Optimizing the Reinforcement of Polymer-Based Nanocomposites by Graphene

Abstract

The stress transfer between the internal layers of multilayer graphene within polymer-based nanocomposites has been investigated from the stress-induced shifts of the 2D Raman band. This has been undertaken through the study of the deformation of an ideal composite system where the graphene flakes were placed upon the surface of a polymer beam and then coated with an epoxy polymer. It is found that the rate of band shift per unit strain for a monolayer graphene flake is virtually independent of whether it has one or two polymer interfaces (i.e., with or without an epoxy top coating). In contrast, the rate of band shift is lower for an uncoated bilayer specimen than a coated one, indicating relatively poor stress transfer between the graphene layers. Mapping of the strain in the coated bilayer regions has shown that there is strain continuity between adjacent monolayer and bilayer regions, indicating that they give rise to similar levels of reinforcement. Strain-induced Raman band shifts have also been evaluated for separate flakes of graphene with different numbers of layers, and it is found that the band shift rate tends to decrease with an increase in the number of layers, indicating poor stress transfer between the inner graphene layers. This behavior has been modeled in terms of the efficiency of stress transfer between the inner graphene layers. Taking into account the packing geometry of polymer-based graphene nanocomposites and the need to accommodate the polymer coils, these findings enable the optimum number of graphene layers for the best reinforcement to be determined. It is demonstrated that, in general, multilayer graphene will give rise to higher levels of reinforcement than monolayer material, with the optimum number of layers depending upon the separation of the graphene flakes in the nanocomposite.

Graphene reinforced nanocomposites: 3D simulation of damage and fracture

“…It was observed that a crack initiates at the graphene-matrix interface in both cases. This corresponds to the observation by Gong et al [8] that the adhesion between graphene and polymer is relatively poor. Then crack grows throughout the whole interface region and propagates into the matrix, they deflect on the nanosheets.…”

“…Novoselov, Young and their colleagues at the University Manchester [42][43][44] studied the change in the strain distribution on graphene, and observed that the strain across the flake is uniform at the applied strain up to 0.6%. After that cracks form in polymer coating layers, with the graphene remaining intact.…”

“…This modification was motivated by the experimental observations by Gong et al [30], who estimated the thickness of graphene trilayer as 1 nm (just 3 times of the monolayer thickness, 0.34 nm) and Mahmoud [31] (who measured the thickness of four layers graphene sheets as 1.4 nm, 4 times of a single graphene sheet). It also means that the internal debonding between graphene in each graphene multilayer cluster was neglected.…”

High Strength Metallurgical Graphene – Mechanisms of Growth and Properties / Grafen Metalurgiczny O Wysokiej Wytrzymałości – Mechanizmy Wzrostu I Właściwości

“…Perfect graphene has extremely high strength ~ 130 GPa and a modulus of ~ 1 TPa [1,2]. These properties make graphene a material with potential for use in the polymer industry, such as in future graphene-reinforced composites.…”

“…These properties make graphene a material with potential for use in the polymer industry, such as in future graphene-reinforced composites. Measurable and satisfactory strengthening effects can be achieved by encapsulating graphene sheets (up to two layers) between layers of the polymer [1]. For graphene electronic applications, it is important to establish a relationship between the electrical properties and the material stress state.…”