Modeling and Design of Composite Materials for Thermal Management

Composites are attractive as they can be directly tailored for a given thermal management application. While bulk thermal conductivity and coefficient of thermal expansion (CTE) can be measured, the structural and mechanical phenomena that dominate this behavior for a given system are less efficiently described experimentally. In this work, microstructural finite element analysis tools are developed to describe and guide the design of composite material systems. To predict bulk thermal properties of the composite, asymptotic homogenization modeling has been implemented to predict interfacial stress, thermal conductivity, and coefficient of thermal expansion (CTE). Example analyses are presented for a heat-cure epoxy matrix and diamond inclusion material system. The effects of composition, constituent geometry, processing and thermal resistance on bulk properties and local interfaces are described. Additionally, modeled thermal conductivities are compared to measured values obtained using the guarded hot plate method. Model predictions compared favorably to experimental results which supports the use of such models in materials design. Though targeted performance may be based on composite formulation, reliability is dominated by the interfacial integrity among the constituents and the package.