Interfacial characterization in defective graphene/PET substrate structure through traction separation models : A molecular dynamics study

Among various graphene-based flexible electronic devices, the graphene/polymer substrate is one of the most common microstructures. Its interfacial mechanical properties directly determine the performance and reliability of these devices. Accordingly, the interaction between single-layer two-dimensional material such as graphene and polymer substrate has become an urgent research field in the manufacture and application of flexible electronic devices. In this study, traction-separation (T–S) models are established to study the interfacial mechanical behaviors of graphene/polyethylene terephthalate (PET) substrate structures using molecular dynamics (MD) simulations. The calculated interface parameters are verified by simulating the blister test with MD simulation and finite element analysis (FEA). Two common types of defects (Stone-Wales (S–W) and single vacancy (S–V)) are considered. By monitoring the aromatic ring distribution (order parameter and concentration) in PET substrate, the results reveal that under the normal loading, the S-W defect in graphene enhances the interfacial strength, while the separation energy is not sensitive to the existence of the S–W defect. The S–V defect in graphene degrades both the normal interfacial strength and separation energy owing to the loss of carbon atoms. Under the shear loading, it is found that the surface roughness of graphene caused by defects is an essential factor affecting the interfacial shear properties at the nanoscale. In addition, the results indicate that a low-concentration S–V defect can increase the surface roughness of graphene to obtain stronger mechanical interlocking, thereby enhancing the interfacial shear properties.