Rigid and flexible polyimide aerogels with less fatigue for use in harsh conditions

•High strength and high toughness were achieved simultaneously in polyimide aerogel.•A multi-level force mechanism was proposed based on in-situ observation.•A spring-like bridge played a key role in increasing compression recovery.•PI aerogel with an isotropic compressive performance in horizontal direction.•The application of PI aerogel could cover extreme high and low temperature. Polyimide aerogels possess various applications in harsh environment but are often limited by poor mechanical property. The ice template method to construct a layered aerogel has structural advantages, but there are still problems of insufficient compression recovery and anisotropy. We investigated the method of forming a spring-like bridge in layered structure, and verified the effect of bridges on the compression deformation, compressive strength, energy dissipation, and fatigue properties. Based on structural observations, a corresponding force mechanism was proposed. After 10,000-cyclic compression at 50% strain, PI aerogels had only 5.8% plastic deformation, 82% stress retention and stable energy dissipation coefficient below 0.3. Interestingly, the compressive performance was isotropic in horizontal direction. Combined with low thermal conductivity, PI aerogels had high structural stability when repeatedly used at 300 °C. This research may provide an available method for design of high-strength and high-toughness polymer aerogels suitable for harsh environment.