Thermal reliability of graphene/polymer nanocomposites

石墨烯单分子膜和纳米片层(GNPs)由于其优异的力学、热学、电学和光学性能，在能源、生物医学、交通运输、人工智能和航空航天等领域被越来越多地用作聚合物的超级增强材料。石墨烯纳米复合材料的制备和加工需要高能量密度的短激光脉冲等集中能源。由石墨烯纳米复合材料制成的功能器件在极端的热条件下应用，如氦气温度或纳秒、皮秒或飞秒的热冲击，会产生随时间变化的动态热应力，而这些热应力不能用经典的傅立叶热传导理论来表示。由石墨烯/聚合物复合材料制成的柔性功能器件的可靠使用需要在各种热环境下的疲劳和断裂标准。此外，石墨烯/聚合物纳米复合材料的粘弹性行为不能用现有的纳米复合材料的微观力学模型来解释。拟议的计划将解决石墨烯/聚合物纳米复合材料制造和应用中的上述主要挑战。首先，我们将设计一种新的测试方法来确定材料的相关热弛豫时间。此外，还将进行分子动力学模拟来模拟热波在这些材料中的传播，并验证测试结果。以典型的石墨烯/聚合物纳米复合材料为例，说明该测试方法的有效性。通过热机械疲劳试验，建立了模型石墨烯/聚合物纳米复合材料玻璃化转变温度附近各温度谱的S-N曲线。为了处理热场与其他物理场的直接耦合，通过实验-数值-理论相结合的分析，建立了一个非局部、非傅立叶、热-粘弹性的理论框架。我们将使用这个理论框架来分析各种功能纳米复合材料系统的热机械行为，并将结果用于抗老化、不稳定和失效的热可靠性设计。本研究将对石墨烯纳米复合材料器件的热疲劳设计产生重大影响。热-粘弹性本构模型、断裂准则和S-N曲线将在基于石墨烯/聚合物纳米复合材料和其他聚合物纳米复合材料的柔性功能器件的设计和制造中得到广泛的应用。开发的方法将扩展到处理其他纳米复合材料的热可靠性。拟议项目的成功完成将极大地惠及加拿大的能源、先进材料和制造业。

Graphene monolayers and nano-platelets (GNPs) have been increasingly used as a super-reinforcement of polymer for energy, biomedical, transportation and artificial intelligence and aerospace industries due to their outstanding mechanical, thermal, electrical and optical performance. Fabrication and processing of graphene nanocomposites require concentrated energy source such as short laser pulse of high energy density. Application of functional devices made of graphene nanocomposite in extreme thermal conditions such as helium temperature or thermal impact of nano-, pico- or femtoseconds duration leads to time-dependent, dynamic thermal stresses, which are unable to be formulated using the classical, Fourier heat conduction theory. Reliable service of flexible, functional devices made of graphene/polymer composite requires fatigue and fracture criteria under various thermal circumstances. In addition, viscoelastic behavior of graphene/polymer nanocomposite cannot be accommodated with the available micromechanical models for nanocomposite materials. The proposed program will address the above main challenges in manufacturing and application of graphene/polymer nanocomposites. First, we will design a novel testing method to determine related thermal relaxation times for the materials. In addition, molecular dynamic simulations will be conducted to simulate thermal wave propagations in these materials and validate the test results. Typical graphene/polymer nanocomposites will be used as an example to illustrate the efficiency of the test methodology. Thermomechanical fatigue test will be performed to build S-N curves for various temperature spectra around glass transition temperature for the model graphene/polymer nanocomposites. To deal with the direct coupling of the thermal field with other physical fields, a nonlocal, non-Fourier, thermal-viscoelastic theoretical framework will be built through combined experimental-numerical-theoretical analysis. We will use this theoretical framework to analyze the thermomechanical behavior of various functional, nanocomposite systems, and the results will be used for thermal reliability design against aging, instability and failure. The present research will bring a strong impact on the thermal fatigue design of graphene nanocomposites devices. The thermal-viscoelastic constitutive models, the fracture criteria and the thermomechanical S-N curves will see wide application in design and manufacturing of flexible, functional devices based on graphene/polymer nanocomposite and other polymer nanocomposite. The methodology developed will be extended to deal with thermal reliability of other nanocomposite materials. The successful completion of the proposed program will greatly benefit the energy, advanced materials and manufacturing sectors of Canada.