Gardea F, Naraghi M, Lagoudas D
Department of Aerospace Engineering, Texas A&M University , 3409 TAMU College Station, Texas 77843-3409, United States.
ACS Appl Mater Interfaces. 2014 Jan 22;6(2):1061-72. doi: 10.1021/am4046102. Epub 2013 Dec 31.
The thermal transport process in carbon nanofiber (CNF)/epoxy composites is addressed through combined micromechanics and finite element modeling, guided by experiments. The heat exchange between CNF constituents and matrix is studied by explicitly accounting for interface thermal resistance between the CNFs and the epoxy matrix. The effects of nanofiber orientation and discontinuity on heat flow and thermal conductivity of nanocomposites are investigated through simulation of the laser flash experiment technique and Fourier's model of heat conduction. Our results indicate that when continuous CNFs are misoriented with respect to the average temperature gradient, the presence of interfacial resistance does not affect the thermal conductivity of the nanocomposites, as most of the heat flow will be through CNFs; however, interface thermal resistance can significantly alter the patterns of heat flow within the nanocomposite. It was found that very high interface resistance leads to heat entrapment at the interface near to the heat source, which can promote interface thermal degradation. The magnitude of heat entrapment, quantified via the peak transient temperature rise at the interface, in the case of high thermal resistance interfaces becomes an order of magnitude more intense as compared to the case of low thermal resistance interfaces. Moreover, high interface thermal resistance in the case of discontinuous fibers leads to a nearly complete thermal isolation of the fibers from the matrix, which will marginalize the contribution of the CNF thermal conductivity to the heat transfer in the composite.
在实验的指导下，通过结合微观力学和有限元建模来研究碳纳米纤维（CNF）/环氧树脂复合材料中的热传输过程。通过明确考虑CNF与环氧基质之间的界面热阻，研究了CNF组分与基质之间的热交换。通过模拟激光闪光实验技术和傅里叶热传导模型，研究了纳米纤维取向和不连续性对纳米复合材料热流和热导率的影响。我们的结果表明，当连续的CNF相对于平均温度梯度发生取向错误时，界面电阻的存在不会影响纳米复合材料的热导率，因为大部分热流将通过CNF；然而，界面热阻会显著改变纳米复合材料内部的热流模式。研究发现，非常高的界面电阻会导致热源附近界面处的热量截留，这会促进界面热降解。通过界面处的峰值瞬态温度升高来量化的热量截留程度，在高耐热性界面的情况下比低耐热性界面的情况高出一个数量级。此外，在不连续纤维的情况下，高界面热阻会导致纤维与基质几乎完全热隔离，这将使CNF热导率对复合材料中热传递的贡献边缘化。
