The mechanisms of embrittlement are similar to those of metals. Inorganic glass embrittlement can be manifested via static fatigue. Embrittlement in glasses, such as Pyrex, is a function of humidity. Growth rate of cracks vary linearly with humidity, suggesting a first-order kinetic relationship. The static fatigue of Pyrex by this mechanism requires dissolution to be concentrated at the tip of the crack. If the dissolution is uniform along the crack flat surfaces, the crack tip will be blunted. This blunting can actually increase the fracture strength of the material by 100 times.
The embrittlement of SiC/alumina composites serves as an instructive example. The mechanism for this system is primarily the diffusion of oxygen into the material through cracks in the matrix. The oxygen reaches the SiC fibers and produces silicate. Stress concentrates around the newly formed silicate and the fibers strength is degraded. This ultimately leads to fracture at stresses less than the materials typical fracture stress.