Methods for fabricating high-temperature composite structures (e.g., structures comprising carbon-carbon composite materials or ceramic composite matrix (CMC) materials and configured for use at temperature at or exceeding about 2000 F. (1093 C.)) include forming precursor structures by additive manufacturing (AM) (e.g., 3D printing) with a filament drawn from a spool. The precursor structures are exposed to high temperatures to pyrolyze a precursor matric material of the initial 3D printed structure. A liquid resin is used to impregnate the pyrolyzed structure, to densify the structure into a near-net final shape. Use of expensive and time-consuming molds and post-processing machining may be avoided. Large, unitary, integrally formed parts conducive for use in high-temperature environments may be formed using the methods of the disclosure.

Embodiments of the invention include articles incorporating fibrous fragments of mats of silica fibers and methods for producing such articles. The fiber mats may be formed via electrospinning of a sol gel produced with a silicon alkoxide reagent, such as tetraethyl ortho silicate, alcohol solvent, and an acid catalyst.