Test geometries for measuring interfacial fracture toughness

Two types of test specimen for determining interfacial fracture toughness are calibrated in this paper. Previous studies have shown that interfacial fracture toughness is strongly dependent on mode mixity. Both specimen types presented are well-suited for investigating interfacial toughness over a wide range of mode mixities. The structure of the near tip elastic fields for an interface crack is examined and in particular near tip contact and the variation of mode mixity with distance are dealt with. The concept of K dominance for interface cracks is discussed and a zone of K dominance is shown to exist for the specimens calibrated, provided the zone of non-linear effects is small. A procedure for determining the effect of residual stresses on the stress intensity factor is presented.