Theoretical and computational modeling of clustering effect on effective thermal conductivity of cement composites filled with natural hemp fibers

This paper investigates the effects of clustering on the effective transverse thermal conductivity of unidirectional cement composites filled with natural hemp fibers. A typical clustering pattern with four hemp fibers embedded into cement matrix is designed as the representative two-dimensional unit cell, which is taken from the periodic cement composite under consideration, and a clustering degree parameter is introduced to adjust the distance between clustered fibers. For this heterogeneous two-component composite model, distributions of the heat flux component are obtained using finite element simulation for various clustering cases involving different global fiber volume concentrations, clustering degree parameters, and thermal conductivity of both fiber and matrix, to evaluate the effective thermal conductivity of the composite. To further reveal the effects caused by clustered fibers, a random cluster pattern of hemp fibers in the unit cell is considered for comparison with the present regular clustering pattern. Further, a simple theoretical model with specified flexible factor f is developed by matching the theoretical and numerical predictions.