Thermal reliability of graphene/polymer nanocomposites

石墨烯单层和纳米薄片（GNPs）由于其优异的机械、热学、电学和光学性能，已越来越多地用作能源、生物医学、交通运输、人工智能和航空航天工业的聚合物超级增强材料。石墨烯纳米复合材料的制备和加工需要集中的能量源，如高能量密度的短激光脉冲。石墨烯纳米复合材料制成的功能器件在极端热条件下的应用，如氦温度或纳米、皮秒或飞秒持续时间的热冲击，会导致时间依赖的动态热应力，这是无法用经典的傅立叶热传导理论来表述的。由石墨烯/聚合物复合材料制成的柔性功能器件需要在各种热环境下的疲劳和断裂准则。此外，石墨烯/聚合物纳米复合材料的粘弹性行为不能与现有纳米复合材料的微观力学模型相适应。该计划将解决石墨烯/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松弛时间。此外，将进行分子动力学模拟，模拟热波在这些材料中的传播，并验证测试结果。将以典型的石墨烯/聚合物纳米复合材料为例，说明测试方法的有效性。通过热-机械疲劳试验，建立模型石墨烯/聚合物纳米复合材料玻璃化转变温度周围不同温度谱的S-N曲线。为了处理热场与其他物理场的直接耦合，将通过实验-数值-理论相结合的方法建立一个非局部、非傅立叶、热粘弹性的理论框架。我们将使用这一理论框架来分析各种功能纳米复合材料系统的热力学行为，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要影响。热粘弹性本构模型、断裂准则和热力学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应用。所开发的方法将扩展到处理其他纳米复合材料的热可靠性。该项目的顺利完成将大大有利于加拿大的能源、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.