Thermally insulating and multifunctional glass fiber-silica aerogel composites via in situ growth

Silica aerogels are attractive thermal insulators because of their ultralow thermal conductivity. Nonetheless, their practical deployment is often limited by intrinsic brittleness and poor mechanical robustness. A weavable glass-fiber-reinforced silica aerogel composite is demonstrated, fabricated via in situ sol-gel growth on chemically modified fibers. Unlike traditional impregnation methods, silica nucleates and forms directly on the surface of the modified fiber to form an integrated network of fibers and aerogels with continuous interfacial connectivity. The interface is primarily stabilized through covalent Si-O-Si linkages between the silica network and the surface-functionalized fibers, whereas hydrogen bonding serves as a secondary interaction that further enhances interfacial stability. The resulting composite exhibits an ultralow thermal conductivity of 0.0150 W m^-1 K^-1 together with a high tensile strength, while preserving the intrinsic flexibility and weavability of the fiber scaffold. The material remains stable under direct flame exposure up to ∼1000 °C, exhibiting only 1.3% mass loss after cycling tests. In addition, hydrophobic modification imparts long-term water repellency, yielding a static water contact angle of 150°. This study establishes an interfacial engineering strategy for stabilizing aerogels within flexible and mechanically robust composites, providing a viable pathway toward aerogel-based thermal insulation in demanding environments.