STF-filled biomimetic variable stiffness hierarchic porous material with impact resistance, thermal insulation, and sensing

Inspired by the hierarchic structure of the loofah sponge and the stiffness transformation behavior of sea cucumbers, a novel strategy to achieve multi-physics protection through a biomimetic structural design was proposed. This biomimetic structure (STF-BIPM) effectively improved the stiffness of polyurethane (PU) foam. Furthermore, the stiffness of STF-BIPM increased with the compressive strain rate. STF-BIPM exhibited excellent impact resistance under dynamic loading. Compared with PU foam, the impact force of STF-BIPM was attenuated by 57.6 % and the energy absorption was improved by 25.7 %. Due to the porous structure of the PU part, STF-BIPM also had extremely low thermal conductivity (0.084 W m−1 k−1). Its upper surface temperature was only 39.0 °C after heating for 1000 s at 100.0 °C. Additionally, the STF-BIPM could act as a sensor to respond to the impact process and monitor human movement. Finally, based on the impact resistance, thermal insulation, and sensing of STF-BIPM, a smart fire suit was developed. The fire suit could not only achieve mechanical and thermal protection but also monitor mechanical injury behavior, which had a broad application prospect in the field of fire protection. This study provided an innovative means for the development of intelligent multi-physics protection.