A multiscale homogenization model on thermal conductivity of bio-based building composite considering anisotropy, imperfect interface and moisture

Bio-based materials are considered as one of the solutions to reduce energy consumption in buildings due to their excellent thermal insulation properties. However, previous studies often do not consider multiple complex microstructural characteristics in one model. In this study, a novel iterative multi-scale homogenization model was developed to predict the effective thermal conductivity of bio-based materials. This model is based on micro-geometric features at three scales and considers plant fiber orientation and shape, imperfect contact, moisture, and different pores’ size. Further, the model was verified by comparison with finite element models and experimental data from the literature. The results show that the present model demonstrates reliable predictions on the scale of binder, plant fiber, and bio-based composites. The application on hemp verified the accuracy of the imperfect contact in the model, while the application on wheat straw showed the non-negligibility of moisture. Additionally, this study also has good applicability to other plant fibers. In conclusion, this model links microstructure and macroscopic behavior, which can effectively predict and evaluate the thermal conductivity of a wide range of bio-based materials, and thus contribute to reducing building energy consumption.