We deal with the interaction between three coplanar Griffith
cracks located symmetrically in the mid plane of an orthotropic
layer of finite thickness 2h. The Fourier transform technique
is used to reduce the elastostatic problem to the solution of a
set of integral equations which have been solved by using the
finite Hilbert transform technique and Cooke's result. The
analytical expressions for the stress intensity factors at the
crack tips are obtained for large h. Numerical values of the
interaction effect have been computed for and results show that
interaction effects are either shielding or amplification
depending on the location of each crack with respect to each other
and crack tip spacing as well as the thickness of the layer.