Development and Material Characterization of Quartz-Reinforced UHTR/Aerogel Composites: Morphology, Thermal, and Flammability Properties

Aerogels are a class of highly porous solid materials with nano-sized open pores. It exhibits unique properties, such as extremely low density and thermal conductivity. Taking advantage of its unique properties, the applications of aerogel include acoustic and thermal insulation, fluid and gas absorption and filtration etc. The highly porous nature of silica aerogel combined with its high thermal stability also makes it an ideal candidate for thermal insulation under extreme environments. Quartz fibers are almost completely composed of silicon dioxide (SiO2) and has commonly been used as reinforcement material due to its favorable mechanical and thermal properties. Traditionally, SiO2 nanofillers have been used as reinforcement material, however, using quartz fiber may provide even greater improvements in mechanical properties than nanosilica powders. The solventless polysiloxane resin (UHTR) is a colorless semi-solid resin system that exhibits very high char yields and thermal stability. This grade of UHTR is formulated using proprietary polysiloxane chemistries to tailor it for flame shielding applications. In this study, the objectives are (a) to develop processing methods to disperse aerogels and chopped quartz fibers thoroughly and homogenously into a polysiloxane resin and (b) to investigate the processing conditions on morphology and thermal properties of a quartz fiber-reinforced aerogel composite material. The proposed composite will have high char yield, low density, and low thermal conductivity properties. These properties will be evaluated using thermal and flammability testing instruments such as micro-scale combustion calorimeter and thermogravimetric analysis. Furthermore, micro-CT analysis using synchrotron micro-tomography is conducted to create 3D renders of the sample and use software to estimate material properties and validate it against experimental data. The goal of this study is to create a quartz fiber-reinforced polysiloxane/aerogel composite that possesses low thermal conductivity and high char yield suitable for advanced aerospace and defense applications.