  The interaction of an interfacial crack with small impurities is analysed on
the basis of an asymptotic formula derived by the authors. The interaction
between the main crack and the defects (e.g. small cracks or inclusions) is
described asymptotically by analysing the dipole fields and the corresponding
dipole matrices of the defects in question. The method is generic, and it
serves interfacial cracks with general distributed loading on the crack faces,
taking into account possible asymmetry in the boundary conditions, and in a
particular configuration for a crack in a homogeneous medium results agree with
those obtained earlier by Gong (1995). Shielding and amplification effects of
the defects on the propagation of the main crack along the interface are
investigated. Numerical computations based on the explicit analytical formulae
show potential applications in the design of composite and fiber reinforced
materials.
