Mechanisms Underpinning Dynamic Impact Resistance Reinforcement by Multi-Scale Synergistic Effect Through Nano-Silica and Carbon Hollow Microsphere

Synergistic improvements in lightweight design, flexibility, and energy absorption efficiency are a long-standing issue of flexible impact protection materials. This study proposed a multi-scale synergistic enhancement method, where nano-scale nano-silica (NS) and micro-scale carbon hollow microspheres (CHMs) were adopted to enhance the dynamic impact property of the flexible polydimethylsiloxane (PDMS). The mechanical behavior of the as-prepared composites under a broad range of strain rates (10^-3-4500 s^-1) was systematically investigated. For the composite with 1 wt.% NS and 3 wt.% CHM, the compressive strength under quasi-static conditions reached 39.73 MPa, representing a 67% improvement over the pure PDMS. Under dynamic impact (4500 s^-1 strain rate), the force transmits through the NS nanonet with the energy absorbed through crushing of the CHM with a hollow structure, which elevates the specific energy absorption properties to 40.18 J/g (for the composite with 1 wt.% NS and 3 wt.% CHM), which owns a 179% enhancement compared to the composite with only 4 wt.% CHM. This work established a novel method for a hierarchical "rigid-flexible energy absorption" structural design of lightweight impact-resistant materials.