions were measured by a dynamic methods.
(1) The Young's modulus and the resonant frequency of glass fibers increased with increasing of spinning speed, and with decreasing of spinning temperature.
(2) The apparent activation energy for thermal relaxation was 14∼17kcal/mol.
(3) The effect of hydrofluoric acid etching on elastic moduli of glass fibers was studied. On etching the Young's modulus increased rapidly until the surface layer had been removed down to the depth of about 10∼15% of fiber radius. With further etching, however, the Young's modulus increased only slightly.
These results were used to discuss the difference in glass structure between the surface layer and the interior of glass fiber.
