Strength of multi-component glass fibers

The initial strength and degradation of strength in multi-component glass fibers are reported. Plastic-coated glass fibers with an initial strength of 300–350 km/mm² are obtained by excluding the causes of extrinsic origins of fracture; bubbles, small crystals and platinum particles. Degradation of strength is strongly dependent on the glass composition, especially on the network modifier content. The addition of Al₂O₃ and B₂O₃ is useful for suppressing degradation of strength. Multi-component glass fibers which show no degradation of strength for 5000 h under stress-free and atmospheric conditions have been prepared with borosilicate glasses containing 1–5 mol.% Al₂O₃.