石墨烯-碳纳米管/环氧树脂混杂复合材料热传导协同效应机理的多尺度仿真研究

The synergistic effect of hybrid graphene and carbon nanotube in the heat conduction can significantly enhance the thermal conductivity of polymer composites. In addition, the synergistic effect and the improvement of the interface have an additive effect for enhancing the thermal conductivity of epxoy composites. This effect provides us a new method to design polymer composites with a higher thermal conductivity. However, the mechanism of synergistic effects in composites with hybrid graphene and carbon nanotube is the lack of thorough study. The different percolation effects in the networks formed with different nanostructured carbon materials still need to be further analyzed. The potential of synergistic effects in the heat conduction needs to be urgently exploited. In this project, we will take graphene-carbon nanotube/epoxy hybrid composites as the main study object, develop a three-dimensional multi-scale representative volume element of hybrid composites based on molecular dynamics and finite element methods, verify the models with experiments, compare with graphene/epoxy composites and carbon nanotube/epoxy composites, study the thermal behavior of the matrix, the nanostructured carbon fillers and the interface in terms of the morphology, distribution, contact and interface, give an explanation of the different percolation effects in the networks formed with different nanostructured carbon materials, reveal the mechanism of synergistic effects in the heat conduction of graphene-carbon nanotube/epoxy hybrid composites and provide a basic theory for further thermal conductivity enhancement of polymer composites.

石墨烯和碳纳米管的热传导协同效应能够大幅提高高分子复合材料的热导率，而且协同效应与界面改善对复合材料热导率的增强具有叠加效应。这就为设计更高热导率的高分子复合材料提供了新思路。然而，现阶段热传导协同效应的机理还不够明确，不同纳米碳填料形成的交联网络所产生不同渗流现象还有待合理解释，热传导协同效应的潜力亟待开发。本项目以石墨烯-碳纳米管/环氧树脂混杂复合材料为主要研究对象，结合分子动力学和有限元方法建立石墨烯-碳纳米管/环氧树脂混杂复合材料的三维跨尺度热传导代表性体积元模型并辅以实验验证，与石墨烯/环氧树脂复合材料和碳纳米管/环氧树脂复合材料对比，从纳米碳填料的形态、分布、接触以及界面等多角度研究基体、纳米碳填料和界面热行为，解释不同纳米碳材料交联网络所产生不同渗流现象，揭示石墨烯-碳纳米管/环氧树脂混杂复合材料热传导协同效应机理，为进一步增强高分子复合材料热导率提供理论依据。

石墨烯(GNPs)和碳纳米管(CNTs)的热传导协同效应能够大幅提高高分子复合材料的热导率。然而，现阶段热传导协同效应的机理还不够明确。本项目以GNPs-CNTs/环氧树脂混杂复合材料为主要研究对象，结合MATLAB和ANSYS软件建立GNPs-CNTs/环氧树脂混杂复合材料的三维跨尺度热传导代表性体积元模型并辅以实验验证，从纳米碳填料的形态、分散、接触以及界面等多角度研究其对复合材料热导率的影响，以揭示GNPs-CNTs/环氧树脂混杂复合材料热传导协同效应机理。..建立了不同的空间弯曲随机分布CNTs/环氧树脂、团聚CNTs/环氧树脂复合材料三维数值模型，得到了相关文献数据的验证。结果表明：CNTs分散越好，有效长度越高，直径越大，界面和接触性能越好，复合材料热导率越高,且存在一个热导约为1E6w/(m2k)临界值。创新性地提出用CNTs间重叠热影响区的数目和分布系数的概念来表征空间弯曲CNTs的分散质量，揭示此概念适用于描述CNTs对复合材料热导率的影响规律。. 采用具有一定直径和厚度的圆盘模拟GNPs的形态，建立了多个不同的随机分布GNPs/环氧树脂、团聚GNPs/环氧树脂复合材料有限元模型，结果显示：界面热导越大，GNPs/环氧树脂复合材料的热导率越高，且也存在一个界面热导约为1.8E7 w/(m2k)的临界值；GNPs/环氧树脂复合材料在能够形成交联网络且交联处接触热导较大的条件下能发生渗流现象，GNPs体积含量越高，交联点数越多，渗流效应越明显。. 成功合成了CNTs/环氧树脂、GNPs/环氧树脂、GNPs-CNTs/环氧树脂复合材料并进行了测试，结果显示：GNPs-CNTs混杂填料彼此连接形成了空间交联网络。建立了相同体积含量的CNTs/环氧树脂、GNPs/环氧树脂、GNPs-CNTs/环氧树脂复合材料三维数值模型，模型得到可靠验证。结果显示：CNTs-GNPs混杂填料构成的交联网络相互促进分散能有效提升复合材料热导率；CNTs-GNPs间较大的接触热导在一定程度上触发了渗流效应。交联网络和渗流效应共同促进了热传导，提高了热导率，CNTs-GNPs/环氧树脂复合材料的热传导协同机理通过仿真模拟研究已得到初步揭示。