Solid–Fluid Synergistic Mechanism Energy Absorption of Bioinspired Multiscale Cellular Composites

The distinguishing response ratio between the impulsive loadings and macroscale materials is one of the main challenges to develop efficient energy-dissipative materials. A multiscale cellular solid–fluid composite (SFC) consisting of open-cell metallic foam and nanofluidic composite (NLC) is developed and analyzed in this work. The effects of strain rate, pore size, and skeletal materials are performed experimentally to determine the mechanical response and energy absorption of SFCs under quasi-static and dynamic compressions. The results demonstrate that the intrinsic property of skeletal foams determines the quasi-static responses of SFCs. The mechanical response and macroscale failure modes are insensitive to the strain rate, while the yield stress of SFCs experiences a noteworthy increase of more than 1000% at elevated strain rates, indicating the excellent potential for various dynamic scenarios. The enhancement effect is significantly determined by the nanofluidic behavior, which is confirmed to have a considerable influence on the energy absorption capacity. Across a wide range of strain rates, the energy absorption of SFCs is categorized into three phases based on the distinct solid–fluid interactions, where the plastic domain, along with weak and strong multiscale solid–fluid synergistic interactions, are identified as the key mechanisms of response and energy absorption. This study deepens the understanding of multiscale SFCs and offers significant strategic insights and inspiration for developing efficient and hierarchical energy-absorbing materials.