This thesis presents the synthesis and characterization of flexible polyimide aerogels and glass fibre-reinforced polyimide aerogels prepared through a sol-gel process followed by supercritical CO₂ drying. Polyimide aerogels were selected due to their ultralow density, high porosity, and excellent thermal and mechanical stability. The synthesized materials were evaluated in terms of homogeneity, envelope density, flexibility, and mechanical strength. Results showed that the flexible polyimide aerogel exhibited superior uniformity, lower density, and excellent elastic recovery, while the glass fibre-reinforced aerogel displayed higher density, reduced flexibility, and significantly improved tear resistance. The observed differences confirm the effect of reinforcement on structural and mechanical properties. Overall, the study demonstrates the versatility of polyimide aerogels and highlights the trade-off between flexibility and strength when glass fibres are incorporated.