Molecular modeling of thermo-physical properties of BMI matrix and its interface with amorphous carbon fiber

Very rapid heating of composite material leads to matrix thermal decomposition, amorphous char formation, ablation, etc. and results in the variability of local thermophysical properties. It is desired to delay the onset of matrix degradation by incorporating/tailoring the fiber-matrix interface for efficient thermal energy transfer and helping in faster dispersion/distributi on of supplied thermal energy and thus, necessitates the understanding of the interface as well as interfacial thermal transfer across the fiber/matrix interface. Within the context of modeling laser irradiation based rapid heating of nanocomposites, i.e., modeling of thermal energy transfer across the composite's interfaces and subsequent polymeric ablation, this study focuses on building a model and investigating physical and thermal properties of high temperature imide-based resin (BMI-5292) matrix using molecular dynamics simulations. A molecular model of BMI-5292 based on AMBER force field and GAUSSIAN-derived RESP charges is developed and validated against several experimentally measured thermo-physical properties such as density, glass transition, thermal conductivity, etc. In parallel, to mimic the carbon fiber surface, a model of amorphous carbon is developed using the Ter soff (bond-order) potential. Subsequently, using non-equilibrium molecular dynamics simulations, interfacial thermal energy exchange is investigated in terms of thermal conductance at carbon fiber-matrix interfaces for different degrees of crystallinity within the carbonaceous region. The obtained thermo-physical results are found to be in good agreement with available literature, thus providing an accurate and reliable foundation of the molecular force-field to tackle more complex phenomenon (such as polymeric ablation) from molecular dynamics simulations with respect to high-temperature resins.