Evaluation of effective thermal diffusivity and conductivity of fibrous materials through computational micromechanics

The aim of present study is to investigate the effective thermal properties of composite material via micromechanical modeling of the composite material as a heterogeneous material. These properties mainly include the thermal diffusivity and the thermal conductivity of composites. For this purpose, a definition is presented for effective thermal diffusivity for heterogeneous materials based on heat diffusion rate into the material in a transient heat transfer. A micromechanical model based on the Representative Volume Element (RVE) is presented for modeling the heat conduction in the fibrous composite materials. An appropriate heat transfer problem for the RVE is defined so that by the analogy of the numerical results the effective properties of the RVE can be estimated. A numerical method is employed to analyze the steady-state and transient heat flux and temperature in the RVE. To validate the model, the predictions of present model are compared with results of analytical method, FEM and some available experimental data in the open literature. The effective thermal conductivity and thermal diffusivity are then obtained for fibrous composites via the present micromechanical model. The SiC/Ti, SiC/Ti6%Al4%V and Glass/Epoxy composites with various fiber volume fractions are considered in this study.