Engineering Thermal and Mechanical Properties of Multilayer Aligned Fiber-Reinforced Aerogel Composites

Abstract

This paper demonstrates a controllable way to fabricate multilayer aligned fiber-reinforced aerogel composites with low thermal conductivity (e.g., 0.022–0.028 W m−1 K−1) and greatly improved bending and compressive strengths compared to pure aerogels. Four-layer aligned fibers reinforced aerogel composites with six laminated structures were successfully synthesized by impregnating four layers of aligned glass fibers in silica aerogels via sol–gel technique and drying at ambient pressure. The fiber alignments and the laminated structures greatly affected the compressive and bending strengths of the aerogel composites. For instance, as the orthogonal number of the fiber layers was increased, the bending strength and stability of the aerogel composites were improved while the compressive strength of the aerogel composites was degraded. A heat transfer model based on the unit cell of surface contact hollow cubic structure and the parallel law of equivalent thermal resistance concerning the as-prepared aerogel composites was proposed to explore the heat transfer mechanism at three directions in the aerogel composites. The calculated thermal conductivities were validated with the experimental results. The findings open a possible way to controlling the thermal and mechanical properties of the fiber-reinforced aerogel composites by regulating the fiber alignments and the laminated structures.