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Nanofluids with enhanced thermal properties are candidates for thermal management in automotive systems, with scope for improving energy efficiency. In particular, many studies have reported on dispersions of nanoparticles with long-term stability in the base fluid, with qualitative evaluations of the dispersion stability via either the naked eye or optical instruments. Additives such as surfactants can be used to enhance the dispersion of nanoparticles; however, this may diminish their intrinsic thermal properties. Here, we describe molecular dynamics simulations of nanofluids containing graphene sheets dispersed in ethylene glycol and water. We go on to suggest a quantitative evaluation method for the degree of dispersion, based on the ratio of the total number of nanoparticles to the number of clustered nanoparticles. Moreover, we investigate the effects of functional groups on the surface of graphene, which are expected to improve the dispersion without requiring additives such as surfactants due to steric hindrance and chemical affinity for the surrounding fluid. We find that, for pure graphene, the degree of dispersion decreased as the quantity of graphene sheets increased, which is attributed to an increased probability of aggregation at higher loadings; however, the presence of functional groups inhibited the graphene sheets from forming aggregates.

An analytical method was presented to determine the delamination buckling load and the growth of one-dimensional delaminated beam-plates. In this study, the symmetry in delamination with respect to the center of the beam-plate was not assumed. The delamination was arbitrarily located in the longitudinal and thickness directions. The effects of the delamination length, and location on the buckling load and the growth were investigated with consideration of the transverse shear deformation. Results of the analysis showed that the delamination buckling load was dependent on the configuration of the delamination. For the relatively thick delamination, the buckling load of a center located delamination was higher than that of an off-center delamination. The shear deformation effect lowered the buckling loads and increased the energy-release rates. The expreiments on delaminated graphite/epoxy unidirectional specimens were also performed to determine the buckling load and to observe the growth characteristics. Results of the experiments showed good agreement with analytic results and there existed various postbuckling characteristics depending on the configuration of delamination.