Super-flexible silica based aerogels with additive reinforcement for aeronautics’ insulation application

We have developed a reinforced aerogel hybrid material which is super-flexible, light weight and hydrophobic. Also, the thermal insulation of approx. 30 mW K-1m-1 already surpasses aviation guidelines by 25 %. The aerogel is made of silica derivatives based on functionalized silane precursors and a pH value-induced gelation process. The water-repellant surface of the aerogel inhibits water infusion and guarantees constant insulating properties. Acoustic absorbance of the compound is shifted significantly towards the 500 Hz region compared to commercially available porous absorbers. Fleece-reinforced flexible silica aerogels were tested under uniaxial quasistatic compression in a thermal chamber at three different temperatures, -50, 0, and 50°C. While a change in the temperature environment, from 50°C to 0°C, shows a negligible influence on their mechanical response, they exhibit a pronounced stiffness (2-4 times) at -50°C. Furthermore, inelastic effects such as cyclic stress softening, Mullins effect, and residual deformation are also investigated. Combining these properties a multifunctional material with improved thermal properties for aeronautic application was designed which potentially contributes to a comfort increase in aviation. A full characterization of the materials is carried out and theoretical models are developed to understand the impact of the aerogel structure on the compound properties and - vice versa - calculate potentially beneficial aerogel structures and realize them synthetically.