A special planar orthotropic material

This paper shows the existence of a particular type of planar orthotropic material, here denoted for the sake of brevity as R-0-orthotropic. The number of independent elastic constants for these materials is three, and not four as for a general orthotropic layer, but these constants have only two orthogonal axes of symmetry. The way to obtain a R-0-orthotropic layer is discussed in the paper, along with the advantages in its use.