Modified four-point bending specimen for determining the interface fracture energy for thin, brittle layers

A well-known four-point bending test has been modified such that the critic al energy release rate cal G(c) for delaminating cracks propagating at the interface of a thin, brittle layer bonded to a substrate can be measured. T he energy release rate cal G required for crack delaminating at those inter faces is obtained by attaching a stiffening layer to the layer system. Anot her advantage of this modification is that segmentation of the layer and pl astic deformation of the substrate during bending are avoided. The interfac e fracture energy cal G(c) of a plasma sprayed ZrO2-ceramic layer on a flam e sprayed high alloyed steel substrate has been measured.