Delamination, a major cause of composite failure, is often simulated in experiments using artificial film inserts. In many cases the material used to create these inserts in not carefully controlled. Here a series of tensile tests were performed on central cut ply specimens with different insert film materials in both glass fibre epoxy (E-glass/913) and carbon fibre epoxy (IM7/8552) from which the mode II energy release rate can be calculated from the load at failure. When compared to specimens without inserts, some of the film inserts give a mode II the energy release rate, with considerable variation with film material. Also it was found that a change in specimen material can influence the effectiveness of the insert used.
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