The intrinsic fracture property of a rubber-modified epoxy adhesive: Geometrical transferability

•Direct measurement of the fracture process zone using SEM, TEM and OM.•Determination of intrinsic fracture energy associated with fracture process zone.•Extraction of cohesive zone model parameters from intrinsic fracture properties.•Linking SENB and TDCB fracture tests via geometry independent fracture properties. This study presents recent achievements in understanding the fracture behaviour of rubber-modified epoxy adhesives, notably the determination of the fully developed fracture process zone (FPZ) and its associated intrinsic fracture energy, G0. The shape and size of the FPZ are identified by inspecting the fracture surfaces using SEM, and exploring subsurface damage using optical microscopy and TEM. The thickness and failure strain of the FPZ are found to be essentially the same for different fracture tests, i.e. tapered double cantilever beam and single edge notched bending tests. As a consequence, the results from different fracture tests are linked by using the geometrically transferable, true fracture properties, i.e. FPZ thickness and G0. The variation of total fracture energy observed in different fracture tests is attributed to varying plastic deformation energy dissipated in plastic deformation zone (outside FPZ). The fracture behaviour of the adhesive is then successfully predicted by a cohesive zone model using parameters extracted from experiments.