The mechanics of interface fracture: (5) adhesion energy of multilayer graphene membranes

The presence of sliding in multilayer graphene membranes increases the fracture mode ratio G_I/G_II , leading to a decrease in adhesion energy measurements when using the circular blister test. In the case of a silicon oxide substrate and pressure loading, the mode mixity jumps up from 43% in the monolayer graphene membranes to above 71% in the two layer graphene membranes. This increase in the mode mixity has the effect of lowering the adhesion energy G_c from 0.424 J/m² to 0.362 J/m² . As the number of graphene layers is increased further, the mode mixity increases slightly and the average adhesion energy of the multi-layered membranes is 0.364 J/m² . The critical mode I and mode II adhesion toughness are found to be G_Ic = 0.226 J/m² and G_IIc = 0.683 J/m², respectively.