Browsing by Author "Li, Han"

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    Simulation of thermal behavior of glass fiber/phenolic composites exposed to heat flux on one side
    (MDPI, 2020-01-16) Li, Han; Wang, Nasidan; Han, Xuefei; Fan, Baoxin; Feng, Zhenyu; Guo, Shijun
    A 3D thermal response model is developed to evaluate the thermal behavior of glass fiber/phenolic composite exposed to heat flux on one side. The model is built upon heat transfer and energy conservation equations in which the heat transfer is in the form of anisotropic heat conduction, absorption by matrix decomposition, and diffusion of gas. Arrhenius equation is used to characterize the pyrolysis reaction of the materials. The diffusion equation for the decomposition gas is included for mass conservation. The temperature, density, decomposition degree, and rate are extracted to analyze the process of material decomposition, which is implemented by using the UMATHT (User subroutine to define a material’s thermal behavior) and USDFLD (User subroutine to redefine field variables) subroutines via ABAQUS code. By comparing the analysis results with experimental data, it is found that the model is valid to simulate the evolution of a glass fiber/phenolic composite exposed to heat flux from one side. The comparison also shows that longer time is taken to complete the pyrolysis reaction with increasing depth for materials from the numerical simulation, and the char region and the pyrolysis reaction region enlarge further with increasing time. Furthermore, the decomposition degree and temperature are correlated with depths, as well as the peak value of decomposition rate and the time to reach the peak value.
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    Thermal response study of carbon epoxy laminates exposed to fire
    (Wiley, 2020-08-12) Li, Han; Fan, Baoxin; Wang, Nasidan; Han, Xuefei; Feng, Zhenyu; Guo, Shijun
    In this article, a three‐dimensional thermal response model is developed to investigate the thermal behavior of carbon epoxy composite impacted directly by propane flame. The model is established in consideration of heat transfer and energy conservation in which the heat transfer is in the form of anisotropic heat conduction, absorption by matrix decomposition, and diffusion of gas. Arrhenius equation is utilized to present the decomposition process of the materials. The diffusion equation for the decomposition gas is included for mass conservation. The thermal response model is implemented with the UMATHT and USDFLD subroutines via ABAQUS code, from which the temperature, density, decomposition degree, and decomposition rate can be extracted to analysis the process of material decomposition by finite element simulation. The model shows its capability to analysis the evolution of a carbon epoxy composite in fire by the comparison between the numerical and experimental results. Furthermore, the numerical results show that thermal conductivities in different directions of fiber have a significant influence on the heat transfer. In addition, the relationship between the decomposition degree and temperature is correlated with depths, as well as the peak value of decomposition rate and the time to reach that