HIGH-MODULUS GLASS-FIBERS FOR NEW TRANSPORTATION AND INFRASTRUCTURE COMPOSITES AND NEW INFRARED USES

Calcium aluminate glass fibers offer major new opportunities in transportation, infrastructure composites and new infrared sensor applications. They possess a higher modulus than S-glass, an advantage that can yield major weight and energy savings in car, aircraft and aerospace composites, or stiffer composite parts in emerging bridge and construction markets. Their superior alkali resistance is an important advantage in cement composites. They also possess sapphire-like infrared transmission, a property that is obtained at a fraction of the cost of single crystal sapphire fibers. Quaternary non-silica calcium aluminates with 40-50% alumina have high melt viscosities (much greater than 10 Pa s). Experimental fibers were obtained by potentially commercial processes (up-drawing from supercooled melts and down-drawing from preforms). Binary compositions with >50% alumina have low viscosities (much less than 10 Pa s). Glass fibers were obtained by an experimental process (inviscid melt spinning) from melts with up to 81% alumina. Infrared optical aluminum tellurite fibers were obtained from supercooled melts. New glass theory is applied. Melt viscosity and glassy modulus are rheology controlled and their magnitude is due to differences in size, shape and orientation of nanocrystalline domains. Not surprisingly, the silicate and aluminate glass (or glass ceramic) fibers with the highest modulus (160-180 versus 69 GPa for E-glass) had the most pronounced nanocrystallinity.