The scattered field arising from diffraction of a plane flexural wave by a semi-infinite
crack in an orthotropic Kirchhoff thin plate is analysed. The crack is aligned with
a principal direction of the material, so that two of the plate’s three planes of
symmetry are preserved. An asymptotic approximation is derived via the method
of steepest descents, and explicit expressions are given for the most significant
contributions. The effects of anisotropy upon the scattered field are made clear,
and numerical results are presented for typical engineering materials.