Glass Matrix Composites

Glass and glass–ceramic matrix composites represent a very particular type of composite materials. As in most ceramic matrix composites, the reinforcements are mainly intended to increase the resistance to crack propagation, that is, the most significant weakness of the matrices, due to several toughening mechanisms. Unlike polycrystalline ceramic matrices, however, glasses offer the distinctive feature of viscous flow, being readily deformed and flowed in their low viscosity state, with the possibility of incorporating secondary phases at moderately high temperatures. Fibrous reinforcements (mainly C and SiC fibers) are at the basis of materials with impressive properties, for example, strength above 1 GPa, fracture toughness up to 35 MPa m0.5, almost zero thermal expansion, and service temperature up to 1500°C, but still facing high costs, although known for many years. Recent applications, such as that of “optomechanical materials,” that is, transparent materials with improved crack resistance, may stimulate research investments and production. As an alternative, dispersion-reinforced composites, first seen as lower value category, owing to the limited improvements in fracture toughness, are currently the candidates for extensive industrial production, since the low cost treatments applied may be combined with complex combinations of different functionalities.