Micromechanics of Thermal Conductive Composites: Review, Developments and Applications

Micromechanics investigations of composites with fiber-shaped reinforcement are extensively applied in the engineering design and theoretical analysis of thermal composites in the aerospace engineering and high-tech industry. In this paper, a critical review of various classical micromechanics approaches is provided based on the classification framework and the development of micromechanics tools. Several numerical micromechanics tools have been developed to overcome limitations through exactly/approximately solving the internal governing equations of microstructures. The connections and limitations of those models are also investigated and discussed, based on which three recently developed numerical or semi-analytical models are explained, including finite-element micromechanics, finite-volume direct averaging micromechanics, and locally exact homogenization theory, as well as machine learning tools. Since it is almost inevitable to mention the interfacial effects on thermal behavior of fibrous composites, we review the new mathematical relations that interrupt the original continuity conditions due to the existence of interphase/interface within unit cells. Generally speaking, the interphase/interface is demonstrated to play a significant role in influencing the effective coefficients and localized thermal fields. The present work also briefly reviews the application of micromechanics tools in emerging engineered woven composites, natural fibrous composites, and ablative thermal protection composites. It is demonstrated that sophisticated micromechanics tools are always demanded for investigating the effective and localized responses of thermal fibrous composites.