Size Effect of the Interfacial Mechanical Behavior of Graphene on a Stretchable Substrate

The size effect and deformation transfer of the interface between graphene and a polymer substrate are experimentally investigated. Eight composite specimens, containing polyethylene terephthalate substrate (PET) and eight different sizes of graphene, are designed. The specimens are studied by a series of experiments to explore how the mechanical properties of the tangential interface between graphene and the substrates can be influenced by the size of graphene. Micro-Raman spectroscopy is employed to measure the full-field strain of graphene subjected to a uniaxial tensile loading process, based on which the evolution of the bonding states of the interface is obtained. The existence of a size effect in the interfacial strain transfer process at the graphene/PET interface is observed, and this phenomenon is characterized by a size threshold and an innovatively defined parameter called the critical relative transfer length. Combined with previous experimental results on the tangential interface of graphene, we observe that the size effect of the interfacial shear stress of graphene is the main cause for the inconformity of experimental data published in previous reports.