Buoyancy‐Induced Bioinspired Gradient Design Enabled High‐Performance Energy Absorbing Materials

ABSTRACT Energy absorbing materials are essential in our lives but designing lightweight energy absorbing material with a long plateau stage and stable plateau stress remains a significant challenge. Here, inspired by the gradient design strategy of natural energy absorbers, a novel buoyancy‐induced assembly method based on in situ cross‐linking and gelatinization process to prepare an energy absorbing material with a unique gradient structure is reported. Such a gradient design brings a progressive failure character during the crushing process, which endows an ultralong plateau stage and stable stress during the failure process. Besides, under a relatively low density of 0.42 g cm − 3 , this material demonstrated an energy absorption capacity and specific energy absorption of up to 14.1 MJ m − 3 and 33.6 kJ kg −1 , about 6 times and 8 times that of aluminum alloy foams, respectively. This work presents a versatile and convenient buoyancy‐induced assembly method for fabricating gradient materials. Furthermore, the gradient design facilitates a progressive failure mechanism, which provides valuable guidance for the future development of advanced energy‐absorbing systems and a broader class of lightweight structural materials.