Effect of damage by hydroxyl generation on strength of silica fibers

When water diffuses into silica glass, a chemical reaction between the water and the glass damages the ring structure of the glass, causing a reduction in the Young's modulus, a lowering of the intrinsic strength and a reduction in the crack‐growth resistance of the glass. In the absence of swelling of the glass within the water penetrated zone, the damage caused by hydroxyl group generation will have no effect on the strength of the glass fibers, provided the water‐affected surface zone is much thinner than the bulk material. In contrast, swelling stresses within the water penetrated zone at the fiber glass surface will increase the strength of the glass fibers.