Deformation mechanism of graphene in amorphous polyethylene: A molecular dynamics based study

Abstract: The current paper focuses on investigating deformation mechanism of
graphene sheets in a graphene reinforced polyethylene (Gn–PE)
nanocomposite. Classical molecular dynamics (MD) simulation was
conducted on large Gn–PE systems. Different spatial arrangements of
graphene sheets were considered in order to study the effect of nonlocal
interaction among the graphenes. In all the cases 5% weight
concentration of graphene was considered in order to prepare atomistic
models for Gn–PE. As expected, graphene seemed to enhance the overall
Young’s modulus and tensile strength of the Gn–PE nanocomposite.
Randomly oriented graphenes with strong nonlocal interaction were
observed to be comparatively preferable than the other spatial
arrangements of graphenes. The high strength and stiffness of graphene
sheets can be properly utilized if the graphenes are randomly oriented
and have strong long range interactions. Finally, the failure mechanism
of the graphene and role of voids in the polymer were discussed both
qualitatively and quantitatively. It was seen that the randomly oriented
graphenes were firstly pulled out from the polyethylene matrix during
deformation prior to breaking into pieces. This can explain the loss of
stiffness and strength in graphene sheets embedded in the polymer
matrix. From the current work it is clearly understood that the
necessity of the long range graphene–graphene interaction is important
in both elastic as well as plastic regime of the deformation.

Highlights:

- We have investigated the deformation and failure of graphenes embedded in polymer.

- Poor nonlocal interaction among graphenes causes reduction in stiffness.

- Interfacial pullout failure initiates before C–C bonds in graphene start to break.

 

- Agglomerated graphenes are expected to create larger voids in the polymer.