Decohesion of graphene from a uniaxially-stretched substrate: Failure analysis of a frictional adhesive interface

Composite structures consisting of two-dimensional (2D) materials deposited on elastic substrates have a wide range of potential applications in flexible electronics. For such devices, robust 2D film/substrate interfacial adhesion is essential for their reliable performance when subjected to external thermal and mechanical loads. To better understand the strength and failure behavior of the 2D film/substrate interfaces, two types of graphene/polymer samples with distinct interfacial adhesion properties are fabricated and tested by uniaxially stretching the substrates. Depending on the interfacial adhesion, two drastically different debonding rates are observed, i.e., rapid snap-through debonding and more progressive crack propagation. Motivated by the experimental observation, we propose an improved shear-lag model with a trapezoidal-shaped cohesive zone to derive an analytical solution for the decohesion behavior. The theoretical model reveals that the decohesion behavior of the frictional adhesive interface is governed by three dimensionless parameters. Particularly, the dimensionless length of the film essentially determines the decohesion rate; while the other two parameters affect the critical substrate strain to initiate debonding. By fitting the experimental data with the theoretical model, the intrinsic adhesion properties of the two samples are obtained with physically meaningful values. This work offers an analytical solution to describing the decohesion behavior of general thin film/substrate systems with a frictional adhesive interface, which is beneficial for characterizing and optimizing the mechanical properties of various thin film/polymer devices.