Experimental investigation and multi-level modeling of the effective thermal conductivity of hybrid micro-fiber reinforced cementitious composites at elevated temperatures

Abstract The knowledge on the thermal conductivity of fiber reinforced composites (FRCs) is essential for developing energy-efficient buildings, as well as minimizing the thermal damage of the infrastructures. The thermal properties of FRCs are strongly dependent on hybrid fibers and elevated temperatures, which remain far from being fully understood. In this study, the evolution of the thermal conductivity of various FRCs (i.e., polypropylene, basalt, carbon, and glass fiber reinforced composites) with temperature is measured using a transient approach. In what follows, a multi-level model is developed to predict the thermal conductivity of FRCs through a step-by-step homogenization based on the effective medium theory. The multi-level model, validated by experimental results over a wide temperature range, is then utilized to guide the materials design of FRCs. The results show that the interfacial thermal resistance plays an important role in determining the thermal conductivity of FRCs at elevated temperatures, and the variation of fiber-to-matrix thermal conductivity ratio can lead to the transformation of the effective thermal conductivity at different scales. The findings can help predict the thermal conductivity of sustainable FRCs accurately and improve the fire-resistant of engineering structures using hybrid fibers rationally.