Inert failure strain studies of sodium silicate glass fibers

Abstract The inert failure strains of glass fibers with the molar compositions x Na 2 O · (1 − x )SiO 2 , where 0 ⩽ x ⩽ 0.35, were measured under liquid nitrogen (77 K) using a two-point bending technique. Failure strain increases with increasing Na 2 O content, from 17.7% for x = 0.00–23.5% for x = 0.35. The inert failure strain depends on the face-plate velocity ( V fp ) of the two-point bending test, increasing with increasing V fp for silica and decreasing with increasing V fp for the sodium silicate glasses. The magnitude of the latter ‘inert delayed failure effect’ increases with increasing x . The addition of Na 2 O to a silicate glass weakens the glass network through the formation of non-bridging oxygens, and the weaker network distorts more at high strains and slower V fp .