Lightweight and dual-functional composites with stiff-soft microstructure for energy absorption and thermal insulation

Abstract Lightweight composite materials with high energy absorption performance can find wide applications in mechanical protection yet the design and synthesis of them is a big challenge. Inspired from the bones, dual functional composites with stiff-soft microstructure have been designed and synthesized, whereas polydimethylsiloxane (PDMS) and fly ash cenospheres (FACs) were adopted as soft matrix and stiff filler, respectively. The as-prepared composites exhibited low density (0.668 g/cm3), low thermal conductivity (0.39 W/mK), and high specific energy absorption capacity (8.13 J/g at 2.8 × 10−3 s−1 and 15.49 J/g at 3000 s−1). Besides, the enhancement mechanism of energy absorption is proposed, and a percolation threshold of 60 wt% FAC contents has been revealed. In sum, the proposed study may open a new and simple strategy to synthesize lightweight energy absorption and thermal insulation composites.