Critical Study of the Optical and Mechanical Properties of Glass Fibers

The cooling rate for fine glass fibers in the 6–16 μ diameter range has been calculated by means of a new cooling equation. Typical strength vs diameter data are compared with the ratio of quenching time to the Maxwell relaxation; ts/τ. Strength increases rapidly for ts/τ ≤ 1.0 and τ is most probably of the order 10−4 sec at 1100°C. The refractive index decreases slightly in the critical region but the change does not indicate a significant rise in the fictive with increased quenching. For this reason structural changes are considered of secondary importance as a factor contributing to high strength. New strength measurements of glass fibers fit a distribution law with reasonable accuracy. It is therefore concluded that the flaw theory of high strength is valid. The influence of ``hydrostatic'' cooling upon flaw generation is discussed.