A Heat Transfer-Combustion Model for Epoxy Resin/Boron Nitride Nanosheets Composite Materials

Boron nitride nanosheets (BNNS) has garnered significant attention in the field of epoxy resin (EP) flame retardancy due to its high thermal stability and excellent thermal insulation properties. However, the analysis of its flame-retardant mechanism remains insufficiently explored. At the same time, heat transfer-combustion simulation models of the materials offer a superior solution for accurately characterizing material flame-retardant performance. In this study, EP/BNNS composite materials were investigated by cone calorimetry to elucidate the effects of BNNS loading, incident heat flux, and burning time on the intumescent char height, and a predictive model for the intumescent char layer height was established. On this basis, a coupled heat transfer – combustion physical and numerical model was developed for EP/BNNS composite materials, incorporating the intumescent char layer height model. Sensitivity analyses were further performed for thermal conductivity, specific heat capacity, density, and surface emissivity to quantify their influences on the temperature; the results indicate that specific heat capacity of the virgin material and char layer, surface emissivity of the virgin layer are the most influential parameters. Model predictions were validated against experiments, and the root mean square errors for internal temperature, mass loss rate, heat release rate, and the moving boundary between the char layer and the virgin layer were 23.54°C, 0.57 mg·cm−2 ·s−1 , 190.32 kW·m−2 , and 0.164 cm, respectively, demonstrating good consistency in predicting temperature trends and combustion characteristics. The proposed model can accurately describe and predict the flame-retardant performance of EP/BNNS composite materials.