Interfaces fracture energy

Fig. 4.17. Low interface fracture energy, F 10 J/m, of a pure Ni-AlgOa interface in ambient air. Upon switching from moist air to dry nitrogen, the interface fracture energy rises to a value in excess of 100 J/m. Adapted from Stolken and Evans (1998).

Fig. 4.18. Experimentally determined interface fracture energy F as a function of the local stress state phase angle for the epoxy—glass bilayer system. The measurements were made using an edge-cracked bimaterial strip specimen on which prescribed values of normal and shear displacements were imposed. The different symbols represent four different sets of experiments conducted for this material system. Adapted from Liechti and Ghai (1992).

When 5min is equated with the interface fracture energy at the appropriate local stress state phase angle V , a critical wavelength or radius for the interface imperfection ao = a r, can be extracted by combining (5.41) and (5.17) to yield... 

He, M. Y., Turner, M. R. and Evans, A. G. (1995), Analysis of the double cleavage drilled compression specimen for interface fracture energy measurements over a range of mode mixities, Acta Metallurgica et Materialia 43, 3453-3458. 

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