Thermal reliability of graphene/polymer nanocomposites

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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.