Computational microstructure modeling of transverse thermal behavior in cementitious composites filled with randomly dispersed natural fibers coated by functionally graded interphase.

• The computational microstructure modeling including randomly dispersed coated fibers is established. • The graded interphase has significant influence on the effective thermal conductivity. • The linear form of interphase property can cause higher prediction than the nonlinear form. • The high-conductivity fiber causes a plateau value of the prediction. • The magnitude of plateau value dramatically increases with the increase of interphase thickness. To assess the overall thermal properties of lightweight natural fiber-reinforced cementitious composites (NFRCCs) developed for low-carbon constructions, the comprehensive understanding of properties and characteristics of graded interphase between fiber and matrix is vital. However, there is rare study on the graded interphase in the NFRCCs so far. The main objective of this work is to present a comprehensive numerical investigation of the influence of functionally graded interphase on the effective thermal conductivity of such composites. A computational microstructure model including randomly dispersed fibers coated by functionally graded interphase is established and verified by comparison to the experimental results. Then, the effective thermal conductivity of the composites is characterized with respect to the microstructure parameters. It is found that the overall thermal conductivity is weakly dependent of the fiber distribution, whilst it is significantly affected by fiber content, constituent properties, as well as interphase graded form and thickness. Moreover, the study reveals that the linear variation of the interphase property can cause higher predictions than the nonlinear variation. The proposed work will provide fundamental insight about the role of functionally graded interphase in NFRCCs, which is helpful in guiding the designing and processing of NFRCCs. [ABSTRACT FROM AUTHOR]