Harnessing Friction in Intertwined Structures for High-Capacity Reusable Energy-Absorbing Architected Materials.

Energy-absorbing materials with both high absorption capacity and high reusability are ideal candidates for impact protection. Despite great demands, the current designs either exhibit limited energy-absorption capacities or perform well only for one-time usage. Here a new kind of energy-absorbing architected materials is created with both high absorption capacity and superior reusability, reaching 10 kJ kg per cycle for more than 200 cycles, that is, unprecedentedly 2000 kJ kg per lifetime. The extraordinary performance is achieved by exploiting the rate-dependent frictional dissipation between prestressed stiff cores and a porous soft elastomer, which is reinforced by an intertwined stiff porous frame. The vast interfaces between the cores and elastomer enable high energy dissipation, while the magnitude of the friction force can adapt passively with the loading rate. The intertwined structure prevents stress concentration and ensures no damage and reusability of the constituents after hundreds of loading cycles. The behaviors of the architected materials, such as self-recoverability, force magnitude, and working stroke, are further tailored by tuning their structure and geometry. This design strategy opens an avenue for developing high-performance reusable energy-absorbing materials that enable novel designs of machines or structures.