Tandem ceramic composite

Abstract

The composite comprises ceramic fiberformed insulation bonded to a fiber reinforced ceramic matrix laminate. Ceramic insulation has a mat of intersecting, discrete ceramic fibers bonded with a sol-gel glass binder. The insulation is prepared by forming a slurry of ceramic fibers, molding the slurry to form a soft felt mat, drying the mat, and incrementally introducing the binder into the mat with a multiple-impregnation technique, which controls shrinkage of the ceramic fiber mat. This process provides a layering technique that permits formation of a continuous fibrous structure having layers that impart distinct characteristics at desired regions within the structure. By using different ceramic fibers and fibers of differing physical dimension, or by including additives with the slurries, tailoring of the physical characteristics of the insulation is achieved. The reinforced ceramic matrix laminate is laid up on the ceramic insulation in a wet lay-up technique and includes a continuous ceramic fiber reinforcement and a cementaceous matrix that includes a ceramic filler, like mullite; ceramic reinforcing whiskers, such as silicon nitride or silicon carbide whiskers; and a binder, such as colloidal silica. An activator may also be used in the matrix. Matrix is worked into the ceramic insulation and fiber reinforcement during the lay-up. The tandem composite exhibits resistance to high temperatures for extended exposure without degradation and possesses improved flexural strength over conventional ceramics made without exotic pressure fabricating processes. The tandem composite can readily be formed into complex curvatures and can include integral mounting flanges (strengthened with the matrix laminate) for fastening the composite to structural materials.